ui中最近播放列表如果有关联的曲目列表元素，则不显示“预览”按钮

Author: zhongyang219

MusicPlayer2/UIElement/RecentPlayedList.cpp

@@ -139,25 +139,31 @@ void UiElement::RecentPlayedList::OnHoverButtonClicked(int btn_index, int row)
 void UiElement::RecentPlayedList::OnSelectionChanged()
 {
     //获取关联的trackList元素
-    if (!track_list_element_id.empty())
+    FindTrackList();
+    if (track_list != nullptr && track_list->IsShown())
     {
-        TrackList* track_list = FindRelatedElement<TrackList>(track_list_element_id);
-        if (track_list != nullptr && track_list->IsShown())
+        int row = GetItemSelected();
+        if (row >= 0 && row < GetRowCount())
+        {
+            ListItem list_item = m_list_cache.GetItem(row);
+            track_list->SetListItem(list_item);
+        }
+        else
         {
-            int row = GetItemSelected();
-            if (row >= 0 && row < GetRowCount())
-            {
-                ListItem list_item = m_list_cache.GetItem(row);
-                track_list->SetListItem(list_item);
-            }
-            else
-            {
-                track_list->ClearListItem();
-            }
+            track_list->ClearListItem();
         }
     }
 }
 
+void UiElement::RecentPlayedList::FindTrackList()
+{
+    if (!find_track_list)
+    {
+        track_list = FindRelatedElement<TrackList>(track_list_element_id);
+        find_track_list = true;  //找过一次没找到就不找了
+    }
+}
+
 void UiElement::RecentPlayedList::FromXmlNode(tinyxml2::XMLElement* xml_node)
 {
     AbstractListElement::FromXmlNode(xml_node);

MusicPlayer2/UIElement/RecentPlayedList.h

@@ -1,8 +1,10 @@
-#pragma once
+#pragma once
 #include "AbstractListElement.h"
 namespace UiElement
 {
-    //最近播放
+    class TrackList;
+
+    //最近播放
     class RecentPlayedList : public AbstractListElement
     {
     public:
@@ -13,7 +15,7 @@ namespace UiElement
             COL_MAX
         };
 
-        //鼠标指向一行时显示的按钮
+        //鼠标指向一行时显示的按钮
         enum BtnKey
         {
             BTN_PLAY,
@@ -25,7 +27,7 @@ namespace UiElement
 
         virtual void Draw() override;
 
-        // 通过 AbstractListElement 继承
+        // 通过 AbstractListElement 继承
         std::wstring GetItemText(int row, int col) override;
         int GetRowCount() override;
         int GetColumnCount() override;
@@ -44,9 +46,15 @@ namespace UiElement
 
         virtual void FromXmlNode(tinyxml2::XMLElement* xml_node);
 
+    private:
+        void FindTrackList();        //查找TrackList
+
     protected:
-        static CListCache m_list_cache;     // 为RecentPlayedList的绘制缓存最近播放的ListItem，Draw之前调用reload
+        static CListCache m_list_cache;     // 为RecentPlayedList的绘制缓存最近播放的ListItem，Draw之前调用reload
         std::string track_list_element_id;
+
+        TrackList* track_list;
+        bool find_track_list{};      //如果已经查找过TrackList，则为true
     };
 }