0.添加个lab：
UILabel *lab = [[UILabel alloc] initWithFrame:CGRectMake(20, 100, 200, 20)];
lab.text = @"左间距，上间距有效，貌似右间距没用。原本以为和contentSize有关，调了也没用。这一点还不太清楚。PS：上间距会根据文字内容多少和UITextView的高度来判断是否取消。所以最好还是设contentInset的时候就把上间距搞掉。";
lab.numberOfLines = 0;
lab.backgroundColor = [UIColor greenColor];
lab.font = [UIFont systemFontOfSize:15];
lab.textColor = [UIColor blackColor];
[self.view addSubview:lab];
1.普通的lab，就是根据字体大小，计算高度
NSDictionary *dic = @{NSFontAttributeName : [UIFont systemFontOfSize:15]};//
CGSize size = [lab.text boundingRectWithSize:CGSizeMake(200, MAXFLOAT) options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:dic context:nil].size;
lab.frame = CGRectMake(20, 100, 200, size.height);
1.1.png
2.设置的lab需要设置行间距、字体、字体颜色啥的，就成富文本了。
NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
style.lineSpacing = 10;
NSDictionary *dic = @{NSFontAttributeName : [UIFont systemFontOfSize:15],
NSParagraphStyleAttributeName : style, //行间距
NSKernAttributeName : @5};//字间距
CGSize size = [lab.text boundingRectWithSize:CGSizeMake(200, MAXFLOAT) options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:dic context:nil].size;
NSMutableAttributedString *attS = [[NSMutableAttributedString alloc] initWithString:lab.text attributes:dic];
lab.attributedText = attS;
lab.frame = CGRectMake(20, 100, 200, size.height);
2.2.png
