Question

我使用以下代码在我的UIScrollView后代中生成“固定”行标题。它适用于模拟器，但不幸的是，它在iPad上闪烁。（在行标题视图的左侧，出现白色1px行并消失。）可以改进哪些内容？

- (void)initSubviews
{
    const int ROW_COUNT = 20;
    rowHeaderViews = [[NSMutableArray alloc]initWithCapacity:ROW_COUNT];
    rowViews = [[NSMutableArray alloc]initWithCapacity:ROW_COUNT];

    [self setContentSize:CGSizeMake(2000, [self frame].size.height)];

    for (int i = 0; i < ROW_COUNT; i++)
    {
        UIView *header = [self createRowHeaderViewForRowNum:i];
        [rowHeaderViews addObject:header];

        UIView *row = [self createRowViewForRowNum:i];
        [rowViews addObject:row];

        [self addSubview:row];
        [self addSubview:header];
    }
    [self layoutSubviews];
}

- (void)layoutSubviews
{
    int x = [self contentOffset].x;
    for (UIView *view in rowHeaderViews) {
        [view setFrame:CGRectMake(x, view.frame.origin.y, view.frame.size.width, view.frame.size.height)];
    }
}

- (UIView *)createRowHeaderViewForRowNum: (int)rowNum
{
    UILabel *view = [[UILabel alloc]initWithFrame:CGRectMake(0, rowNum * 20, 200, 20)];
    [view setBackgroundColor:[UIColor colorWithWhite:0.8*(20-rowNum)/20 alpha:1]];
    [view setText:[NSString stringWithFormat:@"Row Header %d", rowNum]];
    return view;
}

- (UIView *)createRowViewForRowNum: (int)rowNum
{
    UILabel *view = [[UILabel alloc]initWithFrame:CGRectMake(200, rowNum * 20, 1800, 20)];
    [view setBackgroundColor:[UIColor colorWithRed:rowNum/20.0 green:0 blue:0 alpha:1]];
    [view setText:[NSString stringWithFormat:@"Row Content %d", rowNum]];
    return view;
}

非常感谢您的帮助！

编辑：iPad上有Retina显示屏。将模拟器与“普通”iPad一起使用时，它不会闪烁。将模拟器切换到“Retina显示器”iPad时，也会出现这种情况。也许这是关于点/像素差异的东西？

Answer 1

我自己发现了这个错误。对不起，打扰你。如果其他人遇到同样的问题： contentOffset.x是一个浮点值，包含Retina显示的.5值。将它分配给layoutSubviews中的int变量会导致问题。这是修复（注意我用'CGFloat'替换'int'）：

- (void)layoutSubviews
{
    CGFloat x = [self contentOffset].x;
    for (UIView *view in rowHeaderViews) {
        [view setFrame:CGRectMake(x, view.frame.origin.y, view.frame.size.width, view.frame.size.height)];
    }
}

UIScrollView使用固定子视图闪烁

1 个答案: