/// <summary>
/// 出栈 UIPanel，隐藏当前的UIPanel，并恢复上一界面的状态
/// </summary>
public void PopUIPanel()
{
//安全校验，如果栈为空， new 一个
if (panelStack == null)
{
panelStack = new Stack <BaseUIPanel>();
}
// 安全校验，因为是出栈，所以先判断，栈是否为空，空则返回，不进行出栈
if (panelStack.Count <= 0)
{
return;
}
//出栈，并获得栈顶的 UIPanel
//栈顶的 UIPanel，进行退出回调操作
BaseUIPanel topPanel = panelStack.Pop();
topPanel.OnExitCallBack();
// 安全校验，因为是出栈，所以先判断，栈是否为空，空则返回，不进行出栈
if (panelStack.Count <= 0)
{
return;
}
// 出栈后，获取新栈顶成员，并进行恢复操作
topPanel = panelStack.Peek();
topPanel.OnResumeCallBack();
}
/// <summary>
/// 把UIPanel入栈，显示UI，如果之前有UI则暂停当前UIPanel
/// </summary>
/// <param name="panelType">UIPanel 的哪个UIPanel</param>
public void PushUIPanel(UIPanelType panelType)
{
//安全校验，如果栈为空， new 一个
if (panelStack == null)
{
panelStack = new Stack <BaseUIPanel>();
}
//判断栈内是否有成员，有则获得当前UIPanel，暂停当前 UIPanel
if (panelStack.Count > 0)
{
BaseUIPanel topPanel = panelStack.Peek();
topPanel.OnPauseCallBack();
}
//根据 UIPanelType 获得 UIPanel 实体
//引进该 UIPanel 并且显示
//把该 UIPanel 入栈
BaseUIPanel panel = GetUIPanelByPanelType(panelType);
panel.OnEnterCallBack();
panelStack.Push(panel);
}
