发掘ListBox的潜力(三):显示即时提示(Tips)

ListBox显示即时提示(Tips)

  Listbox内容太长时超出Listbox宽度的部分将无法显示,一种解决方法是让Listbox产生横向滚动条,滚动显示内容(见前面的《发掘ListBox的潜力(一):自动调整横向滚动条宽度 》),另一种方法是让Listbox以Tips的方法显示完整内容。本文要实现的是后一种方式。

  Tips其实是一个特殊的窗体,类名为:tooltips_class32(在Commctrl(D6)有定义),可使用CreateWindow函数创建;Windows定义了一组以TTM_开头的消息用来与之通信,比如设置显示内容使用TTM_SETTITLE、删除显示内容使用TTM_DELTOOL。下面是例子:

hWndTip := CreateWindow(TOOLTIPS_CLASS, 'kktListBoxToolTips',
    WS_POPUP or TTS_NOPREFIX or TTS_ALWAYSTIP, 0, 0, 0, 0, hWndTip, 0, HInstance, nil);
SendMessage(hWndTip, TTM_ADDTOOL, 0, Integer(@ti));
SendMessage(hWndTip, TTM_DELTOOL, 0, Integer(@ti));

Tips有两种显示时机:鼠标指向某ListItem时和鼠标点击某ListItem时,这里提供了一个选项供用户,默认为鼠标点击ListItem时显示,因此在type作如下声明:

TToolTipShowEvent = (tsMouseOver, tsClick);

并在控件published处声明ShowToolTipWhen属性:

property ShowToolTipWhen: TToolTipShowEvent read FShowToolTipWhen writeSetShowToolTipWhen default tsClick;

接下来处理WM_LBUTTONDOWN消息判断是否应该显示内容,及处理要显示的内容:

procedure TkktListBox.WMMouseLBDown(var Message: TMessage);
var
  
X, Y, i: integer;
begin
  inherited;
  if (FShowToolTipWhen = tsMouseOver) then Exit;
  X := LOWORD(Message.lParam);
  Y := HIWORD(Message.lParam);
  i := ItemAtPos(Point(X, Y), true); //ItemIndex
  if (i = -1) and (TipsIndex <> -1) then HideToolTip;
  if i<>-1 then ShowToolTip(X, Y, i);
end;

对WM_MOUSEMOVE的处理方式类似:

procedure TkktListBox.WMMouseMove(var Message: TMessage);
var
  X, Y, i: integer;
begin
  if (FShowToolTipWhen = tsClick) then Exit;
  X := LOWORD(Message.lParam);
  Y := HIWORD(Message.lParam);
  i := ItemAtPos(Point(X, Y), true);
  if (i = -1) and (TipsIndex <> -1) then HideToolTip;
  if i<>-1 then ShowToolTip(X, Y, i);
  inherited;
end;

Tips的消隐则在CM_MOUSELEAVE消息里处理:

procedure TkktListBox.CMMouseLeave(var Message: TMessage);
begin
  inherited;
  HideToolTip;
end;

下面给出TkktListBox的完整代码:

unit kktListBox;
interface
uses
Windows, Messages, SysUtils, Classes, Controls, StdCtrls, Commctrl; const
TTM_SETTITLE = (WM_USER + 32); type
TGetHintTextEvent = procedure(Index: integer; var HintText: string; Sender: TObject) of object;
TToolTipShowEvent = (tsMouseOver, tsClick); TkktListBox = class(TListBox)
private

hWndTip: THandle;
ti: TOOLINFO;
TipsIndex: integer;
FOnGetHintText: TGetHintTextEvent;
FHintTitle: String;
FShowToolTipWhen: TToolTipShowEvent;

发掘ListBox的潜力(三):显示即时提示(Tips)

    procedure SetHintText(Index: integer);
procedure SetHintTitle(const Value: String);
procedure SetShowToolTipWhen(const Value: TToolTipShowEvent); protected
property ScrollWidth stored False;
public

constructor Create(AOwner: TComponent); override;
procedure CreateWnd; override;
destructor Destroy; override; published
property HintTitle: String read FHintTitle write SetHintTitle;
property ShowToolTipWhen: TToolTipShowEvent read FShowToolTipWhen write SetShowToolTipWhen default tsClick;
property OnGetHintText: TGetHintTextEvent Read FOnGetHintText write FOnGetHintText; end; procedure Register; implementation { TkktListBox }

procedure TkktListBox.CMMouseLeave(var Message: TMessage);
begin
inherited;
HideToolTip;
end; constructor TkktListBox.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
TipsIndex := -1;
FShowToolTipWhen := tsClick;
end;

发掘ListBox的潜力(三):显示即时提示(Tips)

    //uId := Handle;

hinst := hInstance;
lpszText := nil;
//LPSTR_TEXTCALLBACK;
//CALLBACK将导致回调次数太多
Rect.Left := 0;
Rect.Top := 0;
Rect.Bottom := 0;
Rect.Right := 0;
end;
sendMessage(hWndTip, WM_SETFONT, Self.Font.Handle, Integer(LongBool(False)));
SendMessage(hWndTip, TTM_ADDTOOL, 0, Integer(@ti));
SendMessage(hWndTip, TTM_SETTITLE, 0, Integer(Pchar(FHintTitle)));
end; destructor TkktListBox.Destroy;
begin
if hWndTip<>0 then SendMessage(hWndTip, WM_CLOSE, 0, 0);
inherited;
end; procedure TkktListBox.HideToolTip;
begin
TipsIndex := -1;
SendMessage(hWndTip, TTM_TRACKACTIVATE, 0, 0);
end; procedure TkktListBox.ShowToolTip(X, Y, Index: integer);
var
APoint: TPoint;
ARect: TRect;
begin
if (FShowToolTipWhen = tsClick) and (Index = TipsIndex) then Exit; if FShowToolTipWhen = tsMouseOver then begin
APoint := Point(X+20, Y+20);
end else begin //FShowToolTipWhen = tsClick
ARect := ItemRect(Index);
APoint := ARect.TopLeft;
end;
APoint := Self.ClientToScreen(APoint); SendMessage(hWndTip, TTM_TRACKPOSITION, 0, MAKELPARAM(APoint.X, APoint.Y));
if Index = TipsIndex then Exit;
SetHintText(Index);
SendMessage(hWndTip, TTM_TRACKACTIVATE, 1, integer(@ti));
TipsIndex := Index;
end; procedure TkktListBox.WMMouseLBDown(var Message: TMessage);
var
X, Y, i: integer;
begin
inherited;
if (csDesigning in ComponentState) or (FShowToolTipWhen = tsMouseOver) then Exit;
X := LOWORD(Message.lParam);
Y := HIWORD(Message.lParam);
i := ItemAtPos(Point(X, Y), true); //ItemIndex
if (i = -1) and (TipsIndex <> -1) then HideToolTip;
if i<>-1 then ShowToolTip(X, Y, i);
end; procedure TkktListBox.WMMouseMove(var Message: TMessage);
var
X, Y, i: integer;
begin
if (csDesigning in ComponentState) or (FShowToolTipWhen = tsClick) then Exit;
X := LOWORD(Message.lParam);
Y := HIWORD(Message.lParam);
i := ItemAtPos(Point(X, Y), true);
if (i = -1) and (TipsIndex <> -1) then HideToolTip;
if i<>-1 then ShowToolTip(X, Y, i);
inherited;
end; procedure TkktListBox.SetHintTitle(const Value: String);
begin
if FHintTitle = Value then Exit;
FHintTitle := Value;
SendMessage(hWndTip, TTM_SETTITLE, 0, Integer(Pchar(FHintTitle)));
end; procedure TkktListBox.SetHintText(Index: integer);
var
HintText: string;
begin
if Index<0 then Exit;
SendMessage(hWndTip, TTM_DELTOOL, 0, Integer(@ti));
HideToolTip;
HintText := Items[Index];
if Assigned(FOnGetHintText) then FOnGetHintText(Index, HintText, Self);
ti.lpszText := @HintText[1];
SendMessage(hWndTip, TTM_ADDTOOL, 0, Integer(@ti));
end; procedure TkktListBox.SetShowToolTipWhen(const Value: TToolTipShowEvent);
begin
if FShowToolTipWhen <> Value then begin
FShowToolTipWhen := Value;
HideToolTip;
end;
end; procedure Register;
begin
RegisterComponents('Kacarton', [TkktListBox]);
end; end.

http://blog.csdn.net/nhconch/article/details/520164

上一篇:python 中的map 详解


下一篇:由实现JavaScript中的Map想到的