AsyncTask and error handling on Android

Question

I\'m converting my code from using Handler to AsyncTask. The latter is great at what it does - asynchronous updates and handling of results in the

Answer 1

I made my own AsyncTask subclass with an interface that defines callbacks for success and failure. So if an exception is thrown in your AsyncTask, the onFailure function gets passed the exception, otherwise the onSuccess callback gets passed your result. Why android doesn't have something better available is beyond me.

public class SafeAsyncTask
extends AsyncTask  {
    protected Exception cancelledForEx = null;
    protected SafeAsyncTaskInterface callbackInterface;

    public interface SafeAsyncTaskInterface  {
        public Object backgroundTask(cbInBackgroundType[] params) throws Exception;
        public void onCancel(cbResultType result);
        public void onFailure(Exception ex);
        public void onSuccess(cbResultType result);
    }

    @Override
    protected void onPreExecute() {
        this.callbackInterface = (SafeAsyncTaskInterface) this;
    }

    @Override
    protected resultType doInBackground(inBackgroundType... params) {
        try {
            return (resultType) this.callbackInterface.backgroundTask(params);
        } catch (Exception ex) {
            this.cancelledForEx = ex;
            this.cancel(false);
            return null;
        }
    }

    @Override
    protected void onCancelled(resultType result) {
        if(this.cancelledForEx != null) {
            this.callbackInterface.onFailure(this.cancelledForEx);
        } else {
            this.callbackInterface.onCancel(result);
        }
    }

    @Override
    protected void onPostExecute(resultType result) {
        this.callbackInterface.onSuccess(result);
    }
}