白色屏幕然后滚动uitableview

Question

我正在使用带有原型单元的故事板：

之后我添加了子视图的动态计数：

white screen

uitableviewcell in app

问题有时白色屏幕出现在uitableviewcell的一半然后滚动。

并且单元格== nil未调用。

或者只是解释如何将子视图的动态计数添加到uitableviewcell。

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

    cellIdentifer = @"PhotoWorkCell";


    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifer];

    if (cell == nil){
        NSLog(@"is nil");
    }
    [self addSubviews:cell atIndexPath:indexPath];
    [self configureCell:cell atIndexPath:indexPath];//just setting images and text to views

    return cell;
}

-(void)addSubviews:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath{
    PhotoWork *work = [self.tableData objectAtIndex:indexPath.row];

    PhotoWorkCell *workCell = (PhotoWorkCell*)cell;

    for(UIView *view in workCell.contentView.subviews){
        if ([view isKindOfClass:[CustomPoints class]])
            [view removeFromSuperview];
    }

    for(int i=0; i <[work.pointsArray count];i++)
    {
        NSArray *subviewArray = [[NSBundle mainBundle] loadNibNamed:@"CustomPoints" owner:self options:nil];
        CustomPoints *customPoints = [subviewArray objectAtIndex:0];
        customPoints.frame = CGRectMake(10, 135+i*customPoints.frame.size.height, customPoints.frame.size.width, customPoints.frame.size.height);

        customPoints.label= @"test";

        workCell.photoButton.tag = indexPath.row;
        [workCell.photoButton addTarget:self action:@selector(onHistory:) forControlEvents:UIControlEventTouchDown];

        [workCell.contentView addSubview:customPoints];
    }
}

- (CGFloat)tableView:(UITableView *)t heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    PhotoWork *work = [self.tableData objectAtIndex:indexPath.row];
    return 135+[work.pointsArray count]*57;
}

Answer 1

来自Apple的dequeueReusableCellWithIdentifier:方法文档：

This method dequeues an existing cell if one is available or creates a new one using the class or nib file you previously registered. If no cell is available for reuse and you did not register a class or nib file, this method returns nil.

这意味着，如果存在具有该标识符的单元格，该方法将永远不会返回nil，而是通过初始化方法initWithStyle:reuseIdentifier:为您初始化单元格。

然后从UITableViewCell的方法prepareForReuse的文档：

The table view's delegate in tableView:cellForRowAtIndexPath: should always reset all content when reusing a cell.

这意味着您应该在addSubviews:atIndexPath:方法中添加新的子视图之前删除它可能具有的其他子视图。

你可以这样做：

NSMutableArray* tmpArray = [NSMutableArray arrayWithArray:workCell.contentView.subviews];

然后，假设您添加到contentView的唯一额外子视图是此CustomPoints，只需执行：

[tmpArray removeObject:tmpArray.lastObject];
workCell.contentView.subviews = tmpArray;

相反，如果您想要安全，请执行以下操作：

__block NSInteger foundIndex = NSNotFound;
[tmpArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    if ([obj isKindOfClass:[CustomPoints class]]) {
        foundIndex = idx;
        // stop the enumeration
        *stop = YES;
    }
}];
if (foundIndex != NSNotFound){ 
    [tmpArray removeObjectAtIndex:foundIndex];
    workCell.contentView.subviews = tmpArray;
}

请告诉我这是否对您有用！