running more than one AsyncTask in android Activity

Question

I need to download some images from json urls.I have two urls.In this two urls tags are different .So i am unable to use same method to filer data.Can i use two AsyncTask operation in same class to download this images?

Answer 1

Check this one it will help you.

Example Activity.

public class AsyncTaskActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        String url1= "";
        String url2= "";

        new ExampleAsynTask().execute(url1,url2);  
    }
}

Asyntask :

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


    @Override
    protected void onPreExecute() {
    // Do the Operations like updating the UI in android before the background operation is   finished
    }

    @Override
    protected String doInBackground(String... params) {
        // Perform background operations that take longer time to run
        String url1= params[0]; 

        backgroundTask(params[0])
         backgroundTask(params[1])

        return "Done";
    }

    @Override
    protected void onProgressUpdate(Void... values) {
    // Do the Operations like updating the UI in android during the background operation is running
    }


    @Override
    protected void onPostExecute(String result) {
       // Do the Operations like updating the UI in android after the background operation is finished
    }
    public void backgroundTask(String url){
    //To do coding
    }
}

Answer 2

Use the async task as following ,

class asyncFirst extends AsyncTask<String, Integer, String>{


    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();

        progressDialog = new ProgressDialog(this);
        progressDialog.show();

    }

    @Override
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub

        try {

            HttpClient client = new DefaultHttpClient();
            URI website = new URI("http:// your first link here ");
            HttpPost request = new HttpPost();

            // Add your code  

            // get your first url response here

            }
            }catch (Exception e) {
                e.printStackTrace();
           }


        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub

        new asyncSecond ().execute();

    }
}


class asyncSecond extends AsyncTask<String, Integer, String>{

    @Override
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub

        try {

            HttpClient client = new DefaultHttpClient();
            URI website = new URI("http:// your second link here ");
            HttpPost request = new HttpPost();

            // Add your code  

           // get your second url response here 


            }
            }catch (Exception e) {
                e.printStackTrace();
           }


        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub

        // dismiss your progress dialog here

        progressDialog.dismiss();

    }
}

Answer 3

Just use a single Async task, and perform two server requests in them

---

Sample:: This is best suitable if you need a result from first http-request to be passed to second http-request

AsyncTaskActivity.java

public class AsyncTaskActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        new LongOperation().execute("");  
    }

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


        @Override
        protected void onPreExecute() {
        // Do the Operations like updating the UI in android before the background operation is   finished
        }

        @Override
        protected String doInBackground(String... params) {
            // Perform background operations that take longer time to run

            backgroundOperNoOne(){
               //Write a Http request for First url contain the image name and the dates
               //Store the value in a local variable if you want to use the data obtained from this network request to next network request
            }

             backgroundOperNoTwo(){
               //Write a Http request for Second url contain the date and the image url
            }

            return "Executed";
        }

        @Override
        protected void onProgressUpdate(Void... values) {
        // Do the Operations like updating the UI in android during the background operation is running
        }


        @Override
        protected void onPostExecute(String result) {
           // Do the Operations like updating the UI in android after the background operation is finished
        }
    }
}

---

Note::

• You can also call the second async task from first async task from onPostExecute of first Async Task
• If you want two different independent async tasks. just call one below another but they will run independently depending on their time complexity
• If you want to handle images look at picasso, imageLoader,Volly for your use

Always better to use a single Async task

Answer 4

Yes you can, but I would advise you to use ExecutorService for this. As if you need to download more images simultaneously like 10 or 15 then using that much AsyncTask would be an issue.

So

Just make a Runnable, e.g:

class ImageDownloader implements Runnable{
    public String picID = "";
    public ImageDownloader(String id){
        picID = id;
    }
    @Override
    public void run(){
        // image downloading code
    }
}

and use ExecutorService like:

ExecutorService executorService = Executors.newFixedThreadPool(2);
executorService.execute(new ImageDownloader(somePicID));