1
我想解決的問題是向用戶顯示字段中剩餘的字符，因爲它們鍵入到TDBEdit中。使TDBEdit顯示剩餘的字符
目前我正在做沿着
lCharRemaining.Caption := Field.Size - length(dbedit.text);
即在OnChange事件的TDBEdit，這工作完全正常更新標籤線的東西。不過，我想爲一些TDBEdits做這件事，並試圖編寫一個自定義組件，它將顯示右側編輯框中剩餘的長度。但是它會干擾編輯。我可能認爲我可以在有人打字的時候顯示提示，表明該領域的剩餘空間 - 有什麼建議嗎？
這裏是我的組件代碼（如果有人可以提出改進建議）。
unit DBEditWithLenghtCountdown;
interface
uses
SysUtils, Classes, Controls, StdCtrls, Mask, DBCtrls, messages, Graphics;
type
TDBEditWithLenghtCountdown = class(TDBEdit)
private
{ Private declarations }
FCanvas: TCanvas;
procedure WMPaint(var Message: TWMPaint); message WM_PAINT;
protected
{ Protected declarations }
property Canvas: TCanvas read FCanvas;
procedure WndProc(var Message: TMessage); override;
public
{ Public declarations }
function CharactersRemaining : integer;
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
{ Published declarations }
end;
procedure Register;
implementation
uses
db, Types;
procedure Register;
begin
RegisterComponents('Samples', [TDBEditWithLenghtCountdown]);
end;
{ TDBEditWithLenghtCountdown }
function TDBEditWithLenghtCountdown.CharactersRemaining: integer;
begin
result := -1;
if Assigned(Field)then
begin
result := Field.Size - Length(Text);
end;
end;
constructor TDBEditWithLenghtCountdown.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FCanvas := TControlCanvas.Create;
TControlCanvas(FCanvas).Control := Self;
end;
destructor TDBEditWithLenghtCountdown.Destroy;
begin
FCanvas.Free;
inherited;
end;
procedure TDBEditWithLenghtCountdown.WMPaint(var Message: TWMPaint);
var
R: TRect;
Remaining : string;
WidthOfText: Integer;
x: Integer;
begin
inherited;
if not focused then
exit;
Remaining := IntToStr(CharactersRemaining);
R := ClientRect;
Inc(R.Left, 1);
Inc(R.Top, 1);
Canvas.Brush.Assign(Self.Brush);
Canvas.Brush.Style := bsClear;
Canvas.Font.Assign(Self.Font);
Canvas.Font.Color := clRed;
WidthOfText := Canvas.TextWidth(Remaining);
x := R.right - WidthOfText - 4;
Canvas.TextOut(x,2, Remaining);
end;
procedure TDBEditWithLenghtCountdown.WndProc(var Message: TMessage);
begin
inherited WndProc(Message);
with Message do
case Msg of
CM_MOUSEENTER, CM_MOUSELEAVE, WM_LBUTTONUP, WM_LBUTTONDOWN,
WM_KEYDOWN, WM_KEYUP,
WM_SETFOCUS, WM_KILLFOCUS,
CM_FONTCHANGED, CM_TEXTCHANGED:
begin
Invalidate;
end;
end; // case
end;
end.
它如何「干擾編輯？」你基本上只是說「它不工作」，這是調試歷史中最不有用的短語。當你嘗試做什麼時出了什麼問題？ –
@MasonWheeler當您接近編輯框的末尾時，剩餘長度文本會覆蓋當前正在鍵入的內容。 – Alister
但爲什麼你想要一個新的組件？它可以推廣到所有派生自TCustomEdit的類 –