Prevent RecyclerView from scrolling under AppBarLayout before AppBarLayout is collapsed

Possible solution (untested). Add an OnOffsetChangedListener to your AppBarLayout, and keep note of the offset value. First, declare this field:

private boolean shouldScroll = false;

Then, onCreate:

AppBarLayout appbar = findViewById(...);
appbar.addOnOffsetChangedListener(new OnOffsetChangedListener() {
    @Override
    void onOffsetChanged(AppBarLayout appbar, int offset) {
        // Allow recycler scrolling only if we started collapsing.
        this.shouldScroll = offset != 0;
    }
});

Now, add a scroll listener to your RecyclerView. Whenever it tries to scroll, revert the scroll if the AppBarLayout is still expanded:

RecyclerView recycler = findViewById(...);
recycler.addOnScrollListener(new OnScrollListener() {
    @Override
    void onScrolled(RecyclerView recycler, int dx, int dy) {
        // If AppBar is fully expanded, revert the scroll.
        if (!shouldScroll) {
            recycler.scrollTo(0,0);
        }
    }
});

This might need some tweaking though. I see two issues:

• Possible stack overflow if scrollTo() calls onScrolled() back. Can be solved with a boolean or by removing/adding the scroll listener
• Possibly you want to prevent scrolling not only when AppBarLayout is fully expanded, but more generally when AppBarLayout is not collapsed. This means you don’t have to check for offset != 0, but rather for offset == appBarLayout.getTotalScrollRange(). I think.