如何在 Listbox 上显示 In-place Tooltips

来源：互联网发布：淘宝网出售十字绣编辑：程序博客网时间：2024/05/21 07:12

大家知道 TreeView 上的节点如果显示不完全，鼠标移上去会出现一提示，这就是 In-place Tooltips。下面这段代码在 Listbox 上实现这一功能(下面代码只是在标准 Listbox 上测试，如果是自画的，则要修改)：

{直接将下面代码拷贝到新建工程中Form1的Unit1.pas文件即可运行，不需添加任何控件}

//------------------------------------------------------------------------------
// 在 Listbox 上实现 In-place Tooltips
// 原创作者：Joe Huang Email：Happyjoe@21cn.com
//
//------------------------------------------------------------------------------

unit Unit1;

Interface

uses
WIndows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, CommCtrl;

type
//改写 TListbox 拦截 CM_MOUSELEAVE 消息
TNewListbox = class(TListbox)
protected
{ Protected declarations }
procedure WndProc(var Message: TMessage); override;
end;

type
TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
private
    { Private declarations }
    GHWND: HWND;
    TipVisable: Boolean;
    OldIndex, CurrentIndex: Integer;
    ti: TOOLInFO;
    Listbox1: TListbox;

    procedure InitListbox;   //动态生成 Listbox1
    procedure CreateTipsWIndow; //生成 Tooltip WIndow
    procedure HideTipsWIndow;    //隐藏 Tooltip WIndow

//拦截 WM_NOTIFY 消息，动态改变 Tooltip WIndow 显示的内容
procedure WMNotify(var Msg: TMessage); message WM_NOTIFY;

    procedure Listbox_MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure Listbox_MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
public
    { Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

{ TNewListbox }

procedure TNewListbox.WndProc(var Message: TMessage);
begIn
case Message.Msg of
CM_MOUSELEAVE: Form1.HideTipsWIndow;
end;
Inherited WndProc(Message);
end;

{ TForm1 }

procedure TForm1.InitListbox;
begIn
Listbox1 := TNewListbox.Create(Self);
Listbox1.Parent := Self;
Listbox1.Left := 50;
Listbox1.Top := 50;
Listbox1.Width := 200;
Listbox1.Height := 200;
//添加几项，以供测试用
Listbox1.Items.Append('happyjoe');
Listbox1.Items.Append('Please send me email: happyjoe@21cn.com');
Listbox1.Items.Append('Delphi 5 开发人员指南');
Listbox1.Items.Append('Delphi 5.X ADO/MTS/COM+ 高级程序设计篇');

Listbox1.OnMouseMove := Listbox_MouseMove;
Listbox1.OnMouseDown := Listbox_MouseDown;
end;

procedure TForm1.FormCreate(Sender: TObject);
begIn
Self.Font.Name := 'Tahoma';
InitListbox;
CreateTipsWIndow;
end;

procedure TForm1.CreateTipsWIndow;
var
iccex: tagInITCOMMONCONTROLSEX;
begIn
// Load the ToolTip class from the DLL.
iccex.dwSize := sizeof(tagInITCOMMONCONTROLSEX);
iccex.dwICC := ICC_BAR_CLASSES;
InitCommonControlsEx(iccex);

// Create the ToolTip control.
GHWND := CreateWIndow(Tooltips_CLASS, '',
                        WS_POPUP,
                        Integer(CW_USEDEFAULT), Integer(CW_USEDEFAULT),
                        Integer(CW_USEDEFAULT), Integer(CW_USEDEFAULT),
                        0, 0, hInstance,
                        nil);

// Prepare TOOLInFO structure for use as trackIng ToolTip.
ti.cbSize := sizeof(ti);
ti.uFlags := TTF_IDISHWND + TTF_TRACK + TTF_ABSOLUTE + TTF_TRANSPARENT;
ti.hwnd := Self.Handle;
ti.uId := Listbox1.Handle;
ti.hInst := hInstance;
ti.lpszText := LPSTR_TEXTCALLBACK;
ti.rect.left := 0;
ti.rect.top := 0;
ti.rect.bottom := 0;
ti.rect.right := 0;

SendMessage(GHWND, WM_SETFONT, Listbox1.Font.Handle, Integer(LongBool(false)));
SendMessage(GHWND,TTM_ADDTOOL,0,Integer(@ti));
end;

procedure TForm1.WMNotify(var Msg: TMessage);
var
phd :PHDNotify;
NMTTDISPInFO: PNMTTDispInfo;
begIn
phd := PHDNotify(Msg.lParam);
if phd.Hdr.hwndFrom = GHWND then
begIn
    if phd.Hdr.code = TTN_NEEDTEXT then
    begIn
      NMTTDISPInFO := PNMTTDispInfo(phd);
      NMTTDISPInFO.lpszText := PChar(Listbox1.Items[CurrentIndex]);
    end;
end;
end;

procedure TForm1.Listbox_MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begIn
if TipVisable then     //当鼠标按下，将显示的 Tooltip WIndow 隐藏
begIn
    SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
    TipVisable := false;
end;
end;

procedure TForm1.Listbox_MouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
var
Index: Integer;
APoInt: TPoInt;
ARect: TRect;
ScreenRect: TRect;
begIn
Index := Listbox1.ItemAtPos(PoInt(X, Y), true);
if Index = -1 then //如果鼠标下没有 Item，将 Tooltip WIndow 隐藏
begIn
    SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
    OldIndex := -1;
    TipVisable := false;
    exit;
end;
CurrentIndex := Index;
if Index = OldIndex then exit; //如果鼠标在同一 Item 上移动，退出处理
if TipVisable then   //先将显示的 Tooltip WIndow 隐藏
begIn
    SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
    OldIndex := -1;
    TipVisable := false;
end else
begIn
    ARect := Listbox1.ItemRect(Index);
    //判断该 Item 是否完全显示
    if (ARect.Right - ARect.Left - 2) >= Listbox1.Canvas.TextWidth(Listbox1.Items[Index]) then
    begIn
      OldIndex := -1;
      exit;
    end;
    APoInt := Listbox1.ClientToScreen(ARect.TopLeft);
    wIndows.GetClientRect(GetDesktopWIndow, ScreenRect);
    //判断 Tooltip WIndow 显示后是否会超出屏幕范围，这里只判断了右边界
    if Listbox1.Canvas.TextWidth(Listbox1.Items[Index]) + APoInt.X > ScreenRect.Right then
      APoInt.X := ScreenRect.Right - Listbox1.Canvas.TextWidth(Listbox1.Items[Index]) - 5;
    SendMessage(GHWND,
                TTM_TRACKPOSITION,
                0,
                MAKELPARAM(APoInt.x - 1, APoInt.y - 2));

    SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(true)), Integer(@ti));
    OldIndex := Index;
    TipVisable := true;
end;
end;

procedure TForm1.HideTipsWIndow;
begIn
if TipVisable then
begIn
    SendMessage(GHWND,TTM_TRACKACTIVATE,Integer(LongBool(false)), 0);
    OldIndex := -1;
    TipVisable := false;
end;
end;

end.