今天犯了一个很愚蠢的错误，喷血中...
开始的时候代码是这么写的，注意separateView、progressLabel和customProgressView的位置。

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
        static NSString * string = @"string";
        UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:string];
        if(cell == nil)
        {
            cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:string];
            cell.selectionStyle = UITableViewCellSelectionStyleNone;
            _MyTableView.separatorColor = UITableViewCellSeparatorStyleNone;
            
        }
            //separateView
            UIView * separateView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, SCREENWIDTH, 20)];
            separateView.backgroundColor = RGBACOLOR(247, 247, 247, 1);
            [cell.contentView addSubview:separateView];
            //progressLabel
            UILabel * progressLabel = [[UILabel alloc]initWithFrame:CGRectMake(15, 79, 39, 21)];
            progressLabel.text = @"进度";
            progressLabel.textAlignment = NSTextAlignmentLeft;
            progressLabel.font = [UIFont systemFontOfSize:15];
            progressLabel.textColor = LABELTEXTCOLOR;
            [cell.contentView addSubview:progressLabel];
            //customProgressView
            CustomProgressView * customProgressView = [[CustomProgressView alloc]init];
            customProgressView.frame = CGRectMake(70, 45, SCREENWIDTH - 90, 90);
            customProgressView.backgroundColor = [UIColor clearColor];
            [cell.contentView addSubview:customProgressView];
            _customProgressView = customProgressView;

        //任务已经完成
        if([_stateStr isEqualToString:@"show"])
        {
            _customProgressView.userInteractionEnabled = NO;
        }
        return cell;
}

我的customProgressView是一个自定义的带有滑块的的进度条，每次该cell滑出屏幕再滑进屏幕时，我的真机屏幕上就会多出一个customProgressView，画面彻底混乱了...

然后责怪单元格的复用机制没有起到作用...(汗啊...)

其实因为没有理解单元格的复用机制，代码放错了位置，正确的做法是把separateView、progressLabel和customProgressView的代码放在if(cell == nil){} 内。如下：

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
        static NSString * string = @"string";
        UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:string];
        if(cell == nil)
        {
            cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:string];
            cell.selectionStyle = UITableViewCellSelectionStyleNone;
            _MyTableView.separatorColor = UITableViewCellSeparatorStyleNone;
            //separateView
            UIView * separateView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, SCREENWIDTH, 20)];
            separateView.backgroundColor = RGBACOLOR(247, 247, 247, 1);
            [cell.contentView addSubview:separateView];
            //progressLabel
            UILabel * progressLabel = [[UILabel alloc]initWithFrame:CGRectMake(15, 79, 39, 21)];
            progressLabel.text = @"进度";
            progressLabel.textAlignment = NSTextAlignmentLeft;
            progressLabel.font = [UIFont systemFontOfSize:15];
            progressLabel.textColor = LABELTEXTCOLOR;
            [cell.contentView addSubview:progressLabel];
            //customProgressView
            CustomProgressView * customProgressView = [[CustomProgressView alloc]init];
            customProgressView.frame = CGRectMake(70, 45, SCREENWIDTH - 90, 90);
            customProgressView.backgroundColor = [UIColor clearColor];
            [cell.contentView addSubview:customProgressView];
            _customProgressView = customProgressView;
        }
        //任务已经完成
        if([_stateStr isEqualToString:@"show"])
        {
            _customProgressView.userInteractionEnabled = NO;
        }
        return cell;
}

出错的图片稍后补上...