Expanding And Collapsing Toolbar In Android

Question

I am implementing expanding and collapsing toolbar with the help of collapsing toolbar but I am stuck when my toolbar is collapsed I want to show different toolbar. I have s

Answer 1

Here's another approach that doesn't use a custom CoordinatorLayoutBehavior.

It uses an OnOffsetChangedListener which comes from AppBarLayout.

Here's a snippet:

class OnOffsetChangedListener implements AppBarLayout.OnOffsetChangedListener {

        @Override
        public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {

            final int scrollRange = appBarLayout.getTotalScrollRange();
            float offsetFactor = (float) (-verticalOffset) / (float) scrollRange;
            ...

This shows you how to find the total scroll range and then find the ratio between the total scroll range and the current scroll position. This is what you need to figure out how to scale and position your toolbar views.

For a custom layout (like I did), you can override onAttachedToWindow and add the listener there:

        // Add an OnOffsetChangedListener if possible
        final ViewParent parent = getParent();
        if (parent instanceof AppBarLayout) {
            if (mOnOffsetChangedListener == null) {
                mOnOffsetChangedListener = new OnOffsetChangedListener();
            }
            ((AppBarLayout) parent).addOnOffsetChangedListener(mOnOffsetChangedListener);
        }

I found this approach to be a little simpler than creating a custom behavior.

I created an example project on GitHub. The app looks like this:

You can see the whole project at https://github.com/klarson2/Collapsing-Image