线程中使用ADOQuery的问题。

Question

unit UClearthread;interfaceuses
  Windows, Messages,Classes, DB,Forms, ADODB,SysUtils;type
  ClearThread = class(TThread)
  private
    { Private declarations }
  protected
    procedure Execute; override;
  end;implementation
uses
   Umain,UInfo;
procedure ClearThread.Execute;
var
   SqlStr,sDate,str:String;
   qryClear:TADOQuery;
begin
    qryClear.Create(nil);       //运行至此就报错，为什么？try
....
   SqlStr:="";....
   if qryClear.Active then
      qryClear.Close;
   qryClear.ConnectionString:=frmMain.ConnStr;
   qryClear.SQL.Clear;
   qryClear.SQL.Add(SqlStr);
      try
       qryClear.Open;
     except
       qryClear.Close;
       Application.MessageBox('打开数据库错误!','错误信息',MB_OK + MB_ICONSTOP);
       Application.Terminate;
     end;
  end;
finally
  qryClear.Free;
end; end;end.

Answer 1

qryClear := TADOQuery.Create(nil);

Answer 2

应该改为：  qryClear:=TADOQuery.Create(nil);
  try
     some stament
  finally
    qryClear.Free;
  end;

Answer 3

还是不行,提示"尚未调用Coinitialize"

Answer 4

// 在 uses 中加入 ActiveX 单元, 下面代码以供参考.
unit UClearthread;interfaceuses
  Windows, Messages,Classes, DB, Forms, ADODB,SysUtils;type
  ClearThread = class(TThread)
  private
    { Private declarations }
    FConnStr: String;
    FSuccess: Boolean;
  protected
    procedure Execute; override;
  public
    constructor Create(AConnStr: String);    // 是否运行成功
    property IsSuccess: Boolean read FSuccess;
  end;implementationuses
   UInfo, ActiveX;
constructor ClearThread.Create(AConnStr: String);
begin
   FConnStr := AConnStr;
   FSuccess := False;   inherited Create(False);
end;
procedure ClearThread.Execute;
var
   SqlStr,sDate,str:String;
   qryClear:TADOQuery;
begin
   // ADO 的初始化
   CoInitialize(nil);
   try
      qryClear := TADOQuery.Create(nil);
      try
         // ... ...
         SqlStr:="";
         // ... ...         qryClear.Close;
         qryClear.ConnectionString := FConnStr;
         qryClear.SQL.Clear;
         qryClear.SQL.Add(SqlStr);
         qryClear.Open;
         FSuccess := True;
      finally
         qryClear.Close;
         qryClear.Free;
      end;
   except
   end;   // ADO 的释放
   CoUninitialize;
end;end.

Answer 5

unit UClearthread;interfaceuses
  Windows, Messages,Classes, DB,Forms, ADODB,SysUtils;type
  ClearThread = class(TThread)
  private
    { Private declarations }
  protected
    procedure OneProgress;
    procedure Execute; override;
  end;implementation
uses
   Umain,UInfo;
procedure ClearThread.Execute;
begin
  Synchronize(OneProgress);
end;procedure OneProgress;
var
   SqlStr,sDate,str:String;
   qryClear:TADOQuery;
begin
    qryClear.Create(nil);   try
....
   SqlStr:="";....
   if qryClear.Active then
      qryClear.Close;
   qryClear.ConnectionString:=frmMain.ConnStr;
   qryClear.SQL.Clear;
   qryClear.SQL.Add(SqlStr);
      try
       qryClear.Open;
     except
       qryClear.Close;
       Application.MessageBox('打开数据库错误!','错误信息',MB_OK + MB_ICONSTOP);
       Application.Terminate;
     end;
end;finally
  qryClear.Free;
end; end;end.

Answer 6

因為在 Execute 中不能用其它窗體上的控件或自定控件義隻能用一些函數，所以要自定一個函數在用 Synchronize 調用即可。