如何在向上滚动开始时使fab可见并在向下滚动开始时隐藏

Question

我想在向下滚动开始时立即隐藏 fab，并在向上滚动开始时立即显示我该怎么做，现在我正在尝试这个，但它仅在到达顶部时出现并在到达底部时隐藏：

 @Override
public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child, final View directTargetChild, final View target, final int nestedScrollAxes) {
    // Ensure we react to vertical scrolling
    return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
            || super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
}

@Override
public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child, final View target, final int dxConsumed, final int dyConsumed, final int dxUnconsumed, final int dyUnconsumed) {
    super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);

    if (CoordinatorLayout.SCROLL_INDICATOR_START == 16 && dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
        child.hide();
    } else if (CoordinatorLayout.SCROLL_INDICATOR_START == 16 && dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
        child.show();
    }
} 

Answer 1

如果您的布局中有一个 recyclerView，则此代码将为您提供帮助：

recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrolled(recyclerView: RecyclerView?, dx: Int, dy: Int) {
            if (dy > 0) {
                fab?.hide()
            } else if (dy < 0) {
                fab?.show()
            }
        }
    })

Answer 2

请这样做，希望对您有所帮助。

 @Override
 public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final View child,final View directTargetChild, final View target,final int nestedScrollAxes) {

// Ensure we react to vertical scrolling

 return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
        || super.onStartNestedScroll(coordinatorLayout, child,
           directTargetChild, target, nestedScrollAxes);
 }

 @Override
 public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final View child,final View target, final int dxConsumed, final int dyConsumed, final int dxUnconsumed, final int dyUnconsumed) {

 super.onNestedScroll(coordinatorLayout, child, target,dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
 if (dyConsumed > 0) {

  // User scrolled down -> hide the FAB

  List<View> dependencies = coordinatorLayout.getDependencies(child);
   for (View view : dependencies) {
     if (view instanceof FloatingActionButton) {
      ((FloatingActionButton) view).hide();
    }
  }
} else if (dyConsumed < 0) {
  // User scrolled up -> show the FAB
  List<View> dependencies = coordinatorLayout.getDependencies(child);
  for (View view : dependencies) {
    if (view instanceof FloatingActionButton) {
      ((FloatingActionButton) view).show();
    }
  }
}