我的工具栏在 API 级别 19 (Kitkat) 上不显示，而在 API 级别 21 上显示

我的代码没有在 Kitkat 上显示工具栏。
这是我针对两个 Android 版本的屏幕截图。

奇巧版本：

棒棒糖版本：

这背后的原因可能是什么。

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.global.market">
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/image_front"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".detailactivity"
            android:label="@string/app_name" />
        <activity
            android:name="com.google.android.gms.ads.AdActivity"
            android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>

        <meta-data android:name="com.google.android.gms.version" android:value="6111000" />
    </application>

</manifest>

样式.xml 文件

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->

    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    <item name="windowActionBarOverlay">false</item>
    <item name="windowNoTitle">true</item>
    <item name="windowActionBar">false</item>
</style>

<style name="AppTheme.NoActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    <item name="windowActionBar">false</item>
    <item name="windowNoTitle">true</item>
</style>

<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />

<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

Activity_main.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:ads="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"
        android:clickable="true">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

    <ExpandableListView
        android:id="@+id/exp_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="160dp"
        android:indicatorRight="?android:attr/expandableListPreferredItemIndicatorRight"
        android:background="@android:color/white"
        android:footerDividersEnabled="true"
        android:groupIndicator="@null">
    </ExpandableListView>

            <!--<ListView-->
                <!--android:background="@android:color/white"-->
                <!--android:id="@+id/menuList"-->
                <!--android:layout_width="match_parent"-->
                <!--android:layout_height="match_parent"-->
                <!--android:layout_marginTop="10dp" />-->
        </LinearLayout>
    </android.support.design.widget.NavigationView>

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

MainActivity.java

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

                setContentView(R.layout.activity_main);
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
                if (toolbar != null) {
                    toolbar = (Toolbar) findViewById(R.id.toolbar);
                    setSupportActionBar(toolbar);
                   getSupportActionBar().setDisplayHomeAsUpEnabled(true);
                }
}

构建.gradle 文件

 apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.3"

    ext {
        supportLibVersion = '23.4.0'  // variable that can be referenced to keep support libs consistent
    }

    defaultConfig {
        applicationId "com.global.market"
        minSdkVersion 14
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"

    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.4.0'
    compile 'com.android.support:design:23.4.0'
    compile 'com.loopj.android:android-async-http:1.4.9'
    compile 'com.android.support:cardview-v7:23.0.+'
    compile 'com.android.support:recyclerview-v7:23.0.+'
    compile 'com.google.code.gson:gson:2.6.2'
    compile 'com.squareup.retrofit2:retrofit:2.1.0'
    compile 'com.squareup.retrofit2:converter-gson:2.1.0'
    compile 'com.github.gabrielemariotti.cards:cardslib-core:2.1.0'
    compile 'com.github.gabrielemariotti.cards:cardslib-cards:2.1.0'
    compile 'com.github.PhilJay:MPAndroidChart:v2.2.4'
    compile files('libs/GoogleAdMobAdsSdk-6.4.1.jar')
    compile 'com.google.android.gms:play-services:6.1.11'



}

默认情况下，AppBar 具有在棒棒糖之后起作用的高度。因此，尽管布局层次结构不同，它始终可见。但在较低版本（棒棒糖下方）上，工具栏可能会绘制在其他布局下方。

因此，请重新排序布局项目以使工具栏可见。