通用查询组件设计(续二)

保存参数值

procedure TDBFilterDialog.SaveParamValues;

var

  i : Integer;

begin

//保存参数值

   for i := 0 to FOriginalVariables.Count - 1 do

     TDBVariable(FOriginalVariables[i]).VariableValue :=

        TQuery(FDataSet).ParamByName(TDBVariable(FOriginalVariables[i]).VariableName).Value;

end;

点击确定按钮

procedure TMyDBFilterDialog.btnOkClick(Sender: TObject);

var

  i : Integer;

  f : TMyFieldInfo;

begin

//点击确定按钮

  for i := FPreviousList.Count - 1 downto 0 do

  begin

    TMyFieldInfo(FPreviousList[i]).Free;

    FPreviousList.Delete(i);

  end;

  GetCriteria;//获取标准

  SetCriteria;//设置标准

  for i := 0 to FFilterList.Count - 1 do

  begin

    f := TMyFieldInfo.Create;//字段定义类

    f.Assign(TMyFieldInfo(FFilterList[i]));

    FPreviousList.Add(f);

  end;

end;

获取标准

procedure TMyDBFilterDialog.GetCriteria ;

//获取标准

var

  FilterIndex, i : Integer;

begin

  FilterIndex := -1;

  i := 0;

  while (i < FFilterList.Count) and (FilterIndex < 0) do

  begin

    if TMyFieldInfo(FFilterList[i]).DisplayLabel = lstAllFields.Items[LastIndex] then

      FilterIndex := i;

    Inc(i);

  end;

  // This is only enabled when at least one of the fields has entry

  if btnNewSearch.Enabled then

  begin

    // The user added a new criteria

    if FilterIndex < 0 then

    begin

      FFilterList.Add(TMyFieldInfo.Create);

      FilterIndex := FFilterList.Count - 1;

      lstSelectedFields.Items.AddObject(lstAllFields.Items[LastIndex],

        lstAllFields.Items.Objects[LastIndex]);

    end;

    // Set the fields

    with TMyFieldInfo(FFilterList[FilterIndex])  do

    begin

      CaseSensitive := cbxCaseSensitive.Checked;

      DisplayLabel := lstAllFields.Items[LastIndex];

      // Save off the TField for this field

      FieldName := TField(lstAllFields.Items.Objects[LastIndex]).FieldName;

      FieldOrigin := TField(lstAllFields.Items.Objects[LastIndex]).Origin;

      FieldType := TField(lstAllFields.Items.Objects[LastIndex]).DataType;

      // Match Criteria is either Range or one of the other 4

      if pgeCriteria.ActivePage = tabByRange then

        MatchType := fdMatchRange

      else

        MatchType := TDBFilterMatchType(grpSearchType.ItemIndex);

      // Only save the criteria that they want to work with

      if MatchType = fdMatchRange then

      begin

        EndingValue := edtEndingRange.Text;

        StartingValue := edtStartingRange.Text;

        FilterValue := '';

      end

      else

      begin

        EndingValue := '';

        StartingValue := '';

        FilterValue := edtFieldValue.Text;

      end;

      NonMatching := cbxNonMatching.Checked;

    end;

  end

  else

    // The user removed a criteria that existed

    if FilterIndex >= 0 then

    begin

      // remove the Selected list item

      lstSelectedFields.Items.Delete(lstSelectedFields.Items.IndexOf(

           TMyFieldInfo(FFilterList[FilterIndex]).DisplayLabel));

      // Free the FieldInfo Object

      TMyFieldInfo(FFilterList[FilterIndex]).Free;

      // Delete it from the list

      FFilterList.Delete(FilterIndex);

      if FFilterList.Count = 0 then

        btnViewSummary.Enabled := false;

    end;

end;

设置标准

procedure TMyDBFilterDialog.SetCriteria;

var

  FilterIndex, i : Integer;

  DisplayName : String;

begin

  DisplayName := lstAllFields.Items[lstAllFields.ItemIndex];

  i := 0;

  FilterIndex := -1;

  // Find the Item in the list if it exists

  while (i < FFilterList.Count) and (FilterIndex < 0) do

  begin

    if TMyFieldInfo(FFilterList[i]).DisplayLabel = DisplayName then

      FilterIndex := i;

    Inc(i);

  end;

  if FilterIndex < 0 then

    // This has no current criteria

    ClearCriteria

  else

  begin

    with TMyFieldInfo(FFilterList[FilterIndex])  do

    begin

      cbxCaseSensitive.Checked := CaseSensitive;

      edtEndingRange.Text := EndingValue;

      edtFieldValue.Text := FilterValue;

      if MatchType <> fdMatchRange then

        grpSearchType.ItemIndex := Integer(MatchType);

      cbxNonMatching.Checked := NonMatching;

      edtStartingRange.Text := StartingValue;

      if MatchType = fdMatchRange then

        pgeCriteria.ActivePage := tabByRange

      else

        pgeCriteria.ActivePage := tabByValue;

    end;

  end;

end;

重建SQL语句

procedure TDBFilterDialog.ReBuildSQL;

var

  s, s1 : String;

  SQL, NewSQL : TStringStream;

  p, i : Integer;

  hasWhere : boolean;

begin

//生成SQL语句

 if FDialog.lstSelectedFields.Items.Count = 0 then //如果没有已选字段，则

  begin

    if TStrings(GetOrdProp(FDataSet, SQLProp)) <> FOriginalSQL then

      RestoreSQL;

    exit;

  end;

  NewSQL := TStringStream.Create(s1);

  SQL := TStringStream.Create(s);

  try                              //保存到流

    FOriginalSQL.SaveToStream(SQL);

    SQL.Seek( 0, soFromBeginning);

    p := WordPos('WHERE', SQL.DataString);

    if p = 0 then  //如果SQL语句中没有WHERE子句

    begin

      hasWhere := false;

      p := WordPos('GROUP', SQL.DataString);

      if p = 0 then  //如果SQL语句中没有GROUP子句

        p := WordPos('HAVING', SQL.DataString);

        if p = 0 then  //如果SQL语句中没有HAVING子句

          P := WordPos('ORDER', SQL.DataString);

          if p = 0 then  //如果SQL语句中没有ORDER子句

            p := SQL.Size;

    end

    else

    begin //SQL语句中有WHERE子句

      hasWhere := true;

      Inc(p, 5);

    end;

    NewSQL.WriteString(SQL.ReadString(p - 1));

    if not hasWhere then  //如果SQL语句中没有WHERE子句

      NewSQL.WriteString(' WHERE ');

    for i := 0 to FDialog.FilterList.Count - 1 do

    begin

      NewSQL.WriteString(FDialog[i].CreateSQL);

      if i < FDialog.FilterList.Count - 1 then

        NewSQL.WriteString(' AND ')

      else

        if hasWhere then

          NewSQL.WriteString(' AND ');

    end;

    NewSQL.WriteString(SQL.ReadString(SQL.Size));

    // 在执行SQL时暂停有所的控件

     Application.MessageBox(PChar(NewSQL.DataString),'123',MB_OK);

      if FDataSet is TQuery then

        with FDataSet as TQuery do

        begin

          DisableControls;

          Close;

          SQL.Clear;

          SQL.Add(NewSQL.DataString);

          for i := 0 to FOriginalVariables.Count - 1 do

          begin

            ParamByName(TDBVariable(FOriginalVariables[i]).VariableName).Value :=

                  TDBVariable(FOriginalVariables[i]).VariableValue;

          end;

          // 设置新的变量

          for i := 0 to FDialog.FilterList.Count - 1 do

            FDialog[i].SetVariables(FDataSet);

          try

            Open;

          except

            RestoreSQL;  //如果出错，则恢复原来的SQL语句

          end;

        end;

    SetFields;

    FDataSet.EnableControls;

    FModifiedSQL.Assign(TStrings(GetOrdProp(FDataSet, SQLProp)));

  finally

    SQL.Free;

    NewSQL.Free;

  end;

end;