Android 如何隐藏导航栏

我有一个Android应用程序的问题

我使用此代码隐藏导航栏

public class Initer {
    public static void fullScreen(Window window) {
        if (Build.VERSION.SDK_INT >= 19) {
            View decor = window.getDecorView();
            fullScreen(decor);
        } else {
            window.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                    WindowManager.LayoutParams.FLAG_FULLSCREEN);
        }
    }

    public static void fullScreen(View decor) {
        if (Build.VERSION.SDK_INT >= 19) {
            decor.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |    
                    View.SYSTEM_UI_FLAG_FULLSCREEN |
                    View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
        }
    }
}

但当我显示

PopupWindow

或

对话框

时，导航栏会再次出现

我试过这么做

PopupWindow popupWindow =new PopupWindow(getWindow().getContext());
View popupWindowView = LayoutInflater.from(getWindow().getContext()).
        inflate(R.layout.dialog_interval_insert, null);
Initer.fullScreen(popupWindowView);

...

popupWindow.showAsDropDown(button_start);

显示

PopupWindow

时隐藏导航栏。但它不起作用。当我调用

弹出窗口
时，导航栏将显示，然后再次隐藏。当我退出时，导航栏就会出现

如何在整个应用程序中永久隐藏导航栏？
您可以使用此代码

public void FullScreen_Activity(Activity activity) {
    activity.requestWindowFeature(Window.FEATURE_NO_TITLE);
    activity.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
}

并使用更改状态栏颜色

public void setStatusBarColor(Activity activity, int RecColor) {
        if (isApi21()) {
            Window window = activity.getWindow();
            // clear FLAG_TRANSLUCENT_STATUS flag:
            window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
            // add FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS flag to the window
            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
            // finally change the color
            window.setStatusBarColor(ContextCompat.getColor(activity, RecColor));
        }
    }

以及如何使用全屏活动方法

public class SplashActivity extends AppCompatActivity {
@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getMethod().FullScreen_Activity(this);
    setContentView(R.layout.activity_splash);
    }
}

我认为代码就是如何隐藏动作栏和状态栏。但我只想隐藏导航栏。