TreeView.BeginUpdate 方法
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
停用任何樹狀檢視的重繪作業。
public:
void BeginUpdate();
public void BeginUpdate ();
member this.BeginUpdate : unit -> unit
Public Sub BeginUpdate ()
範例
下列程式碼範例會在 控制項中 TreeView 顯示客戶資訊。 根樹狀節點會顯示客戶名稱,而子樹狀節點會顯示指派給每個客戶的訂單編號。 在此範例中,每個客戶會顯示 1,000 個訂單 15 個。 的重新繪製 TreeView 會使用 BeginUpdate 和 EndUpdate 方法來隱藏,並在建立和繪製 TreeNode 物件時 TreeView 顯示等候 Cursor 。 此範例會要求您有 Customer
可以保存物件集合的 Order
物件。 它也需要您在應用程式目錄中命名 MyWait.cur
的資料指標檔案,而且您已在 上 Form 建立 控制項的 TreeView 實例。
// The basic Customer class.
ref class Customer: public System::Object
{
private:
String^ custName;
protected:
ArrayList^ custOrders;
public:
Customer( String^ customername )
{
custName = "";
custOrders = gcnew ArrayList;
this->custName = customername;
}
property String^ CustomerName
{
String^ get()
{
return this->custName;
}
void set( String^ value )
{
this->custName = value;
}
}
property ArrayList^ CustomerOrders
{
ArrayList^ get()
{
return this->custOrders;
}
}
};
// End Customer class
// The basic customer Order class.
ref class Order: public System::Object
{
private:
String^ ordID;
public:
Order( String^ orderid )
{
ordID = "";
this->ordID = orderid;
}
property String^ OrderID
{
String^ get()
{
return this->ordID;
}
void set( String^ value )
{
this->ordID = value;
}
}
};
// End Order class
void FillMyTreeView()
{
// Add customers to the ArrayList of Customer objects.
for ( int x = 0; x < 1000; x++ )
{
customerArray->Add( gcnew Customer( "Customer " + x ) );
}
// Add orders to each Customer object in the ArrayList.
IEnumerator^ myEnum = customerArray->GetEnumerator();
while ( myEnum->MoveNext() )
{
Customer^ customer1 = safe_cast<Customer^>(myEnum->Current);
for ( int y = 0; y < 15; y++ )
{
customer1->CustomerOrders->Add( gcnew Order( "Order " + y ) );
}
}
// Display a wait cursor while the TreeNodes are being created.
::Cursor::Current = gcnew System::Windows::Forms::Cursor( "MyWait.cur" );
// Suppress repainting the TreeView until all the objects have been created.
treeView1->BeginUpdate();
// Clear the TreeView each time the method is called.
treeView1->Nodes->Clear();
// Add a root TreeNode for each Customer object in the ArrayList.
myEnum = customerArray->GetEnumerator();
while ( myEnum->MoveNext() )
{
Customer^ customer2 = safe_cast<Customer^>(myEnum->Current);
treeView1->Nodes->Add( gcnew TreeNode( customer2->CustomerName ) );
// Add a child treenode for each Order object in the current Customer object.
IEnumerator^ myEnum = customer2->CustomerOrders->GetEnumerator();
while ( myEnum->MoveNext() )
{
Order^ order1 = safe_cast<Order^>(myEnum->Current);
treeView1->Nodes[ customerArray->IndexOf( customer2 ) ]->Nodes->Add( gcnew TreeNode( customer2->CustomerName + "." + order1->OrderID ) );
}
}
// Reset the cursor to the default for all controls.
::Cursor::Current = Cursors::Default;
// Begin repainting the TreeView.
treeView1->EndUpdate();
}
// The basic Customer class.
public class Customer : System.Object
{
private string custName = "";
protected ArrayList custOrders = new ArrayList();
public Customer(string customername)
{
this.custName = customername;
}
public string CustomerName
{
get{return this.custName;}
set{this.custName = value;}
}
public ArrayList CustomerOrders
{
get{return this.custOrders;}
}
} // End Customer class
// The basic customer Order class.
public class Order : System.Object
{
private string ordID = "";
public Order(string orderid)
{
this.ordID = orderid;
}
public string OrderID
{
get{return this.ordID;}
set{this.ordID = value;}
}
} // End Order class
// Create a new ArrayList to hold the Customer objects.
private ArrayList customerArray = new ArrayList();
private void FillMyTreeView()
{
// Add customers to the ArrayList of Customer objects.
for(int x=0; x<1000; x++)
{
customerArray.Add(new Customer("Customer" + x.ToString()));
}
// Add orders to each Customer object in the ArrayList.
foreach(Customer customer1 in customerArray)
{
for(int y=0; y<15; y++)
{
customer1.CustomerOrders.Add(new Order("Order" + y.ToString()));
}
}
// Display a wait cursor while the TreeNodes are being created.
Cursor.Current = new Cursor("MyWait.cur");
// Suppress repainting the TreeView until all the objects have been created.
treeView1.BeginUpdate();
// Clear the TreeView each time the method is called.
treeView1.Nodes.Clear();
// Add a root TreeNode for each Customer object in the ArrayList.
foreach(Customer customer2 in customerArray)
{
treeView1.Nodes.Add(new TreeNode(customer2.CustomerName));
// Add a child treenode for each Order object in the current Customer object.
foreach(Order order1 in customer2.CustomerOrders)
{
treeView1.Nodes[customerArray.IndexOf(customer2)].Nodes.Add(
new TreeNode(customer2.CustomerName + "." + order1.OrderID));
}
}
// Reset the cursor to the default for all controls.
Cursor.Current = Cursors.Default;
// Begin repainting the TreeView.
treeView1.EndUpdate();
}
Public Class Customer
Inherits [Object]
Private custName As String = ""
Friend custOrders As New ArrayList()
Public Sub New(ByVal customername As String)
Me.custName = customername
End Sub
Public Property CustomerName() As String
Get
Return Me.custName
End Get
Set(ByVal Value As String)
Me.custName = Value
End Set
End Property
Public ReadOnly Property CustomerOrders() As ArrayList
Get
Return Me.custOrders
End Get
End Property
End Class
Public Class Order
Inherits [Object]
Private ordID As String
Public Sub New(ByVal orderid As String)
Me.ordID = orderid
End Sub
Public Property OrderID() As String
Get
Return Me.ordID
End Get
Set(ByVal Value As String)
Me.ordID = Value
End Set
End Property
End Class
' Create a new ArrayList to hold the Customer objects.
Private customerArray As New ArrayList()
Private Sub FillMyTreeView()
' Add customers to the ArrayList of Customer objects.
Dim x As Integer
For x = 0 To 999
customerArray.Add(New Customer("Customer" + x.ToString()))
Next x
' Add orders to each Customer object in the ArrayList.
Dim customer1 As Customer
For Each customer1 In customerArray
Dim y As Integer
For y = 0 To 14
customer1.CustomerOrders.Add(New Order("Order" + y.ToString()))
Next y
Next customer1
' Display a wait cursor while the TreeNodes are being created.
Cursor.Current = New Cursor("MyWait.cur")
' Suppress repainting the TreeView until all the objects have been created.
treeView1.BeginUpdate()
' Clear the TreeView each time the method is called.
treeView1.Nodes.Clear()
' Add a root TreeNode for each Customer object in the ArrayList.
Dim customer2 As Customer
For Each customer2 In customerArray
treeView1.Nodes.Add(New TreeNode(customer2.CustomerName))
' Add a child TreeNode for each Order object in the current Customer object.
Dim order1 As Order
For Each order1 In customer2.CustomerOrders
treeView1.Nodes(customerArray.IndexOf(customer2)).Nodes.Add( _
New TreeNode(customer2.CustomerName + "." + order1.OrderID))
Next order1
Next customer2
' Reset the cursor to the default for all controls.
Cursor.Current = System.Windows.Forms.Cursors.Default
' Begin repainting the TreeView.
treeView1.EndUpdate()
End Sub
備註
若要在專案一次新增至 TreeView 時維持效能,請呼叫 BeginUpdate 方法。 方法 BeginUpdate 會防止控制項繪製,直到 EndUpdate 呼叫 方法為止。
將專案新增至樹狀檢視控制項的慣用方法是使用 AddRange 方法,將樹狀節點專案的陣列加入樹狀檢視。 不過,如果您想要一次新增一個專案,請使用 BeginUpdate 方法來防止 TreeView 控制項在新增作業期間繪製。 若要讓控制項繼續繪製,請在所有樹狀節點都已新增至樹狀檢視時呼叫 EndUpdate 方法。
適用於
另請參閱
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