修复DBGrideh使用TMemTableEh在Footers求平均值为0的Bug

在一个项目中，使用DBGrideh，当使用自带的内存数据集时，对于Footers添加的求平均值，一直显示为0，其他汇总数据都是可以的，而切换使用TClientDataSet或者TADODataSet，所有汇总数据包括平均值都有值。

打开相关部分源码查看了下，发现DBGrideh自带的内存数据集关于汇总平均数这块，竟然没有处理……，什么情况？

原始相关函数：

procedure TCustomMemTableEh.GetAggregatedValuesForRange(FromBM, ToBM: TUniBookmarkEh;  FieldName: String; var ResultArr: TAggrResultArr; AggrFuncs: TAggrFunctionsEh);var  FromRN, ToRN: Integer;  i: Integer;  v: Variant;  VarTypeNum: Integer;  FieldIndex: Integer;begin  ResultArr[agfSumEh] := Null;  ResultArr[agfCountEh] := 0;  ResultArr[agfAvg] := Null;  ResultArr[agfMin] := Null;  ResultArr[agfMax] := Null;  if not Active then Exit;  if FromBM <> NilBookmarkEh then    if UniBookmarkValid(FromBM)      then FromRN := UniBookmarkToRecNo(FromBM)      else Exit  else    FromRN := 1;  if ToBM <> NilBookmarkEh then    if UniBookmarkValid(ToBM)      then ToRN := UniBookmarkToRecNo(ToBM)      else Exit  else    ToRN := RecordCount;  if (FieldName = '') and (AggrFuncs = [agfCountEh]) then  begin    for i := FromRN-1 to ToRN-1 do      ResultArr[agfCountEh] := ResultArr[agfCountEh] + 1;    Exit;    end;  if FRecordsView.MemTableData.DataStruct.FindField(FieldName) = nil then    Exit;  VarTypeNum := FRecordsView.MemTableData.DataStruct.FieldByName(FieldName).GetVarDataType;  FieldIndex := FRecordsView.MemTableData.DataStruct.FieldIndex(FieldName);  for i := FromRN-1 to ToRN-1 do  begin    v := FRecordsView.RecordView[i].Rec.Value[FieldIndex, dvvValueEh];    if not VarIsNullEh(v) then    begin      if (agfCountEh in AggrFuncs) or (agfAvg in AggrFuncs) then        ResultArr[agfCountEh] := ResultArr[agfCountEh] + 1;<span style="white-space:pre"></span>//当设置求平均值时，此处仅仅做了一次记数累计      if (VarTypeNum in [varSmallint, varInteger, varSingle, varDouble, varCurrency,{$IFDEF EH_LIB_6}         varShortInt, varWord, varInt64, varLongWord,{$ENDIF}         varByte, varDate]) or (VarTypeNum = varFMTBcd) then      begin        if (agfSumEh in AggrFuncs) and (VarTypeNum <> varDate) then          if VarIsNullEh(ResultArr[agfSumEh])            then ResultArr[agfSumEh] := v            else ResultArr[agfSumEh] := ResultArr[agfSumEh] + v;        if agfMin in AggrFuncs then        if VarIsNullEh(ResultArr[agfMin]) then            ResultArr[agfMin] := v          else if ResultArr[agfMin] > v then            ResultArr[agfMin] := v;        if agfMax in AggrFuncs then          if VarIsNullEh(ResultArr[agfMax]) then            ResultArr[agfMax] := v          else if ResultArr[agfMax] < v then            ResultArr[agfMax] := v;      end    end;  end;  if <span style="color:#ff0000;">agfMax</span> in AggrFuncs then<span style="white-space:pre"></span>//求平均值，此处的触发条件竟然是 agfMax ....    if not VarIsNullEh(ResultArr[agfSumEh]) then      ResultArr[agfAvg] := <span style="color:#ff0000;">ResultArr[agfSumEh]</span> / ResultArr[agfCountEh];  //此处因为没有在agfAvg时对agfSumEh 求和汇总，该值应为0;end;

修改方法：

1、打开MemTableEh.pas

2、找到GetAggregatedValuesForRange函数，修改成如下：

procedure TCustomMemTableEh.GetAggregatedValuesForRange(FromBM, ToBM: TUniBookmarkEh;  FieldName: String; var ResultArr: TAggrResultArr; AggrFuncs: TAggrFunctionsEh);var  FromRN, ToRN: Integer;  i: Integer;  v: Variant;  VarTypeNum: Integer;  FieldIndex: Integer;begin  ResultArr[agfSumEh] := Null;  ResultArr[agfCountEh] := 0;  ResultArr[agfAvg] := Null;  ResultArr[agfMin] := Null;  ResultArr[agfMax] := Null;  if not Active then Exit;  if FromBM <> NilBookmarkEh then    if UniBookmarkValid(FromBM)      then FromRN := UniBookmarkToRecNo(FromBM)      else Exit  else    FromRN := 1;  if ToBM <> NilBookmarkEh then    if UniBookmarkValid(ToBM)      then ToRN := UniBookmarkToRecNo(ToBM)      else Exit  else    ToRN := RecordCount;  if (FieldName = '') and (AggrFuncs = [agfCountEh]) then  begin    for i := FromRN-1 to ToRN-1 do      ResultArr[agfCountEh] := ResultArr[agfCountEh] + 1;    Exit;    end;  if FRecordsView.MemTableData.DataStruct.FindField(FieldName) = nil then    Exit;  VarTypeNum := FRecordsView.MemTableData.DataStruct.FieldByName(FieldName).GetVarDataType;  FieldIndex := FRecordsView.MemTableData.DataStruct.FieldIndex(FieldName);  for i := FromRN-1 to ToRN-1 do  begin    v := FRecordsView.RecordView[i].Rec.Value[FieldIndex, dvvValueEh];    if not VarIsNullEh(v) then    begin      if (agfCountEh in AggrFuncs) or (agfAvg in AggrFuncs) then        ResultArr[agfCountEh] := ResultArr[agfCountEh] + 1;      if (VarTypeNum in [varSmallint, varInteger, varSingle, varDouble, varCurrency,{$IFDEF EH_LIB_6}         varShortInt, varWord, varInt64, varLongWord,{$ENDIF}         varByte, varDate]) or (VarTypeNum = varFMTBcd) then      begin        if <span style="color:#009900;">((agfSumEh in AggrFuncs) or (agfAvg in AggrFuncs))</span> and (VarTypeNum <> varDate) then  <span style="color:#3333ff;">//此处修改</span>          if VarIsNullEh(ResultArr[agfSumEh])            then ResultArr[agfSumEh] := v            else ResultArr[agfSumEh] := ResultArr[agfSumEh] + v;        if agfMin in AggrFuncs then<span style="white-space:pre"></span>        if VarIsNullEh(ResultArr[agfMin]) then            ResultArr[agfMin] := v          else if ResultArr[agfMin] > v then            ResultArr[agfMin] := v;        if agfMax in AggrFuncs then          if VarIsNullEh(ResultArr[agfMax]) then            ResultArr[agfMax] := v          else if ResultArr[agfMax] < v then            ResultArr[agfMax] := v;      end    end;  end;  if <span style="color:#009900;">agfAvg </span>in AggrFuncs then    <span style="color:#3333ff;">//此处修改</span>    if not VarIsNullEh(ResultArr[agfSumEh]) then      ResultArr[agfAvg] := ResultArr[agfSumEh] / ResultArr[agfCountEh];end;