Android 应用退到后台

Android 应用退到后台

2016-4-21 10:29:26
Android L

moveTaskToBack(boolean nonRoot)

把包含这个Activity的任务转到后台。并不是finish。
传入Boolean参数：如果是false，在这个Activity是任务的根Activity时，方法才会起效。
传入true，任务中任意Activity都会起效。

/**
* Move the task containing this activity to the back of the activity
 * stack.  The activity's order within the task is unchanged.
*
* @param nonRoot If false then this only works if the activity is the root
 *                of a task; if true it will work for any activity in
 *                a task.
*
* @return If the task was moved (or it was already at the
 *         back) true is returned, else false.
*/
public boolean moveTaskToBack(boolean nonRoot) {
    try {
        return ActivityManagerNative.getDefault().moveActivityTaskToBack(
                mToken, nonRoot);
    } catch (RemoteException e) {
        // Empty
    }
    return false;
}

我们可以监听菜单键，按菜单键把APP退到后台：

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_MENU) {
        moveTaskToBack(true);// 点击菜单键即转入后台，vivo X6Plus Android5.1也适用
        return true;
    }
}

点击返回键，退出当前Activity

点击返回键，执行onBackPressed()，最后会调用finish()。但是进程并没有被杀死。
Activity会进入onPause()。在合适的时机，Activity会进入onResume()，恢复状态。

/**
* Take care of popping the fragment back stack or finishing the activity
* as appropriate.
*/
public void onBackPressed() {
    if (!mFragments.getSupportFragmentManager().popBackStackImmediate()) {
        supportFinishAfterTransition();
    }
}

/**
* Reverses the Activity Scene entry Transition and triggers the calling Activity
* to reverse its exit Transition. When the exit Transition completes,
* {@link #finish()} is called. If no entry Transition was used, finish() is called
* immediately and the Activity exit Transition is run.
*
* <p>On Android 4.4 or lower, this method only finishes the Activity with no
* special exit transition.</p>
*/
public void supportFinishAfterTransition() {
    ActivityCompat.finishAfterTransition(this);
}

/**
* Reverses the Activity Scene entry Transition and triggers the calling Activity
* to reverse its exit Transition. When the exit Transition completes,
* {@link Activity#finish()} is called. If no entry Transition was used, finish() is called
* immediately and the Activity exit Transition is run.
*
* <p>On Android 4.4 or lower, this method only finishes the Activity with no
* special exit transition.</p>
*/
public static void finishAfterTransition(Activity activity) {
    if (Build.VERSION.SDK_INT >= 21) {
        ActivityCompat21.finishAfterTransition(activity);
    } else {
        activity.finish();
    }
}