Android退出应用的方式

一、容器式

建立一个全局容器，把所有的Activity存储起来，退出时循环遍历finish所有Activity

import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;

public class BaseActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 添加Activity到堆栈
        AtyContainer.getInstance().addActivity(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 结束Activity&从栈中移除该Activity
        AtyContainer.getInstance().removeActivity(this);
    }
}

class AtyContainer {
    private AtyContainer() {
    }

    private static AtyContainer instance = new AtyContainer();
    private static List<Activity> activityStack = new ArrayList<Activity>();
    public static AtyContainer getInstance() {
        return instance;
    }
    
    public void addActivity(Activity aty) {
        activityStack.add(aty);
    }

    public void removeActivity(Activity aty) {
        activityStack.remove(aty);
    }

    /**
    * 结束所有Activity
    */
    public void finishAllActivity() {
        for (int i = 0, size = activityStack.size(); i < size; i++) {
            if (null != activityStack.get(i)) {
                activityStack.get(i).finish();
            }
        }
        activityStack.clear();
    }
}

这种方法比较简单，但是可以看到activityStack持有这Activity的强引用，也就是说当某个Activity异常退出时，activityStack没有及时释放掉引用，就会导致内存问题，接下来我们看一种类似的方式，但是会稍微优雅一点点

二、广播式

通过在BaseActivity中注册一个广播，当退出时发送一个广播，finish退出

public class BaseActivity extends Activity {
    private static final String EXITACTION = "action.exit";
    private ExitReceiver exitReceiver = new ExitReceiver();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        IntentFilter filter = new IntentFilter();
        filter.addAction(EXITACTION);
        registerReceiver(exitReceiver, filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(exitReceiver);
    }

    class ExitReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            BaseActivity.this.finish();
        }
    }
}

三、进程式

通过直接杀死当前应用的进程来结束应用，简单粗暴，而且有（wu）效！

android.os.Process.killProcess(android.os.Process.myPid());

System.exit(0);

ActivityManager manager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
manager.killBackgroundProcesses(getPackageName());

这三种都能达到同样的效果，但是在模拟器上都会弹出 Unfortunately , XXX has stopped 消息提示框，但确实能退出应用。部分真机直接失效，只能finish当前Activity（比如我手上这台小米note，国产的几款ROM fw层改动太多，使用这种方式需慎重）。

四、 RS优雅式

什么是RS式呢？即Receiver+singleTask 。我们知道Activity有四种加载模式，而singleTask就是其中的一种，使用这个模式之后，当startActivity时，它先会在当前栈中查询是否存在Activity的实例，如果存在，则将其至于栈顶，并将其之上的所有Activity移除栈。我们打开一个app，首先是一个splash页面，然后会finish掉splash页面。跳转到主页。然后会在主页进行N次的跳转，期间会产生数量不定的Activity，有的被销毁，有的驻留在栈中，但是栈底永远是我们的HomeActivity。这样就让问题变得简单很多了。我们只需两步操作即可优雅的实现app的退出。

1、在HomeActivity注册一个退出广播，和第二个广播式一样，但是这里只需要在HomeActivity一个页面注册即可。

2、设置HomeActivity的启动模式为singleTask。

当我们需要退出的时候只需要startActivity(this,HomeActivity,class)，再发送一个退出广播。上面代码首先会把栈中HomeActivity之上的所有Activity移除出栈，然后接到广播finish自己。一切OK ! 没有弹框，不用考虑机型Rom适配。不会有内存问题，就是那么的优雅，简单！

监听app切换前后台

import android.app.Activity;
import android.app.Application;
import android.content.Context;
import android.os.Bundle;
import android.os.Handler;

import com.xm597.common.debug.DebugLog;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

public class ForegroundCallbacks implements Application.ActivityLifecycleCallbacks {
    public static final long CHECK_DELAY = 500;
    public static final String TAG = ForegroundCallbacks.class.getName();

    public interface Listener {
        public void onBecameForeground();

        public void onBecameBackground();
    }

    private static ForegroundCallbacks instance;
    private boolean foreground = false, paused = true;
    private Handler handler = new Handler();
    private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
    private Runnable check;

    public static ForegroundCallbacks init(Application application) {
        if (instance == null) {
            instance = new ForegroundCallbacks();
            application.registerActivityLifecycleCallbacks(instance);
        }
        return instance;
    }

    public static ForegroundCallbacks get(Application application) {
        if (instance == null) {
            init(application);
        }
        return instance;
    }

    public static ForegroundCallbacks get(Context ctx) {
        if (instance == null) {
            Context appCtx = ctx.getApplicationContext();
            if (appCtx instanceof Application) {
                init((Application) appCtx);
            }
            throw new IllegalStateException(
                    "Foreground is not initialised and " +
                            "cannot obtain the Application object");
        }
        return instance;
    }

    public static ForegroundCallbacks get() {
        if (instance == null) {
            throw new IllegalStateException(
                    "Foreground is not initialised - invoke " +
                            "at least once with parameterised init/get");
        }
        return instance;
    }

    public boolean isForeground() {
        return foreground;
    }

    public boolean isBackground() {
        return !foreground;
    }

    public void addListener(Listener listener) {
        listeners.add(listener);
    }

    public void removeListener(Listener listener) {
        listeners.remove(listener);
    }

    @Override
    public void onActivityResumed(Activity activity) {
        paused = false;
        boolean wasBackground = !foreground;
        foreground = true;
        if (check != null)
            handler.removeCallbacks(check);
        if (wasBackground) {
            DebugLog.log("went foreground");

            for (Listener l : listeners) {
                try {
                    l.onBecameForeground();
                } catch (Exception exc) {
                    DebugLog.log("Listener threw exception!:" + exc.toString());
                }
            }
        } else {
            DebugLog.log("still foreground");
        }
    }

    @Override
    public void onActivityPaused(Activity activity) {
        paused = true;
        if (check != null)
            handler.removeCallbacks(check);
        handler.postDelayed(check = new Runnable() {
            @Override
            public void run() {
                if (foreground && paused) {
                    foreground = false;
                    DebugLog.log("went background");
                    for (Listener l : listeners) {
                        try {
                            l.onBecameBackground();
                        } catch (Exception exc) {
                            DebugLog.log("Listener threw exception!:" + exc.toString());
                        }
                    }
                } else {
                    DebugLog.log("still foreground");
                }
            }
        }, CHECK_DELAY);
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
    }

    @Override
    public void onActivityStarted(Activity activity) {
    }

    @Override
    public void onActivityStopped(Activity activity) {
    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
    }
}

使用：

在自定义Application#onCreate中

ForegroundCallbacks.init(this);
ForegroundCallbacks.get().addListener(new ForegroundCallbacks.Listener() {
    @Override
    public void onBecameForeground() {
        DebugLog.log("当前程序切换到前台");
    }

    @Override
    public void onBecameBackground() {
        DebugLog.log("当前程序切换到后台");
        for (Activity activity: AppActivityMgr.INST.getActivities()) {
            activity.finish();
        }
        //添加延迟是为了异常捕获能有时间写好错误文件
        new Handler().postDelayed(() -> android.os.Process.killProcess(android.os.Process.myPid()), 500);
    }
});

Just do IT Now.

功能-Android退出应用的方式