delphi开发回忆录——面向对象的基础,继承(续)

在事件中声明
var
  testform:TfrmBasic;
并创建窗体对象,然后进行赋值操作,从前面的代码中我们不难看出这样写程序有太多的弊端,比如:代码重复,死板等等。
其实我们可以通过TRzGroupBar控件的TRzGroupItem对象的Tag或者Caption来创建相应的窗体对象,例如:
procedure TfrmMain.rgBaseDatumItems0Click(Sender: TObject);
begin
    CreateFormSelect(Sender);
end;
函数CreateFormSelect如下:
procedure TfrmMain.CreateFormSelect(Sender: TObject);
begin
  MsgBox((Sender as TRzGroupItem).Caption,0);
end;

根据上面,我们在全局单元文件中创建一个创建窗体对象的函数:Procedure CreateForm(TBTag:Integer;aCaption:String);
然后在CreateFormSelect中调用CreateForm,如下:
procedure TfrmMain.CreateFormSelect(Sender: TObject);
begin
   CreateForm(TRzGroupItem(Sender).tag,(Sender as TRzGroupItem).Caption);
end;
我们可以在过程CreateForm中对所创建的窗体不同而赋相应的对象,比如设置控件的显示,赋于不同的数据集对象等等

接下来,我们在数据窗体中放入两组ADOQuery和DataSource分别命名为:dsEmployeeqryEmployeedsDepartmentqryDepartment,然后设置dsEmployee的Dataset属性为qryEmployee,dsDepartment的Dataset属性为qryDepartment,再设置qryEmployeeqryDepartment的SQL属性分别为:
select * from Employee和select * from Department,当然需要在数据库分别创建表Employee和Department。
函数CreateForm根据传入的参数不同而创建不同类型的三种窗体:基本资料窗体,单据窗体和报表窗体,代码如下:
Procedure CreateForm(TBTag:Integer;aCaption:String);
begin
  case TBTag of
  100..199:
    begin
       CreateBasicForm(TBTag,aCaption);
    end;
  200..299:
    begin
      CreateBillForm(TBTag,aCaption);
    end;
  300..399:
    begin
      CreateReportForm(TBTag,aCaption);
    end;
  end;
end;

在此代码中我们发现调用了CreateBasicForm,而这个方法才是我们真正创建基本资料窗体的函数,现在来揭开她的神秘面纱,看她到底有什么魔力。
Procedure CreateBasicForm(TBTag:Integer;aCaption:String);
  var
  LableList,LableDetail:string;
  tempstr:string;
begin
  Case TBTag of
  100:
    begin
      LableList:='员工列表';
      LableDetail:='员工资料';
      frmDM.dsMaster:=frmDM.dsEmployee;
    end;
  101:
    begin
      LableList:='部门列表';
      LableDetail:='部门资料';
      frmDM.dsMaster:=frmDM.dsDepartment;
    end;
  end;
  LockWindowUpdate(frmMain.Handle);
  if Assigned(vBasicForm) then
  begin
    MsgBox('窗体创建错误!',MB_ICONINFORMATION);
    exit;
  end;
  if Not Assigned(vBasicForm) then
  begin
    vBasicForm:=TfrmBasic.Create(Application);
    vBasicForm.Caption:=aCaption;
    with vBasicForm do
    begin
      dbgrdhList.DataSource:=frmDM.dsMaster;
      dxdbinsEdit.DataSource:=frmDM.dsMaster;
    end;
    frmDM.dsMaster.DataSet.Active:=True;
    with vBasicForm.dbgrdhList do
    begin
      Columns.Clear;
      Columns.Add;
      Columns[0].Title.Caption:=copy(LableList,1,4)+'编码';
      Columns[0].Width:=100;
      Columns[0].FieldName:=frmDM.dsMaster.DataSet.Fields[1].FieldName;
      Columns.Add;
      Columns[1].Title.Caption:=copy(LableList,1,4)+'名称';
      Columns[1].Width:=160;
      Columns[1].FieldName:=frmDM.dsMaster.DataSet.Fields[2].FieldName;
    end;
    InitDataSetInspectorl(frmDM.dsMaster.DataSet.Tag);
    vBasicForm.Show;
  end
  else
    vBasicForm.show;
  LockWindowUpdate(0);
end;

从代码中可以看出,根据传入的参数,来对一些变量进行赋值,特别注意的一行代码是frmDM.dsMaster:=frmDM.dsEmployee;
此行代码是对数据组件窗体中的组件进行赋值,目的是为了在基窗体中引用的类TBaseClass中的数据操作保证是对相同的数据集操作。
回顾一下TBaseClass类中对数据的操作,都是对数据窗体中的dsMaster数据源进行操作的。因为我们在窗体时要将相应的数据源码赋值给数据窗体中的dsMaster数据源。继续看代码,可以知道已经将数据窗体中的dsMaster数据源赋值到创建窗体中的dbgrdhList和dxdbinsEdit控件,代码如下:dbgrdhList.DataSource:=frmDM.dsMaster;
dxdbinsEdit.DataSource:=frmDM.dsMaster;
接下来的代码是对两个数据显示控件进行初始化,而dxdbinsEdit则是通过方法InitDataSetInspectorl进行初始化,方法InitDataSetInspectorl的源码如下:
Procedure InitDataSetInspectorl(TableTag:Integer);
var
  i,j,TempWidth,MaxWidth:integer;
  StrTableID,StrList:String;
  TempQuery:TADOQuery;
  TableValue:Boolean;
  varRow:integer;
  vFL:integer;
  vFieldList:array [0..19] of String;
begin
  StrTableID:=GetFieldName(TableTag,2);
  StrTableID:='01';
  TempQuery:=TADOQuery.Create(Application);
  Try
    TempQuery.Connection:=frmDM.conDB;
    TempQuery.SQL.Clear;
    TempQuery.SQL.Text:=Format('Select * From DataDictContent where TableID=''%s'' order by TableID,FieldID',[StrTableID]);
    TempQuery.Open;
    i:=0;
    MaxWidth:=0;
    if vBasicForm.dxdbinsEdit.TotalRowCount>0 then
      vBasicForm.dxdbinsEdit.ClearRows;
    if Not TempQuery.IsEmpty then
    While Not TempQuery.Eof do
    begin
      if TempQuery.FieldByName('DisplayFlag').AsBoolean then
      with vBasicForm do
      with dxdbinsEdit do
      begin
        BeginUpdate;
        DefaultFields := False;
        case TempQuery.FieldByName('InspectorRowType').AsInteger of
        0:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBRow,TempQuery,0);  //TdxInspectorDBRow  类型引用单元文件dxDBInsp
        1:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBRow,TempQuery,1);
        2:
          CreateInspectRow(dxdbinsEdit,TdxInspectorComplexRow,TempQuery,2);  //TdxInspectorComplexRow    类型引用单元文件dxInspct
        3:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBMaskRow,TempQuery,3);
        4:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBDateRow,TempQuery,4);
        5:
          CreateInspectRow(dxdbinsEdit,TdxInspectorLookupRow,TempQuery,5);
        6:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBCheckRow,TempQuery,6);
        7:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBCalcRow,TempQuery,7);
        8:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBButtonRow,TempQuery,8);
        9:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBSpinRow,TempQuery,9);
        10:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBPickRow,TempQuery,10);  //TdxInspectorDBPickRow    类型引用单元文件dxDBInRw
        11:
          CreateInspectRow(dxdbinsEdit,TdxInspectorBlobRow,TempQuery,11);
        12:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBImageRow,TempQuery,12);
        13:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBTimeRow,TempQuery,13);
        14:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBCurrencyRow,TempQuery,14);
        15:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBHyperLinkRow,TempQuery,15);
        16:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBPopupRow,TempQuery,16);
        17:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBMRURow,TempQuery,17);
        18:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBMemoRow,TempQuery,18);
        19:
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBGraphicRow,TempQuery,19);
        else
          CreateInspectRow(dxdbinsEdit,TdxInspectorDBRow,TempQuery,1);
        end;
        EndUpdate;
      end;
      TempQuery.next;
    end;
  finally
    TempQuery.Free;
  end;
end;
上面方法又调用了CreateInspectRow方法,代码如下:
procedure CreateInspectRow(varDBInspector:TdxDBInspector;IR: TdxInspectorRowClass;
                    varADOQuery:TADOQuery;RowFlag:integer);
var
  RowButton:TdxEditButtonClass;   //TdxEditButtonClass类型所引用单元文件dxExEdtr
  varInt:integer;
  StrList:string;
  j:integer;
begin
  with varDBInspector do
    with TdxInspectorDBRow(CreateRow(IR)) do
    begin
      Caption:=varADOQuery.FieldByName('DisplayCaption').AsString;
      FieldName :=varADOQuery.FieldByName('FieldName').AsString;
      if varADOQuery.FieldByName('ReadOnlyFlag').AsBoolean then
        ReadOnly:=True;
      name:='ir'+FieldName;
      if RowFlag=8 then
      begin
         varInt:=varDBInspector.IndexOfRow(varDBInspector.RowByName(Name));
         (varDBInspector.Rows[varInt] as TdxInspectorDBButtonRow).OnButtonClick:=frmBasic.DBInspectorRowOnButtonClick;
      end;
      if FieldName='Password' then
        PasswordChar:='*';
      if RowFlag=10 then
      if varADOQuery.FieldByName('DictionaryFlag').AsBoolean then
        begin
          if varADOQuery.FieldByName('DictionaryType').AsBoolean then
          begin
            //Items[i].ButtonStyle:=ibsAuto;
            //Items[i].PickList.Clear;
            varInt:=varDBInspector.IndexOfRow(varDBInspector.RowByName(Name));
            StrList:=varADOQuery.FieldByName('DictionaryTypeID').AsString;
            j:=POS(';',StrList);
            while j<>0 do
            begin
              (varDBInspector.Rows[varInt] as TdxInspectorDBPickRow).Items.Add(Copy(StrList,1,j-1));
              //Items[i].PickList.Add(Copy(StrList,1,j-1));
              StrList:=Copy(StrList,j+1,Length(StrList)-j);
              j:=POS(';',StrList);
            end;
          end
          //else
          //Items[i].ButtonStyle:=ibsEllipsis;
        end;

    end;
end;
上面两个
过程代码较多,其实也很简单,只要对控件TdxDBInspector多了解一下就会明白。主要是动态创建数据字段。在此不再多做介绍。
上面代码中有这样两行代码: 
StrTableID:=GetFieldName(TableTag,2);
 StrTableID:='01';
显然有些问题,既然通过函数赋值,那为什么又对StrTableID赋值为'01'呢?
还有对数据显示控件TdxDBInspector进行初始化显示时用到的DataDictContent 表,等等问题,下次再做介绍

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