Manipulating views of HorizontalScrollView

As I wrote in the previous question (Simple image gallery with HorizontalScrollView) I work at a simple image gallery with use HorizontalScrollView. Now I'm solving the following task: to load and show images dynamically, the goal is while an image is load the progress bar have to be shown on the display. So I use android.os.AsyncTask for loading an image. But at first I made custom horizontal scroll view for adding and scrolling images, the goal method is processScroll that is called from public method of android.widget.HorizontalScrollView - android.lessons.custom_horizontal_scroll.ImageHorizontalScrollView#onFling, it looks like:

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    Log.d("IHSV", "GestureDetectorListener onFling event. " +
        "Info scrollX " + getScrollX() +
        " Info velocityX " + velocityX +
        " Info ev1X " + e1.getAxisValue(MotionEvent.AXIS_X) +
        " Info ev2X " + e2.getAxisValue(MotionEvent.AXIS_X));

    ev1X = (int) e1.getAxisValue(MotionEvent.AXIS_X);
    ev2X = (int) e2.getAxisValue(MotionEvent.AXIS_X);

    processScroll();

    return true;
}

and the processScroll method is

private void processScroll() {
    boolean isForward = ev1X > ev2X;
    boolean isPaging = isForward ? getImageSizeList().get(imageIndex)[0] / 2 >= ev2X :
        getImageSizeList().get(imageIndex)[0] / 2 <= ev2X;

    Log.d("IHSV", "processScroll imageIndex: " + imageIndex + " isForward: " + isForward + " isPaging: " + isPaging);

    if (isPaging) {
        boolean isSmoothScroll;
        // to page forward
        if (isForward) {
            isSmoothScroll = imageIndex + 1 != imageItems.length;
            imageIndex = ++imageIndex % imageItems.length;
        } else {
        // to page back
            isSmoothScroll = imageIndex - 1 >= 0;
            imageIndex = imageIndex - 1 < 0 ? imageItems.length - 1 : --imageIndex;
        }

        boolean isLoad = imageItems[imageIndex].isLoad;
        if (!imageItems[imageIndex].isLoad) {
            // show a progress bar 
            **innerLayout.addView(getPbl());**
        }

        if (isSmoothScroll) {
            if (isLoad) {
                smoothScrollTo(imageIndex * displayMetrics[0], 0);
            } else {
                innerLayout.scrollTo(imageIndex * displayMetrics[0], 0);
            }
        } else {
            scrollTo(imageIndex * displayMetrics[0], 0);
        }
        // load an image in the background task
        if (!imageItems[imageIndex].isLoad) {
            ImageLoaderTask imgLoader = new ImageLoaderTask(this, innerLayout);
            **imgLoader.execute(imageItems[imageIndex].id);**
        }
    } else {
        smoothScrollTo(imageIndex * displayMetrics[0], 0);
    }
}

Where as you can see before I make a loading image I add a progress bar to my inner layout (the single child of the horizontal scroll view). The main layout is

    <?xml version="1.0" encoding="utf-8"?>
    <android.lessons.custom_horizontal_scroll.ImageHorizontalScrollView
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/horizontalScrollView"
            android:orientation="horizontal"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >
<!-- **the inner layout** -->
        <LinearLayout android:orientation="horizontal"
                      android:id="@+id/mainLayout"
                      android:layout_width="wrap_content"
                      android:layout_height="match_parent">
        </LinearLayout>
</android.lessons.custom_horizontal_scroll.ImageHorizontalScrollView>

The progress bar layout is

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
             android:id="@+id/progress_bar_layout"
             android:orientation="horizontal"
             android:layout_gravity="center"
             android:gravity="center"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content">
    <ProgressBar android:id="@+id/progress_bar"
                 android:layout_height="wrap_content"
                 android:layout_width="wrap_content"/>
</LinearLayout>

The task of loading image looks like that

public class ImageLoaderTask extends AsyncTask<Integer, String, String> {


    @Override
    protected String doInBackground(Integer... params) {
       // load an image
    }

    @Override
    protected void onPostExecute(String result) {
        // remove the progess bar
        innerLayout.removeView(innerLayout.findViewById(R.id.progress_bar_layout));
        // add the load image
        innerLayout.addView(addImageView);
        ...
    }

}

I inflate the progress bar in the following method:

View getPbl() {
    if (pbl == null) {
        LayoutInflater inflater = (LayoutInflater) getContext().getSystemService
            (Context.LAYOUT_INFLATER_SERVICE);

        pbl = inflater.inflate(R.layout.progress_bar, this, false);
        LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(displayMetrics[0],
            displayMetrics[1]);

        lp.gravity = Gravity.FILL_HORIZONTAL | Gravity.CENTER_VERTICAL;
        pbl.setLayoutParams(lp);
    }
    return pbl;
}

So let's go to the questions: 1) I call innerLayout.scrollTo(...) in the processScroll method because android.widget.HorizontalScrollView#smoothScrollTo doesn't work: it doesn't scroll to the progress bar view, why does it behave that way? It scrolls itself after the image is load (after the ImageLoaderTask#onPostExecute method is accomplished).

2) So with innerLayout.scrollTo(...) I'm getting a strange behavior: the first scroll works right, the next one doesn't add an image it leave black space :) in the place where the load image should be. So I think View#addView and View#removeView don't work correctly, but Why? Should I call any refresh methods of the horizontal scroll view?