Zoom avanti e zoom indietro di ImageView Android

Voglio ingrandire e rimpicciolire un ImageView Android. Ho provato la maggior parte dei campioni, ma in tutti l'immagine nella ImageView stessa viene ingrandita e rimpicciolita, mentre voglio ingrandire e rimpicciolire ImageView. Voglio aumentare la larghezza e l'altezza di ImageView durante lo zoom avanti e ridurre la larghezza e l'altezza di ImageView durante lo zoom indietro. Come posso ottenerlo?

Crea due classi Java

Classe di zoom

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;

public class Zoom extends View {

    private Drawable image;
    ImageButton img,img1;
    private int zoomControler=20;

    public Zoom(Context context){
            super(context);

            image=context.getResources().getDrawable(R.drawable.j);
            //image=context.getResources().getDrawable(R.drawable.icon);

            setFocusable(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //here u can control the width and height of the images........ this line is very important
        image.setBounds((getWidth()/2)-zoomControler, (getHeight()/2)-zoomControler, (getWidth()/2)+zoomControler, (getHeight()/2)+zoomControler);
        image.draw(canvas);
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {

            if(keyCode==KeyEvent.KEYCODE_DPAD_UP){
                    // zoom in
                    zoomControler+=10;
            }
            if(keyCode==KeyEvent.KEYCODE_DPAD_DOWN){
                    // zoom out
                    zoomControler-=10;
            }
            if(zoomControler<10){
                    zoomControler=10;
            }

            invalidate();
            return true;
    }
}

fare la seconda classe

import android.app.Activity;
import android.os.Bundle;

public class Zoomexample extends Activity {
   /** Called when the activity is first created. */

   @Override
   public void onCreate(Bundle icicle) {
       super.onCreate(icicle);
       setContentView(new Zoom(this));
   }
}

Si prega di seguire la classe seguente, che viene utilizzata per Zoom avanti e Zoom indietro per ImageView.

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

public class ZoomInZoomOut extends Activity implements OnTouchListener 
{
    private static final String TAG = "Touch";
    @SuppressWarnings("unused")
    private static final float MIN_ZOOM = 1f,MAX_ZOOM = 1f;

    // These matrices will be used to scale points of the image
    Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();

    // The 3 states (events) which the user is trying to perform
    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;
    int mode = NONE;

    // these PointF objects are used to record the point(s) the user is touching
    PointF start = new PointF();
    PointF mid = new PointF();
    float oldDist = 1f;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView view = (ImageView) findViewById(R.id.imageView);
        view.setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) 
    {
        ImageView view = (ImageView) v;
        view.setScaleType(ImageView.ScaleType.MATRIX);
        float scale;

        dumpEvent(event);
        // Handle touch events here...

        switch (event.getAction() & MotionEvent.ACTION_MASK) 
        {
            case MotionEvent.ACTION_DOWN:   // first finger down only
                                                savedMatrix.set(matrix);
                                                start.set(event.getX(), event.getY());
                                                Log.d(TAG, "mode=DRAG"); // write to LogCat
                                                mode = DRAG;
                                                break;

            case MotionEvent.ACTION_UP: // first finger lifted

            case MotionEvent.ACTION_POINTER_UP: // second finger lifted

                                                mode = NONE;
                                                Log.d(TAG, "mode=NONE");
                                                break;

            case MotionEvent.ACTION_POINTER_DOWN: // first and second finger down

                                                oldDist = spacing(event);
                                                Log.d(TAG, "oldDist=" + oldDist);
                                                if (oldDist > 5f) {
                                                    savedMatrix.set(matrix);
                                                    midPoint(mid, event);
                                                    mode = ZOOM;
                                                    Log.d(TAG, "mode=ZOOM");
                                                }
                                                break;

            case MotionEvent.ACTION_MOVE:

                                                if (mode == DRAG) 
                                                { 
                                                    matrix.set(savedMatrix);
                                                    matrix.postTranslate(event.getX() - start.x, event.getY() - start.y); // create the transformation in the matrix  of points
                                                } 
                                                else if (mode == ZOOM) 
                                                { 
                                                    // pinch zooming
                                                    float newDist = spacing(event);
                                                    Log.d(TAG, "newDist=" + newDist);
                                                    if (newDist > 5f) 
                                                    {
                                                        matrix.set(savedMatrix);
                                                        scale = newDist / oldDist; // setting the scaling of the
                                                                                    // matrix...if scale > 1 means
                                                                                    // zoom in...if scale < 1 means
                                                                                    // zoom out
                                                        matrix.postScale(scale, scale, mid.x, mid.y);
                                                    }
                                                }
                                                break;
        }

        view.setImageMatrix(matrix); // display the transformation on screen

        return true; // indicate event was handled
    }

    /*
     * --------------------------------------------------------------------------
     * Method: spacing Parameters: MotionEvent Returns: float Description:
     * checks the spacing between the two fingers on touch
     * ----------------------------------------------------
     */

    private float spacing(MotionEvent event) 
    {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    /*
     * --------------------------------------------------------------------------
     * Method: midPoint Parameters: PointF object, MotionEvent Returns: void
     * Description: calculates the midpoint between the two fingers
     * ------------------------------------------------------------
     */

    private void midPoint(PointF point, MotionEvent event) 
    {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    /** Show an event in the LogCat view, for debugging */
    private void dumpEvent(MotionEvent event) 
    {
        String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE","POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
        StringBuilder sb = new StringBuilder();
        int action = event.getAction();
        int actionCode = action & MotionEvent.ACTION_MASK;
        sb.append("event ACTION_").append(names[actionCode]);

        if (actionCode == MotionEvent.ACTION_POINTER_DOWN || actionCode == MotionEvent.ACTION_POINTER_UP) 
        {
            sb.append("(pid ").append(action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
            sb.append(")");
        }

        sb.append("[");
        for (int i = 0; i < event.getPointerCount(); i++) 
        {
            sb.append("#").append(i);
            sb.append("(pid ").append(event.getPointerId(i));
            sb.append(")=").append((int) event.getX(i));
            sb.append(",").append((int) event.getY(i));
            if (i + 1 < event.getPointerCount())
                sb.append(";");
        }

        sb.append("]");
        Log.d("Touch Events ---------", sb.toString());
    }
}

Le altre implementazioni qui hanno tutte una sorta di difetto. quindi sostanzialmente li ho mescolati e ho pensato a questo.

Crea una visualizzazione personalizzata come questa:

ZoomableImageView.java:

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;

public class ZoomableImageView extends ImageView
{
    Matrix matrix = new Matrix();

    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;
    static final int CLICK = 3;
    int mode = NONE;

    PointF last = new PointF();
    PointF start = new PointF();
    float minScale = 1f;
    float maxScale = 4f;
    float[] m;

    float redundantXSpace, redundantYSpace;
    float width, height;
    float saveScale = 1f;
    float right, bottom, origWidth, origHeight, bmWidth, bmHeight;

    ScaleGestureDetector mScaleDetector;
    Context context;

    public ZoomableImageView(Context context, AttributeSet attr)
    {
        super(context, attr);
        super.setClickable(true);
        this.context = context;
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        matrix.setTranslate(1f, 1f);
        m = new float[9];
        setImageMatrix(matrix);
        setScaleType(ScaleType.MATRIX);

        setOnTouchListener(new OnTouchListener()
        {

            @Override
            public boolean onTouch(View v, MotionEvent event)
            {
                mScaleDetector.onTouchEvent(event);

                matrix.getValues(m);
                float x = m[Matrix.MTRANS_X];
                float y = m[Matrix.MTRANS_Y];
                PointF curr = new PointF(event.getX(), event.getY());

                switch (event.getAction())
                {
                    //when one finger is touching
                    //set the mode to DRAG
                    case MotionEvent.ACTION_DOWN:
                        last.set(event.getX(), event.getY());
                        start.set(last);
                        mode = DRAG;
                        break;
                    //when two fingers are touching
                    //set the mode to ZOOM
                    case MotionEvent.ACTION_POINTER_DOWN:
                        last.set(event.getX(), event.getY());
                        start.set(last);
                        mode = ZOOM;
                        break;
                    //when a finger moves
                    //If mode is applicable move image
                    case MotionEvent.ACTION_MOVE:
                        //if the mode is ZOOM or
                        //if the mode is DRAG and already zoomed
                        if (mode == ZOOM || (mode == DRAG && saveScale > minScale))
                        {
                            float deltaX = curr.x - last.x;// x difference
                            float deltaY = curr.y - last.y;// y difference
                            float scaleWidth = Math.round(origWidth * saveScale);// width after applying current scale
                            float scaleHeight = Math.round(origHeight * saveScale);// height after applying current scale
                            //if scaleWidth is smaller than the views width
                            //in other words if the image width fits in the view
                            //limit left and right movement
                            if (scaleWidth < width)
                            {
                                deltaX = 0;
                                if (y + deltaY > 0)
                                    deltaY = -y;
                                else if (y + deltaY < -bottom)
                                    deltaY = -(y + bottom);
                            }
                            //if scaleHeight is smaller than the views height
                            //in other words if the image height fits in the view
                            //limit up and down movement
                            else if (scaleHeight < height)
                            {
                                deltaY = 0;
                                if (x + deltaX > 0)
                                    deltaX = -x;
                                else if (x + deltaX < -right)
                                    deltaX = -(x + right);
                            }
                            //if the image doesnt fit in the width or height
                            //limit both up and down and left and right
                            else
                            {
                                if (x + deltaX > 0)
                                    deltaX = -x;
                                else if (x + deltaX < -right)
                                    deltaX = -(x + right);

                                if (y + deltaY > 0)
                                    deltaY = -y;
                                else if (y + deltaY < -bottom)
                                    deltaY = -(y + bottom);
                            }
                            //move the image with the matrix
                            matrix.postTranslate(deltaX, deltaY);
                            //set the last touch location to the current
                            last.set(curr.x, curr.y);
                        }
                        break;
                    //first finger is lifted
                    case MotionEvent.ACTION_UP:
                        mode = NONE;
                        int xDiff = (int) Math.abs(curr.x - start.x);
                        int yDiff = (int) Math.abs(curr.y - start.y);
                        if (xDiff < CLICK && yDiff < CLICK)
                            performClick();
                        break;
                    // second finger is lifted
                    case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;
                        break;
                }
                setImageMatrix(matrix);
                invalidate();
                return true;
            }

        });
    }

    @Override
    public void setImageBitmap(Bitmap bm)
    {
        super.setImageBitmap(bm);
        bmWidth = bm.getWidth();
        bmHeight = bm.getHeight();
    }

    public void setMaxZoom(float x)
    {
        maxScale = x;
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener
    {

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector)
        {
            mode = ZOOM;
            return true;
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector)
        {
            float mScaleFactor = detector.getScaleFactor();
            float origScale = saveScale;
            saveScale *= mScaleFactor;
            if (saveScale > maxScale)
            {
                saveScale = maxScale;
                mScaleFactor = maxScale / origScale;
            }
            else if (saveScale < minScale)
            {
                saveScale = minScale;
                mScaleFactor = minScale / origScale;
            }
            right = width * saveScale - width - (2 * redundantXSpace * saveScale);
            bottom = height * saveScale - height - (2 * redundantYSpace * saveScale);
            if (origWidth * saveScale <= width || origHeight * saveScale <= height)
            {
                matrix.postScale(mScaleFactor, mScaleFactor, width / 2, height / 2);
                if (mScaleFactor < 1)
                {
                    matrix.getValues(m);
                    float x = m[Matrix.MTRANS_X];
                    float y = m[Matrix.MTRANS_Y];
                    if (mScaleFactor < 1)
                    {
                        if (Math.round(origWidth * saveScale) < width)
                        {
                            if (y < -bottom)
                                matrix.postTranslate(0, -(y + bottom));
                            else if (y > 0)
                                matrix.postTranslate(0, -y);
                        }
                        else
                        {
                            if (x < -right)
                                matrix.postTranslate(-(x + right), 0);
                            else if (x > 0)
                                matrix.postTranslate(-x, 0);
                        }
                    }
                }
            }
            else
            {
                matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY());
                matrix.getValues(m);
                float x = m[Matrix.MTRANS_X];
                float y = m[Matrix.MTRANS_Y];
                if (mScaleFactor < 1) {
                    if (x < -right)
                        matrix.postTranslate(-(x + right), 0);
                    else if (x > 0)
                        matrix.postTranslate(-x, 0);
                    if (y < -bottom)
                        matrix.postTranslate(0, -(y + bottom));
                    else if (y > 0)
                        matrix.postTranslate(0, -y);
                }
            }
            return true;
        }
    }

    @Override
    protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec)
    {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        width = MeasureSpec.getSize(widthMeasureSpec);
        height = MeasureSpec.getSize(heightMeasureSpec);
        //Fit to screen.
        float scale;
        float scaleX =  width / bmWidth;
        float scaleY = height / bmHeight;
        scale = Math.min(scaleX, scaleY);
        matrix.setScale(scale, scale);
        setImageMatrix(matrix);
        saveScale = 1f;

        // Center the image
        redundantYSpace = height - (scale * bmHeight) ;
        redundantXSpace = width - (scale * bmWidth);
        redundantYSpace /= 2;
        redundantXSpace /= 2;

        matrix.postTranslate(redundantXSpace, redundantYSpace);

        origWidth = width - 2 * redundantXSpace;
        origHeight = height - 2 * redundantYSpace;
        right = width * saveScale - width - (2 * redundantXSpace * saveScale);
        bottom = height * saveScale - height - (2 * redundantYSpace * saveScale);
        setImageMatrix(matrix);
    }
}

Quindi aggiungi l'immagine in questo modo:

ZoomableImageView touch = (ZoomableImageView)findViewById(R.id.IMAGEID);
touch.setImageBitmap(bitmap);

Aggiungi la vista in questo modo in XML:

<PACKAGE.ZoomableImageView
android:id="@+id/IMAGEID"
android:layout_width="match_parent"
android:layout_height="match_parent"/>

Modo semplice:

PhotoViewAttacher pAttacher;
pAttacher = new PhotoViewAttacher(Your_Image_View);
pAttacher.update();

Aggiungi sotto la riga in build.gradle:

compile 'com.commit451:PhotoView:1.2.4'

usa questa classe: TouchImageView

Questa è un'altra implementazione basata sul codice pubblicato da Nicolas Tyler.

I seguenti bug sono stati corretti:

• L'impostazione minScalesu un numero inferiore a 1 ora funziona
• Non è necessario utilizzare setImageBitmap()per impostare l'immagine (è possibile utilizzare, ad esempiosetImageResource()
• Tutti i costruttori ora funzionano correttamente

Le seguenti cose, tra le altre, vengono riordinate:

• Un OnTouchListenernon viene utilizzato, non è necessario perché la classe può semplicemente implementare il onTouchEvent()metodo.

• Il compito right = width * saveScale - width - (2 * redundantXSpace * saveScale);è stato semplificato a Il right = (originalBitmapWidth * saveScale) - widthche, a mio avviso, è molto meno confuso.

• Alcune variabili membro vengono rimosse (è possibile rimuovere più stato da questa classe)

Non è perfetto ma eccoti qui:

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;

/**
 * Created by alex on 23/02/16.
 * Based on code posted by Nicolas Tyler here:
 * /programming/6650398/android-imageview-zoom-in-and-zoom-out
 */
public class ZoomableImageView extends ImageView {

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            mode = ZOOM;
            return true;
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            float scaleFactor = detector.getScaleFactor();
            float newScale = saveScale * scaleFactor;
            if (newScale < maxScale && newScale > minScale) {
                saveScale = newScale;
                float width = getWidth();
                float height = getHeight();
                right = (originalBitmapWidth * saveScale) - width;
                bottom = (originalBitmapHeight * saveScale) - height;

                float scaledBitmapWidth = originalBitmapWidth * saveScale;
                float scaledBitmapHeight = originalBitmapHeight * saveScale;

                if (scaledBitmapWidth <= width || scaledBitmapHeight <= height) {
                    matrix.postScale(scaleFactor, scaleFactor, width / 2, height / 2);
                } else {
                    matrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
                }
            }
            return true;
        }

    }

    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;
    static final int CLICK = 3;

    private int mode = NONE;

    private Matrix matrix = new Matrix();

    private PointF last = new PointF();
    private PointF start = new PointF();
    private float minScale = 0.5f;
    private float maxScale = 4f;
    private float[] m;

    private float redundantXSpace, redundantYSpace;
    private float saveScale = 1f;
    private float right, bottom, originalBitmapWidth, originalBitmapHeight;

    private ScaleGestureDetector mScaleDetector;

    public ZoomableImageView(Context context) {
        super(context);
        init(context);
    }

    public ZoomableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public ZoomableImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    private void init(Context context) {
        super.setClickable(true);
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        m = new float[9];
        setImageMatrix(matrix);
        setScaleType(ScaleType.MATRIX);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int bmHeight = getBmHeight();
        int bmWidth = getBmWidth();

        float width = getMeasuredWidth();
        float height = getMeasuredHeight();
        //Fit to screen.
        float scale = width > height ? height / bmHeight :  width / bmWidth;

        matrix.setScale(scale, scale);
        saveScale = 1f;

        originalBitmapWidth = scale * bmWidth;
        originalBitmapHeight = scale * bmHeight;

        // Center the image
        redundantYSpace = (height - originalBitmapHeight);
        redundantXSpace = (width - originalBitmapWidth);

        matrix.postTranslate(redundantXSpace / 2, redundantYSpace / 2);

        setImageMatrix(matrix);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mScaleDetector.onTouchEvent(event);

        matrix.getValues(m);
        float x = m[Matrix.MTRANS_X];
        float y = m[Matrix.MTRANS_Y];
        PointF curr = new PointF(event.getX(), event.getY());

        switch (event.getAction()) {
            //when one finger is touching
            //set the mode to DRAG
            case MotionEvent.ACTION_DOWN:
                last.set(event.getX(), event.getY());
                start.set(last);
                mode = DRAG;
                break;
            //when two fingers are touching
            //set the mode to ZOOM
            case MotionEvent.ACTION_POINTER_DOWN:
                last.set(event.getX(), event.getY());
                start.set(last);
                mode = ZOOM;
                break;
            //when a finger moves
            //If mode is applicable move image
            case MotionEvent.ACTION_MOVE:
                //if the mode is ZOOM or
                //if the mode is DRAG and already zoomed
                if (mode == ZOOM || (mode == DRAG && saveScale > minScale)) {
                    float deltaX = curr.x - last.x;// x difference
                    float deltaY = curr.y - last.y;// y difference
                    float scaleWidth = Math.round(originalBitmapWidth * saveScale);// width after applying current scale
                    float scaleHeight = Math.round(originalBitmapHeight * saveScale);// height after applying current scale

                    boolean limitX = false;
                    boolean limitY = false;

                    //if scaleWidth is smaller than the views width
                    //in other words if the image width fits in the view
                    //limit left and right movement
                    if (scaleWidth < getWidth() && scaleHeight < getHeight()) {
                        // don't do anything
                    }
                    else if (scaleWidth < getWidth()) {
                        deltaX = 0;
                        limitY = true;
                    }
                    //if scaleHeight is smaller than the views height
                    //in other words if the image height fits in the view
                    //limit up and down movement
                    else if (scaleHeight < getHeight()) {
                        deltaY = 0;
                        limitX = true;
                    }
                    //if the image doesnt fit in the width or height
                    //limit both up and down and left and right
                    else {
                        limitX = true;
                        limitY = true;
                    }

                    if (limitY) {
                        if (y + deltaY > 0) {
                            deltaY = -y;
                        } else  if (y + deltaY < -bottom) {
                            deltaY = -(y + bottom);
                        }

                    }

                    if (limitX) {
                        if (x + deltaX > 0) {
                            deltaX = -x;
                        } else if (x + deltaX < -right) {
                            deltaX = -(x + right);
                        }

                    }
                    //move the image with the matrix
                    matrix.postTranslate(deltaX, deltaY);
                    //set the last touch location to the current
                    last.set(curr.x, curr.y);
                }
                break;
            //first finger is lifted
            case MotionEvent.ACTION_UP:
                mode = NONE;
                int xDiff = (int) Math.abs(curr.x - start.x);
                int yDiff = (int) Math.abs(curr.y - start.y);
                if (xDiff < CLICK && yDiff < CLICK)
                    performClick();
                break;
            // second finger is lifted
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                break;
        }
        setImageMatrix(matrix);
        invalidate();
        return true;
    }

    public void setMaxZoom(float x) {
        maxScale = x;
    }

    private int getBmWidth() {
        Drawable drawable = getDrawable();
        if (drawable != null) {
            return drawable.getIntrinsicWidth();
        }
        return 0;
    }

    private int getBmHeight() {
        Drawable drawable = getDrawable();
        if (drawable != null) {
            return drawable.getIntrinsicHeight();
        }
        return 0;
    }
}

È vecchio, ma questo potrebbe aiutare qualcun altro.

Sotto la classe TouchImageView supporta lo zoom avanti / indietro sia con il pizzico che con il doppio tocco

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;

public class TouchImageView extends ImageView implements GestureDetector.OnGestureListener, GestureDetector.OnDoubleTapListener {

    Matrix matrix;

    // We can be in one of these 3 states
    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;
    int mode = NONE;

    // Remember some things for zooming
    PointF last = new PointF();
    PointF start = new PointF();
    float minScale = 1f;
    float maxScale = 3f;
    float[] m;

    int viewWidth, viewHeight;
    static final int CLICK = 3;
    float saveScale = 1f;
    protected float origWidth, origHeight;
    int oldMeasuredWidth, oldMeasuredHeight;

    ScaleGestureDetector mScaleDetector;

    Context context;

    public TouchImageView(Context context) {
        super(context);
        sharedConstructing(context);
    }

    public TouchImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        sharedConstructing(context);
    }

    GestureDetector mGestureDetector;

    private void sharedConstructing(Context context) {
        super.setClickable(true);
        this.context = context;
        mGestureDetector = new GestureDetector(context, this);
        mGestureDetector.setOnDoubleTapListener(this);

        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        matrix = new Matrix();
        m = new float[9];
        setImageMatrix(matrix);
        setScaleType(ScaleType.MATRIX);

        setOnTouchListener(new OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                mScaleDetector.onTouchEvent(event);
                mGestureDetector.onTouchEvent(event);

                PointF curr = new PointF(event.getX(), event.getY());

                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        last.set(curr);
                        start.set(last);
                        mode = DRAG;
                        break;

                    case MotionEvent.ACTION_MOVE:
                        if (mode == DRAG) {
                            float deltaX = curr.x - last.x;
                            float deltaY = curr.y - last.y;
                            float fixTransX = getFixDragTrans(deltaX, viewWidth,
                                    origWidth * saveScale);
                            float fixTransY = getFixDragTrans(deltaY, viewHeight,
                                    origHeight * saveScale);
                            matrix.postTranslate(fixTransX, fixTransY);
                            fixTrans();
                            last.set(curr.x, curr.y);
                        }
                        break;

                    case MotionEvent.ACTION_UP:
                        mode = NONE;
                        int xDiff = (int) Math.abs(curr.x - start.x);
                        int yDiff = (int) Math.abs(curr.y - start.y);
                        if (xDiff < CLICK && yDiff < CLICK)
                            performClick();
                        break;

                    case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;
                        break;
                }

                setImageMatrix(matrix);
                invalidate();
                return true; // indicate event was handled
            }

        });
    }

    public void setMaxZoom(float x) {
        maxScale = x;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onDoubleTap(MotionEvent e) {
        // Double tap is detected
        Log.i("MAIN_TAG", "Double tap detected");
        float origScale = saveScale;
        float mScaleFactor;

        if (saveScale == maxScale) {
            saveScale = minScale;
            mScaleFactor = minScale / origScale;
        } else {
            saveScale = maxScale;
            mScaleFactor = maxScale / origScale;
        }

        matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2,
                viewHeight / 2);

        fixTrans();
        return false;
    }

    @Override
    public boolean onDoubleTapEvent(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onDown(MotionEvent e) {
        return false;
    }

    @Override
    public void onShowPress(MotionEvent e) {

    }

    @Override
    public boolean onSingleTapUp(MotionEvent e) {
        return false;
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        return false;
    }

    @Override
    public void onLongPress(MotionEvent e) {

    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        return false;
    }

    private class ScaleListener extends
            ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            mode = ZOOM;
            return true;
        }

        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            float mScaleFactor = detector.getScaleFactor();
            float origScale = saveScale;
            saveScale *= mScaleFactor;
            if (saveScale > maxScale) {
                saveScale = maxScale;
                mScaleFactor = maxScale / origScale;
            } else if (saveScale < minScale) {
                saveScale = minScale;
                mScaleFactor = minScale / origScale;
            }

            if (origWidth * saveScale <= viewWidth
                    || origHeight * saveScale <= viewHeight)
                matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2,
                        viewHeight / 2);
            else
                matrix.postScale(mScaleFactor, mScaleFactor,
                        detector.getFocusX(), detector.getFocusY());

            fixTrans();
            return true;
        }
    }

    void fixTrans() {
        matrix.getValues(m);
        float transX = m[Matrix.MTRANS_X];
        float transY = m[Matrix.MTRANS_Y];

        float fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale);
        float fixTransY = getFixTrans(transY, viewHeight, origHeight
                * saveScale);

        if (fixTransX != 0 || fixTransY != 0)
            matrix.postTranslate(fixTransX, fixTransY);
    }

    float getFixTrans(float trans, float viewSize, float contentSize) {
        float minTrans, maxTrans;

        if (contentSize <= viewSize) {
            minTrans = 0;
            maxTrans = viewSize - contentSize;
        } else {
            minTrans = viewSize - contentSize;
            maxTrans = 0;
        }

        if (trans < minTrans)
            return -trans + minTrans;
        if (trans > maxTrans)
            return -trans + maxTrans;
        return 0;
    }

    float getFixDragTrans(float delta, float viewSize, float contentSize) {
        if (contentSize <= viewSize) {
            return 0;
        }
        return delta;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        viewWidth = MeasureSpec.getSize(widthMeasureSpec);
        viewHeight = MeasureSpec.getSize(heightMeasureSpec);

        //
        // Rescales image on rotation
        //
        if (oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight
                || viewWidth == 0 || viewHeight == 0)
            return;
        oldMeasuredHeight = viewHeight;
        oldMeasuredWidth = viewWidth;

        if (saveScale == 1) {
            // Fit to screen.
            float scale;

            Drawable drawable = getDrawable();
            if (drawable == null || drawable.getIntrinsicWidth() == 0
                    || drawable.getIntrinsicHeight() == 0)
                return;
            int bmWidth = drawable.getIntrinsicWidth();
            int bmHeight = drawable.getIntrinsicHeight();

            Log.d("bmSize", "bmWidth: " + bmWidth + " bmHeight : " + bmHeight);

            float scaleX = (float) viewWidth / (float) bmWidth;
            float scaleY = (float) viewHeight / (float) bmHeight;
            scale = Math.min(scaleX, scaleY);
            matrix.setScale(scale, scale);

            // Center the image
            float redundantYSpace = (float) viewHeight
                    - (scale * (float) bmHeight);
            float redundantXSpace = (float) viewWidth
                    - (scale * (float) bmWidth);
            redundantYSpace /= (float) 2;
            redundantXSpace /= (float) 2;

            matrix.postTranslate(redundantXSpace, redundantYSpace);

            origWidth = viewWidth - 2 * redundantXSpace;
            origHeight = viewHeight - 2 * redundantYSpace;
            setImageMatrix(matrix);
        }
        fixTrans();
    }
}

Utilizzo: puoi sostituire il tuo ImageViewcon TouchImageView sia in XML che in java

1. Per XML

<?xml version="1.0" encoding="utf-8"?>
<com.example.android.myapp.TouchImageView 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/imViewedImage"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clickable="true"
    android:focusable="true" />

2. Per Java

TouchImageView imViewedImage = findViewById(R.id.imViewedImage);

Ho migliorato la risposta che ho ottenuto dallo stack per ZOOM (due dita) / ROTAZIONE (due dita) / DRAG (dito singolo) impeccabili .

// ============================ codice XML ==================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.flochat.imageviewzoomforstack.MainActivity">

    <ImageView
        android:id="@+id/imageview_trash"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/trash" />

</LinearLayout>

// ============================ Codice Java ================== ========

public class MainActivity extends AppCompatActivity {

    ImageView photoview2;
    float[] lastEvent = null;
    float d = 0f;
    float newRot = 0f;
    private boolean isZoomAndRotate;
    private boolean isOutSide;
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private int mode = NONE;
    private PointF start = new PointF();
    private PointF mid = new PointF();
    float oldDist = 1f;
    private float xCoOrdinate, yCoOrdinate;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        setContentView(R.layout.activity_main);

        photoview2 = findViewById(R.id.imageview_trash);

        photoview2.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                ImageView view = (ImageView) v;
                view.bringToFront();
                viewTransformation(view, event);
                return true;
            }
        });
    }


    private void viewTransformation(View view, MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
            xCoOrdinate = view.getX() - event.getRawX();
            yCoOrdinate = view.getY() - event.getRawY();

                start.set(event.getX(), event.getY());
                isOutSide = false;
                mode = DRAG;
                lastEvent = null;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                oldDist = spacing(event);
                if (oldDist > 10f) {
                    midPoint(mid, event);
                    mode = ZOOM;
                }

                lastEvent = new float[4];
                lastEvent[0] = event.getX(0);
                lastEvent[1] = event.getX(1);
                lastEvent[2] = event.getY(0);
                lastEvent[3] = event.getY(1);
                d = rotation(event);
                break;
            case MotionEvent.ACTION_UP:
                isZoomAndRotate = false;
                if (mode == DRAG) {
                    float x = event.getX();
                    float y = event.getY();
                }
            case MotionEvent.ACTION_OUTSIDE:
                isOutSide = true;
                mode = NONE;
                lastEvent = null;
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                lastEvent = null;
                break;
            case MotionEvent.ACTION_MOVE:
                if (!isOutSide) {
                    if (mode == DRAG) {
                        isZoomAndRotate = false;
                        view.animate().x(event.getRawX() + xCoOrdinate).y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                    }
                    if (mode == ZOOM && event.getPointerCount() == 2) {
                        float newDist1 = spacing(event);
                        if (newDist1 > 10f) {
                            float scale = newDist1 / oldDist * view.getScaleX();
                            view.setScaleX(scale);
                            view.setScaleY(scale);
                        }
                        if (lastEvent != null) {
                            newRot = rotation(event);
                            view.setRotation((float) (view.getRotation() + (newRot - d)));
                        }
                    }
                }
                break;
        }
    }

    private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (int) Math.sqrt(x * x + y * y);
    }

    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

}

// ======================== Basta passare qualsiasi vista che si desidera ingrandire / ruotare / trascinare al metodo viewTransformation (). Molto applicabile per lo zoom di visualizzazione del testo. Non pixelerà il testo.

Ho creato la mia visualizzazione immagine personalizzata con pizzico per ingrandire. Non ci sono limiti / confini sul codice di Chirag Raval , quindi l'utente può trascinare l'immagine fuori dallo schermo.

Ecco la classe CustomImageView:

    public class CustomImageVIew extends ImageView implements OnTouchListener {


    private Matrix matrix = new Matrix();
    private Matrix savedMatrix = new Matrix();

    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;

    private int mode = NONE;

    private PointF mStartPoint = new PointF();
    private PointF mMiddlePoint = new PointF();
    private Point mBitmapMiddlePoint = new Point();

    private float oldDist = 1f;
    private float matrixValues[] = {0f, 0f, 0f, 0f, 0f, 0f, 0f, 0f, 0f};
    private float scale;
    private float oldEventX = 0;
    private float oldEventY = 0;
    private float oldStartPointX = 0;
    private float oldStartPointY = 0;
    private int mViewWidth = -1;
    private int mViewHeight = -1;
    private int mBitmapWidth = -1;
    private int mBitmapHeight = -1;
    private boolean mDraggable = false;


    public CustomImageVIew(Context context) {
        this(context, null, 0);
    }

    public CustomImageVIew(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CustomImageVIew(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        this.setOnTouchListener(this);
    }

    @Override
    public void onSizeChanged (int w, int h, int oldw, int oldh){
        super.onSizeChanged(w, h, oldw, oldh);
        mViewWidth = w;
        mViewHeight = h;
    }

    public void setBitmap(Bitmap bitmap){
        if(bitmap != null){
            setImageBitmap(bitmap);

            mBitmapWidth = bitmap.getWidth();
            mBitmapHeight = bitmap.getHeight();
            mBitmapMiddlePoint.x = (mViewWidth / 2) - (mBitmapWidth /  2);
            mBitmapMiddlePoint.y = (mViewHeight / 2) - (mBitmapHeight / 2);

            matrix.postTranslate(mBitmapMiddlePoint.x, mBitmapMiddlePoint.y);
            this.setImageMatrix(matrix);
        }
    }

    @Override
    public boolean onTouch(View v, MotionEvent event){
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            savedMatrix.set(matrix);
            mStartPoint.set(event.getX(), event.getY());
            mode = DRAG;
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            oldDist = spacing(event);
            if(oldDist > 10f){
                savedMatrix.set(matrix);
                midPoint(mMiddlePoint, event);
                mode = ZOOM;
            }
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_POINTER_UP:
            mode = NONE;
            break;
        case MotionEvent.ACTION_MOVE:
            if(mode == DRAG){
                drag(event);
            } else if(mode == ZOOM){
                zoom(event);
            } 
            break;
        }

        return true;
    }



   public void drag(MotionEvent event){
       matrix.getValues(matrixValues);

       float left = matrixValues[2];
       float top = matrixValues[5];
       float bottom = (top + (matrixValues[0] * mBitmapHeight)) - mViewHeight;
       float right = (left + (matrixValues[0] * mBitmapWidth)) -mViewWidth;

       float eventX = event.getX();
       float eventY = event.getY();
       float spacingX = eventX - mStartPoint.x;
       float spacingY = eventY - mStartPoint.y;
       float newPositionLeft = (left  < 0 ? spacingX : spacingX * -1) + left;
       float newPositionRight = (spacingX) + right;
       float newPositionTop = (top  < 0 ? spacingY : spacingY * -1) + top;
       float newPositionBottom = (spacingY) + bottom;
       boolean x = true;
       boolean y = true;

       if(newPositionRight < 0.0f || newPositionLeft > 0.0f){
           if(newPositionRight < 0.0f && newPositionLeft > 0.0f){
               x = false;
           } else{
               eventX = oldEventX;
               mStartPoint.x = oldStartPointX;
           }
       }
       if(newPositionBottom < 0.0f || newPositionTop > 0.0f){
           if(newPositionBottom < 0.0f && newPositionTop > 0.0f){
               y = false;
           } else{
               eventY = oldEventY;
               mStartPoint.y = oldStartPointY;
           }
       }

       if(mDraggable){
           matrix.set(savedMatrix);
           matrix.postTranslate(x? eventX - mStartPoint.x : 0, y? eventY - mStartPoint.y : 0);
           this.setImageMatrix(matrix);
           if(x)oldEventX = eventX;
           if(y)oldEventY = eventY;
           if(x)oldStartPointX = mStartPoint.x;
           if(y)oldStartPointY = mStartPoint.y;
       }

   }

   public void zoom(MotionEvent event){
       matrix.getValues(matrixValues);

       float newDist = spacing(event);
       float bitmapWidth = matrixValues[0] * mBitmapWidth;
       float bimtapHeight = matrixValues[0] * mBitmapHeight;
       boolean in = newDist > oldDist;

       if(!in && matrixValues[0] < 1){
           return;
       }
       if(bitmapWidth > mViewWidth || bimtapHeight > mViewHeight){
           mDraggable = true;
       } else{
           mDraggable = false;
       }

       float midX = (mViewWidth / 2);
       float midY = (mViewHeight / 2);

       matrix.set(savedMatrix);
       scale = newDist / oldDist;
       matrix.postScale(scale, scale, bitmapWidth > mViewWidth ? mMiddlePoint.x : midX, bimtapHeight > mViewHeight ? mMiddlePoint.y : midY); 

       this.setImageMatrix(matrix);


   }





    /** Determine the space between the first two fingers */
    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);

        return (float)Math.sqrt(x * x + y * y);
    }

    /** Calculate the mid point of the first two fingers */
    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }


}