响应 UI 可见性变化

本课程介绍了如何注册侦听器，以便您的应用程序可以收到系统 UI 可见性变化的通知。如果您希望将 UI 的其他部分与系统栏的隐藏/显示同步，这将很有用。

注册侦听器

要接收系统 UI 可见性变化的通知，请将 View.OnSystemUiVisibilityChangeListener 注册到您的视图。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您的活动的 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.
        }
    }
});

通常，最好让 UI 与系统栏可见性变化保持同步。例如，您可以使用此侦听器在状态栏隐藏和显示时隐藏和显示操作栏。