谢谢你的回答@克里斯蒂安，我得到了错误

android.util.AndroidRuntimeException:必须调用requestFeature() 添加内容前

我用

@Override
protected void onCreate(Bundle savedInstanceState) {

    requestWindowFeature(Window.FEATURE_NO_TITLE);

    super.onCreate(savedInstanceState);

    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

    setContentView(R.layout.activity_login);

    -----
    -----
}

根据安卓开发者培训

你应该做到以下几点:

科特林：

private fun hideSystemBars() {
  val windowInsetsController =
      ViewCompat.getWindowInsetsController(window.decorView) ?: return
  // Configure the behavior of the hidden system bars
  windowInsetsController.systemBarsBehavior =
      WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
  // Hide both the status bar and the navigation bar
  windowInsetsController.hide(WindowInsetsCompat.Type.systemBars())
}

Java:

private void hideSystemBars() {
  WindowInsetsControllerCompat windowInsetsController =
      ViewCompat.getWindowInsetsController(getWindow().getDecorView());
  if (windowInsetsController == null) {
    return;
  }
  // Configure the behavior of the hidden system bars
  windowInsetsController.setSystemBarsBehavior(
      WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
  );
  // Hide both the status bar and the navigation bar
  windowInsetsController.hide(WindowInsetsCompat.Type.systemBars());
}

你可以通过编程来实现:

public class ActivityName extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // remove title
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.main);
    }
}

或者你也可以通过AndroidManifest.xml文件来实现:

<activity android:name=".ActivityName"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen"/>

编辑:

如果你正在使用AppCompatActivity，那么你需要添加新的主题

<style name="Theme.AppCompat.Light.NoActionBar.FullScreen" parent="@style/Theme.AppCompat.Light.NoActionBar">
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowActionBar">false</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowContentOverlay">@null</item>
</style>

然后使用它。

<activity android:name=".ActivityName"
    android:label="@string/app_name"
    android:theme="@style/Theme.AppCompat.Light.NoActionBar.FullScreen"/>

感谢https://stackoverflow.com/a/25365193/1646479

在AndroidManifest.xml文件:

<activity
    android:name=".Launch"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen" > <!-- This line is important -->

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>  

或者在Java代码中:

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

AndroidManifest.xml

<activity ...
          android:theme="@style/FullScreenTheme"
    >
</activity>

I.你的主应用的主题是theme . appcompat . light . darkactionbar

隐藏ActionBar / StatusBar style.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    ...
</style>

<style name="FullScreenTheme" parent="AppTheme">
    <!--this property will help hide the ActionBar-->
    <item name="windowNoTitle">true</item>
    <!--currently, I don't know why we need this property since use windowNoTitle only already help hide actionbar. I use it because it is used inside Theme.AppCompat.Light.NoActionBar (you can check Theme.AppCompat.Light.NoActionBar code). I think there are some missing case that I don't know-->
    <item name="windowActionBar">false</item>
    <!--this property is used for hiding StatusBar-->
    <item name="android:windowFullscreen">true</item>
</style>

隐藏系统导航栏

public class MainActivity extends AppCompatActivity {

    protected void onCreate(Bundle savedInstanceState) {
        getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
        setContentView(R.layout.activity_main)
        ...
    }
 }

2你的主应用主题是theme . appcompat . light . noactionbar

隐藏ActionBar / StatusBar style.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
    ...
</style>

<style name="FullScreenTheme" parent="AppTheme">
    <!--don't need any config for hide ActionBar because our apptheme is NoActionBar-->
    <!--this property is use for hide StatusBar-->
    <item name="android:windowFullscreen">true</item> // 
</style>

隐藏系统导航栏

类似于theme。appcompat。light。darkactionbar。

演示

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

}