深入delphi编程理解之消息(五)重写(override)dispatch、wndproc方法和Application.OnMessage事件
dispatch、wndproc是VCL framework在TWinCtronl定义的虚拟方法,下面程序通过重写(override)这两函数拦截WM_LBUTTONDOWN消息,来与Application.OnMessage事件比较,测试消息流程的先后顺序。
一、程序代码
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type TForm1 = class(TForm) ListBox1: TListBox; Button1: TButton; Button2: TButton; Button3: TButton; procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); procedure Button3Click(Sender: TObject); procedure FormCreate(Sender: TObject); private { Private declarations } public procedure WndProc(var AMessage: TMessage); override; procedure dispatch(var AMessage); override; procedure FonMessage(var AMessage: TMsg;var Handled: Boolean); procedure AppMsg(Info: string); { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} procedure TForm1.AppMsg(Info: string); begin ListBox1.Items.Add(Info); ListBox1.Items.Add('-------------'); ListBox1.Perform(WM_VSCROLL,SB_BOTTOM,0); end; procedure Tform1.WndProc(var AMessage: TMessage); begin inherited; if AMessage.Msg = WM_LBUTTONDOWN then AppMsg('WndProc½Óµ½ÁËÐÅÏ¢'); end; procedure Tform1.dispatch(var AMessage); begin inherited; if Tmessage(AMessage).Msg = WM_LBUTTONDOWN then AppMsg('dispatch½Óµ½ÁËÐÅÏ¢'); end; procedure Tform1.FonMessage(var AMessage: TMsg;var Handled: Boolean); begin if Amessage.message = WM_LBUTTONDOWN then AppMsg('AppOnMessage½Óµ½ÐÅÏ¢'); end; procedure TForm1.Button1Click(Sender: TObject); begin SendMessage(Handle, WM_LBUTTONDOWN, 0, 0); end; procedure TForm1.Button2Click(Sender: TObject); begin PostMessage(Handle, WM_LBUTTONDOWN, 0, 0); end; procedure TForm1.Button3Click(Sender: TObject); begin Self.Perform(WM_LBUTTONDOWN, 0, 0); end; procedure TForm1.FormCreate(Sender: TObject); begin Application.OnMessage:=FonMessage; end; end.
二、程序界面
从程序运行结果来看,Application.OnMessage先拦截到消息,然后是dispatch,最后才是wndproc方法。
分类: 深入delphi编程理解之消息
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