delphi - 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？

Question

概述

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，一旦您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 属性中编写一个无法接受的字符串，然后单击离开对象检查器。将显示一条消息，关闭它后，它将重新聚焦到 Name 行。

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获得焦点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 和 OnExit 事件，我一直面临着各种奇怪的问题，在某些情况下，我陷入了验证周期例如，重复显示错误消息(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;

您可以尝试的一些事情:

• 点击一行
• 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 是在我的检查器的 WMMouseDown(var Message: TMessage); 代码之后调用的。

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行为。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，就地编辑器验证就会发生。

Answer 1

I just can't seem to figure out what is been called first and what is blocking events been fired, it becomes confusing because the way I draw my selected row is determined by where the mouse was when clicking on the inspector control.

这是您的事件流程:

• TMyCustomInspector.WMMouseDown 被调用
  1. 其中调用了Parent.SetFocus
     • 焦点将从“编辑”控件中移除，并调用 TMyPropertyInspector.InplaceStringEditorExit
     • 消息对话框由SetPropertyValue显示
  2. FSelectedRow 正在重置
  3. TMyPropertyInspector.SelectRow 被调用(通过 TMyCustomInspector.FOnSelectRow)，它将焦点重置到替换的编辑控件。

您需要做的是防止在验证失败的情况下重置FSelectedRow。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:

• 将 FCanSelect 设为 TMyCustomInspector 的 protected 或私有(private)字段，
• 您需要检查 TMyCustomInspector.MousePositionToRowIndex 中的限制才能返回 -1。