Delphi:如何捕捉TStreamWriter磁盘满错误？

Question

我想知道，为什么这段代码不能像它应该的那样捕获“磁盘已满”错误？

这一点很重要，因为如果用户没有注意到保存失败，他们可能会丢失数据。

我不明白这个..。

procedure TForm2.Button1Click(Sender: TObject);
var
  Writer: TStreamWriter;
  n : integer;
begin
Writer := TStreamWriter.Create('MyUTF8Text.txt', false, TEncoding.UTF8);
  Try //Finally
    Try //Except
      
      for n := 1 to 1000 do
      begin
        Writer.WriteLine('Testing text writing to the UTF-8 file.');
      end;
    Except
      on E: Exception do
      begin
        ShowMessage('Exception Class name: ' + E.ClassName);
        ShowMessage('Exception Message: ' + E.Message);
      end;
    end; // except
  Finally
    Writer.Free(); 
  End; //finally
end;

“顺便说一句，‘编写器可能没有被初始化’的警告，真的很严重吗？”

编辑:出现此警告是因为TStreamWriter.Create是在尝试之后。谢谢您的建议，我将这行代码更正为(！)试试看。

Answer 1

试试这个：

procedure WriteStream;
var
  Writer: TStreamWriter;
  fs: TFileStream;
  s: String;
  n, bytesWritten : integer;
begin
  bytesWritten := 0;
  fs := TFileStream.Create('MyUTF8Text.txt', fmCreate);
  try
    //avoid warning by initiaizing before try
    Writer := TStreamWriter.Create(fs);
    try //Finally
      try //Except
        for n := 1 to 10 do
        begin
          s := 'Testing text writing to the UTF-8 file.'  + '#13#10';
          //keep count of bytes written
          bytesWritten := bytesWritten + TEncoding.UTF8.GetByteCount(s);
          Writer.Write(s);
        end;
        Writer.Flush;
        Writer.Close;
        //Check stream size to make sure all bytes written
        if bytesWritten <> Writer.BaseStream.Size then
          raise Exception.Create(String.Format('Expected %d bytes, wrote %d', [Writer.BaseStream.Size, bytesWritten]));
      except
        on E: Exception do
        begin
          Showmessage('Exception Class name: ' + E.ClassName);
          Showmessage('Exception Message: ' + E.Message);
        end;
      end; // except
    finally
      Writer.Free; // Will only free if it has been constructed
    end; //finally
  finally
    fs.Free;
  end;
end;