操作說明:逐一查看 Windows Forms TreeView 控制項的所有節點
有時候,檢查 Windows Forms TreeView 控制項中的每個節點,以便在節點值上執行一些計算會很有用。 這項作業可以使用遞迴方法(VB.NET 中的遞迴程式)來逐一查看樹狀結構每個集合中的每個節點。
樹狀檢視中的每個 TreeNode 物件都有可用來巡覽樹狀檢視的屬性: FirstNode 、、 LastNode 、 NextNodePrevNode 、 和 Parent 。 屬性的值 Parent 是目前節點的父節點。 如果有的話,目前節點的子節點會列在其 屬性中 Nodes 。 控制項 TreeView 本身具有 TopNode 屬性,這是整個樹狀檢視的根節點。
遞迴方法
遞迴方法會使用處理樹狀節點的方法,然後為每個子節點呼叫相同的方法。 這會重複,直到處理樹狀結構中的每個節點為止。 此方法的缺點是,如果樹狀結構很大,您可能會遇到堆疊溢位錯誤,而且記憶體不足。
下列範例示範如何列印每個 TreeNode 物件的 Text 屬性:
private void PrintRecursive(TreeNode treeNode)
{
// Print the node.
System.Diagnostics.Debug.WriteLine(treeNode.Text);
MessageBox.Show(treeNode.Text);
// Visit each node recursively.
foreach (TreeNode tn in treeNode.Nodes)
{
PrintRecursive(tn);
}
}
// Call the procedure using the TreeView.
private void CallRecursive(TreeView treeView)
{
// Print each node recursively.
foreach (TreeNode n in treeView.Nodes)
{
//recursiveTotalNodes++;
PrintRecursive(n);
}
}
Private Sub PrintRecursive(n As TreeNode)
System.Diagnostics.Debug.WriteLine(n.Text)
MessageBox.Show(n.Text)
Dim aNode As TreeNode
For Each aNode In n.Nodes
PrintRecursive(aNode)
Next
End Sub
' Call the procedure using the top nodes of the treeview.
Private Sub CallRecursive(aTreeView As TreeView)
Dim n As TreeNode
For Each n In aTreeView.Nodes
PrintRecursive(n)
Next
End Sub
private:
void PrintRecursive(TreeNode^ treeNode)
{
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
// Print each node recursively.
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ tn = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(tn);
}
}
finally
{
delete(myNodes);
}
}
// Call the procedure using the TreeView.
void CallRecursive(TreeView^ treeView)
{
// Print each node recursively.
TreeNodeCollection^ nodes = treeView->Nodes;
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ n = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(n);
}
}
finally
{
delete(myNodes);
}
}
非遞迴方法
下列範例是使用集合周遊樹 Queue<T> 狀結構節點的替代反復方法。 此方法不會遵循節點的父子式關聯性,只會確保列印每個節點。 如果您想要處理每個樹狀節點及其子系,請先使用 Stack<T> 集合
private void PrintNonRecursive(TreeNode treeNode)
{
if (treeNode != null)
{
//Using a queue to store and process each node in the TreeView
Queue<TreeNode> staging = new Queue<TreeNode>();
staging.Enqueue(treeNode);
while (staging.Count > 0)
{
treeNode = staging.Dequeue();
// Print the node.
System.Diagnostics.Debug.WriteLine(treeNode.Text);
MessageBox.Show(treeNode.Text);
foreach (TreeNode node in treeNode.Nodes)
{
staging.Enqueue(node);
}
}
}
}
// Call the procedure using the TreeView.
private void CallNonRecursive(TreeView treeView)
{
// Print each node.
foreach (TreeNode n in treeView.Nodes)
{
PrintNonRecursive(n);
}
}
Private Sub PrintNonrecursive(n As TreeNode)
If n IsNot Nothing Then
Dim staging As Queue(Of TreeNode) = New Queue(Of TreeNode)
staging.Enqueue(n)
While staging.Count > 0
n = staging.Dequeue()
'Print the node.
System.Diagnostics.Debug.WriteLine(n.Text)
MessageBox.Show(n.Text)
Dim node As TreeNode
For Each node In n.Nodes
staging.Enqueue(node)
Next
End While
End If
End Sub
Private Sub CallNonRecursive(aTreeView As TreeView)
Dim n As TreeNode
For Each n In aTreeView.Nodes
PrintNonrecursive(n)
Next
End Sub
private:
void PrintNonRecursive(TreeNode^ treeNode)
{
//Using a queue to store and process each node in the TreeView
Queue^ staging = gcnew Queue();
staging->Enqueue(treeNode);
while (staging->Count > 0)
{
treeNode = safe_cast<TreeNode^>(staging->Dequeue());
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
System::Collections::IEnumerator^ children = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (children->MoveNext())
{
staging->Enqueue(children->Current);
}
}
finally
{
delete(children);
}
}
// Print the node.
System::Diagnostics::Debug::WriteLine(treeNode->Text);
MessageBox::Show(treeNode->Text);
// Print each node recursively.
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(treeNode->Nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ tn = safe_cast<TreeNode^>(myNodes->Current);
PrintRecursive(tn);
}
}
finally
{
delete(myNodes);
}
}
// Call the procedure using the TreeView.
void CallNonRecursive(TreeView^ treeView)
{
// Print each node recursively.
TreeNodeCollection^ nodes = treeView->Nodes;
System::Collections::IEnumerator^ myNodes = (safe_cast<System::Collections::IEnumerable^>(nodes))->GetEnumerator();
try
{
while (myNodes->MoveNext())
{
TreeNode^ n = safe_cast<TreeNode^>(myNodes->Current);
PrintNonRecursive(n);
}
}
finally
{
delete(myNodes);
}
}
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