锚定到应用栏的FAB在向上滚动时不会隐藏

Question

我已将FAB锚定到AppBarLayout。但是，在向上滚动时，FAB的预期行为是在工具栏折叠时隐藏。这不会发生。

这是否必须特别处理？

我定义的布局如下：

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

<android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="256dp"
    android:fitsSystemWindows="true"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.design.widget.CollapsingToolbarLayout
        android:id="@+id/collapsing_toolbar"
        android:layout_width="match_parent"
        android:layout_height="206dip"
        android:background="@color/my_primary"
        android:fitsSystemWindows="true"
        app:contentScrim="?attr/colorPrimary"
        app:expandedTitleMarginBottom="20dp"
        app:expandedTitleMarginEnd="64dp"
        app:expandedTitleMarginStart="16dp"
        app:layout_scrollFlags="scroll|exitUntilCollapsed">

        <!--<ImageView-->
        <!--android:id="@+id/backdrop"-->
        <!--android:layout_width="match_parent"-->
        <!--android:layout_height="match_parent"-->
        <!--android:fitsSystemWindows="true"-->
        <!--android:scaleType="centerCrop"-->
        <!--app:layout_collapseMode="parallax" />-->

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_collapseMode="pin"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

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

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="bottom"
        app:tabMode="scrollable" />

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

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:clickable="true"
    android:src="@drawable/ic_stop_white_24dp"
    app:layout_anchor="@id/appbar"
    app:layout_anchorGravity="bottom|right|end" />

Answer 1

也许将滚动监听器设置为scrollview并按需隐藏fab。

Answer 2

@MufaddalGulshan，View Pager可能是个问题。使用recycleler视图或NestedScrollView。我从here读到，只有支持“嵌套滚动”的视图才能使用此行为。

Answer 3

我不知道它是否还没有解决。但我会留在这里希望它可以帮助某人。我也遇到了这个问题并通过实现AppBarStateChangeListener然后以编程方式隐藏/显示浮动操作按钮来解决。

这是完整的实现：

public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {

public enum State {
    EXPANDED,
    COLLAPSED,
    IDLE
}

private State mCurrentState = State.IDLE;

@Override
public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
    if (i == 0) {
        if (mCurrentState != State.EXPANDED) {
            onStateChanged(appBarLayout, State.EXPANDED);
        }
        mCurrentState = State.EXPANDED;
    } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
        if (mCurrentState != State.COLLAPSED) {
            onStateChanged(appBarLayout, State.COLLAPSED);
        }
        mCurrentState = State.COLLAPSED;
    } else {
        if (mCurrentState != State.IDLE) {
            onStateChanged(appBarLayout, State.IDLE);
        }
        mCurrentState = State.IDLE;
    }
}

public abstract void onStateChanged(AppBarLayout appBarLayout, State state);
}

然后申请：

appBarLayout.addOnOffsetChangedListener(new AppBarStateChangeListener() {
@Override
public void onStateChanged(AppBarLayout appBarLayout, State state) {
    if(state == State.COLLAPSED){
                fab.hide();
            }else if(state == State.EXPANDED){
                fab.show();
            }   
});

Answer 4

<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"
        tools:context=".ScrollingActivity">

    <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar"
            android:fitsSystemWindows="true"
            android:layout_height="@dimen/app_bar_height"
            android:layout_width="match_parent"
            android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/toolbar_layout"
                android:fitsSystemWindows="true"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:toolbarId="@+id/toolbar"
                app:layout_scrollFlags="scroll|exitUntilCollapsed"
                app:contentScrim="?attr/colorPrimary">

            <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    android:layout_height="?attr/actionBarSize"
                    android:layout_width="match_parent"
                    app:layout_collapseMode="pin"
                    app:popupTheme="@style/AppTheme.PopupOverlay"/>

        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_scrolling"/>

    <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="@dimen/fab_margin"
            app:layout_anchor="@id/app_bar"
            app:layout_anchorGravity="bottom|end"
            app:srcCompat="@android:drawable/ic_dialog_email"/>

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