使用AppBarLayout在CoordinatorLayout中滚动显示/隐藏BottomNavigationView [英] Show/hide BottomNavigationView on scroll in CoordinatorLayout with AppBarLayout

问题描述

我正在尝试在单个CoordinatorLayout中同时使用AppBarLayout和BottomNavigationLayout，并且在

I am trying to use both AppBarLayout and BottomNavigationLayout in a single CoordinatorLayout and I'm having difficulties hiding the BottomNavigationLayout as required by the material guideline.

我的意思是这样的:

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

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_insetEdge="top"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:popupTheme="@style/AppTheme.PopupOverlay"
            app:layout_scrollFlags="scroll|enterAlways"/>
    </android.support.design.widget.AppBarLayout>


    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottom_nav"
        android:layout_width="match_parent"
        android:layout_height="56dp"
        android:layout_gravity="bottom"
        app:menu="@menu/menu_bottom_navigation"/>

    <FrameLayout
        android:id="@+id/content_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

</android.support.design.widget.CoordinatorLayout>

如您所见，我还有一个FrameLayout，用于包含具有实际内容的片段.当前，BottomNavigationView没有默认/内置的行为-视图本身或其同级都没有.现有的appbar_scrolling_view_behavior与appbar一起处理内容视图，但忽略其他同级项.

As you can see, I also have a FrameLayout that's used to contain a fragment with the actual content. Currently there are no default/built-in behaviors for the BottomNavigationView - neither for the view itself, nor for its siblings. The existing appbar_scrolling_view_behavior handles the content view in coordination with the appbar but ignores other siblings.

我正在寻找一种解决方案，以隐藏和显示滚动条上的应用程序栏和底部导航视图.

I am looking for a solution to hide and show both the appbar and the bottom navigation view on scroll.

推荐答案

经过一两天的搜索，我使用了自定义的

After a day or two of searching I settled with a custom Behavior attached to the BottomNavigationView. Its main idea is to detect when the BottomNavigationView's sibling is scrolled so that it can hide the BottomNavigationView. Something like this:

public class BottomNavigationBehavior extends CoordinatorLayout.Behavior<BottomNavigationView> {

    public BottomNavigationBehavior() {
        super();
    }

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

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, BottomNavigationView child, View dependency) {
        boolean dependsOn = dependency instanceof FrameLayout;
        return dependsOn;
    }

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

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, BottomNavigationView child, View target, int dx, int dy, int[] consumed) {
        if(dy < 0) {
            showBottomNavigationView(child);
        }
        else if(dy > 0) {
            hideBottomNavigationView(child);
        }
    }

    private void hideBottomNavigationView(BottomNavigationView view) {
        view.animate().translationY(view.getHeight());
    }

    private void showBottomNavigationView(BottomNavigationView view) {
        view.animate().translationY(0);
    }
}

如您所见，我正在使用简单的 ViewPropertyAnimator ，使用子视图的 animate 方法获得.这导致了一个简单的动画，它实际上与AppBarLayout的行为不匹配，但是足够好看，而且实现起来也很简单.

As you can see, I'm using simple ViewPropertyAnimator, obtained using the child views's animate method. This leads to a simple animation that doesn't really match the AppBarLayout's behavior but it's decent enough to look good and at the same time it's simple enough to implement.

我希望Android团队有时会在支持库中为BottomNavigationView添加默认行为，因此我认为花费大量时间来完全复制AppBarLayout的行为是不合理的.

I expect that at some point the Android team will add a default Behavior for the BottomNavigationView in the support library so I don't think it's reasonable to invest a lot more time to exactly duplicate the AppBarLayout's behavior.

编辑(2018年4月):有关onStartNestedScroll和onNestedPreScroll及其新版本的次要说明，请参见评论部分.

edit (April 2018): see the comments section for a minor clarification about onStartNestedScroll and onNestedPreScroll and their new versions.

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