Android面试题-如何退出Activity？如何安全退出已调用多个Activity的Application？

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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

public class BaseActivity extends AppCompatActivity {
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState ) {
        super.onCreate(savedInstanceState);
        ActivityManager.getActivityManager().addActivity(this);
    }
    @Override protected void onDestroy() {
        super.onDestroy();
       //  结束Activity&从栈中移除该Activity
        ActivityManager.getActivityManager().finishActivity();
    }

}



public class ActivityManager {
        // Activity栈
        private static Stack<Activity> activityStack;
        // 单例模式
        private static ActivityManager instance;

        private ActivityManager() {
        }

        /**
         * 单一实例
         */
        public static ActivityManager getActivityManager() {
            if (instance == null) {
                instance = new ActivityManager();
            }
            return instance;
        }

        /**
         * 添加Activity到堆栈
         */
        public void addActivity(Activity activity) {
            if (activityStack == null) {
                activityStack = new Stack<Activity>();
            }
            activityStack.add(activity);
        }

        /**
         * 获取当前Activity（堆栈中最后一个压入的）
         */
        public Activity currentActivity() {
            Activity activity = activityStack.lastElement();
            return activity;
        }

        /**
         * 结束当前Activity（堆栈中最后一个压入的）
         */
        public void finishActivity() {
            Activity activity = activityStack.lastElement();
            finishActivity(activity);
        }

        /**
         * 结束指定的Activity
         */
        public void finishActivity(Activity activity) {
            if (activity != null) {
                activityStack.remove(activity);
                activity.finish();
                activity = null;
            }
        }

        /**
         * 结束指定类名的Activity
         */
        public void finishActivity(Class<?> cls) {
            for (Activity activity : activityStack) {
                if (activity.getClass().equals(cls)) {
                    finishActivity(activity);
                }
            }
        }

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

        /**
         * 退出应用程序
         */
        public void AppExit(Context context) {
            try {
                finishAllActivity();
                //根据进程ID，杀死该进程
                android.os.Process.killProcess(android.os.Process.myPid());
                //退出真个应用程序
                System.exit(0);
            } catch (Exception e) {
            }
        }

}

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 BaseActivity2 extends AppCompatActivity {
    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) {
            BaseActivity2.this.finish(); 
        } 
    }

}

三 RxBus优雅式

首先，在基类BaseActivity里，注册RxBus监听：

public class BaseActivity3 extends AppCompatActivity {
    Subscription mSubscription;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initRxBus();
    }
    //接收退出的指令，关闭所有activity
    private void initRxBus() {
        mSubscription = RxBus.getInstance().toObserverable(NormalEvent.class)
                .subscribe(new Action1<NormalEvent>() {
                               @Override
                               public void call(NormalEvent userEvent) {
                                   if (userEvent.getType() == -1) {
                                       finish();
                                   }
                               }
                           },
                        new Action1<Throwable>() {
                            @Override
                            public void call(Throwable throwable) {
                            }
                        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (!mSubscription.isUnsubscribed()) {
            mSubscription.unsubscribe();
        }
    }
}

这是事件实体NormalEvent:

public class NormalEvent {
    private int type;

    public NormalEvent(int type) {
        this.type = type;
    }

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }
}

新建RxBus类

public class RxBus {

    private static volatile RxBus mInstance;

    private final Subject bus;


    public RxBus()
    {
        bus = new SerializedSubject<>(PublishSubject.create());
    }

    /**
     * 单例模式RxBus
     *
     * @return
     */
    public static RxBus getInstance()
    {

        RxBus rxBus2 = mInstance;
        if (mInstance == null)
        {
            synchronized (RxBus.class)
            {
                rxBus2 = mInstance;
                if (mInstance == null)
                {
                    rxBus2 = new RxBus();
                    mInstance = rxBus2;
                }
            }
        }

        return rxBus2;
    }


    /**
     * 发送消息
     *
     * @param object
     */
    public void post(Object object)
    {

        bus.onNext(object);

    }

    /**
     * 接收消息
     *
     * @param eventType
     * @param <T>
     * @return
     */
    public <T> Observable<T> toObserverable(Class<T> eventType)
    {
        return bus.ofType(eventType);
    }
}

最后，在需要退出的地方调用：

 RxBus.getInstance().post(new NormalEvent(-1));//发送退出指令

四：SingleTask

1、设置MainActivity的加载模式为singleTask

android:launchMode="singleTask"

2、将退出出口放置在MainActivity

private boolean mIsExit;
    @Override /** * 双击返回键退出 */
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if (mIsExit) {
                this.finish();
            } else {
                Toast.makeText(this, "再按一次退出", Toast.LENGTH_SHORT).show();
                mIsExit = true;
                new Handler().postDelayed(new Runnable() {

                    @Override public void run() {
                        mIsExit = false;
                    }
                }, 2000);
            } return true;
        } return super.onKeyDown(keyCode, event);
    }

五、SingleTask改版式

第一步设置MainActivity的加载模式为singleTask

android:launchMode="singleTask"

第二步重写onNewIntent()方法

private static final String TAG_EXIT = "exit"; 
    @Override
    protected void onNewIntent(Intent intent) { 
        super.onNewIntent(intent); 
        if (intent != null) { 
            boolean isExit = intent.getBooleanExtra(TAG_EXIT, false); 
            if (isExit) { this.finish();
            }
        } 
    }

第三步退出

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Intent intent = new Intent(this,MainActivity.class); intent.putExtra(MainActivity.TAG_EXIT, true); startActivity(intent);

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