Android AsyncTask: Error occured while executing doInBackground()

Question

I want to put my function in AsyncTask, but It cause error when I do it. Here is my code:

@Override
public void onClick(final View v) {
    // TODO Auto-generated method stub
    switch (v.getId())
    {
        case R.id.btnCreateVideo:
        {
            MP4VideoParams mParams = new MP4VideoParams(v.getContext(), "mnt/sdcard/out.mp4", "MOBILE");
            new MyMP4VideoCreator().execute(mParams);
        }
        break;
        default:
        {
            Toast.makeText(this, "Nothing", Toast.LENGTH_SHORT).show();
        }
    }
}

An my AsyncTask is simple:

private class MyMP4VideoCreator extends AsyncTask<MP4VideoParams, Void, Void> {

    @Override
    protected Void doInBackground(MP4VideoParams... MP4Video) {
        // TODO Auto-generated method stub

        try {
            CreateMP4Video.CreateVideo(MP4Video[0].getContext(), MP4Video[0].getOutput(), MP4Video[0].getQuality());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

The LogCat:

java.lang.RuntimeException: An error occured while executing doInBackground()
Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

This is my first time using AsyncTask, please help me. Thank you in advance.

Answer 1

Basically the exception Can't create handler inside thread that has not called Looper.prepare() throws while you try to access UI directly from a worker thread.

The method CreateMP4Video.CreateVideo , is it your own implementation or any 3rd party library? Make sure you are not trying to directly access UI in that function (Such as Toast). Use a handler for creating Toasts while inside worker thread.

Answer 2

You are trying to access Main thread from background thread .

In Asynctask doinbackground() method runs on background thread where as postexecute() runs on Main thread .

So try to capture video in onPostexecute or you can ovveride runonUithread() in doinbackground()

Answer 3

I create a Context variable, two String variables (output, quality) and pass those variables when I new a class MyMP4VideoCreator.

I also check those functions when I create a MP4Video and remove all functions belong to Toast.

Luckily for me, it worked. Big thanks to everyone.