ios - 如何正确重用 UITableView 中的单元格

Question

我是新手。我使用此代码创建 UITableViewCell 但当我重新加载表格时，按钮的图像并不总是正确的，尽管所有标签都工作正常。我不知道为什么。我该如何解决这个问题？

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [_tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];

        UILabel *FileNameLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 0, 100, 30)];
        FileNameLabel.tag = 1000;
        FileNameLabel.backgroundColor = [UIColor clearColor];
        FileNameLabel.font = [UIFont fontWithName:@"Helvetica" size:16];
        FileNameLabel.font = [UIFont boldSystemFontOfSize:16];
        FileNameLabel.textColor = [UIColor blackColor];
        [cell.contentView addSubview: FileNameLabel];
        [FileNameLabel release];


        UILabel *UploadTimeLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 20, 150, 25)];
        UploadTimeLabel.tag = 2000;
        UploadTimeLabel.backgroundColor = [UIColor clearColor];
        UploadTimeLabel.font = [UIFont fontWithName:@"Helvetica" size:12];
        UploadTimeLabel.textColor = [UIColor grayColor];
        [cell.contentView addSubview: UploadTimeLabel];
        [UploadTimeLabel release];


        UILabel *pricelabel = [[UILabel alloc] initWithFrame:CGRectMake(80, 0, 80, 30)];
        pricelabel.backgroundColor = [UIColor clearColor];
        pricelabel.font = [UIFont fontWithName:@"Helvetica" size:16];
        pricelabel.font = [UIFont boldSystemFontOfSize:16];
        pricelabel.textColor = [UIColor darkGrayColor];
        pricelabel.tag = 3000;
        //pricelabel.hidden = YES;
        pricelabel.textAlignment = NSTextAlignmentRight;
        [cell.contentView addSubview: pricelabel];
        [pricelabel release];


        market = [[UIButton alloc] init];;
        [market setFrame:CGRectMake(200, 6, 30, 30)];
         market.tag = 4000;

        [market addTarget:self action:@selector(marketPressedAction:) forControlEvents:UIControlEventTouchDown];


        [cell.contentView addSubview:market];
   }

    if( [temp count] > 0)
    {
        UILabel *fileNameLbl = (UILabel*)[cell.contentView viewWithTag:1000];
        fileNameLbl.text =[temp objectAtIndex:indexPath.row];

        UILabel *uploadlbl = (UILabel*)[cell.contentView viewWithTag:2000];
        uploadlbl.text =[UploadTimeAllArr objectAtIndex:indexPath.row];
    }

    UIButton *marketButton = (UIButton*)[cell.contentView viewWithTag:4000];
    [marketButton setTag:indexPath.row];
    if([sellingArray count]>0)
    {
        NSLog(@"sellingArray %@",sellingArray);
        if([[sellingArray objectAtIndex:indexPath.row] isEqualToString:@"0"]) // nothing
        {

            [marketButton setSelected:NO];
            [marketButton setImage:[UIImage imageNamed:@"Marketplace.png"] forState:UIControlStateNormal];
            marketButton.enabled = YES;

        }
        else if([[sellingArray objectAtIndex:indexPath.row] isEqualToString:@"2"])  // marketplace
        {

            [marketButton setSelected:YES];
            [marketButton setImage:[UIImage imageNamed:@"MarketplaceSelect.png"] forState:UIControlStateNormal];
            marketButton.enabled = YES;

        }
    }


    return cell;
}

Answer 1

这里的主要问题是，每次调用此方法时，您都会在单元格中重新创建新 View 。您希望在 if(cell == nil) 内创建所有可重用元素，否则会产生重复。任何动态的东西都必须在此之外创建。我拿了你的代码并修改了它。这应该效果更好。

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        // Everything that does not change should go in here!

        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
        UILabel *pricelabel = [[UILabel alloc] initWithFrame:CGRectMake(80, 0, 80, 30)];


        pricelabel.backgroundColor = [UIColor clearColor];
        pricelabel.font = [UIFont fontWithName:@"Helvetica" size:16];
        pricelabel.font = [UIFont boldSystemFontOfSize:16];
        pricelabel.textColor = [UIColor darkGrayColor];
        pricelabel.tag = 3000;
        //pricelabel.hidden = YES;
        pricelabel.textAlignment = NSTextAlignmentRight;
        [cell addSubview:pricelabel];

        UIButton *market = [UIButton buttonWithType:UIButtonTypeCustom];
        [market setFrame:CGRectMake(200, 6, 30, 30)];
        [market addTarget:self action:@selector(marketPressedAction:) forControlEvents:UIControlEventTouchDown];
        [cell addSubview:market];
    }

    // find market button, since we could be reusing a cell we cannot rely on a tag
    // value to find it. (This would only work with one button though).
    UIButton *market;
    for (UIView *subview in cell.subviews) {
    if ([subview isKindOfClass:[UIButton class]]) {
            market = (UIButton *)subview;
            break;
        }
    }

    // set all defaults in case of reuse
    [market setImage:[UIImage imageNamed:@"DefaultImage.png"] forState:UIControlStateNormal];
    market.selected = YES;
    market.enabled = NO;
    market.clearsContextBeforeDrawing = NO;

    if([sellingArray count] > 0) {
        NSLog(@"sellingArray %@",sellingArray);
        if([[sellingArray objectAtIndex:indexPath.row] isEqualToString:@"0"]) {
            // not sure if this is supposed to be YES or NO
            market.clearsContextBeforeDrawing = YES;
            [market setSelected:NO];
            [market setImage:[UIImage imageNamed:@"Marketplace.png"] forState:UIControlStateNormal];
            market.enabled = YES;
        }
    }
    [market setTag:indexPath.row];

    return cell;
}

由于您似乎没有使用 ARC，因此请确保查看此代码以获取任何所需的引用计数。