关于UILabel产生黑边的原因及去除方法

原因：因为label自适应宽度得出来的labelsize.width是小数，才会有黑边

去除方法: 将labelsize.width转换成整数，如下：

CGSize size = CGSizeMake(SCREEN_WIDTH,timeLabelHeight);

CGSize labelsize = [_message[@"time"] sizeWithFont:[UIFont fontWithName:@"STHeitiSC-Light" size:timeLabelFontSize]constrainedToSize:size lineBreakMode:UILineBreakModeWordWrap];

_timeLabel.frame = CGRectMake((SCREEN_WIDTH-labelsize.width-10)/2, 10, (int)labelsize.width+10, timeLabelHeight);

_timeLabel.text = _message[@"time"];