Progress dialog - AsyncTask

Question

I am using ActionBar Tablistener with ViewPager and I have three fragments.

On launch my App is downloading my XML file data source from where my ListView in fragments is being populated.

How can I add as simple progress dialog while downloading my XML file(when there is slow internet connetion) in AsyncTask when I start application, so that my Activity runs after xml is downloaded?

Currently I'm using SystemClock.sleep(2760); so there is enough time to download on normal connection speed...

My main Activity:

public class MainActivity extends FragmentActivity implements ActionBar.TabListener {

    TextView mSearchText;

    ViewPager viewPager=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = (ViewPager) findViewById(R.id.pager);

        final ActionBar actionBar=getActionBar();

        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        actionBar.setDisplayShowTitleEnabled(false);

        addTabs(actionBar);
        viewPager.setAdapter(new MyAdapter(getSupportFragmentManager()));
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int i, float v, int i2) {
                Log.d("VIVZ","onPageScrolled "+i+" "+v+" "+i2);
            }

            @Override
            public void onPageSelected(int i) {
                actionBar.setSelectedNavigationItem(i);
                Log.d("VIVZ","onPageSelected "+i);
            }

            @Override
            public void onPageScrollStateChanged(int i) {
                if(i==ViewPager.SCROLL_STATE_IDLE)
                Log.d("VIVZ","onPageScrollStateChanged scroll state idle "+i);
                if(i==ViewPager.SCROLL_STATE_DRAGGING)
                    Log.d("VIVZ","onPageScrollStateChanged scroll state dragging "+i);
                if(i==ViewPager.SCROLL_STATE_SETTLING)
                    Log.d("VIVZ","onPageScrollStateChanged scroll state settling "+i);
            }
        });


        if(isNetworkAvailable()){       
                    Log.i("mobAppModel", "starting download Task");
                    AppDownloadTask download = new AppDownloadTask();
                    download.execute();
                    SystemClock.sleep(2760);                        
            }
    }

    private boolean isNetworkAvailable() {
        ConnectivityManager connectivityManager 
              = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
        return activeNetworkInfo != null && activeNetworkInfo.isConnected();
    } 
    private class AppDownloadTask extends AsyncTask<Void, Void, Void>{
        @Override
        protected Void doInBackground(Void... arg0) {
            //Download the file
            try {
                Downloader.DownloadFromUrl("https://URL_on_kategorijeXML.xml", openFileOutput("XMLsource.xml", Context.MODE_PRIVATE));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

            return null;
        } 

    }   

}

Answer 1

Don't call SystemClock.sleep() in your Activity.onCreate() method, you'll block the UI completely and likely get your app to crash. You'll need to provide AsyncTask method implementation for onPostExecute . Your onPostExecute will run on the UI thread, therefore it can call through to a method in your Activity which dismisses your dialog and updates your adapter or whatever else. Consider using a loader backed by an AsyncTask for this as it will be lifecycle aware. If you do not, you'll need to make sure your Activity properly handles the lifecycle cleanup of the AsyncTask (ie call AsyncTask.cancel() .

Answer 2

AsyncTask have 3 main basic overridden method..

1) onPreExecute

2) doInBackGround

3) onPostExecute

onPreExcute get calls when AsyncTask start to run..before doInBackGround.. so here you can show your progress dialog..

doInBackground : here you can process with your service or any other long process. eg call webserivice. it's not work on UI thread.

onPostExecute : it gets called after doInbackGround complete.. so here you can hide progress bar. it's work on UI thread.

eg

private class DownloadFilesTask extends AsyncTask<Void,Void,Void> {

protected void onPreExecute() {
     showDialog();
 } 

 protected Void doInBackground(Void... args) {
     //Download the file
        try {
            Downloader.DownloadFromUrl("https://URL_on_kategorijeXML.xml", openFileOutput("XMLsource.xml", Context.MODE_PRIVATE));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

 }

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

 protected void onPostExecute(Void result) {
     //dismiss dialog..
 }
 }

Answer 3

Personally I would use a interface which is called on the postexecute of your asynctask, then start a progress dialog in your onpreexecute and then close it before you call your interface class on the post execute, implement this from your main task and run your next code when the event is fired.

eg

Main Class

public void taskdone();

Async Task

OnPostExecute

MyInterface.taskdone();


Interface

public taskdone();