Android列表视图未显示第一项

Question

我的列表视图不显示第一项；看起来尺寸占据了所有屏幕。您可以看到它显示在应用栏布局的后面。我不知道为什么我尝试了很多次，但仍然无法正常工作。我把内容主xml包括应用栏主。

主要活动xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
        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:id="@+id/drawer_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        tools:openDrawer="start">

    <include
            layout="@layout/app_bar_main"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>


    <android.support.design.widget.NavigationView
            android:id="@+id/nav_view"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            android:fitsSystemWindows="true"
            app:headerLayout="@layout/nav_header_main"
            app:menu="@menu/activity_main_drawer"/>

</android.support.v4.widget.DrawerLayout>

内容主xml

   <?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.ConstraintLayout
            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:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            tools:context=".MainActivity" android:layout_gravity="top">

        <android.support.design.widget.AppBarLayout
                android:id="@+id/appbar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    app:title="@string/app_name"
                    android:layout_width="match_parent"
                    android:layout_height="?attr/actionBarSize"
                    android:layout_weight="1"
                    android:background="?attr/colorPrimary"
                    app:popupTheme="@style/AppTheme.PopupOverlay"
                    app:layout_scrollFlags="scroll|enterAlways">

            </android.support.v7.widget.Toolbar>

            <android.support.design.widget.TabLayout
                    android:id="@+id/sliding_tabs"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content" android:background="@color/design_default_color_primary_dark">

                <android.support.design.widget.TabItem
                        android:id="@+id/tabItem2"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="الوصول"/>
                <android.support.design.widget.TabItem
                        android:id="@+id/tabItem"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="المغادرون"/>
                <android.support.design.widget.TabItem
                        android:id="@+id/tabItem3"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="الطقس"/>


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

        <android.support.v4.view.ViewPager
                android:id="@+id/viewpager_main"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                app:layout_behavior="@string/appbar_scrolling_view_behavior" app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintTop_toTopOf="parent" app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintBottom_toBottomOf="parent" android:foregroundGravity="top"/>

    </android.support.constraint.ConstraintLayout>

应用栏主xml

    <?xml version="1.0" encoding="utf-8"?>
    <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"
            tools:context=".MainActivity">

        <android.support.design.widget.AppBarLayout
                android:layout_height="wrap_content"
                android:layout_width="match_parent"
                android:theme="@style/AppTheme.AppBarOverlay">



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

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


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