Reshow a progress dialog from Async Task if it gets dismissed

Question

I have a progress dialog that shows how many files are left for uploading in my Async Task and the user can dismiss this dialog if he wants to. However I want to have a button that will be able to show again that progress dialog at its current stage and I don't know how to do that since you I can't just create a function in the Async Task and call it from a different activity. Any thoughts?

Answer 1

You can make a singleton class to handle the Async Task progress which holds only one listener (the Activity who wants to listen for the progress of your AsyncTask). Your Singleton class can be like below:

public class ProgressDialogUtil {

    public interface ProgressDialogUtilListener{
        void showProgressDialog();
        void dismissProgressDialog();
        void updateProgressDialog(int value);
        void setProgressDialogMessage(String message);
    }

    private ProgressDialogUtilListener listener;
    private static ProgressDialogUtil mInstance;
    public static ProgressDialogUtil getInstance() {
        if (mInstance == null) {
            synchronized (ProgressDialogUtil.class) {
                if (mInstance == null) {
                    mInstance = new ProgressDialogUtil();
                }
            }
        }
        return mInstance;
    }

    public void setListener(ProgressDialogUtilListener listener) {
        this.listener = listener;
    }

    public void showProgressDialog(){
        if(listener!=null)
            listener.showProgressDialog();
    }

    public void dismissProgressDialog(){
        if(listener!=null)
            listener.dismissProgressDialog();
    }

    public void updateProgressDialog(int value){
        setProgressDialogMessage("Files Downloaded: "+ value);
        if(listener!=null)
            listener.updateProgressDialog(value);
    }

    public void setProgressDialogMessage(String message){
        if(listener!=null)
            listener.setProgressDialogMessage(message);
    }
}

Then you can use this Singleton class (ProgressDialogUtil) in your AsyncTask like below to inform for any update occurred:

public class MyAsyncTask extends AsyncTask<Void, Integer, Boolean> {

    public final ProgressDialogUtil progressDialogUtil;

    public MyAsyncTask(ProgressDialogUtil progressDialogUtil){
       this.progressDialogUtil = progressDialogUtil;
    }

    @MainThread
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialogUtil.setProgressDialogMessage("Start Download files..");
        progressDialogUtil.showProgressDialog();
    }

    @WorkerThread
    @Override
    protected Boolean doInBackground(Void... params) {
        //download your files here in the Background Thread...
        //below is a sample loop
        for (int i=0; i <= 50; i++) {
            try {
                Thread.sleep(1000);
                publishProgress(i);
            } catch (InterruptedException e) {
                e.printStackTrace();
                return false;
            }
        }
        return true;
    }

    @MainThread
    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
        progressDialogUtil.updateProgressDialog(values[0]);
    }

    @MainThread
    @Override
    protected void onPostExecute(Boolean result) {
        super.onPostExecute(result);
        progressDialogUtil.setProgressDialogMessage("Finished Download!");
        progressDialogUtil.dismissProgressDialog();
    }
}

Then in your first Activity where you start the AsyncTask you can create a new instance of your Progress Dialog and set a listener ProgressDialogUtilListener to listen for any AsyncTask progress to show/hide/update the Progress Dialog like below:

ProgressDialog pd = new ProgressDialog(this);
ProgressDialogUtil progressDialogUtil = ProgressDialogUtil.getInstance();
progressDialogUtil.setListener(new ProgressDialogUtil.ProgressDialogUtilListener()
{
    @Override
    public void showProgressDialog() {
       if (!pd.isShowing())
          pd.show();
    }
    @Override
    public void dismissProgressDialog() {
        if (pd.isShowing())
            pd.dismiss();
    }
    @Override
    public void updateProgressDialog(int value) {
       pd.setProgress(value);
    }
    @Override
    public void setProgressDialogMessage(String message) {
       pd.setMessage(message);
    }
});
new MyAsyncTask(progressDialogUtil).execute();

Finally when you navigate to a new Activity you can use the same Singleton Instance ProgressDialogUtil and change the listener to the new Activity now all AsyncTask events will be handled to the new Activity and the dialog can be opened/closed via a button through this singleton class like below:

ProgressDialog pd = new ProgressDialog(this);
ProgressDialogUtil progressDialogUtil = ProgressDialogUtil.getInstance();
progressDialogUtil.setListener(new ProgressDialogUtil.ProgressDialogUtilListener()
{
   @Override
   public void showProgressDialog() {
       if (!pd.isShowing())
           pd.show();
   }
   @Override
   public void dismissProgressDialog() {
       if (pd.isShowing())
           pd.dismiss();
   }
   @Override
   public void updateProgressDialog(int value) {
          pd.setProgress(value);
   }
   @Override
   public void setProgressDialogMessage(String message) {
         pd.setMessage(message);
   }
 });

 //Show Progress Dialog from a Button Click
 showButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        progressDialogUtil.showProgressDialog();
    }
});

//Dismiss Progress Dialog from a Button Click
dismissButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
       progressDialogUtil.dismissProgressDialog();
    }
});