???????????????????????????? WPF中TreeView.BringIntoView方法的替代方案

?????????????????????????????????????? 周銀輝

WPF中TreeView.BringIntoView（）方法并不是那么地好用，不少時候會沒有效果，這里有一個替代方案，調用SelectItem（）方法可以展開并呈現TreeView上指定的Item：

? public static class TreeViewHelper

??? {

??????? /// <summary>

??????? /// Expands all children of a TreeView

??????? /// </summary>

??????? /// <param name="treeView">The TreeView whose children will be expanded</param>

??????? public static void ExpandAll(this TreeView treeView)

??????? {

??????????? ExpandSubContainers(treeView);

??????? }

?

??????? /// <summary>

??????? /// Expands all children of a TreeView or TreeViewItem

??????? /// </summary>

??????? /// <param name="parentContainer">The TreeView or TreeViewItem containing the children to expand</param>

??????? private static void ExpandSubContainers(ItemsControl parentContainer)

??????? {

??????????? foreach (Object item in parentContainer.Items)

??????????? {

??????????????? TreeViewItem currentContainer = parentContainer.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

??????????????? if (currentContainer != null && currentContainer.Items.Count > 0)

??????????????? {

??????????????????? //expand the item

??????????????????? currentContainer.IsExpanded = true;

?

??????????????????? //if the item's children are not generated, they must be expanded

??????????????????? if (currentContainer.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated)

??????????????????? {

??????????????????????? //store the event handler in a variable so we can remove it (in the handler itself)

??????????????????????? EventHandler eh = null;

??????????????????????? eh = new EventHandler(delegate

??????????????????????????? {

?????????????? ?????????????????//once the children have been generated, expand those children's children then remove the event handler

??????????????????????????????? if (currentContainer.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)

??????????? ????????????????????{

??????????????????????????????????? ExpandSubContainers(currentContainer);

??????????????????????????????????? currentContainer.ItemContainerGenerator.StatusChanged -= eh;

??????????????????????????????? }

??????????????????????????? });

?

??????????????????????? currentContainer.ItemContainerGenerator.StatusChanged += eh;

??????????????????? }

??????????????????? else //otherwise the children have already been generated, so we can now expand those children

??????????????????? {

?????? ?????????????????ExpandSubContainers(currentContainer);

??????????????????? }

??????????????? }

??????????? }

??????? }

?

??????? /// <summary>

??????? /// Searches a TreeView for the provided object and selects it if found

??????? /// </summary>

??????? /// <param name="treeView">The TreeView containing the item</param>

??????? /// <param name="item">The item to search and select</param>

??????? public static void SelectItem(this TreeView treeView, object item)

??????? {

??????????? ExpandAndSelectItem(treeView, item);

??????? }

?

??????? /// <summary>

??????? /// Finds the provided object in an ItemsControl's children and selects it

??????? /// </summary>

??????? /// <param name="parentContainer">The parent container whose children will be searched for the selected item</param>

??????? /// <param name="itemToSelect">The item to select</param>

??????? /// <returns>True if the item is found and selected, false otherwise</returns>

??????? private static bool ExpandAndSelectItem(ItemsControl parentContainer, object itemToSelect)

??????? {

??????????? //check all items at the current level

??????????? foreach (Object item in parentContainer.Items)

??????????? {

??????????????? TreeViewItem currentContainer = parentContainer.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

?

??????????????? //if the data item matches the item we want to select, set the corresponding

??????????????? //TreeViewItem IsSelected to true

??????????????? if (item == itemToSelect && currentContainer != null)

??????????????? {

??????????????????? currentContainer.IsSelected = true;

??????????????????? currentContainer.BringIntoView();

??????????????????? currentContainer.Focus();

?

??????????????????? //the item was found

??????????????????? return true;

??????????????? }

??????????? }

?

??????????? //if we get to this point, the selected item was not found at the current level, so we must check the children

??????????? foreach (Object item in parentContainer.Items)

??????????? {

??????????????? TreeViewItem currentContainer = parentContainer.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

?

??????????????? //if children exist

??????????????? if (currentContainer != null && currentContainer.Items.Count > 0)

???????? ???????{

??????????????????? //keep track of if the TreeViewItem was expanded or not

??????????????????? bool wasExpanded = currentContainer.IsExpanded;

?

??????????????????? //expand the current TreeViewItem so we can check its child TreeViewItems

??????? ????????????currentContainer.IsExpanded = true;

?

??????????????????? //if the TreeViewItem child containers have not been generated, we must listen to

??????????????????? //the StatusChanged event until they are

??????????????????? if (currentContainer.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated)

??????????????????? {

??????????????????????? //store the event handler in a variable so we can remove it (in the handler itself)

??????????????????????? EventHandler eh = null;

?????????? ?????????????eh = new EventHandler(delegate

??????????????????????? {

??????????????????????????? if (currentContainer.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)

??????????????????????????? {

??????????????????????????????? if (ExpandAndSelectItem(currentContainer, itemToSelect) == false)

??????????????????????????????? {

??????????????????????????????????? //The assumption is that code executing in this EventHandler is the result of the parent not

??????????????????????????????? ????//being expanded since the containers were not generated.

??????????????????????????????????? //since the itemToSelect was not found in the children, collapse the parent since it was previously collapsed

??????????????????????????????????? currentContainer.IsExpanded = false;

??????????????????????????????? }

?

??????????????????????????????? //remove the StatusChanged event handler since we just handled it (we only needed it once)

???????????????????????? ???????currentContainer.ItemContainerGenerator.StatusChanged -= eh;

??????????????????????????? }

??????????????????????? });

??????????????????????? currentContainer.ItemContainerGenerator.StatusChanged += eh;

??????????????????? }

??????????????????? else //otherwise the containers have been generated, so look for item to select in the children

??????????????????? {

??????????????????????? if (ExpandAndSelectItem(currentContainer, itemToSelect) == false)

??????????????????????? {

???????????????????????? ???//restore the current TreeViewItem's expanded state

??????????????????????????? currentContainer.IsExpanded = wasExpanded;

??????????????????????? }

??????????????????????? else //otherwise the node was found and selected, so return true

?????????????? ?????????{

??????????????????????????? return true;

??????????????????????? }

??????????????????? }

??????????????? }

??????????? }

?

??????????? //no item was found

??????????? return false;

??????? }

??? }

?

轉載于:https://www.cnblogs.com/zhouyinhui/archive/2008/12/22/1360033.html

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