SafeAsyncTask.java

package com.iranfmcg.dokan.customer.helper;

import android.os.AsyncTask;
import android.support.annotation.MainThread;
import android.support.annotation.WorkerThread;

/* Copyright (C) Farzad Tabashir <ftabashir@gmail.com> 15 February 2017, 8:38 AM
*  All Rights Reserved
*/
public abstract class SafeAsyncTask<Params, Progress, Result> {

    private AsyncTask<Params, Progress, Result> asyncTask;

    private boolean safePre, safeBackground, safePost;
    private ExceptionHandler preExceptionHandler, backgroundExceptionHandler, postExceptionHandler;

    public SafeAsyncTask() {
        asyncTask = new Task();
    }

    public SafeAsyncTask(boolean throttleExceptions) {
        this();
        if (throttleExceptions) {
            ExceptionHandler exceptionHandler = exception -> {
                //do nothing, throttle exception
            };
            setPreExceptionHandler(exceptionHandler);
            setBackgroundExceptionHandler(exceptionHandler);
            setPostExceptionHandler(exceptionHandler);
        }
    }

    public SafeAsyncTask<Params, Progress, Result> setPreExceptionHandler(ExceptionHandler exceptionHandler) {
        this.safePre = true;
        this.preExceptionHandler = exceptionHandler;
        return this;
    }

    public SafeAsyncTask<Params, Progress, Result> setBackgroundExceptionHandler(ExceptionHandler exceptionHandler) {
        this.safeBackground = true;
        this.backgroundExceptionHandler = exceptionHandler;
        return this;
    }

    public SafeAsyncTask<Params, Progress, Result> setPostExceptionHandler(ExceptionHandler exceptionHandler) {
        this.safePost = true;
        this.postExceptionHandler = exceptionHandler;
        return this;
    }

    @MainThread
    protected void onPreExecute() {
    }

    @SuppressWarnings("unchecked")
    @WorkerThread
    protected abstract Result doInBackground(Params... params);

    @MainThread
    protected void onPostExecute(Result result) {
    }

    @SafeVarargs
    @MainThread
    protected final void onProgressUpdate(Progress... values) {
    }

    @MainThread
    protected void onCancelled() {
    }

    @MainThread
    protected void onCancelled(Result result) {
        onCancelled();
    }

    public void execute(Params... params) {
        asyncTask.execute(params);
    }

    public interface ExceptionHandler {
        void handle(Exception exception);
    }

    private class Task extends AsyncTask<Params, Progress, Result> {
        @SafeVarargs
        @Override
        protected final Result doInBackground(Params... params) {
            if (safeBackground) {
                try {
                    return SafeAsyncTask.this.doInBackground(params);
                } catch (Exception exception) {
                    backgroundExceptionHandler.handle(exception);
                    return null;
                }
            } else {
                return SafeAsyncTask.this.doInBackground(params);
            }
        }

        @Override
        protected void onPreExecute() {
            if (safePre) {
                try {
                    SafeAsyncTask.this.onPreExecute();
                } catch (Exception exception) {
                    preExceptionHandler.handle(exception);
                }
            } else {
                SafeAsyncTask.this.onPreExecute();
            }
        }

        @Override
        protected void onPostExecute(Result result) {
            if (safePost) {
                try {
                    SafeAsyncTask.this.onPostExecute(result);
                } catch (Exception exception) {
                    postExceptionHandler.handle(exception);
                }
            } else {
                SafeAsyncTask.this.onPostExecute(result);
            }
        }

        @SafeVarargs
        @Override
        protected final void onProgressUpdate(Progress... values) {
            SafeAsyncTask.this.onProgressUpdate(values);
        }

        @Override
        protected void onCancelled(Result result) {
            SafeAsyncTask.this.onCancelled(result);
        }

        @Override
        protected void onCancelled() {
            SafeAsyncTask.this.onCancelled();
        }
    }
}