delphi - 如何设置带有红色边框的必填编辑字段？

Question

我想需要一些字段。而当他们不会被填写时，他们将是红色的，需要填写。在帖子可以完成之前

这是我想要实现的屏幕截图：

Answer 1

我会添加一个TShape，它可以在您的编辑框周围画一条红线。如果您希望红色边框替换正常的 TEdit 边框，您可以修改 Edit 控件的属性，使其没有边框。

如果您希望形状未填充，请将画笔样式更改为bsClear

Answer 2

如果需要，您可以挂钩 WM_Paint 消息并在 ControlCanvas 上绘制一个矩形。一种方法可能如下所示：

unit Edit_WithFrame_If_Needed_But_Empty;

interface

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

type
  TEdit = Class(StdCtrls.TEdit)
    procedure WMPaint(var Message: TWMPaint); message WM_PAINT;
    procedure CMTextChanged(var Message: TMessage); message CM_TEXTCHANGED;
    procedure WMKEYUP(var Message: TWMPaint); message WM_KEYUP;
  private
    FPaintedRed: Boolean;
    FRequired: Boolean;
    procedure CheckForInvalidate;
  published
  public
    Property Required: Boolean read FRequired Write FRequired;
  End;

  TForm2 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    procedure FormCreate(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

{ TEdit }
procedure TEdit.CheckForInvalidate;
begin
  if Required and (Length(Trim(Text)) = 0) then
  begin
    if not FPaintedRed then
      Invalidate;
  end
  else if FPaintedRed then
    Invalidate;
end;

procedure TEdit.CMTextChanged(var Message: TMessage);
begin
  inherited;
  CheckForInvalidate;
end;

procedure TEdit.WMKEYUP(var Message: TWMPaint);
begin
  CheckForInvalidate;
end;

procedure TEdit.WMPaint(var Message: TWMPaint);
var
  CC: TControlCanvas;
begin
  inherited;
  if Required and (Length(Trim(Text)) = 0) then
  begin
    FPaintedRed := true;
    CC := TControlCanvas.Create;
    try
      CC.Control := Self;
      CC.Pen.Color := clRed;
      CC.Pen.Width := 3;
      CC.Rectangle(ClientRect);
    finally
      CC.Free;
    end;
  end
  else
    FPaintedRed := false;
end;

procedure TForm2.FormCreate(Sender: TObject);
begin
  Edit1.Required := true;
  Edit3.Required := true;
end;

end.