将数据从 BroadcastReceiver 传递到 MainActivity 只能正确运行一次

Question

我有一个 PushNotificationReceiver（扩展 BroadcastReceiver） 和 MainActivity。接收方通过 Intent 向 MainActivity 发送一些数据（例如字符串值“New value”）。然后，MainActivity 使用此值更新其 TextView。 在我将此 TextView 值更改为其他值（例如将其重置为“UNSPECIFIED”）并将 Activity 移至后台并再次移至前台之前，此方法工作正常。 MainActivity 已恢复，其 TextView 包含“新值”，但我预计它是“UNSPECIFIED” - 这就是问题。

我的应用程序出了什么问题？

整个原型项目可以在此处下载。

这是我的 MainActivity 代码

private TextView tvValue;
private EditText etNewValue;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    tvValue = (TextView)findViewById(R.id.value);
    etNewValue = (EditText)findViewById(R.id.new_value);

    findViewById(R.id.reset).setOnClickListener(new OnClickListener() {         
        @Override
        public void onClick(View v) {
            tvValue.setText(getResources().getString(R.string.not_specified));
        }
    });

    findViewById(R.id.send_notification).setOnClickListener(new OnClickListener() {         
        @Override
        public void onClick(View v) {
            sendNotification(etNewValue.getText().toString());
        }
    });

    processDataFromBroadcast(getIntent());        
}

@Override
public void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    processDataFromBroadcast(intent);
}

private void sendNotification(String value){
    NotificationManager mNotificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

    String title = "Proto App Notif";

    Notification notification = new Notification(
            android.R.drawable.ic_notification_overlay,
            title,
            System.currentTimeMillis());
    notification.flags |= Notification.FLAG_AUTO_CANCEL;

    Context ctxApp = getApplicationContext();

    Intent notificationIntent = new Intent()
        .setAction(PushNotificationReceiver.ACTION_NOTIFICATION)
        .putExtra("value", value);
    PendingIntent contentIntent = PendingIntent.getBroadcast(
            ctxApp, 
            0, 
            notificationIntent, 
            PendingIntent.FLAG_UPDATE_CURRENT);     

    notification.setLatestEventInfo(
            ctxApp,
            title,
            value,
            contentIntent);

    notification.audioStreamType = AudioManager.STREAM_NOTIFICATION;

    mNotificationManager.notify(1, notification);           
}

private void processDataFromBroadcast(Intent intent) {
    if (!intent.hasExtra("value")){
        return;
    }

    String val = intent.getStringExtra("value");

    tvValue.setText(val); // Updating my activity look
}

PushNotificationReceiver

private static final String LOG_CAT = "PushNotificationReceiver";
static final String ACTION_NOTIFICATION = "com.mobiwolf.proto.NOTIFICATION_RECEIVER";

@Override
public void onReceive(Context context, Intent intent) {
    if (!intent.getAction().equals(ACTION_NOTIFICATION)) {
        return;
    }

    String value = intent.getStringExtra("value");

    Log.d(LOG_CAT, "Received notification message: "+value); // Log always contains the value sent on first time

    Intent i = new Intent();
    i.setClass(context, MainActivity.class);
    i.putExtra("value", value);
    i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

    context.startActivity(i);
}

和清单

    <receiver android:name="com.mobiwolf.proto.PushNotificationReceiver">
        <intent-filter>
            <action android:name="com.mobiwolf.proto.NOTIFICATION_RECEIVER" />
        </intent-filter>
    </receiver>    

    <activity android:name=".MainActivity"
              android:label="@string/app_name"
              android:launchMode="singleTask">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

Answer 1

替换

i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

为

i.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | 
    Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);

Answer 2

为了解决这个问题，我添加了全局静态触发器

  /**
  * This class triggers whether pushnotification was handled by MainActivity
  * (Preventing handling this push notification twice when the MainActivity 
  * is moved to background and restored from background
  */
  public final class PushNotifHandledTrigger {
private static boolean handled = true;

public static boolean wasHandled(){
    return handled;
}

public static void set(){
    handled = true;
}

public static void reset(){
    handled = false;
}
  }

然后在startActivity之前我重置了这个触发器并在处理后设置（当然，仅在未设置触发器时才执行处理）

Answer 3

定义一个 public static boolean newUpdate; 变量，在 context.startActivity(i); 之前将其设置为 true。然后，当您在 MainActivity 中检查意图是否有 extra 时，还要验证 newUpdate 是否为 true >，如果是，请将其重置为 false 并更新您的 TextView 字段。最后一个函数将如下所示

private void processDataFromBroadcast(Intent intent) {
   if ( !intent.hasExtra("value") || (newUpdate == false) ){ //So only new updates are processed.
      return;
   }
   newUpdate = false; //This action will not be repeated unless another notification arrives
   String val = intent.getStringExtra("value");

   tvValue.setText(val); // Updating my activity look
}