android - 使用向上按钮时，不会调用 onRestoreInstanceState

Question

我对 Android 开发和 StackOverflow 都很陌生，我希望我问的不是一个愚蠢的问题，这个问题以前有人问过，但我在上面找不到任何东西。

我正在制作一个应用程序，它在连接到蓝牙设备时启动(最初未绑定(bind)的)服务，并且只有在我告诉它断开连接或断开连接时才应该停止。服务启动后，主要 Activity 绑定(bind)到它，并在调用 onDestroy() 时解除绑定(bind)。当调用 onStart 并且 mIsBound 为真时，它也会重新绑定(bind)。mIsBound bool 值与 onRestoreInstanceState() 一起存储。

*mIsConnected 可能是比 mIsBound 更好的名称，但您明白了

当我正常重新打开应用程序时，从多任务菜单或通过服务图标，mIsBound 仍设置为正确的值。屏幕方向不是问题，当打开辅助 Activity 并通过后退按钮返回主要 Activity 时，一切仍然顺利。但是，当我在辅助 Activity 中使用向上按钮时，mIsBound 值会丢失并且不会调用 onRestoreInstanceState()。

我需要这个来确定服务是否已经在运行，因为如果它没有运行，我调用 bindService() 它会在不需要它的情况下启动，当它自行停止但仍处于绑定(bind)状态时我会收到错误消息。

服务:

public class BluetoothService extends Service {

@Override
public IBinder onBind(Intent intent) {
    return mBinder;

}

public class LocalBinder extends Binder {
    BluetoothService getService() {
        return BluetoothService.this;
    }
}


private void connectionLost() {
Log.e(TAG, "connection lost");
disconnect();
}


public synchronized void disconnect() {
    Log.d(TAG, "disconnect");
    stopSelf();
}


private void showNotification(String s) {

    // Set the icon, scrolling text and timestamp
    Notification notification = new Notification(R.drawable.ic_launcher, s,
            System.currentTimeMillis());

    // The PendingIntent to launch our activity if the user selects this notification
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
            new Intent(this, LedAndIrControlActivity.class), 0);

    // Set the info for the views that show in the notification panel.
    notification.setLatestEventInfo(this, s, s, contentIntent);

    // Send the notification.
    startForeground(NOTIFICATION, notification);
}

主要 Activity :

public class MainActivity extends Activity {   

private static boolean mIsBound = false;
private BluetoothService Com;

@Override
public void onStart() {
    super.onStart();
    if(mIsBound){
        doBindService();
 }

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    Log.i(TAG, "onSaveInstanceState");
    outState.putBoolean("mIsBound", mIsBound);
}

public void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);          
    Log.i(TAG, "onRestoreInstanceState");
    mIsBound = savedInstanceState.getBoolean("mIsBound");
    if(mIsBound){
        doBindService();
    }
}

protected void onDestroy() {
    super.onDestroy();
    Log.i(TAG, "onDestroy");
    doUnbindService();
}

public boolean onOptionsItemSelected(MenuItem item) {
    Intent serverIntent = null;
    switch (item.getItemId()) {
    case android.R.id.home:
        return true;
    case R.id.item1:
         // Launch the DeviceListActivity to see devices and do scan
         serverIntent = new Intent(this, DeviceListActivity.class);
         startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE);
         startService(new Intent(this, BluetoothService.class));
         doBindService();
         return true;
     case R.id.item2:
         // Disconnect device
        Com.disconnect();
        doUnbindService();
         return true;
     case R.id.item3:
          serverIntent = new Intent(this, SecondaryActivity.class);
          //serverIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
          startActivity(serverIntent);
        return true;    
    default:
        return super.onOptionsItemSelected(item);
     }      
 } 

 void doBindService() {
     Log.d(TAG, "doBindService");
     // Establish a connection with the service.  We use an explicit
     // class name because we want a specific service implementation that
     // we know will be running in our own process (and thus won't be
     // supporting component replacement by other applications).
     bindService(new Intent(getBaseContext(), //Binding.this
             BluetoothService.class), mConnection, Context.BIND_AUTO_CREATE);
     mIsBound = true;
 }

 void doUnbindService() {
     if (mIsBound) {
         Log.d(TAG, "doUnbindService");
         // Detach our existing connection.
         unbindService(mConnection);
         mIsBound = false;
     }
     Com = null;
 }


 private ServiceConnection mConnection = new ServiceConnection() {

     public void onServiceConnected(ComponentName className, IBinder service) {
         // This is called when the connection with the service has been
         // established, giving us the service object we can use to
         // interact with the service.  Because we have bound to a explicit
         // service that we know is running in our own process, we can
         // cast its IBinder to a concrete class and directly access it.
         Com = ((BluetoothService.LocalBinder)service).getService();
         invalidateOptionsMenu();
         Log.i(TAG, "Service connected");

         // Tell the user about this for our demo.
         Toast.makeText(getBaseContext(), "local_service_connected",//Binding.this
                 Toast.LENGTH_SHORT).show();
     }

     public void onServiceDisconnected(ComponentName className) {
         // This is called when the connection with the service has been
         // unexpectedly disconnected -- that is, its process crashed.
         // Because it is running in our same process, we should never
         // see this happen.
         Com = null;
         Toast.makeText(getBaseContext(), "local service_disconected",//Binding.this
                 Toast.LENGTH_SHORT).show();
     }
 };

辅助 Activity :

public class SecondaryActivity extends Activity {      


@Override
public boolean onOptionsItemSelected(MenuItem item) {
    Intent serverIntent = null;
    switch (item.getItemId()) {
    case android.R.id.home:
        // app icon in action bar clicked; go home
        serverIntent = new Intent(this, MainActivity.class);
        serverIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(serverIntent);
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }   
}

我的问题是如何确保始终恢复 mIsBound 值？我发现使用 SharedPreferences 是一个选项，但这似乎不是执行此操作的正确方法。

关于如何绑定(bind)到服务的任何其他建议，如果它已经在运行，也非常感谢!

谢谢!

更新:

我想到了另一种解决问题的方法，那就是简单地检查服务是否已经在运行，如果为真则(重新)绑定(bind)。这样做的方法在这里解释: How to check if a service is running on Android?

我仍然不相信这是执行此操作的正确或最佳方法，但现在就可以了。如果您对此发表评论，我们将不胜感激。

Answer 1

我对你的帖子主题有同样的问题(当使用向上按钮时 onRestoreInstanceState 没有被调用)，尽管原因与你在正文中描述的不同。由于我没有找到任何其他帖子回答它，我将在此处发布我对这个特定问题的解决方案。

问:使用向上按钮时没有调用onRestoreInstanceState

答:按下操作栏上的主页(向上导航)按钮确实与按下后退按钮的行为不同。前者不调用父 Activity 的 onRestoreInstanceState()，就像按下后退按钮一样。

如果您想完成与后退按钮相同的行为，您可以通过覆盖子 Activity 中的 onNavigateUp() 方法并调用 onBackPressed() 从它。

在子 Activity 中:

@Override
public boolean onNavigateUp() {
    onBackPressed();
    return true;
}

我不确定返回值，true 似乎工作正常并且满足文档要求:“如果向上导航成功完成且此 Activity 已完成，则为 true，否则为 false”.