delphi - 如何在 TcxExtLookupComboBox 中使用 TcxCustomDataSource？

Question

我使用 Devexpress 的 TcxExtLookupComboBox 并尝试实现自定义数据源。我已经像这样设置了自定义数据源:

procedure TMainForm.FormCreate(Sender: TObject);
begin
  fDataSource := TMyDataSource.Create;
  cbotestSearch.Properties.View.DataController.CustomDataSource := fDataSource;
end;

TMyDataSource 定义如下:

unit Datasource;

interface

uses
  Classes,
  IBQuery,
  SysUtils,
  cxCustomData;

type
  TSearchItem = class
    private
      BoldID: String;
      Display: String
  end;

  TMyDataSource = class(TcxCustomDataSource)
  private
    fSearchList: TList;
  protected
    function GetRecordCount: Integer; override;
    function GetValue(ARecordHandle: TcxDataRecordHandle; AItemHandle: TcxDataItemHandle): Variant; override;
  public
    constructor Create;
    destructor Destroy; override;
    procedure GetData;
  end;

implementation

constructor TMyDataSource.Create;
begin
  inherited Create;
  fSearchList := TList.Create;
end;

destructor TMyDataSource.Destroy;
begin
  FreeAndNil(fSearchList);
  inherited;
end;

procedure TMyDataSource.GetData;
var
  vItem: TSearchItem;
begin
  fSearchList.Clear;

  vItem := TSearchItem.Create;
  vItem.BoldID  := '1000';
  vItem.Display := 'test';
  fSearchList.Add(vItem);

  vItem := TSearchItem.Create;
  vItem.BoldID  := '1100';
  vItem.Display := 'test2';
  fSearchList.Add(vItem);

  DataChanged;    // Don't do anything as provider is nil
end;

function TMyDataSource.GetRecordCount: Integer;
begin
  // Is never entered
  Result := fSearchList.Count;
end;

function TMyDataSource.GetValue(ARecordHandle: TcxDataRecordHandle;
  AItemHandle: TcxDataItemHandle): Variant;
begin
  // Is never entered
  Result := 'Test';
end;

end.

问题是 TMyDataSource.GetValue 从未被调用。有任何提示如何修复吗？

更新 1:我在这里还有另一个提示。如果我单步执行 DataChanged 方法，应该会导致调用 GetValue，如下所示:

procedure TcxCustomDataSource.DataChanged;
begin
  if Provider = nil then Exit;

  // Code using Provider
end;

在这种情况下，Provider 为零。但我已经在 Forms oncreate 中分配了数据源，如您所见。

Answer 1

cxExtLookupComboBox 只能与 DB~views 一起使用。此类 View 无法接受 TcxCustomDataSource 对象的实例作为数据源。因此，您的代码将无法工作:-(。有建议在将来实现此功能，并注册于:

http://www.devexpress.com/Support/Center/ViewIssue.aspx?issueid=AS10025