Hide/Show ProgressBar using AsyncTask

Question

I'm trying to do the simple act of hiding/showing ProgressBar according to AsyncTask state , I have two classes one extends FragmentActivity and second AsyncTask.

MainActivity.java

public class MainActivity extends FragmentActivity {

public static ProgressBar mProgressBar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mProgressBar = (ProgressBar) findViewById(R.id.progress_bar);
}

@Override
protected void onStart() {
    super.onStart();
    // What will happen to the progress bar here?  
}

@Override
protected void onStop() {
    super.onStop();
  // What will happen to the progress bar here? 
}

       @Override
        protected void onResume() {
        super.onResume();

      // What will happen to the progress bar here? 
    }
    }

MyAsyncTask.java

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

@Override
protected Void doInBackground() {
    // start download some images from cloud 
    // Here the progress bar should start to appear in MainActivity
    // mProgressBar.setVisibility(View.VISIBLE);

}

@Override
protected void onPostExecute(Void result) {
    Log.d(TAG, "Finished book downloading images the cloud");
   // Here the progress bar should start to disappear in MainActivity
   // mProgressBar.setVisibility(View.GONE);


}

}

main_activity.xml

      <ProgressBar
    android:id="@+id/progress_bar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:indeterminate="true" />

Hope you understand me, thank to everyone who can help.

http://stackoverflow.com/questions/3028306/download-a-file-with-android-and-showing-the-progress-in-a-progressdialog?rq=1 this can solve your issue. — Ankit Kumar, Aug 18 '16 at 09:58

score 2 · Answer 1 · answered Aug 18 '16 at 09:57

2

The progress bar should appear in onPreExecute() method (still in UI thread). Then you dismiss it when you get back to UI thread in onPostExecute method.

answered Aug 18 '16 at 09:57

Farouk Touzi

3,451
2
19
25

cowboi-peng · Answer 2 · 2016-08-18T10:11:07.063

public class MyAsyncTask extends AsyncTask<Void,Void, Void> {
@Override
protected void onPreExecute(Void result) {
    Log.d(TAG, "Finished book downloading images the cloud");
   // Here the progress bar should start to disappear in MainActivity
    mProgressBar.setVisibility(View.VISIBLE);


}
@Override
protected Void doInBackground() {
// start download some images from cloud 
// there is a time cost operation


}

@Override
protected void onPostExecute(Void result) {
    Log.d(TAG, "Finished book downloading images the cloud");
   // Here the progress bar should start to disappear in MainActivity
   // mProgressBar.setVisibility(View.GONE);


}

}

You should use onPreExecute() method to show the dialog.

Here is MainActivity

@Override
protected void onResume() {
    super.onResume();
    new MyAsyncTask().execute();
}

I think you should read APIs first.

score 0 · Answer 3 · answered Aug 18 '16 at 10:02

0

Use preExecute and postExecute methods as they run on UI thread.

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

ProgressBar pBar;
@Override
protected void onPreExecute(Void result) {
pBar=new ProgressBar(getContext());
pBar.show();
}

@Override
protected void onPostExecute(Void result) {
   if(pBar !=null and pBar.isShowing()){
  pBar.dismiss();
}
}

}

answered Aug 18 '16 at 10:02

Nayan Srivastava

3,655
3
27
49

It's two different classes, I dont understand how it works? – Daniel Levi Aug 18 '16 at 10:04
create constructor in your `MyAsyncTask` and pass `context` as argument in your constructor and then use that context to build `progressBar` then it will work. – Nayan Srivastava Aug 18 '16 at 10:06

score 0 · Answer 4 · answered Aug 18 '16 at 10:14

Use interface in Asyntask class for communicate with Activity class

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

//use context for activity reference
private Context context_;

public MyAsyncTask(Context context) {
    this.context_=context;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected Void doInBackground(Void... voids) {
    return null;
}

@Override
protected void onPostExecute(Void aVoid) {
    super.onPostExecute(aVoid);
    if(mCallBack!=null ){
        mCallBack.onSuccess("Success");
    }else {
        mCallBack.onError("Error");

    }
}

MyAsyncCallBack mCallBack=null;

public MyAsyncCallBack getmCallBack() {
    return mCallBack;
}

public void setmCallBack(MyAsyncCallBack mCallBack) {
    this.mCallBack = mCallBack;
}

public interface MyAsyncCallBack{
    public void onSuccess(String successMessage);
    public void onError(String successMessage);
}

}

Call AsynckTask Class from activity class.Before calling asyntask start progress. and after completing work in asyntask return activity via interface and hide progress.

startProgress();
    MyAsyncTask mTask=new MyAsyncTask(YourActivity.this);
    mTask.setmCallBack(new MyAsyncTask.MyAsyncCallBack() {
        @Override
        public void onSuccess(String successMessage) {
            //do success work and hide progress
            hideProgress();
        }

        @Override
        public void onError(String successMessage) {
            //do error work and hide progress
            hideProgress();
        }
    });
    mTask.execute();

Hide/Show ProgressBar using AsyncTask

4 Answers4