工具栏在AppBarLayout是滚动的，虽然RecyclerView有没有足够的内容来滚动 [英] Toolbar in AppBarLayout is scrollable although RecyclerView has not enough content to scroll

问题描述

难道真的意在工具栏的AppBarLayout是滚动的，虽然与appbar_scrolling_view_behavior有没有足够的内容主要容器，真正滚动？

我已经测试至今：
当我使用一个NestedScrollView（用WRAP_CONTENT属性）作为主容器和一个TextView作为孩子，AppBarLayout正常工作，不会滚动。

然而，当我使用的只有少数项目和WRAP_CONTENT属性（这样就不需要滚动）一个RecyclerView，工具栏上的AppBarLayout是滚动的，即使RecyclerView永远不会收到scroll事件（测试有OnScrollChangeListener）。

下面是我的布局code：

 ＆LT; android.support.design.widget.CoordinatorLayout的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android
    的xmlns：程序=htt​​p://schemas.android.com/apk/res-auto
    机器人：ID =@ + ID / coordinatorLayout
    机器人：layout_width =match_parent
    机器人：layout_height =match_parent＆GT;

    ＆LT; android.support.design.widget.AppBarLayout
        机器人：ID =@ + ID / appBarLayout
        机器人：layout_width =match_parent
        机器人：layout_height =WRAP_CONTENT＆GT;

        ＆LT; android.support.v7.widget.Toolbar
            机器人：ID =@ + ID /工具栏
            机器人：layout_width =match_parent
            机器人：layout_height =？ATTR / actionBarSize
            机器人：ATTR / colorPrimary后台=
            应用程序：layout_scrollFlags =滚动| enterAlways
            应用程序：主题=@风格/ ToolbarStyle/＆GT;
    ＆LT; /android.support.design.widget.AppBarLayout>

    ＆LT; android.support.v7.widget.RecyclerView
        机器人：ID =@ + ID /回收
        机器人：layout_width =WRAP_CONTENT
        机器人：layout_height =WRAP_CONTENT
        应用程序：layout_behavior =@字符串/ appbar_scrolling_view_behavior/＆GT;
＆LT; /android.support.design.widget.CoordinatorLayout>
 

通过下面的效果，该工具栏滚动虽然它不是必需的：

我还发现了一种通过检查所有RecyclerView项目都可见，并使用RecyclerView的setNestedScrollingEnabled（）方法来处理这​​个问题。
然而，它似乎更像是一个错误的意图我。任何意见？ ：D

编辑：谁的人有可能有兴趣在我目前的解决办法，我只好把setNestedScrollingEnabled（）的逻辑与5ms的处理程序的postDelayed（）方法延误是由于布局管理，它总是返回-1时调用方法来判断是否是第一个和最后一个项目是可见的。
我在ONSTART（）方法，用这个code（后我RecyclerView已初始化）和RecyclerView的内容改变后，每次发生。

 最后LinearLayoutManager的layoutManager =（LinearLayoutManager）mRecyclerView.getLayoutManager（）;
新的处理程序（）。postDelayed（新的Runnable（）{
    @覆盖
    公共无效的run（）{
        //在RecyclerView没有项目
        如果（mRecyclerView.getAdapter（）。getItemCount（）== 0）
            mRecyclerView.setNestedScrollingEnabled（假）;
        //如果第一和最后一个项目是可见
        否则，如果（layoutManager.findFirstCompletelyVisibleItemPosition（）== 0
                ＆功放;＆安培; layoutManager.findLastCompletelyVisibleItemPosition（）== mRecyclerView.getAdapter（）getItemCount（） - 。1）
            mRecyclerView.setNestedScrollingEnabled（假）;
        其他
            mRecyclerView.setNestedScrollingEnabled（真正的）;
    }
}，5）;
 

解决方案

在你的工具栏删除滚动标志，只剩下 enterAlways 标志，你应该得到你预期的效果。为了完整起见，你的布局应该是这样的：

 ＆LT; android.support.design.widget.CoordinatorLayout
    的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android
    的xmlns：程序=htt​​p://schemas.android.com/apk/res-auto
    机器人：ID =@ + ID / coordinatorLayout
    机器人：layout_width =match_parent
    机器人：layout_height =match_parent＆GT;

    ＆LT; android.support.design.widget.AppBarLayout
        机器人：ID =@ + ID / appBarLayout
        机器人：layout_width =match_parent
        机器人：layout_height =WRAP_CONTENT＆GT;

        ＆LT; android.support.v7.widget.Toolbar
            机器人：ID =@ + ID /工具栏
            机器人：layout_width =match_parent
            机器人：layout_height =？ATTR / actionBarSize
            机器人：ATTR / colorPrimary后台=
            应用程序：layout_scrollFlags =enterAlways
            应用程序：主题=@风格/ ToolbarStyle/＆GT;
    ＆LT; /android.support.design.widget.AppBarLayout>

    ＆LT; android.support.v7.widget.RecyclerView
        机器人：ID =@ + ID /回收
        机器人：layout_width =WRAP_CONTENT
        机器人：layout_height =WRAP_CONTENT
        应用程序：layout_behavior =@字符串/ appbar_scrolling_view_behavior/＆GT;
＆LT; /android.support.design.widget.CoordinatorLayout>
 

Is it really intended that the Toolbar in a AppBarLayout is scrollable although the main container with the "appbar_scrolling_view_behavior" has not enough content to really scroll?

What I have tested so far:
When I use a NestedScrollView (with "wrap_content" attribute) as main container and a TextView as child, the AppBarLayout works properly and does not scroll.

However, when I use a RecyclerView with only a few entries and the "wrap_content" attribute (so that there is no need to scroll), the Toolbar in the AppBarLayout is scrollable even though the RecyclerView never receives a scroll event (tested with a OnScrollChangeListener).

Here's my layout code:

<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/coordinatorLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

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

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>

With the following effect that the toolbar is scrollable although it's not necessary:

I've also found a way to deal with this by checking if all RecyclerView items are visible and using the setNestedScrollingEnabled() method of the RecyclerView.
Nevertheless, it does seem more like a bug as intended to me. Any opinions? :D

EDIT: For people who are might be interested in my current solution, I had to put the setNestedScrollingEnabled() logic in the postDelayed() method of a Handler with 5 ms delay due to the LayoutManager which always returned -1 when calling the methods to find out whether the first and the last item is visible.
I use this code in the onStart() method (after my RecyclerView has been initialized) and every time after a content change of the RecyclerView occurs.

final LinearLayoutManager layoutManager = (LinearLayoutManager) mRecyclerView.getLayoutManager();
new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        //no items in the RecyclerView
        if (mRecyclerView.getAdapter().getItemCount() == 0)
            mRecyclerView.setNestedScrollingEnabled(false);
        //if the first and the last item is visible
        else if (layoutManager.findFirstCompletelyVisibleItemPosition() == 0
                && layoutManager.findLastCompletelyVisibleItemPosition() == mRecyclerView.getAdapter().getItemCount() - 1)
            mRecyclerView.setNestedScrollingEnabled(false);
        else
            mRecyclerView.setNestedScrollingEnabled(true);
    }
}, 5);

解决方案

In your Toolbar remove the scroll flag, leaving only the enterAlways flag and you should get the effect you intended. For completeness, your layout should look like:

<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/coordinatorLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="enterAlways"
            app:theme="@style/ToolbarStyle" />
    </android.support.design.widget.AppBarLayout>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.design.widget.CoordinatorLayout>

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