编写自定义属性检查器 - 验证值时如何处理就地编辑器焦点？

Overview

我正在尝试编写自己的简单属性检查器，但我面临着一个困难且相当令人困惑的问题。首先，我要说的是，我的组件并不是要使用或处理组件属性，而是允许向其添加自定义值。我的组件的完整源代码位于问题的更下方，一旦将其安装在包中并从新的空项目运行它，它应该看起来像这样：

问题（简要）

问题与就地编辑器的使用和验证属性值有关。这个想法是，如果属性值无效，则向用户显示一条消息，通知他们该值不能被接受，然后将焦点返回到最初关注的行和就地编辑器。

我们实际上可以使用 Delphi 自己的对象检查器来说明我正在寻找的行为，例如尝试在Name无法接受的属性，然后单击远离对象检查器。将显示一条消息，关闭它后，它将返回到Name row.

源代码

如果没有任何代码，问题就变得太模糊了，但由于我试图编写的组件的性质，它也很大。为了问题和示例的目的，我已尽可能地剥离它。我确信会有一些评论问我为什么不这样做或那样做，但重要的是要知道我不是 Delphi 专家，我经常做出错误的决定和选择，但我总是愿意学习，所以所有评论欢迎，特别是如果它有助于找到我的解决方案。

unit MyInspector;

interface

uses
  Winapi.Windows,
  Winapi.Messages,
  System.Classes,
  System.SysUtils,
  Vcl.Controls,
  Vcl.Dialogs,
  Vcl.StdCtrls,
  Vcl.Graphics,
  Vcl.Forms;

type
  TMyInspectorItems = class(TObject)
  private
    FPropertyNames: TStringList;
    FPropertyValues: TStringList;

    procedure AddItem(APropName, APropValue: string);
    procedure Clear;
  public
    constructor Create;
    destructor Destroy; override;
  end;

  TOnMouseMoveEvent = procedure(Sender: TObject; X, Y: Integer) of object;
  TOnSelectRowEvent = procedure(Sender: TObject; PropName, PropValue: string; RowIndex: Integer) of object;

  TMyCustomInspector = class(TGraphicControl)
  private
    FInspectorItems: TMyInspectorItems;
    FOnMouseMove: TOnMouseMoveEvent;
    FOnSelectRow: TOnSelectRowEvent;

    FRowCount: Integer;
    FNamesFont: TFont;
    FValuesFont: TFont;

    FSelectedRow: Integer;

    procedure SetNamesFont(const AValue: TFont);
    procedure SetValuesFont(const AValue: TFont);

    procedure CalculateInspectorHeight;
    function GetMousePosition: TPoint;
    function MousePositionToRowIndex: Integer;
    function RowIndexToMousePosition(ARowIndex: Integer): Integer;
    function GetRowHeight: Integer;
    function GetValueRowWidth: Integer;
    function RowExists(ARowIndex: Integer): Boolean;
    function IsRowSelected: Boolean;

  protected
    procedure Loaded; override;
    procedure Paint; override;
    procedure WMKeyDown(var Message: TMessage); message WM_KEYDOWN;
    procedure WMMouseDown(var Message: TMessage); message WM_LBUTTONDOWN;
    procedure WMMouseMove(var Message: TMessage); message WM_MOUSEMOVE;
    procedure WMMouseUp(var Message: TMessage); message WM_LBUTTONUP;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;

    function RowCount: Integer;

    property Items: TMyInspectorItems read FInspectorItems write FInspectorItems;
    property OnMouseMove: TOnMouseMoveEvent read FOnMouseMove write FOnMouseMove;
    property OnSelectRow: TOnSelectRowEvent read FOnSelectRow write FOnSelectRow;
  published
    property Align;
  end;

  TMyPropertyInspector = class(TScrollBox)
  private
    FInspector: TMyCustomInspector;
    FInplaceStringEditor: TEdit;

    FSelectedRowName: string;
    FLastSelectedRowName: string;
    FLastSelectedRow: Integer;

    function SetPropertyValue(RevertToPreviousValueOnFail: Boolean): Boolean;

    procedure InplaceStringEditorEnter(Sender: TObject);
    procedure InplaceStringEditorExit(Sender: TObject);
    procedure InplaceStringEditorKeyPress(Sender: TObject; var Key: Char);
    procedure SelectRow(Sender: TObject; PropName, PropValue: string; RowIndex: Integer);
    function ValidateStringValue(Value: string): Boolean;
  protected
    procedure Loaded; override;
    procedure WMSize(var Message: TMessage); message WM_SIZE;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;

    procedure AddItem(APropName, APropValue: string);
    function GetSelectedPropertyName: string;
    function GetSelectedPropertyValue: string;
    function RowCount: Integer;
  end;

var
  FCanSelect: Boolean;

implementation

{ TMyInspectorItems }

constructor TMyInspectorItems.Create;
begin
  inherited Create;
  FPropertyNames  := TStringList.Create;
  FPropertyValues := TStringList.Create;
end;

destructor TMyInspectorItems.Destroy;
begin
  FPropertyNames.Free;
  FPropertyValues.Free;
  inherited Destroy;
end;

procedure TMyInspectorItems.AddItem(APropName, APropValue: string);
begin
  FPropertyNames.Add(APropName);
  FPropertyValues.Add(APropValue);
end;

procedure TMyInspectorItems.Clear;
begin
  FPropertyNames.Clear;
  FPropertyValues.Clear;
end;

{ TMyCustomInspector }

constructor TMyCustomInspector.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);

  FInspectorItems     := TMyInspectorItems.Create;

  FNamesFont          := TFont.Create;
  FNamesFont.Color    := clWindowText;
  FNamesFont.Name     := 'Segoe UI';
  FNamesFont.Size     := 9;
  FNamesFont.Style    := [];

  FValuesFont         := TFont.Create;
  FValuesFont.Color   := clNavy;
  FValuesFont.Name    := 'Segoe UI';
  FValuesFont.Size    := 9;
  FValuesFont.Style   := [];
end;

destructor TMyCustomInspector.Destroy;
begin
  FInspectorItems.Free;
  FNamesFont.Free;
  FValuesFont.Free;
  inherited Destroy;
end;

procedure TMyCustomInspector.Loaded;
begin
  inherited Loaded;
end;

procedure TMyCustomInspector.Paint;

  procedure DrawBackground;
  begin
    Canvas.Brush.Color := clWindow;
    Canvas.Brush.Style := bsSolid;
    Canvas.FillRect(Rect(0, 0, Self.Width, Self.Height));
  end;

  procedure DrawNamesBackground;
  begin
    Canvas.Brush.Color := clWindow;
    Canvas.Brush.Style := bsSolid;
    Canvas.FillRect(Rect(0, 0, Self.Width div 2, Self.Height));
  end;

  procedure DrawNamesSelection;
  begin
    if (FRowCount > -1) and (RowExists(MousePositionToRowIndex)) then
    begin
      Canvas.Brush.Color := $00E0E0E0;
      Canvas.Brush.Style := bsSolid;
      Canvas.FillRect(Rect(0, RowIndexToMousePosition(FSelectedRow),
        Self.Width div 2, RowIndexToMousePosition(FSelectedRow) + GetRowHeight));
    end;
  end;

  procedure DrawNamesText;
  var
    I: Integer;
    Y: Integer;
  begin
    FRowCount := FInspectorItems.FPropertyNames.Count;

    Canvas.Brush.Style  := bsClear;
    Canvas.Font.Color   := FNamesFont.Color;
    Canvas.Font.Name    := FNamesFont.Name;
    Canvas.Font.Size    := FNamesFont.Size;

    Y := 0;
    for I := 0 to FInspectorItems.FPropertyNames.Count -1 do
    begin
      Canvas.TextOut(2, Y, FInspectorItems.FPropertyNames.Strings[I]);
      Inc(Y, GetRowHeight);
    end;
  end;

  procedure DrawValuesBackground;
  begin
    Canvas.Brush.Color := clWindow;
    Canvas.Brush.Style := bsSolid;
    Canvas.FillRect(Rect(Self.Width div 2, 0, Self.Width, Self.Height));
  end;

  procedure DrawValuesSelection;
  begin
    if (FRowCount > -1) and (RowExists(MousePositionToRowIndex)) then
    begin
      Canvas.DrawFocusRect(Rect(Self.Width div 2, RowIndexToMousePosition(FSelectedRow),
        Self.Width, RowIndexToMousePosition(FSelectedRow) + GetRowHeight));
    end;
  end;

  procedure DrawValues;
  var
    I, Y: Integer;
  begin
    FRowCount := FInspectorItems.FPropertyValues.Count;

    Y := 0;
    for I := 0 to FInspectorItems.FPropertyValues.Count -1 do
    begin
      Canvas.Brush.Style  := bsClear;
      Canvas.Font.Color   := FValuesFont.Color;
      Canvas.Font.Name    := FValuesFont.Name;
      Canvas.Font.Size    := FValuesFont.Size;

      Canvas.TextOut(Self.Width div 2 + 2, Y + 1, FInspectorItems.FPropertyValues.Strings[I]);
      Inc(Y, GetRowHeight);
    end;
  end;

begin
  DrawNamesBackground;
  DrawNamesSelection;
  DrawNamesText;
  DrawValuesBackground;
  DrawValuesSelection;
  DrawValues;
end;

procedure TMyCustomInspector.WMKeyDown(var Message: TMessage);
begin
  inherited;

  case Message.WParam of
    VK_DOWN:
    begin

    end;
  end;
end;

procedure TMyCustomInspector.WMMouseDown(var Message: TMessage);
begin
  inherited;

  Parent.SetFocus;

  FSelectedRow := MousePositionToRowIndex;

  if FSelectedRow <> -1 then
  begin
    if Assigned(FOnSelectRow) then
    begin
      FOnSelectRow(Self, FInspectorItems.FPropertyNames.Strings[FSelectedRow],
        FInspectorItems.FPropertyValues.Strings[FSelectedRow], FSelectedRow);
    end;
  end;

  Invalidate;
end;

procedure TMyCustomInspector.WMMouseMove(var Message: TMessage);
begin
  inherited;

  if Assigned(FOnMouseMove) then
  begin
    FOnMouseMove(Self, GetMousePosition.X, GetMousePosition.Y);
  end;
end;

procedure TMyCustomInspector.WMMouseUp(var Message: TMessage);
begin
  inherited;
end;

procedure TMyCustomInspector.SetNamesFont(const AValue: TFont);
begin
  FNamesFont.Assign(AValue);
  Invalidate;
end;

procedure TMyCustomInspector.SetValuesFont(const AValue: TFont);
begin
  FValuesFont.Assign(AValue);
  Invalidate;
end;

procedure TMyCustomInspector.CalculateInspectorHeight;
var
  I, Y: Integer;
begin
  FRowCount := FInspectorItems.FPropertyNames.Count;

  Y := GetRowHeight;
  for I := 0 to FRowCount -1 do
  begin
    Inc(Y, GetRowHeight);
  end;

  if Self.Height <> Y then
    Self.Height := Y;
end;

function TMyCustomInspector.GetMousePosition: TPoint;
var
  Pt: TPoint;
begin
  Pt := Mouse.CursorPos;
  Pt := ScreenToClient(Pt);
  Result := Pt;
end;

function TMyCustomInspector.MousePositionToRowIndex: Integer;
begin
  Result := GetMousePosition.Y div GetRowHeight;
end;

function TMyCustomInspector.RowIndexToMousePosition(
  ARowIndex: Integer): Integer;
begin
  Result := ARowIndex * GetRowHeight;
end;

function TMyCustomInspector.GetRowHeight: Integer;
begin
  Result := FNamesFont.Size * 2 + 1;
end;

function TMyCustomInspector.GetValueRowWidth: Integer;
begin
  Result := Self.Width div 2;
end;

function TMyCustomInspector.RowCount: Integer;
begin
  Result := FRowCount;
end;

function TMyCustomInspector.RowExists(ARowIndex: Integer): Boolean;
begin
  Result := MousePositionToRowIndex < RowCount;
end;

function TMyCustomInspector.IsRowSelected: Boolean;
begin
  Result := FSelectedRow <> -1;
end;

{ TMyPropertyInspector }

constructor TMyPropertyInspector.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);

  Self.DoubleBuffered               := True;
  Self.Height                       := 150;
  Self.HorzScrollBar.Visible        := False;
  Self.TabStop                      := True; // needed to receive focus
  Self.Width                        := 250;

  FInspector                        := TMyCustomInspector.Create(Self);
  FInspector.Parent                 := Self;
  FInspector.Align                  := alTop;
  FInspector.Height                 := 0;
  FInspector.OnSelectRow            := SelectRow;

  FInplaceStringEditor              := TEdit.Create(Self);
  FInplaceStringEditor.Parent       := Self;
  FInplaceStringEditor.BorderStyle  := bsNone;
  FInplaceStringEditor.Color        := clWindow;
  FInplaceStringEditor.Height       := 0;
  FInplaceStringEditor.Left         := 0;
  FInplaceStringEditor.Name         := 'MyPropInspectorInplaceStringEditor';
  FInplaceStringEditor.Top          := 0;
  FInplaceStringEditor.Visible      := False;
  FInplaceStringEditor.Width        := 0;
  FInplaceStringEditor.Font.Assign(FInspector.FValuesFont);

  FInplaceStringEditor.OnEnter      := InplaceStringEditorEnter;
  FInplaceStringEditor.OnExit       := InplaceStringEditorExit;
  FInplaceStringEditor.OnKeyPress   := InplaceStringEditorKeyPress;

  FCanSelect                        := True;
end;

destructor TMyPropertyInspector.Destroy;
begin
  FInspector.Free;
  FInplaceStringEditor.Free;
  inherited Destroy;
end;

procedure TMyPropertyInspector.Loaded;
begin
  inherited Loaded;
end;

procedure TMyPropertyInspector.WMSize(var Message: TMessage);
begin
  FInspector.Width := Self.Width;
  Invalidate;
end;


procedure TMyPropertyInspector.AddItem(APropName, APropValue: string);
begin
  FInspector.CalculateInspectorHeight;
  FInspector.Items.AddItem(APropName, APropValue);
  FInspector.Invalidate;
  Self.Invalidate;
end;

function TMyPropertyInspector.GetSelectedPropertyName: string;
begin
  Result := '';

  if FInspector.FSelectedRow <> -1 then
  begin
    Result := FInspector.FInspectorItems.FPropertyNames.Strings[FInspector.FSelectedRow];
  end;
end;

function TMyPropertyInspector.GetSelectedPropertyValue: string;
begin
  Result := '';

  if FInspector.FSelectedRow <> -1 then
  begin
    Result := FInspector.FInspectorItems.FPropertyValues.Strings[FInspector.FSelectedRow];
  end;
end;

function TMyPropertyInspector.RowCount: Integer;
begin
  Result := FInspector.RowCount;
end;

procedure TMyPropertyInspector.InplaceStringEditorEnter(Sender: TObject);
begin
  FCanSelect := False;
  FLastSelectedRow := FInplaceStringEditor.Tag;
end;

procedure TMyPropertyInspector.InplaceStringEditorExit(Sender: TObject);
begin
  if SetPropertyValue(True) then
  begin
    FCanSelect := True;
  end;
end;

procedure TMyPropertyInspector.InplaceStringEditorKeyPress(Sender: TObject;
  var Key: Char);
begin
  if Key = Chr(VK_RETURN) then
  begin
    Key := #0;
    FInplaceStringEditor.SelectAll;
  end;
end;

procedure TMyPropertyInspector.SelectRow(Sender: TObject; PropName, PropValue: string; RowIndex: Integer);
begin
  FSelectedRowName     := PropName;
  FLastSelectedRowName := PropName;

  FInplaceStringEditor.Height   := FInspector.GetRowHeight - 2;
  FInplaceStringEditor.Left     := Self.Width div 2;
  FInplaceStringEditor.Tag      := RowIndex;
  FInplaceStringEditor.Text     := GetSelectedPropertyValue;
  FInplaceStringEditor.Top      := FInspector.RowIndexToMousePosition(FInspector.FSelectedRow) + 1 - Self.VertScrollBar.Position;
  FInplaceStringEditor.Visible  := True;
  FInplaceStringEditor.Width    := FInspector.GetValueRowWidth - 3;
  FInplaceStringEditor.SetFocus;
  FInplaceStringEditor.SelectAll;
end;

function TMyPropertyInspector.SetPropertyValue(
  RevertToPreviousValueOnFail: Boolean): Boolean;
var
  S: string;
begin
  Result := False;

  S := FInplaceStringEditor.Text;

  if ValidateStringValue(S) then
  begin
    Result := True;
  end
  else
  begin
    ShowMessage('"' + S + '"' + 'is not a valid value.');
    Result := False;
  end;
end;

function TMyPropertyInspector.ValidateStringValue(Value: string): Boolean;
begin
  // a quick and dirty way of testing for a valid string value, here we just
  // look for strings that are not zero length.
  Result := Length(Value) > 0;
end;

end.

问题（详细）

我的困惑都归结为谁首先受到关注以及如何正确处理和响应它。因为我自定义绘制行，所以我确定单击检查器控件时鼠标所在的位置，然后绘制所选行以显示这一点。然而，在处理就地编辑器时，尤其是OnEnter and OnExit我一直面临着各种奇怪的问题，在某些情况下，我陷入了重复显示验证错误消息的循环中（因为焦点从我的检查器切换到就地编辑器并来回切换）。

要在运行时填充我的检查器，您可以执行以下操作：

procedure TForm1.Button1Click(Sender: TObject);
begin
  MyPropertyInspector1.AddItem('A', 'Some Text');
  MyPropertyInspector1.AddItem('B', 'Hello World');
  MyPropertyInspector1.AddItem('C', 'Blah Blah');
  MyPropertyInspector1.AddItem('D', 'The Sky is Blue');
  MyPropertyInspector1.AddItem('E', 'Another String');
end;

您可以尝试一些事情：

• 单击一行
• 从就地编辑器中删除内容
• 选择另一行
• 出现验证错误消息框（先不要关闭它）
• 在消息框仍然可见的情况下，将鼠标移到另一行上
• 现在按 Enter 键关闭消息框
• 您会注意到所选行现在已移动到鼠标所在的位置

我需要的是在验证消息框显示并关闭后，我需要将焦点设置回首先验证的行。它变得令人困惑，因为似乎（或者我认为）就地编辑器OnExit在之后被调用WMMouseDown(var Message: TMessage);我的检查员的代码。

如果问题仍然不清楚，我可以尽可能简单地说，Delphi 对象检查器的行为就是我试图在我的组件中实现的。您在就地编辑器中输入一个值，如果验证失败，则显示一个消息框，然后将焦点返回到最后选择的行。一旦焦点从就地编辑器移开，就地编辑器验证就应该发生。

我似乎无法弄清楚首先调用的是什么以及触发的阻塞事件是什么，这变得令人困惑，因为我绘制所选行的方式是由单击检查器控件时鼠标所在的位置决定的。

这是您的事件流程：

• TMyCustomInspector.WMMouseDown is called
  1. Therein, Parent.SetFocus is called
     • 焦点将从编辑控件中移除，并且TMyPropertyInspector.InplaceStringEditorExit叫做
     • 消息对话框显示为SetPropertyValue
  2. FSelectedRow正在重置
  3. TMyPropertyInspector.SelectRow被称为（通过TMyCustomInspector.FOnSelectRow) 将焦点重置到替换的编辑控件。

你需要做的是防止FSelectedRow在验证失败的情况下重置。所有需要的成分都已经存在，只需添加以下一个条件：

  if FCanSelect then
    FSelectedRow := MousePositionToRowIndex;

几点说明：

• Make FCanSelect受保护或私有领域TMyCustomInspector,
• 您需要检查以下限制TMyCustomInspector.MousePositionToRowIndex为了返回-1.