使用不同的 ScrollY 将 TextView 动态添加到 FlipperView

Question

I am developing an app and have begun learning Java a few weeks ago. At this point, there's something that I'm trying to get to work, but I can't figure out what's going wrong.

So the problem is as follows. I have a FlipperView in which I want to dynamically add TextViews between which I should be able to navigate. These TextViews have the same content and layout, the only difference between them is their " ScrollY " attribute. I want the first TextView to have a ScrollY of 0 so that the text can be seen from its beginning. Then, I want the next TextView to have a ScrollY of 0 + x, where x is the height of the TextView (which is originally defined as match_parent). The next one should have a ScrollY of 2x, etc.

I've tried many things to get this work. First I managed to dynamically get the height of the TextView using a.post. For now, I can change the ScrollY of the first TextView. For additional views, I'm using a for a loop. At this point, TextViews are properly created and I can navigate between them with the FlipperView. However, the SetScrollY function doesn't work inside the for loop . I've tried to feed it with an arbitrary integer instead of the dynamic height of the TextView without success, so I guess the function is not working at all in this case. Here's my code (the number of loops is fixed for now):

public int formatText(Context context, ViewFlipper textFlipper) {
    int nbOfViews = 1;
    final int[] viewMaxHeight = {0};
    final int[] lineSpacing = {0};

    textContent = context.getResources().getString(R.string.dummyText);

    final TextView flipperView = new TextView(context, null, R.style.flipperText);

    flipperView.setText(textContent);

    textFlipper.addView(flipperView);

    flipperView.post(new Runnable() {
        @Override
        public void run() {
            viewMaxHeight[0] = flipperView.getHeight();
            lineSpacing[0] = Math.round(flipperView.getLineSpacingExtra());
        }
    });

    for(int i = 0; i < 2; i++) {
        TextView flipperViewExtra = new TextView(context, null, R.style.flipperText);
        flipperViewExtra.setText(textContent);
        flipperViewExtra.setScrollY(viewMaxHeight[0] * nbOfViews + lineSpacing[0]);

        textFlipper.addView(flipperViewExtra);

        nbOfViews++;
    }

    return nbOfViews;
}

Any help is appreciated, thanks!

Answer 1

You are working with THREAD and thread tends to optimize the performance by caching the using variables. Hence any chance OUTSIDE the thread it won't "see" the change in memory. To coerce the thread to look at the change in memory you have to declare the variables to volatile. Example

final volatile int[] viewMaxHeight = {0};
final volatile int[] lineSpacing = {0};