Cómo: Crear subclases de un control TreeView mediante devoluciones de llamada nativas

  • Artículo

Actualización: noviembre 2007

En este ejemplo se muestra cómo crear subclases de un control TreeView para crear un evento NodeMouseClick que no está disponible en .NET Compact Framework.

El formulario muestra el control TreeView con subclases e información acerca de un nodo en el que se hizo clic. Muestra el texto del nodo y las coordenadas x e y en las que se hizo clic en el control TreeView, que cambia al hacer clic en diferentes partes del nodo.

Este programa de ejemplo se describe con detalle en Crear subclases de controles con un procedimiento de ventana administrado.

Para crear subclases de un control TreeView para crear un evento NodeMouseClick

  1. En Microsoft Visual Studio 2005, cree un proyecto de Smart Device para Pocket PC.

  2. Agregue la clase auxiliar Win32 al proyecto. Este código está disponible en Cómo: Usar una clase auxiliar para las invocaciones de la plataforma.

  3. Agregue la clase WinProcHooker al proyecto. Este código está disponible en Cómo: Utilizar una clase para enlazar procedimientos de Windows.

  4. Agregue la clase TreeViewBonus al proyecto.

    // 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;
    }
}

  5. Agregue la clase TreeNodeMouseClickEventArgs al proyecto.

    // 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);
    }
}

  6. Declare una variable de formulario denominada treeViewB de tipo TreeViewBonus.

    private TreeViewBonus treeViewB;

  7. Agregue el código siguiente al constructor de la clase Form1, que debería seguir la llamada a InitializeComponent. Este código también agrega un intervalo de nodos de árbol y organiza su jerarquía.

    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);

  8. Agregue el delegado y el método de control de eventos para el evento NodeMouseClick derivado a la clase Form1.

        // 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();

}

  9. Compile y ejecute la aplicación.

Vea también

Tareas

Cómo: Utilizar una clase para enlazar procedimientos de Windows

Cómo: Usar una clase auxiliar para las invocaciones de la plataforma

Cómo: Crear subclases de un control TreeView mediante devoluciones de llamada nativas

Cómo: Mostrar un relleno de degradado

Conceptos

.Temas "Cómo..." de .NET Compact Framework

Otros recursos

Interoperabilidad en .NET Compact Framework