要放在设置布局之前

/**
 * 隐藏Android底部的虚拟按键
 */
private void hideVirtualKey(){
    Window window = getWindow();
    WindowManager.LayoutParams params = window.getAttributes();
    params.systemUiVisibility = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
    window.setAttributes(params);
}