Custom auto hide floatingActionButton behavior is not working

Question

I'm trying to hide a FloatingActionButton when a NestedScrollView scroll down, and revealed itself when NestedScrollView scroll up.

Here is my layout:

<android.support.design.widget.CoordinatorLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fitsSystemWindows="true"
            app:layout_scrollFlags="scroll|enterAlways">
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.widget.NestedScrollView 
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/grid_2"
        android:layout_gravity="bottom|end"
        android:src="@drawable/ic_place_white"
        android:clickable="true"
        app:backgroundTint="@color/colorPrimary"
        app:layout_behavior="com.myapp.ScrollAnimationFAB"/>
</android.support.design.widget.CoordinatorLayout>

And here is my floatingActionButton behavior:

public class ScrollAnimationFAB extends FloatingActionButton.Behavior {

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

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

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

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

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

These code is not working for me, I wonder if it has something to do with NestedScrollView's behavior. Any help will be appreciated!

UPDATE

I found something wired! If I call fab's method (child.hide(), child.show()) in onNestedScroll, onStartNestedScroll and onNestedScroll never get called again, but if I didn't call methods in fab, onStartNestedScroll and onNestedScroll get called normally.

Answer 1

Take a look at what @woxingxiao is saying here

Pretty much onNestedScroll won't get fired if the visibility of the button is GONE. So, replace:

child.hide();

to:

child.hide(new FloatingActionButton.OnVisibilityChangedListener() {
    @Override
    public void onHidden(FloatingActionButton fab) {
        super.onHidden(fab);
        fab.setVisibility(View.INVISIBLE);
    }
});