响应界面可见度变更

本课介绍如何注册监听器，以便让应用获得系统界面可见性变更通知。如果您希望将界面的其他部分与系统栏的隐藏/显示同步，这会非常有用。

注册监听器

要获得有关系统界面可见性更改的通知，请向您的视图注册 View.OnSystemUiVisibilityChangeListener。 这通常是您用来控制导航可见性的视图。

例如，您可以将以下代码添加到 Activity 的 onCreate() 方法中：

    window.decorView.setOnSystemUiVisibilityChangeListener { visibility ->
        // Note that system bars will only be "visible" if none of the
        // LOW_PROFILE, HIDE_NAVIGATION, or FULLSCREEN flags are set.
        if (visibility and View.SYSTEM_UI_FLAG_FULLSCREEN == 0) {
            // TODO: The system bars are visible. Make any desired
            // adjustments to your UI, such as showing the action bar or
            // other navigational controls.
        } else {
            // TODO: The system bars are NOT visible. Make any desired
            // adjustments to your UI, such as hiding the action bar or
            // other navigational controls.
        }
    }
    

    View decorView = getWindow().getDecorView();
    decorView.setOnSystemUiVisibilityChangeListener
            (new View.OnSystemUiVisibilityChangeListener() {
        @Override
        public void onSystemUiVisibilityChange(int visibility) {
            // Note that system bars will only be "visible" if none of the
            // LOW_PROFILE, HIDE_NAVIGATION, or FULLSCREEN flags are set.
            if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                // TODO: The system bars are visible. Make any desired
                // adjustments to your UI, such as showing the action bar or
                // other navigational controls.
            } else {
                // TODO: The system bars are NOT visible. Make any desired
                // adjustments to your UI, such as hiding the action bar or
                // other navigational controls.
            }
        }
    });
    

一般来说，最好使界面与系统栏可见性变更保持同步。例如，您可以使用此监听器，随着状态栏的隐藏和显示来隐藏和显示操作栏。