Android实现界面完全全屏

实现android界面完全全屏，状态栏也不显示，以下为代码：
1.AndroidManifest.xml内容：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="ln.lg.lxnweather">

    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/weddingclipart"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:name=".Utils.MyApplication">
        <activity android:name=".Main.MainActivity"
                  android:theme="@style/Theme.AppCompat.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            intent-filter>
        activity>
        <activity android:name=".Main.SearchActivity"/>
    application>
manifest>

2.MainActivity.java文件相关内容：

protected void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        }