使用后台线程从服务发送通知 android

Question

这是我的服务代码

public class MyService extends Service {
NotificationManager NM;
ServerSocket serversocket=null;

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Log.i("","startcommand is called");



    return super.onStartCommand(intent, flags, startId);
}


private final IBinder binder=new MyBinder();



//this use for binding with activity
@Override
public IBinder onBind(Intent intent) {
    return binder;
}



//this class used by the Client to access the service
public class MyBinder extends Binder {
        public MyService getService(){
            return MyService.this;
        }
}






public void notify(){


    Notification notify=new Notification(android.R.drawable.ic_dialog_email,"Service is created",System.currentTimeMillis());
    Intent i=new Intent(this, MainActivity.class);
    i.putExtra("json","the notification method");
    PendingIntent pending=PendingIntent.getActivity(
            getApplicationContext(),0, i,0);
    notify.setLatestEventInfo(this,"subject","body",pending);
    NM.notify(0, notify);
}

@Override
public void onCreate() {
    ServerConnection serverConnection=new ServerConnection();
    serverConnection.execute();

}





public class ServerConnection extends AsyncTask<Void,String,Void>{

    @Override
    protected Void doInBackground(Void... params) {
        DataInputStream dataInputStream;

        try {
            serversocket = new ServerSocket(9100);
            while(true){

                Log.i("aa", "Service is listening to port");
                Socket socket =   serversocket.accept();


             NM = (NotificationManager)     getApplicationContext().getSystemService(NOTIFICATION_SERVICE);
               publishProgress("ok");





            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }


    @Override
    protected void onProgressUpdate(String... values) {
        notify();
    }


    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
    }





}

}

我不知道，如果可以在服务中使用 Asynctask，但无论如何，每当我调用发送通知的 notify() 时，我都会收到错误

 java.lang.NullPointerException
        at android.content.ContextWrapper.getPackageName(ContextWrapper.java:127)
        at android.content.ComponentName.<init>(ComponentName.java:75)
        at android.content.Intent.<init>(Intent.java:3301)
        at com.example.com.service.MyService.notify(MyService.java:76)
        at com.example.com.service.MyService$ServerConnection.onProgressUpdate(MyService.java:135)
        at com.example.com.service.MyService$ServerConnection.onProgressUpdate(MyService.java:95)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:647)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4745)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        at dalvik.system.NativeStart.main(Native Method)

发送通知的 notify() 函数如果在 onStartCommand 或除后台线程以外的任何地方使用它就可以正常工作。

我想做的是，每当我使用 serversocket 收到一些数据时，我想向无法正常工作的用户发送通知。

谢谢

Answer 1

检查这 2 行-

    Intent i=new Intent(this, MainActivity.class);
   //// other lines
    notify.setLatestEventInfo(this,"subject","body",pending);

这里的this是asynctask调用方法时的asynctask吧？您应该尝试将其替换为 MyService.this.

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