AsyncTask android exception (Cannot execute task: the task has already been executed)

Question

I have java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once) although I create a new instance of AsyncTask like this

new ClientEngine(ip, port).execute(WindowsEventsEnum.MouseLeftButtonClick);

Here is my code

    public class ClientEngine extends AsyncTask<WindowsEventsEnum, Void, Void>{
    final String ip;
    final int port;
DatagramSocket socket;
    InetAddress remoteAdress;
    DatagramPacket sendingPacket;
    final String VOLUMEUP = "01";
    final String VOLUMEDOWN = "02";
    final String LMBCLICK = "11";
    final String RMBCLICK = "12";
    final String MMBUP = "21";
    final String MMBDOWN = "22";
    final String ENDCONNECTION = "ec";


    public ClientEngine(String ip, int port) throws SocketException, UnknownHostException {
        this.ip = ip;
        this.port = port;
        socket = new DatagramSocket();
        remoteAdress = InetAddress.getByName(ip);
    }

    public void OpenConnection() throws IOException {


    }

    public void CloseConnection() throws IOException {

socket.close();
    }

    public void MouseLeftButtonClick() throws IOException {
byte[] sendDatagram = LMBCLICK.getBytes();
        sendingPacket = new DatagramPacket(sendDatagram, sendDatagram.length, remoteAdress, port);
        socket.send(sendingPacket);
    }

    public void MouseRightButtonClick() throws IOException {
        byte[] sendDatagram = RMBCLICK.getBytes();
        sendingPacket = new DatagramPacket(sendDatagram, sendDatagram.length, remoteAdress, port);
        socket.send(sendingPacket);
    }

    public void SystemVolumeUp() throws IOException {

    }

    public void SystemVolumeDown() throws IOException {

    }

    @Override
    protected Void doInBackground(WindowsEventsEnum... params) {
        switch (params[0]) {
            case MouseLeftButtonClick:
                try {
                    MouseLeftButtonClick();
                    CloseConnection();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                break;
            case MouseRightButtonClick:
                try {
                    MouseRightButtonClick();
                    CloseConnection();
                } catch (IOException e) {
                    e.printStackTrace();
                }
        }
       return null;
    }

}

Answer 1

Sorry if you have already fixed the issue. But generally, whenever you get an exception like this,

java.lang.IllegalStateException: Cannot execute task: the task has already been executed (a task can be executed only once)

Check whether you are following all the below mentioned rules:

1. AsyncTask can be executed only once (an exception will be thrown if a second execution is attempted.)

   Just like the case where it is illegal to start a thread more than once.

It is never legal to start a thread more than once. In particular, a thread may not be restarted once it has completed execution.

So creating a new instance like new asyncTask().execute(); is the only option

2. onPreExecute(), doInBackground(), onProgressUpdate(),onPostExecute() shouldn't be called manually.

3. The AsyncTask class must be loaded on the UI thread. This is done automatically as of JELLY_BEAN.

4. The task instance must be created on the UI thread.

5. execute(Params...) must be invoked on the UI thread.

Make sure you have followed all the 5 rules in your code.

Read more: https://developer.android.com/reference/android/os/AsyncTask.html