Question

在我的应用程序中，我正在使用AsynchTask来显示忙碌的指示器，我正在尝试连接到服务器。当应用程序进入onPause（）时，我取消了AsynchTask 如下面的发布代码所示。当应用程序从onPause进入onResume时，当我尝试连接到服务器时，我希望AsynchTask能够被执行显示繁忙的指标，但会发生的是，AsynchTask执行并显示bsy指标，但之后应用程序崩溃。此行为仅在发生时发生当我来自onPause（onPause-＆gt; onResume）时，我尝试连接到服务器。

所以根据logCat输出，据我所知，当我试图取消AsynchTask时，我正在考虑usig处理程序请让我知道如何解决这个问题。

我离开时收到以下LogCat：

03-09 16:51:27.024: E/AndroidRuntime(26111): FATAL EXCEPTION: pool-1-thread-1
03-09 16:51:27.024: E/AndroidRuntime(26111): Process: com.example.mqtt_designlayout_02, PID: 26111
03-09 16:51:27.024: E/AndroidRuntime(26111): java.lang.IllegalArgumentException: Invalid ClientHandle
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttService.getConnection(MqttService.java:552)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttService.connect(MqttService.java:318)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient.doConnect(MqttAndroidClient.java:427)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient.access$2(MqttAndroidClient.java:417)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient$1.run(MqttAndroidClient.java:395)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.lang.Thread.run(Thread.java:818)

有时候会有以下几点：

03-09 16:51:27.024: E/AndroidRuntime(26111): FATAL EXCEPTION: pool-1-thread-2
03-09 16:51:27.024: E/AndroidRuntime(26111): Process: com.example.mqtt_designlayout_02, PID: 26111
03-09 16:51:27.024: E/AndroidRuntime(26111): java.lang.IllegalArgumentException: Invalid ClientHandle
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttService.getConnection(MqttService.java:552)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttService.connect(MqttService.java:318)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient.doConnect(MqttAndroidClient.java:427)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient.access$2(MqttAndroidClient.java:417)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at org.eclipse.paho.android.service.MqttAndroidClient$1.run(MqttAndroidClient.java:395)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 17:08:57.023: E/AndroidRuntime(26667):    at java.lang.Thread.run(Thread.java:818)

代码：

private void cancelAsynchTask() {
    // TODO Auto-generated method stub
    Log.w(TAG, "@cancelAsynchTask().");

    if (this.MQTTAsynch != null) {
        Log.d(TAG, "asynchTask object was initilised");

        if (this.MQTTAsynch.getStatus() == AsyncTask.Status.PENDING) {
            Log.d(TAG, "AsynchTask has not started yet.");
            boolean cancelledSuccessully = this.MQTTAsynch.cancel(true);
            if (cancelledSuccessully) {
                Log.d(TAG, "AsynchTask is cancelled successfully.");
            } else {
                Log.d(TAG, "AsynchTask failed to cancell");
            }
        }

        if (this.MQTTAsynch.getStatus() == AsyncTask.Status.RUNNING) {
            Log.d(TAG, "AsynchTask still running doing work in the backgroung thread, and it will be intrrupted");
            boolean cancelledSuccessully = this.MQTTAsynch.cancel(true);
            if (cancelledSuccessully) {
                Log.d(TAG, "AsynchTask is cancelled successfully.");
            } else {
                Log.d(TAG, "AsynchTask failed to cancell");
            }
        }
        if (this.MQTTAsynch.getStatus() == AsyncTask.Status.FINISHED) {
            Log.d(TAG, "AsynchTask has finished its work.");
        }
    } else {
        Log.d(TAG, "asynchTask object was not initilised. this.MQTTAsynch == null");
    }
}

doInBackGround ：

@Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        Log.d(TAG, "@MQTTAsynchTask(): doInBackground().");
        do {
            try {
                this.MQTTAndroidClient.connect(this.opts, this.context, synchCONNCallBack);
            } catch (MqttSecurityException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (MqttException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            try {
                Thread.sleep(MQTT_BROKER_TIME_OUT);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            this.totalTimeOut += MQTT_BROKER_TIME_OUT;

        } while ( (!this.isCancelled()) && (this.MQTTAndroidClient != null) && (!isConnectCalled) && (!this.MQTTAndroidClient.isConnected()) && (this.totalTimeOut <= (10 * MQTT_BROKER_TIME_OUT)) );

        return null;
    }

Answer 1

不要为自己造成不必要的复杂化。 onPreExecute()的{{1}}和onPostExecute()在主UI线程上执行。这意味着您可以对UI进行任何更改，包括显示任何对话框。覆盖这些方法并同样修改UI。只有AsyncTask在后台执行，并且对此UI的任何更改都要求您使用doInBackground()。

我可以使用处理程序来执行AsyncTask吗？

1 个答案: