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android – onNestedScroll called only once

Posted by: admin June 15, 2020 Leave a comment

Questions:

I have a class

public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {
    public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
        super();
    }

    public ScrollAwareFABBehavior() {
        super();
    }

    @Override
    public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,final View directTargetChild, final View target, final int nestedScrollAxes) {
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
    }

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

the problem is that onNestedScroll is called only once when I scroll up a recyclerview, so the fab is hiding and never shows again. Here is layout I am using

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/refresh_layout"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <android.support.v7.widget.RecyclerView
            android:id="@+id/list"
            app:layoutManager="@string/vertical_linear_layout_manager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    </android.support.v4.widget.SwipeRefreshLayout>
    <android.support.design.widget.FloatingActionButton
        android:id="@+id/add"
        android:layout_width="wrap_content"
        app:layout_behavior="mypackagename.util.ScrollAwareFABBehavior"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        app:useCompatPadding="true"
        android:layout_margin="16sp"
        android:src="@drawable/ic_add"/>
</android.support.design.widget.CoordinatorLayout>

My support libraries version is 25.1.0

How to&Answers:

I solved the problem changing the visibility from GONE to INVISIBLE with the following code.

 @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(new FloatingActionButton.OnVisibilityChangedListener() {
            @Override
            public void onShown(FloatingActionButton fab) {
                super.onShown(fab);
            }

            @Override
            public void onHidden(FloatingActionButton fab) {
                super.onHidden(fab);
                fab.setVisibility(View.INVISIBLE);
            }
        });
    } else if (dyConsumed <= 0 && child.getVisibility() != View.VISIBLE) {
        child.show();
    }
}

Answer:

I have just answered
to absolutely the same problem in another post, check it.

Speaking shortly, use the following:

compile 'com.android.support:design:25.0.1'

Answer:

@Override
public void onNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull FloatingActionButton child, @NonNull View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int type) {
    super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type);
    if (dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
        child.hide(new FloatingActionButton.OnVisibilityChangedListener() {
            @Override
            public void onHidden(FloatingActionButton fab) {
                super.onHidden(fab);
                fab.setVisibility(View.INVISIBLE);
            }
        });
    } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
        child.show();
    }
}

Answer:

Do not set the visibility of FAB to GONE in child.hide() – use INVISIBLE instead. From 25.1.0, the scroll events are not passed on to views whose visibility is GONE

Answer:

For me i replace child.hide() with ((View)child).setVisibility(View.INVISIBLE).