使用Android设计支持库时，工具栏和ViewPager之间的巨大空白

Question

I started using the Android Design Support Library in my app. I started using the CoordinatorLayout with an AppBarLayout and Toolbar with a ViewPager to create the animation where the Toolbar leaves the screen on scroll.

So far this works fine. The part that's the problem is whenever the orientation is changed to landscape from portrait, and then back to portrait from landscape. The result of this is a large white space in between the Toolbar and the ViewPager. Does anyone know how to fix this? Thanks! The code is below and I would've added screenshots of the problem, but apparently I can't do so until I reach level 10 or something.

Here's the layout file (activity_main.xml):

<android.support.v4.widget.DrawerLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawerLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context=".MainActivity">

<!--Content Container-->
<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!--App Bar Container-->
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appBarContainer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <!--ActionBar-->
        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:background="?attr/colorPrimary"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:layout_scrollFlags="scroll|enterAlways"/>

        <!--Prevents a bug in the App Bar Layout-->
        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="1px"/>

        <!--Tabs-->
        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:visibility="gone"
            app:tabMode="scrollable"
            app:tabGravity="fill"
            app:tabIndicatorHeight="@dimen/toolbar_tab_indicator_height"
            app:tabTextColor="@color/colorPrimaryLight"
            app:tabSelectedTextColor="@color/textColor"/>
    </android.support.design.widget.AppBarLayout>

    <!--Body Content-->
    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
</android.support.design.widget.CoordinatorLayout>


<!--Navigation Drawer-->
<android.support.design.widget.NavigationView
    android:id="@+id/navigationView"
    android:layout_height="match_parent"
    android:layout_width="wrap_content"
    android:layout_gravity="start"
    app:headerLayout="@layout/drawer_header"
    app:menu="@menu/drawer_items"/>
</android.support.v4.widget.DrawerLayout>

Answer 1

I believe the content holder, your ViewPager, belongs inside the CoordinatorLayout. The only thing that I see outside CoordinatorLayout is the nav view or drawer.

Answer 2

While messing around with the layout behavior, I figured out the problem. So I created a custom layout behavior class to handle the height inconstancy:

import android.content.Context;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.View;
import java.util.List;


public class CustomBehavior extends AppBarLayout.ScrollingViewBehavior
{
    public CustomBehavior()
    {
        super();
    }

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


    @Override
    public boolean onMeasureChild(CoordinatorLayout parent, View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed)
    {
        if (child.getLayoutParams().height == -1)
        {
            List dependencies = parent.getDependencies(child);

            if (dependencies.isEmpty())
            {
                return false;
            }

            AppBarLayout appBar = getOriginalLayout(dependencies);

            if (appBar != null && ViewCompat.isLaidOut(appBar))
            {
                if (ViewCompat.getFitsSystemWindows(appBar))
                {
                    ViewCompat.setFitsSystemWindows(child, true);
                }

                int scrollRange = appBar.getTotalScrollRange();
                int parentHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec);
                int height = parentHeight - appBar.getMeasuredHeight() + scrollRange;
                int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.AT_MOST);

                parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);

                return true;
            }
        }

        return false;
    }


    private static AppBarLayout getOriginalLayout(List<View> views)
    {
        int i = 0;

        for (int z = views.size(); i < z; ++i)
        {
            View view = (View)views.get(i);

            if (view instanceof AppBarLayout)
            {
                return (AppBarLayout)view;
            }
        }

        return null;
    }
}