Question

I have an AsyncTask linked to a refresh Button (when I click on my refresh button my AsyncTask is called).

I have on my Layout a LinearLayout field for my ProgressBar :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="@color/grey">
     <Button    android:id="@+id/refresh_p"
                android:text="@string/refresh_promo"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:background="@drawable/custom_button1"/>

   <LinearLayout android:id="@+id/linearlayoutProgressBar"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:gravity="center"/>
   <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:listSelector="@color/tabTransparent"
        android:cacheColorHint="#00000000"/>
      <!--   <ListView android:id="@+id/list_promo"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"/>-->
</LinearLayout>

In my AsyncTask :

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

        pb = new ProgressBar(context);
        LinearLayout ll = (LinearLayout) ((Activity) context).findViewById(R.id.linearlayoutProgressBar);
        ll.addView(pb);
        pb.setVisibility(View.VISIBLE);
    }

    @Override
    protected void onPostExecute(ArrayList<HashMap<String, String>> promoList) 
    {
        ...

        if (pb!=null) 
        {
            pb.setVisibility(View.GONE);
            ((LinearLayout)pb.getParent()).removeView(pb);
        }
    }

The problem I have is when I make more than 2 clicks on my Refresh Button then Multiple ProgressBar are displaying into the screen.. I just want that the new ProgressBar replace the old at the same position ..

Answer 1

My guess is that you are probably starting your AsyncTask in a manner similar to this:

new RefreshTask().execute(params);

Instead of that, create an instance variable in your activity. Let’s say this is named mTask and substitute the above code for the following call:

if(mTask != null && mTask.getState != AsyncTask.State.RUNNING){
    mTask = new RefreshTask();
    mTask.execute(params);
}

This way you will ensure that only one instance of your task is running at a given time and the user will have to wait until the refresh is finished before he can start a new refresh.

If you want the user to be able to cancel an existing refresh task and run a new one, you will have to cancel the old one before starting a new one:

if(mTask != null){
    if(mTask.getStatus() == AsyncTask.Status.RUNNING){
         mTask.cancel(true);
    }
    mTask = new RefreshTask();
    mTask.execute(params);
}

This way the old task and it’s ProgressBar will be properly replaced by the new one.