Making HTTP request using OkHttp library inside doInBackground() of AsyncTask blocks UI operation

Question

I was trying making OkHttp request in AsyncTask using call.execute() -- Synchronous call.

I have two buttons in my layout. Pressing button1 starts AsyncTask, that executes OkHttp request.call.execute().

And pressing button2, I just update a TextView.

Observation: While AsyncTask is running, I can not update TextView.

But, if I don't use AsyncTask and use OkHttpClient.newCall().enqueue() method,then I can update TextView by pressing button2.

Any answer for "Why using AsyncTask in this case not working"?

Source Code Sample:

bpost = (Button) findViewById(R.id.bpost);
    bpost.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            i++;
            tv.setText(""+i);
        }
    });


bstart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        OkHttpHandler handler = new OkHttpHandler();

            byte[] image = new byte[0];
            try {
                image = handler.execute(url).get();
                if (image != null && image.length > 0) {
                    Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
                    imageView.setImageBitmap(bitmap);
                    tv.setText("Total btytes download: " + image.length);
                }
            } catch (Exception e) {
                tv.setText("sorry, something went wrong!");
            }
        }


public class OkHttpHandler extends AsyncTask<String, Void, byte[]> {

    OkHttpClient client = new OkHttpClient();

    @Override
    protected byte[] doInBackground(String... params) {

        Request.Builder builder = new Request.Builder();
        builder.url(params[0]);
        Request request = builder.build();



        try {
            Response response = client.newCall(request).execute();
            return response.body().bytes();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

Answer 1

This is because get() method of AsyncTask waits for the computation to finish in doInBackground method and then retrieves its result. See this link.

This will make your main UIThread in wait mode until doInBackground finish its execution or there is some exception occur(i.e. CancellationException,ExecutionException and InterruptedException).

You should use onPostExecute(Result) override method of AsyncTask.

private class OkHttpHandler extends AsyncTask<String, Void, byte[]> {

        OkHttpClient client = new OkHttpClient();

        @Override
        protected byte[] doInBackground(String... params) {

            Request.Builder builder = new Request.Builder();
            builder.url(params[0]);
            Request request = builder.build();
            try {
                Response response = client.newCall(request).execute();
                return response.body().bytes();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(byte[] bytes) {
            super.onPostExecute(bytes);
            try {
                if (bytes != null && bytes.length > 0) {
                    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                    imageView.setImageBitmap(bitmap);
                    tv.setText("Total btytes download: " + bytes.length);
                }
            } catch (Exception e) {
                tv.setText("sorry, something went wrong!");
            }
        }
    }