delphi中响应鼠标进入或离开控件的方法

Delphi没有MouseEnter与MouseLeave的事件，网上说可以响应CM_MOUSEENTER和CM_MOUSELEAVE消息来实现。这两个消息是VCL自己定义的消息，看了Delphi的Controls.pas果然看到有以下两行：

  CM_MOUSEENTER             = CM_BASE + 19;
  CM_MOUSELEAVE             = CM_BASE + 20;

其中CM_BASE = $B000

可以有两种方式来利用：

方式一：在自定义的控件中添加响应事件来实现

方式二：直接让窗体响应事件，然后判断不同的控件

以下代码从网上参考后修改并运行通过。

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, ExtCtrls;type  TMyPanel=class(tpanel)  public    procedure MSGEnter(var msg:TMessage);message CM_MOUSEENTER;//响应进入的消息    procedure MSGLeave(var msg: TMessage);message CM_MOUSELEAVE;//响应离开的消息  end;  TForm1 = class(TForm)    Panel1: TPanel;    Panel2: TPanel;    procedure FormCreate(Sender: TObject);  private    MYpanel:TMyPanel;    panel:tpanel;    procedure MSGEnter(var msg:TMessage);message CM_MOUSEENTER;//响应进入的消息    procedure MSGLeave(var msg: TMessage);message CM_MOUSELEAVE;//响应离开的消息    { Private declarations }  public    { Public declarations }  end;var  Form1: TForm1;implementation{$R *.dfm}//方式一:对自定义控件定义事件{ TMyPanel }procedure TMyPanel.MSGEnter(var msg: TMessage);begin  Color:=clyellow;end;procedure TMyPanel.MSGLeave(var msg: TMessage);begin  Color:=clred;end;{ TForm1 }procedure TForm1.FormCreate(Sender: TObject);begin  MyPanel:=TMyPanel.Create(self);  MyPanel.Parent:=self;  MyPanel.Caption:='鼠标进入变黄,  鼠标离开变红';  Panel:=TPanel.Create(self);  Panel.Parent:=self;  panel.top:=100;end;//方式二:用窗体事件事响应并进行判断procedure TForm1.MSGEnter(var msg: TMessage);  var    myobj : TObject;  begin    myobj := TObject(msg.LParam);//用LParam进行判断鼠标进入了哪个控件     if (myobj <> nil) and (myobj is TPanel) then      TPanel(myobj).Caption := 'enter';  end;    procedure TForm1.MSGLeave(var msg: TMessage);  var    myobj : TObject;  begin      myobj := TObject(msg.LParam);    if (myobj <> nil) and (myobj is TPanel) then      TPanel(myobj).Caption := 'leave';  end;end.

如果想在设计阶段能直接添加事件以做响应，可以自定义控件并将其注册为可视化控件。

方法如下：（以下代码未经测试）

unit MyEdit;interfaceuses   Classes, Controls, Messages, StdCtrls;type  TMyEdit = class(TEdit)  private    FOnMouseLeave: TNotifyEvent;    FOnMouseEnter: TNotifyEvent;  published    property OnMouseEnter: TNotifyEvent read FOnMouseEnter write FOnMouseEnter;    property OnMouseLeave: TNotifyEvent read FOnMouseLeave write FOnMouseLeave;    procedure CMMouseEnter(var Msg:TMessage);message CM_MOUSEENTER;    procedure CMMouseLeave(var Msg:TMessage);message CM_MOUSELEAVE;  end;procedure Register;implementationprocedure Register;begin  RegisterComponents('Standard', [TMyEdit]);end;{ TMyEdit }procedure TMyEdit.CMMouseEnter(var Msg: TMessage);begin  inherited;  if Assigned(FOnMouseEnter) then    FOnMouseEnter(Self);end;procedure TMyEdit.CMMouseLeave(var Msg: TMessage);begin  inherited;  if Assigned(FOnMouseLeave) then    FOnMouseLeave(Self);end;end.