我來舉個簡單的例子，dbgrid的捲軸相關的。

dbgrid中假如記錄很多，使用滑鼠捲軸滾動的時候，只會在dbgrid當前頁面資料內滾動，而捲軸是不會動的，這樣操作很不方便，需要再拖動捲軸去滾動資料。加了TApplicationEvents就可以去判斷事件觸發對應的方法。

程式碼：新建應用程式工程，直接在介面上放個dbgrid，高度不要太高，寫form的oncreate事件和TApplicationEvents的onmessage事件。

不放和放TApplicationEvents，你可以看下效果。

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

Dialogs,DBClient,DB, Grids, DBGrids, AppEvnts;

type

TForm1 = class(TForm)

DBGrid1: TDBGrid;

ApplicationEvents1: TApplicationEvents;

procedure FormCreate(Sender: TObject);

procedure ApplicationEvents1Message(var Msg: tagMSG;

var Handled: Boolean);

private

{ Private declarations }

cdstemp:TClientDataSet;

ds:TDataSource;

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);

var

i:Integer;

begin

//建立物件

cdstemp:=TClientDataSet.Create(Application);

ds:=TDataSource.Create(Application);

//建立dataset列

with cdstemp do

begin

Active:=False;

FieldDefs.Clear;

FieldDefs.Add("id",ftString,32);

CreateDataSet;

Active:=True;

end;

//生成測試資料

for i:=0 to 20 do

begin

cdstemp.Append;

cdstemp.FieldByName("id").AsInteger:=i;

cdstemp.Post;

end;

//繫結

ds.DataSet:=cdstemp;

DBGrid1.DataSource:=ds;

end;

procedure TForm1.ApplicationEvents1Message(var Msg: tagMSG;

var Handled: Boolean);

begin

//先判斷焦點在不在DBGrid上

if DBGrid1.Focused then

begin

//判斷是不是滑鼠滾輪事件

if Msg.message = WM_MOUSEWHEEL then

begin

if Msg.wParam > 0 then

//捲軸往上滾

SendMessage(DBGrid1.Handle, WM_KEYDOWN, VK_UP, 0)

else

//捲軸往下滾

SendMessage(DBGrid1.Handle, WM_KEYDOWN, VK_DOWN, 0);

Handled := True;

end;

end;

end;

end.