fix(taskManager):实现预览图在切换过程中，先设置宽高，再改变位置的功能

widgets/ukui-task-manager/qml/TaskManagerView.qml

@@ -105,7 +105,7 @@ TaskManager {
         mainItem: viewContent
         type: Platform.WindowType.SystemWindow
         flags: Qt.WindowDoesNotAcceptFocus | Qt.FramelessWindowHint
-        visualParent: viewContent.thumbnailData ? viewContent.thumbnailData.currentTaskItem : null
+
         function updatePosition() {
             switch (Widget.container.position) {
                 case Items.Types.Left:
@@ -184,6 +184,16 @@ TaskManager {
                 updateBlurRegionTimer.stop();
                 updateThumbnailModel()
                 updateBlurRegionTimer.restart();
+                viewContent.determineListViewSize();
+
+                // 先设置mainItem的宽高 再切换visualParent,解决预览图闪烁问题
+                if (viewContent.thumbnailData) {
+                    if (viewContent.thumbnailData.currentTaskItem !== null) {
+                        thumbnailView.visualParent = viewContent.thumbnailData.currentTaskItem;
+                    }
+                } else {
+                    thumbnailView.visualParent = null;
+                }
             }
             property var modelList: []
             ListModel {