AsyncTask executes but only sometimes

问题

So i use this code to call my AsyncTask

Log.d("before","make_connection");
new Make_Connection().execute();
Log.d("after","make_connection");

My class

private class Make_Connection extends AsyncTask<Void,Void,String>{

    final int port = 4445;

    @Override
    protected void onPreExecute() {
        Toast.makeText(KeyboardActivity.this,"This runs",Toast.LENGTH_LONG).show();
    }

    @Override
    protected String doInBackground(Void... params) {
        Log.d("Connection","Started");
        Log.e("Connec","this runs");
        try {
            socket = new Socket(IP,port);
            //dout = new DataOutputStream(socket.getOutputStream());
            //dout.writeUTF("Connection Formed");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    protected void onPostExecute(String result) {
        Toast.makeText(KeyboardActivity.this,"Connection Made",Toast.LENGTH_SHORT).show();
    }


}

Now i can see in the android monitor that these two are always execute

Log.d("before","make_connection");
Log.d("after","make_connection");

But half of the time i cannot see the output produced by

Log.d("Connection","Started");
Log.e("Connec","this runs");

Even though onPreExecute() runs properly everytime. I have tested on two diffent mobilies running 7.1 and 7.0

Can someone please tell me why this is happening

回答1:

Try:

new Make_Connection().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);

instead of only

new Make_Connection().execute();

This is needed, because in Android SDK 13 or higher they run serially by default. So if you want to run more than one AsyncTask simultaneously, use executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR) For more details, see explanation under order of execution from This docs

回答2:

AsyncTasks are run sequentially by default. They all execute on the same executor. Taken from here https://developer.android.com/reference/android/os/AsyncTask.html

If you truly want parallel execution, you can invoke executeOnExecutor(java.util.concurrent.Executor, Object[]) with THREAD_POOL_EXECUTOR.

来源：https://stackoverflow.com/questions/43426810/asynctask-executes-but-only-sometimes

标签

java

android

android-asynctask