Android 應用退到背景

2016-4-21 10:29:26

Android L

moveTaskToBack(boolean nonRoot)

把包含這個Activity的任務轉到背景。并不是finish。

傳入Boolean參數：如果是false，在這個Activity是任務的根Activity時，方法才會起效。

傳入true，任務中任意Activity都會起效。

/**
* 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;
}           

我們可以監聽菜單鍵，按菜單鍵把APP退到背景：

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_MENU) {
        moveTaskToBack(true);// 點選菜單鍵即轉入背景，vivo X6Plus Android5.1也适用
        return true;
    }
}           

點選傳回鍵，退出目前Activity

點選傳回鍵，執行

onBackPressed()

，最後會調用

finish()

。但是程序并沒有被殺死。

Activity會進入onPause()。在合适的時機，Activity會進入onResume()，恢複狀态。

/**
* 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();
    }
}