How to perform background process in android?

Question

I am performing some operations(uploading image to webservice) in IntentService. Please see my code below.

Inside the activity i am calling service like this. I am calling the below method after capturing the image ie inside onActivityResult. The app is getting hanged when i call this method in onActivityResult. I am able to perform the task in IntentService. But the acitivity is getting hanged.

private void callService(){
    Intent intent = new Intent(this, TestIntentService.class);
    intent.putExtra("imageData", imageData);
    startService(intent);
}

This is my IntentService Class. Can i perform webservice call inside callImageUploadAPI(). Am i doing anything wrong here?

public class TestIntentService extends IntentService {

    public TestIntentService() {
        super("com.screens.testapp");
        // TODO Auto-generated constructor stub
    }
//imageData passed from the activity
    @Override
    protected void onHandleIntent(Intent intent) {
        // TODO Auto-generated method stub
    if(intent != null){
        Bundle extras = intent.getExtras();
        imageData= extras.getString("imageData");
    }
        callImageUploadAPI(imageData);
    }

    private void callImageUploadAPI(final String imageData) {

        // TODO Auto-generated method stub
        try {
            if (Log.checkNetworkStatus(TestIntentService.this)) {

            } else {

            }
        } catch (Exception e) {
            // TODO: handle exception

        }
    }

}

Thanks

Answer 1

If you need to do a task in background, Android provides a class called AsyncTask which you can extend and use it for doing a network operation or any other heavy operation. This is an example from Android Developer Website (AsyncTask Page):

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

This may be used in your code this way:

if (Log.checkNetworkStatus(TestIntentService.this)) {
               new DownloadFilesTask().execute(url1, url2, url3);
            } else {

            }

Answer 2

For you to perform actions in the background use Services.

You can launch the services from your activity and you can assign a thread for the service and a handler for communication from that thread to the UIThread.

Check this: http://developer.android.com/guide/components/services.html

A little sneak peek

A Service is an application component that can perform long-running operations in the background and does not provide a user interface.