Show view when toolbar collapses

Question

I have an activity with a CoordinatorLayout, AppBarLayout, CollapsingToolbarLayout and Toolbar. So, basically, a view tha

Answer 1

Instead of trying to replicate when the scrim is supposed to show (collapsed) or not (expanded), a better way is to override the setScrimsShown method, which is called every time inside the CollapsingToolbarLayout's onOffsetChanged, and add a listener to it like this:

public class CollapsingToolbarLayoutWithScrimListener extends CollapsingToolbarLayout {

    public CollapsingToolbarLayoutWithScrimListener(Context context) {
        super(context);
    }

    public CollapsingToolbarLayoutWithScrimListener(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CollapsingToolbarLayoutWithScrimListener(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context,attrs,defStyleAttr);
    }

    private ScrimListener scrimListener = null;

    @Override
    public void setScrimsShown(boolean shown, boolean animate) {
        super.setScrimsShown(shown, animate);
        if (scrimListener != null)
            scrimListener.onScrimShown(shown);
    }

    public void setScrimListener(ScrimListener listener) {
        scrimListener = listener;
    }

    public interface ScrimListener {

        void onScrimShown(boolean shown);
    }
}