Android嵌套滚动：NestedScroll结合ViewPager与PieChart实现求助

Hey there, let's get that nested scrolling working properly! The issue with your current layout is that wrapping everything in a NestedScrollView inside a LinearLayout doesn't let CoordinatorLayout do its job of coordinating scroll interactions between the PieChart, TabLayout, and ViewPager. Here's a revised layout and breakdown of the key changes:

Revised 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:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- AppBarLayout manages the collapsible PieChart and fixed Toolbar -->
    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary">

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

        <!-- PieChart container with scroll flags to collapse on scroll -->
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="150dp"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <com.github.mikephil.charting.charts.PieChart
                android:id="@+id/pchart"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/>
        </RelativeLayout>
    </android.support.design.widget.AppBarLayout>

    <!-- TabLayout stays fixed below the AppBarLayout after collapse -->
    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        style="@style/AppTabLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="@dimen/dimen_ten"
        android:layout_marginRight="@dimen/dimen_ten"
        app:layout_anchor="@id/app_bar"
        app:layout_anchorGravity="bottom">

        <android.support.design.widget.TabItem
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout="@layout/row_open_tab" />

        <android.support.design.widget.TabItem
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout="@layout/row_delivered_tab" />
    </android.support.design.widget.TabLayout>

    <!-- ViewPager links with AppBarLayout for coordinated scrolling -->
    <android.support.v4.view.ViewPager
        android:id="@+id/vp_docket_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/colorBackground"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

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

Key Changes Explained #

• Root CoordinatorLayout: This is essential for enabling coordinated scrolling between different views. It acts as a container that lets child views react to each other's scroll events.
• AppBarLayout with Scroll Flags:
  • The Toolbar uses scroll|enterAlways so it slides back into view when you scroll up.
  • The PieChart's parent layout uses scroll|exitUntilCollapsed to make the PieChart collapse until only the Toolbar remains visible when you scroll down the ViewPager.
• Anchored TabLayout: Using app:layout_anchor and app:layout_anchorGravity keeps the TabLayout fixed directly below the AppBarLayout once the PieChart collapses. It won't scroll off-screen, which is exactly what you want for tab navigation.
• ViewPager Scrolling Behavior: The app:layout_behavior="@string/appbar_scrolling_view_behavior" attribute tells the ViewPager to trigger the AppBarLayout's scrolling actions when its content (like a RecyclerView inside your fragments) is scrolled.

Additional Tips #

• Ensure the fragments inside your ViewPager use scrollable views like RecyclerView (they support nested scrolling by default). If you're using a ScrollView, add android:nestedScrollingEnabled="true" to it.
• If the PieChart is interfering with scroll events, add android:descendantFocusability="blocksDescendants" to its parent RelativeLayout. This ensures scroll events are passed up to the AppBarLayout instead of being intercepted by the chart.

内容的提问来源于stack exchange，提问作者jigar savaliya