Android ha un meccanismo in atto per chiudere un'applicazione in modo sicuro secondo la sua documentazione. Nell'ultima attività che è uscita (di solito l'attività principale che è venuta per la prima volta all'avvio dell'applicazione) basta posizionare un paio di righe nel metodo onDestroy (). La chiamata a System.runFinalizersOnExit (true) garantisce che tutti gli oggetti vengano finalizzati e che la spazzatura venga raccolta alla chiusura dell'applicazione. Puoi anche uccidere rapidamente un'applicazione tramite android.os.Process.killProcess (android.os.Process.myPid ()) se preferisci. Il modo migliore per farlo è inserire un metodo come il seguente in una classe di supporto e quindi chiamarlo ogni volta che l'app deve essere uccisa. Ad esempio nel metodo di distruzione dell'attività radice (supponendo che l'app non uccida mai questa attività):
Inoltre Android non notificherà un'applicazione dell'evento del tasto HOME , quindi non è possibile chiudere l'applicazione quando si preme il tasto HOME . Android si riserva l' evento chiave HOME in modo che uno sviluppatore non possa impedire agli utenti di abbandonare la propria applicazione. Tuttavia è possibile determinare con il tasto HOME premuto premendo un flag su true in una classe helper che presuppone che il tasto HOME sia stato premuto, quindi cambiando il flag in false quando si verifica un evento che mostra che il tasto HOME non è stato premuto e quindi controllando di vedere il tasto HOME premuto nel metodo onStop () dell'attività.
Non dimenticare di gestire il tasto HOME per qualsiasi menu e nelle attività avviate dai menu. Lo stesso vale per il tasto CERCA . Di seguito sono riportate alcune classi di esempio da illustrare:
Ecco un esempio di un'attività di root che uccide l'applicazione quando viene distrutta:
package android.example;
/**
* @author Danny Remington - MacroSolve
*/
public class HomeKey extends CustomActivity {
public void onDestroy() {
super.onDestroy();
/*
* Kill application when the root activity is killed.
*/
UIHelper.killApp(true);
}
}
Ecco un'attività astratta che può essere estesa per gestire il tasto HOME per tutte le attività che lo estendono:
package android.example;
/**
* @author Danny Remington - MacroSolve
*/
import android.app.Activity;
import android.view.Menu;
import android.view.MenuInflater;
/**
* Activity that includes custom behavior shared across the application. For
* example, bringing up a menu with the settings icon when the menu button is
* pressed by the user and then starting the settings activity when the user
* clicks on the settings icon.
*/
public abstract class CustomActivity extends Activity {
public void onStart() {
super.onStart();
/*
* Check if the app was just launched. If the app was just launched then
* assume that the HOME key will be pressed next unless a navigation
* event by the user or the app occurs. Otherwise the user or the app
* navigated to this activity so the HOME key was not pressed.
*/
UIHelper.checkJustLaunced();
}
public void finish() {
/*
* This can only invoked by the user or the app finishing the activity
* by navigating from the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
super.finish();
}
public void onStop() {
super.onStop();
/*
* Check if the HOME key was pressed. If the HOME key was pressed then
* the app will be killed. Otherwise the user or the app is navigating
* away from this activity so assume that the HOME key will be pressed
* next unless a navigation event by the user or the app occurs.
*/
UIHelper.checkHomeKeyPressed(true);
}
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.settings_menu, menu);
/*
* Assume that the HOME key will be pressed next unless a navigation
* event by the user or the app occurs.
*/
UIHelper.homeKeyPressed = true;
return true;
}
public boolean onSearchRequested() {
/*
* Disable the SEARCH key.
*/
return false;
}
}
Ecco un esempio di una schermata del menu che gestisce il tasto HOME :
/**
* @author Danny Remington - MacroSolve
*/
package android.example;
import android.os.Bundle;
import android.preference.PreferenceActivity;
/**
* PreferenceActivity for the settings screen.
*
* @see PreferenceActivity
*
*/
public class SettingsScreen extends PreferenceActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.layout.settings_screen);
}
public void onStart() {
super.onStart();
/*
* This can only invoked by the user or the app starting the activity by
* navigating to the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
}
public void finish() {
/*
* This can only invoked by the user or the app finishing the activity
* by navigating from the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
super.finish();
}
public void onStop() {
super.onStop();
/*
* Check if the HOME key was pressed. If the HOME key was pressed then
* the app will be killed either safely or quickly. Otherwise the user
* or the app is navigating away from the activity so assume that the
* HOME key will be pressed next unless a navigation event by the user
* or the app occurs.
*/
UIHelper.checkHomeKeyPressed(true);
}
public boolean onSearchRequested() {
/*
* Disable the SEARCH key.
*/
return false;
}
}
Ecco un esempio di una classe di supporto che gestisce la chiave HOME in tutta l'app:
package android.example;
/**
* @author Danny Remington - MacroSolve
*
*/
/**
* Helper class to help handling of UI.
*/
public class UIHelper {
public static boolean homeKeyPressed;
private static boolean justLaunched = true;
/**
* Check if the app was just launched. If the app was just launched then
* assume that the HOME key will be pressed next unless a navigation event
* by the user or the app occurs. Otherwise the user or the app navigated to
* the activity so the HOME key was not pressed.
*/
public static void checkJustLaunced() {
if (justLaunched) {
homeKeyPressed = true;
justLaunched = false;
} else {
homeKeyPressed = false;
}
}
/**
* Check if the HOME key was pressed. If the HOME key was pressed then the
* app will be killed either safely or quickly. Otherwise the user or the
* app is navigating away from the activity so assume that the HOME key will
* be pressed next unless a navigation event by the user or the app occurs.
*
* @param killSafely
* Primitive boolean which indicates whether the app should be
* killed safely or quickly when the HOME key is pressed.
*
* @see {@link UIHelper.killApp}
*/
public static void checkHomeKeyPressed(boolean killSafely) {
if (homeKeyPressed) {
killApp(true);
} else {
homeKeyPressed = true;
}
}
/**
* Kill the app either safely or quickly. The app is killed safely by
* killing the virtual machine that the app runs in after finalizing all
* {@link Object}s created by the app. The app is killed quickly by abruptly
* killing the process that the virtual machine that runs the app runs in
* without finalizing all {@link Object}s created by the app. Whether the
* app is killed safely or quickly the app will be completely created as a
* new app in a new virtual machine running in a new process if the user
* starts the app again.
*
* <P>
* <B>NOTE:</B> The app will not be killed until all of its threads have
* closed if it is killed safely.
* </P>
*
* <P>
* <B>NOTE:</B> All threads running under the process will be abruptly
* killed when the app is killed quickly. This can lead to various issues
* related to threading. For example, if one of those threads was making
* multiple related changes to the database, then it may have committed some
* of those changes but not all of those changes when it was abruptly
* killed.
* </P>
*
* @param killSafely
* Primitive boolean which indicates whether the app should be
* killed safely or quickly. If true then the app will be killed
* safely. Otherwise it will be killed quickly.
*/
public static void killApp(boolean killSafely) {
if (killSafely) {
/*
* Notify the system to finalize and collect all objects of the app
* on exit so that the virtual machine running the app can be killed
* by the system without causing issues. NOTE: If this is set to
* true then the virtual machine will not be killed until all of its
* threads have closed.
*/
System.runFinalizersOnExit(true);
/*
* Force the system to close the app down completely instead of
* retaining it in the background. The virtual machine that runs the
* app will be killed. The app will be completely created as a new
* app in a new virtual machine running in a new process if the user
* starts the app again.
*/
System.exit(0);
} else {
/*
* Alternatively the process that runs the virtual machine could be
* abruptly killed. This is the quickest way to remove the app from
* the device but it could cause problems since resources will not
* be finalized first. For example, all threads running under the
* process will be abruptly killed when the process is abruptly
* killed. If one of those threads was making multiple related
* changes to the database, then it may have committed some of those
* changes but not all of those changes when it was abruptly killed.
*/
android.os.Process.killProcess(android.os.Process.myPid());
}
}
}