如何隐藏底部四个虚拟键的黑条，达到完全全屏的效果?

如题，平板底部有个大黑边， 有 返回，主页，菜单，这些虚拟键 如何隐藏这些虚拟键，？

java代码:

protected void hideBottomUIMenu() {  
        //隐藏虚拟按键，并且全屏  
        if (Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) { // lower api  
            View v = this.getWindow().getDecorView();  
            v.setSystemUiVisibility(View.GONE);  
        } else if (Build.VERSION.SDK_INT >= 19) {  
            //for new api versions.  
            View decorView = getWindow().getDecorView();  
            int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION  
                            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY | View.SYSTEM_UI_FLAG_FULLSCREEN;  
            decorView.setSystemUiVisibility(uiOptions);  
        }  
    }