Question

您好我在尝试在AsyncTask中运行警报时遇到了一些麻烦。每当运行带有上下文的内容时，应用程序就会崩溃，就像尝试让警报出现一样。

我正在关注本教程：http://www.androidhive.info/2012/10/android-push-notifications-using-google-cloud-messaging-gcm-php-and-mysql/

我确信，错误是由于错误的＆＃34; context＆＃34;或类似的东西。

我从GCM类调用我的AsyncTask类，如下所示：

GCM.java：

@Override
protected void onMessage(Context context, Intent intent) {
    Log.i(TAG, "Received message");
    String message = intent.getExtras().getString("price");

//    displayMessage(context, message);
    // notifies user
    generateNotification(context, message);
   runAsync(context);
    // update database
}

// here I want to run my asyncTask
private void runAsync(Context context){
    TestActivity = new TestActivity(context);
    task.execute();
}

TestActivity.java：

Context mContext;

public TestActivity(Context context) {
    this.mContext = context;
} 
// Progress Dialog
private ProgressDialog pDialog;

@Override
    protected void onPreExecute() {
        super.onPreExecute();
        productsList = new ArrayList<HashMap<String, String>>();

        pDialog = new ProgressDialog(mContext);
        pDialog.setMessage("Loading products. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
    // here when It shall show the alert it crashes... with the following error
      pDialog.show();

    }

  F/AndroidRuntime(19976): FATAL EXCEPTION: IntentService[GCM-980252920256-1]
  F/AndroidRuntime(19976): android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
  F/AndroidRuntime(19976):  at android.view.ViewRootImpl.setView(ViewRootImpl.java:792)
  F/AndroidRuntime(19976):  at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:265)
  F/AndroidRuntime(19976):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
  F/AndroidRuntime(19976):  at android.app.Dialog.show(Dialog.java:282)
  F/AndroidRuntime(19976):  at com.test.app.TestActivity.onPreExecute(TestActivity.java:72)
  F/AndroidRuntime(19976):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
  F/AndroidRuntime(19976):  at android.os.AsyncTask.execute(AsyncTask.java:534)
  F/AndroidRuntime(19976):  at com.test.app.GCM.asyncTaskRun(GCM.java:63)
  F/AndroidRuntime(19976):  at com.test.app.GCM.onMessage(GCM.java:55)
  F/AndroidRuntime(19976):  at com.google.android.gcm.GCMBaseIntentService.onHandleIntent(GCMBaseIntentService.java:223)
  F/AndroidRuntime(19976):  at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
  F/AndroidRuntime(19976):  at android.os.Handler.dispatchMessage(Handler.java:99)
  F/AndroidRuntime(19976):  at android.os.Looper.loop(Looper.java:176)
  F/AndroidRuntime(19976):  at android.os.HandlerThread.run(HandlerThread.java:60)

我的错误在哪里？

Answer 1

ProgressDialog需要一个Activity作为Context（在Android中这是一个糟糕的设计，Context并不总是必需的Context）。

您应该打开一个看起来像对话框的活动：

请参阅Android Activity as a dialog

Answer 2

将上下文作为Activity传递而不是ApplicationContext。这两个类都扩展了Context类。

运行AsyncTask时出错 - 上下文？

2 个答案: