攔截方向鍵的訊息(100分)

現在在寫一個類似 Tmemo 的編輯控件，是從
TCustomControl 繼承而來的。
Scroll 方面是用兩個 TScrollBar 控件，而不是使用 API 的方法。
這控件是依我自己的意思來寫的，大致分成顯示與編輯兩類，
目前顯示方面已完成，可以讀檔並顯示及使用 Scroll Bar。

而編輯方面，想使用 WM_KEYDOWN、WM_KEYUP ，但是
攔截不到方向鍵，作了一個簡單的程式來測試，主視窗中除了
我的控件外，另還有幾個 Button ，當按下右鍵時，便看見
Button 焦點跑來跑去，到我的控件時，只觸發了 WM_KEYUP
事件，且焦點也跑至下一個 Button。

問題1:如何攔截方向鍵？
問題2:按方向鍵後，焦點不會跑至下一個控件？

這裡是部分程式碼：
procedure WMKEYUP(var msg:TWMKEYUP); message WM_KEYUP;
procedure WMKEYDOWN(var msg:TWMKEYDOWN); message WM_KEYDOWN;
procedure WMGetDlgCode(var Message: TWMGetDlgCode); message WM_GETDLGCODE;


// 實作 ----------------------------------------------------------
procedure TCustomJCMemo.WMGetDlgCode(var Message: TWMGetDlgCode);
begin
//
inherited;

if FWantTab then
Message.Result := Message.Result or DLGC_WANTTAB;

if FWantAllKeys then
Message.Result := Message.Result or DLGC_WANTALLKEYS;

end;

procedure TCustomJCMemo.WMKEYUP(var msg: TWMKEYUP);
begin
inherited;
end;

procedure TCustomJCMemo.WMKEYDOWN(var msg: TWMKEYDOWN);
begin
inherited;
end;

procedure CMChildKey(var Message: TMessage); message CM_CHILDKEY;

unit ArmLabEdit;

interface

uses
Windows, Messages, stdctrls,SysUtils, Classes, Graphics, Controls, Forms, Dialogs;
type
TArmLabEdit = class(TWinControl)
private
FEdit:TEdit;
FLab:TLabel;
FLength:integer;
FExit:tnotifyevent;
FKey:TKeyPressEvent;
function GetCaption: string;
function GetText: string;
//设焦点
procedure WMSetFocus(var Message: TWMSetFocus); message WM_SETFOCUS;
//设计退出事件
procedure CMFocusChanged(var Message: TCMFocusChanged); message CM_FOCUSCHANGED;
//设计击键事件
procedure CMChildKey(var Message: TMessage); message CM_CHILDKEY;

procedure SetText(const Value: string);
procedure SetCaption(const Value: string);
procedure WMSize(var message:tmessage) ;message wm_size;
procedure cmfontchanged(var message :Tmessage);message CM_fontchanged;
protected
public
constructor Create(aowner:tcomponent);override;
destructor Destory;
published
property Text:string read gettext write settext;
property Caption :string read getcaption write setcaption;
property OnExit read FExit write FExit;
property Onkeypress read Fkey write Fkey;
property TxtLength:integer read Flength write Flength;
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('宫雨', [TArmLabEdit]);
end;

{ TArmLabEdit }

procedure TArmLabEdit.CMChildKey(var Message: TMessage);
begin
if Assigned(FKey) then
FEdit.OnKeyPress:=Fkey;

end;



procedure TArmLabEdit.CMFocusChanged(var Message: TCMFocusChanged);
begin
if Assigned(FExit) then
FEdit.OnExit:=FExit;
end;

procedure TArmLabEdit.cmfontchanged(var message: Tmessage);
begin
inherited;
end;


constructor TArmLabEdit.Create(aowner: tcomponent);
begin
inherited Create(aowner);
Width:=200;
Height:=25;
FLab:=tlabel.Create(self);
FLab.Font.Name:='宋体';
FLab.Font.Size:=12;
FLab.Parent:=self;
FLab.Left:=left;
FLab.Width:=75;
FLab.height:=25;
FLab.Visible:=true;
FEdit:=tedit.Create(self);
FEdit.Parent:=self;
FEdit.Left:=left+flab.Width+5;
FEdit.Width:=width-5-flab.Width;
FEdit.height:=25;
FEdit.Font.Name:='宋体';
FEdit.Font.Size:=10;
end;

destructor TArmLabEdit.Destory;
begin
FLab.free;
FEdit.Free;
inherited;
end;


function TArmLabEdit.GetCaption: string;
begin
Result:=Flab.Caption;
end;

function TArmLabEdit.gettext: string;
begin
result:=FEdit.Text;
end;

procedure TArmLabEdit.SetCaption(const Value: string);
begin
FLab.Caption:=Value;
end;

procedure TArmLabEdit.SetText(const Value: string);
begin
if length(value)<=Flength then
FEdit.Text:=value
else
FEdit.Text:=copy(value,1,flength);
end;




procedure TArmLabEdit.WMSetFocus(var Message: TWMSetFocus);
begin
inherited;
FEdit.SetFocus;
end;

procedure TArmLabEdit.wmsize(var message: tmessage);
begin
inherited;
FLab.height:=Height;
FEdit.Width:=Height;
FEdit.Width:=Width-Flab.Width-5;
end;

end.

unit ArmLabEdit;

interface

uses
Windows, Messages, stdctrls,SysUtils, Classes, Graphics, Controls, Forms, Dialogs;
type
TArmLabEdit = class(TWinControl)
private
FEdit:TEdit;
FLab:TLabel;
FLength:integer;
FExit:tnotifyevent;
FKey:TKeyPressEvent;
function GetCaption: string;
function GetText: string;
//设焦点
procedure WMSetFocus(var Message: TWMSetFocus); message WM_SETFOCUS;
//设计退出事件
procedure CMFocusChanged(var Message: TCMFocusChanged); message CM_FOCUSCHANGED;
//设计击键事件
procedure CMChildKey(var Message: TMessage); message CM_CHILDKEY;

procedure SetText(const Value: string);
procedure SetCaption(const Value: string);
procedure WMSize(var message:tmessage) ;message wm_size;
procedure cmfontchanged(var message :Tmessage);message CM_fontchanged;
protected
public
constructor Create(aowner:tcomponent);override;
destructor Destory;
published
property Text:string read gettext write settext;
property Caption :string read getcaption write setcaption;
property OnExit read FExit write FExit;
property Onkeypress read Fkey write Fkey;
property TxtLength:integer read Flength write Flength;
end;

procedure Register;

implementation

procedure Register;
begin
RegisterComponents('宫雨', [TArmLabEdit]);
end;

{ TArmLabEdit }

procedure TArmLabEdit.CMChildKey(var Message: TMessage);
begin
if Assigned(FKey) then
FEdit.OnKeyPress:=Fkey;

end;



procedure TArmLabEdit.CMFocusChanged(var Message: TCMFocusChanged);
begin
if Assigned(FExit) then
FEdit.OnExit:=FExit;
end;

procedure TArmLabEdit.cmfontchanged(var message: Tmessage);
begin
inherited;
end;


constructor TArmLabEdit.Create(aowner: tcomponent);
begin
inherited Create(aowner);
Width:=200;
Height:=25;
FLab:=tlabel.Create(self);
FLab.Font.Name:='宋体';
FLab.Font.Size:=12;
FLab.Parent:=self;
FLab.Left:=left;
FLab.Width:=75;
FLab.height:=25;
FLab.Visible:=true;
FEdit:=tedit.Create(self);
FEdit.Parent:=self;
FEdit.Left:=left+flab.Width+5;
FEdit.Width:=width-5-flab.Width;
FEdit.height:=25;
FEdit.Font.Name:='宋体';
FEdit.Font.Size:=10;
end;

destructor TArmLabEdit.Destory;
begin
FLab.free;
FEdit.Free;
inherited;
end;


function TArmLabEdit.GetCaption: string;
begin
Result:=Flab.Caption;
end;

function TArmLabEdit.gettext: string;
begin
result:=FEdit.Text;
end;

procedure TArmLabEdit.SetCaption(const Value: string);
begin
FLab.Caption:=Value;
end;

procedure TArmLabEdit.SetText(const Value: string);
begin
if length(value)<=Flength then
FEdit.Text:=value
else
FEdit.Text:=copy(value,1,flength);
end;




procedure TArmLabEdit.WMSetFocus(var Message: TWMSetFocus);
begin
inherited;
FEdit.SetFocus;
end;

procedure TArmLabEdit.wmsize(var message: tmessage);
begin
inherited;
FLab.height:=Height;
FEdit.Width:=Height;
FEdit.Width:=Width-Flab.Width-5;
end;

end.

要截获 WM_GETDLGCODE 消息，你的程序才能得到上述的系统键。
DLGC_BUTTON Button.
DLGC_DEFPUSHBUTTON Default push button.
DLGC_HASSETSEL EM_SETSEL messages.
DLGC_RADIOBUTTON Radio button.
DLGC_STATIC Static control.
DLGC_UNDEFPUSHBUTTON Nondefault push button.
<font color = #ff0000><strong>DLGC_WANTALLKEYS</font></strong> All keyboard input.
DLGC_WANTARROWS Direction keys.
DLGC_WANTCHARS WM_CHAR messages.
DLGC_WANTMESSAGE All keyboard input (the application passes this message on to a control).
DLGC_WANTTAB

兩位意見都成功了，奇怪！之前也攔截 WM_GETDLGCODE
，不成功，可能是寫法有誤，重寫後就好了！

請問 arm 兄，不知 CM_CHILDKEY 是代表什麼意思？
要用何種方式來查詢，使用 HELP 查不到，追了一下
Controls 才簡單的寫一個 CM_CHILDKEY = CM_BASE + 46;
那是何意思呢？

我也不知道,CM_CHILDKEY = CM_BASE + 46
我是在写控件时用WINSIGHT 跟踪发现的
然后看了一下TWINCONTORLS
的原码

多人接受答案了。