Gewusst wie: Bilden von Unterklassen für TreeView durch Verwenden von systemeigenen Rückrufen

Artikel
09/02/2008

Aktualisiert: November 2007

In diesem Beispiel wird veranschaulicht, wie Unterklassen eines TreeView-Steuerelements gebildet werden, um ein NodeMouseClick-Ereignis zu erstellen, das in .NET Compact Framework nicht verfügbar ist.

Das Formular zeigt das als Unterklasse erstellte TreeView-Steuerelement sowie Informationen zu einem Knoten an, auf den geklickt wurde. Es zeigt den Knotentext und die x- und y-Koordinaten der Stelle an, auf die im TreeView-Steuerelement geklickt wurde. Diese ändern sich, sobald Sie in einem Knoten auf eine andere Stelle klicken.

Dieses Beispielprogramm wird unter Bilden von Steuerelementunterklassen mit einer verwalteten Fensterprozedur ausführlich beschrieben.

So bilden Sie Unterklassen eines TreeView-Steuerelements zum Erstellen eines NodeMouseClick-Ereignisses

Erstellen Sie in Microsoft Visual Studio 2005 ein Pocket PC-Projekt für intelligente Geräte.
Fügen Sie dem Projekt die Win32-Hilfsklasse hinzu. Dieser Code ist unter Gewusst wie: Verwenden einer Hilfsklasse für Plattformaufrufe verfügbar.
Fügen Sie dem Projekt die WinProcHooker-Klasse hinzu. Dieser Code ist unter Gewusst wie: Verwenden einer Klasse zum Verknüpfen von Windows-Prozeduren verfügbar.

Fügen Sie dem Projekt die TreeViewBonus-Klasse hinzu.

// Extends the standard TreeView control to add an implementation
// of the NodeMouseClick event.
public class TreeViewBonus : TreeView
{
    // The original parent of this control.
    Control prevParent = null;

    // Creates a new instance of the derived TreeView control
    public TreeViewBonus()
    {
    }

    // Called when the control's parent is changed. Here we hook into that
    // parent's WndProc and spy on the WM_NOTIFY message. When the parent
    // changes, we unhook the old parent's WndProc and hook into the new one.
    protected override void OnParentChanged(EventArgs e)
    {
        // unhook the old parent
        if (this.prevParent != null)
        {
            WndProcHooker.UnhookWndProc(prevParent, Win32.WM_NOTIFY);
        }
        // update the previous parent
        prevParent = this.Parent;

        // hook up the new parent
        if (this.Parent != null)
        {
            WndProcHooker.HookWndProc(this.Parent,
            new WndProcHooker.WndProcCallback(this.WM_Notify_Handler),
            Win32.WM_NOTIFY);
        }

        base.OnParentChanged(e);
    }

    // Occurs when the user clicks a TreeNode with the mouse.
    public event TreeNodeMouseClickEventHandler NodeMouseClick;

    // Occurs when the mouse pointer is over the control and a mouse button is clicked.
    protected void OnNodeMouseClick(TreeNodeMouseClickEventArgs e)
    {
        if (NodeMouseClick != null)
            NodeMouseClick(this, e);
   }

    // The method that gets called when a WM_NOTIFY message is received by the
    // TreeView's parent.
    // hwnd - The handle of the window that received the message
    // msg - The message received
    // wParam - The wParam arguments for the message
    // lParam - The lParam arguments for the message
    // handled - Set to true to indicate that this message was handled
    // Returns an appropriate return code for the message handled
    int WM_Notify_Handler(
        IntPtr hwnd, uint msg, uint wParam, int lParam,
        ref bool handled)
    {
        Win32.NMHDR nmHdr = new Win32.NMHDR();
        System.Runtime.InteropServices.Marshal.PtrToStructure((IntPtr)lParam, nmHdr);
        switch (nmHdr.code)
        {
            case Win32.NM_RCLICK:
            case Win32.NM_CLICK:
                // get the cursor coordinates on the client
                Point msgPos = Win32.LParamToPoint((int)Win32.GetMessagePos());
                msgPos = this.PointToClient(msgPos);

                // check to see if the click was on an item
                Win32.TVHITTESTINFO hti = new Win32.TVHITTESTINFO();
                hti.pt.X = msgPos.X;
                hti.pt.Y = msgPos.Y;
                int hitem = Win32.SendMessage(this.Handle, Win32.TVM_HITTEST, 0, ref hti);
                uint htMask = (
                    Win32.TVHT_ONITEMICON |
                    Win32.TVHT_ONITEMLABEL |
                    Win32.TVHT_ONITEMINDENT |
                    Win32.TVHT_ONITEMBUTTON |
                    Win32.TVHT_ONITEMRIGHT |
                    Win32.TVHT_ONITEMSTATEICON);
                if ((hti.flags & htMask) != 0)
                {
                    bool leftButton = (nmHdr.code == Win32.NM_CLICK);
                    RaiseNodeMouseClickEvent(hti.hItem,
                        leftButton ? MouseButtons.Left : MouseButtons.Right,
                        msgPos);
                    return 0;
                }
                break;
            default:
                break;
        }
        return 0;
    }

    // Raises the TreeNodeMouseClick event for the TreeNode with the specified handle.
    // hNode - The handle of the node for which the event is raised
    // button - The [mouse] buttons that were pressed to raise the event
    // coords - The [client] cursor coordinates at the time of the event
    void RaiseNodeMouseClickEvent(IntPtr hNode, MouseButtons button, Point coords)
    {
        TreeNode tn = FindTreeNodeFromHandle(this.Nodes, hNode);

        TreeNodeMouseClickEventArgs e = new TreeNodeMouseClickEventArgs(
            tn,
            button,
            1, coords.X, coords.Y);

        OnNodeMouseClick(e);
    }

    // Finds a TreeNode in the provided TreeNodeCollection that has the handle specified.
    // Warning: recursion!
    // tnc - The TreeNodeCollection to search
    // handle - The handle of the TreeNode to find in the collection
    // Returns tThe TreeNode if found; null otherwise
    TreeNode FindTreeNodeFromHandle(TreeNodeCollection tnc, IntPtr handle)
    {
        foreach (TreeNode tn in tnc)
        {
        if (tn.Handle == handle) return tn;
            // we couldn't have clicked on a child of this node if this node
            // is not expanded!
            if (tn.IsExpanded)
            {
                TreeNode tn2 = FindTreeNodeFromHandle(tn.Nodes, handle);
                if (tn2 != null) return tn2;
            }
        }
        return null;
    }
}

Fügen Sie dem Projekt die TreeNodeMouseClickEventArgs-Klasse hinzu.

// Provides data for the System.Windows.Forms.TreeView.NodeMouseClick event
public class TreeNodeMouseClickEventArgs : MouseEventArgs
{
    // Initializes a new instance of the TreeNodeMouseClickEventArgs class.
    // node - The node that was clicked
    // button - One of the System.Windows.Forms.MouseButtons members
    // clicks - The number of clicks that occurred
    // x - The x-coordinate where the click occurred
    // y - The y-coordinate where the click occurred
    public TreeNodeMouseClickEventArgs(TreeNode node, MouseButtons button, int clicks, int x, int y)
        :
        base(button, clicks, x, y, 0)
    {
        nodeValue = node;
    }

    //
    // Gets the node that was clicked.
    //
    public TreeNode Node
    {
        get { return nodeValue; }
        set { nodeValue = value; }
    }
    TreeNode nodeValue;

    public override string ToString()
    {
        return string.Format(
            "TreeNodeMouseClickEventArgs\r\n\tNode: {0}\r\n\tButton: {1}\r\n\tX: {2}\r\n\tY: {3}",
            nodeValue.Text, Button.ToString(), X, Y);
    }
}

Deklarieren Sie eine Formularvariable mit der Bezeichnung treeViewB und dem Typ TreeViewBonus.
```
private TreeViewBonus treeViewB;
```

Fügen Sie dem Konstruktor der Form1-Klasse den folgenden Code hinzu. Dieser sollte dem Aufruf von InitializeComponent folgen. In diesem Code wird auch ein Bereich von Strukturknoten hinzugefügt und deren Hierarchie angeordnet.

InitializeComponent();
this.treeViewB = new TreeViewBonus();
this.treeViewB.NodeMouseClick += new TreeNodeMouseClickEventHandler(this.tv_NodeMouseClicked);
this.treeViewB.Location = new System.Drawing.Point(18, 16);
this.treeViewB.Size = new System.Drawing.Size(205, 144);
this.treeViewB.Name = "treeViewB";


// Set up the tree nodes.
System.Windows.Forms.TreeNode treeNode1 = new System.Windows.Forms.TreeNode("Node0");
System.Windows.Forms.TreeNode treeNode2 = new System.Windows.Forms.TreeNode("Node2");
System.Windows.Forms.TreeNode treeNode3 = new System.Windows.Forms.TreeNode("Node3");
System.Windows.Forms.TreeNode treeNode4 = new System.Windows.Forms.TreeNode("Node6");
System.Windows.Forms.TreeNode treeNode5 = new System.Windows.Forms.TreeNode("Node7");
System.Windows.Forms.TreeNode treeNode6 = new System.Windows.Forms.TreeNode("Node8");
System.Windows.Forms.TreeNode treeNode7 = new System.Windows.Forms.TreeNode("Node4");
System.Windows.Forms.TreeNode treeNode8 = new System.Windows.Forms.TreeNode("Node1");
System.Windows.Forms.TreeNode treeNode9 = new System.Windows.Forms.TreeNode("Node5");
System.Windows.Forms.TreeNode treeNode10 = new System.Windows.Forms.TreeNode("Node9");
System.Windows.Forms.TreeNode treeNode11 = new System.Windows.Forms.TreeNode("Node10");
System.Windows.Forms.TreeNode treeNode12 = new System.Windows.Forms.TreeNode("Node11");

treeNode2.Text = "Node2";
treeNode4.Text = "Node6";
treeNode5.Text = "Node7";
treeNode6.Text = "Node8";
treeNode3.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode4,
        treeNode5,
        treeNode6});
treeNode3.Text = "Node3";
treeNode7.Text = "Node4";
treeNode1.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode2,
        treeNode3,
        treeNode7});
treeNode1.Text = "Node0";
treeNode12.Text = "Node11";
treeNode11.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode12});
treeNode11.Text = "Node10";
treeNode10.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode11});
treeNode10.Text = "Node9";
treeNode9.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode10});
treeNode9.Text = "Node5";
treeNode8.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode9});
treeNode8.Text = "Node1";
this.treeViewB.Nodes.AddRange(new System.Windows.Forms.TreeNode[] {
        treeNode1,
        treeNode8});

this.Controls.Add(treeViewB);

Fügen Sie den Delegaten und die Ereignisbehandlungsmethode für das abgeleitete NodeMouseClick-Ereignis zur Form1-Klasse hinzu.

    // Delegate represents the method that will handle
    // the NodeMouseClick event of a TreeView.
    // Parameters:
    // sender - The source of the event.
    // e - A TreeNodeMouseClickEventArgs that contains the event data.
    public delegate void TreeNodeMouseClickEventHandler(object sender, TreeNodeMouseClickEventArgs e);

private void tv_NodeMouseClicked(object sender, TreeNodeMouseClickEventArgs e)
{
    // Show the current node and the coordinates
    // in TreeView control where it was clicked.
    // This is just some of the information you
    // can obtain from TreeNodeMouseClickEventArgs.

    // Use a StringBuilder for efficient
    // use of device resources.
    StringBuilder sb = new StringBuilder();
    sb.Append(e.Node.Text + " ");
    sb.Append("X: " + e.X.ToString() + ", ");
    sb.Append("Y: " + e.Y.ToString());

    label1.Text = sb.ToString();

}

Kompilieren Sie die Anwendung, und führen Sie sie aus.

Siehe auch

Freigeben über

Gewusst wie: Bilden von Unterklassen für TreeView durch Verwenden von systemeigenen Rückrufen

So bilden Sie Unterklassen eines TreeView-Steuerelements zum Erstellen eines NodeMouseClick-Ereignisses

Siehe auch

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