CoordinatorLayout doesn't hide the actionbar

问题

This is driving me nuts. I have been trying to make this work for two days, and no progress has been made. I want to have an app bar that hides when I scroll the ViewPager down, and shows when I scroll ViewPager up, and this appears to be the standard way of doing it.

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

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

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways">

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

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

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_scrollFlags="scroll|enterAlways">

            <android.support.design.widget.TabLayout
                android:id="@+id/posts_pager_header"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:tabMode="scrollable"
                app:layout_collapseMode="pin">
            </android.support.design.widget.TabLayout>
        </android.support.design.widget.CollapsingToolbarLayout>

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

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


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

The viewpager contains a bunch of fragments which contain a listview in each. I'm using appcompat and design of version 22.2.0.

I have compared my code with the code here: git@github.com:slidenerd/Android-Design-Support-Library-Demo.git, and found no major difference. Could someone please help? Thanks. I wouldn't post this if I haven't exhausted all my options.

回答1:

I did some testing and here are my findings:

The layout you had originally (without the CollapsingToolbarLayout) was closer. I tweaked your layout and tested with it:

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

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_layout"
        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:theme="@style/ThemeOverlay.AppCompat.ActionBar"
            app:layout_scrollFlags="scroll|enterAlways" />

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

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

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

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

So here are the major points:

• CoordinatorLayout has to have an AppBarLayout and one other child layout.
• AppBarLayout has to have a Toolbar and/or a TabLayout.

• The app:layout_scrollFlags="scroll|enterAlways" attribute goes on the Toolbar and/or the TabLayout.

  Whichever layout has scrollflags (or both) will scroll out of view. So I don't know if you wanted the Toolbar to scroll and not the TabLayout, but either way you can control the behavior.

• You can't use a ListView as your scrolling view. Even inside your ViewPager fragment. Adding the app:layout_behavior="@string/appbar_scrolling_view_behavior" attribute made no difference.

  You have to use a RecyclerView or a NestedScrollView. Oddly, I didn't need the app:layout_behavior="@string/appbar_scrolling_view_behavior" attribute on the RecyclerView. And this was inside the Fragment subclass for the ViewPager.

来源：https://stackoverflow.com/questions/32804037/coordinatorlayout-doesnt-hide-the-actionbar