Android - Adding an item to a scroll view and scroll programmatically

Question

I have an empty scrollview. I create with inflater a text view, add it to the ScrollView programmatically and then do:

rsView.smoothScrollBy((viewLeft + viewWidth / 2) - center, 0);

BUT viewLeft and viewWidth are 0 as the view is not measured yet. Any suggestions on how to make it scroll the view properly?

until now it as fixed text views and I used: int viewLeft = childView.getLeft(); int viewWidth = childView.getWidth(); but now I add views dynamically — Panos, Jan 27 '16 at 02:14

Mike M. · Answer 1 · 2016-01-27T02:25:49.060

Move the smoothScrollBy() call to a Runnable and post that to the new TextView's handler after it's been added, which will cause it to run after it's been laid out. For example:

viewGroup.addView(childView);
childView.post(new Runnable() {
        @Override
        public void run() {
            rsView.smoothScrollBy((childView.getLeft() + childView.getWidth() / 2) - center, 0);
        }
    }
);

I'm not sure how you're calculating center, but if it depends on the new TextView's dimensions, you'll need to move the calculation to the Runnable, as well.

score 1 · Accepted Answer · edited May 23 '17 at 12:30

In this post: getWidth() and getHeight() of View returns 0 you have a lot of good options to solve this problem. Particularly I use this one:

Listen to Draw/Layout Events: ViewTreeObserver

A ViewTreeObserver gets fired for different drawing events. Usually the OnGlobalLayoutListener is what you want for getting the measurement, so the code in the listener will be called after the layout phase, so the measurments are ready:

view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            rsView.smoothScrollBy((viewLeft + viewWidth / 2) - center, 0);
        }
    });

Not exactly, I used the super view to get the tree observer as it was easier but it seems to work. Thank you! — Panos, Jan 27 '16 at 09:28

Android - Adding an item to a scroll view and scroll programmatically

2 Answers2