在 RecyclerView 滚动时隐藏 FloatingActionButton [英] Hide FloatingActionButton on scroll of RecyclerView

问题描述

我想在 RecyclerView 的滚动中隐藏/显示 FloatingActionButton.

I want to hide/show FloatingActionButton on scroll of RecyclerView.

我的 XML 布局:

<android.support.design.widget.CoordinatorLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <android.support.v7.widget.RecyclerView
                android:id="@+id/recyclerview_eventlist"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/fab_createevent"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/fab_margin"
                app:layout_anchor="@id/recyclerview_eventlist"
                app:layout_anchorGravity="bottom|right|end"
                app:layout_behavior="com.eventizon.behavior.ScrollAwareFABBehavior"
                android:src="@drawable/ic_edit"
                app:backgroundTint="@color/custom_color_1"
                app:borderWidth="0dp" />
        </android.support.design.widget.CoordinatorLayout>

DrawerLayout 是这个布局的父布局.

DrawerLayout is the parent layout of this layout.

    public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {


    private static final String TAG = "ScrollAwareFABBehavior";

    public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
        super();
        Log.e(TAG,"ScrollAwareFABBehavior");
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout,
            FloatingActionButton child, View target, int dxConsumed,
            int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        // TODO Auto-generated method stub
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed,
                dxUnconsumed, dyUnconsumed);
        Log.e(TAG,"onNestedScroll called");
        if (dyConsumed > 0 && child.getVisibility() == View.VISIBLE) {
            Log.e(TAG,"child.hide()");
            child.hide();
        } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
            Log.e(TAG,"child.show()");
            child.show();
        }
    }
}

将此布局行为用于 FloatingActionButton.

当我看到 logcat 时，只有构造函数被调用.onNestedScroll() 在我滚动列表时不会被调用.

When I see logcat only constructor is getting called. onNestedScroll() doesn't get called when I scroll the list.

推荐答案

好的，这是你需要的:

首先，由于您的 FAB 依赖于 RecyclerView，请将以下内容添加到您的行为类中:

First, since your FAB depends on the RecyclerView, add the following to your behavior class:

@Override
public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) {
    if(dependency instanceof RecyclerView)
        return true;

    return false;
}

接下来，为了接收 onNestedScroll() 调用，您需要覆盖这个:

Next, in order to receive onNestedScroll() calls, you need to override this:

 public boolean onStartNestedScroll(CoordinatorLayout parent, FloatingActionButton child, View directTargetChild, View target, int nestedScrollAxes) {

    //predict whether you will need to react to the RecyclerView's scroll;
    //if yes, return true, otherwise return false to avoid future calls
    //of onNestedScroll()
    return true;
}

祝你好运！

更新

您的 ScrollAwareFABBehavior 应该如下所示:

Here is what your ScrollAwareFABBehavior should look like:

public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {
    private static final String TAG = "ScrollAwareFABBehavior";

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

    public boolean onStartNestedScroll(CoordinatorLayout parent, FloatingActionButton child, View directTargetChild, View target, int nestedScrollAxes) {
        return true;
    }

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) {
        if(dependency instanceof RecyclerView)
            return true;

        return false;
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout,
                               FloatingActionButton child, View target, int dxConsumed,
                               int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        // TODO Auto-generated method stub
        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();
        }
    }
}

此外，它使用 com.android.support:design:23.0.1

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