半展开的折叠工具栏

Question

How can I create a half-expanded toolbar? Something like that WhatsApp profile page.

I've tried scrollBy and scrollTo , but they don't seem to work.

Even dispatchNestedScroll , onNesterScroll and onNestedPreScroll don't seem to work.

Answer 1

I managed to solve this problem by adapting this answer: https://stackoverflow.com/a/34920495/5369519 and using the following code:

nestedScrollView.post(() -> {
        int appBarHeight = appBar.getHeight()/2;
        nestedScrollView.startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
        nestedScrollView.dispatchNestedPreScroll(0, appBarHeight, null, null);
        nestedScrollView.dispatchNestedScroll(0, 0, 0, 0, new int[]{0, -appBarHeight});
    });

This simulates scrolling halfway down. Just using NestedScrollView.scrollTo() is not enough to trigger the scroll events for the parent.

Answer 2

为了创建折叠工具栏， CollapsingToolbarLayout集成了 AppBarLayout、CoordinatorLayout、Toolbar 和可滚动的内容视图，例如 RecyclerView