UITableView的tableHeaderView在使用约束写的时候最后需要计算高度，使用masonry时最后可以用
[_tableHeaderView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height
计算高度
demo如下：
- (UIView *)tableHeaderView{
if (!_tableHeaderView) {
_tableHeaderView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.width, 0)];
UILabel *titleLab = [[UILabel alloc] init];
titleLab.numberOfLines = 0;
titleLab.text = [NSString stringWithFormat:@"%@",_headerDataDic[@"title"]];
titleLab.font = [UIFont systemFontOfSize:18];
titleLab.textColor = [UIColor hexStringToColor:@"#333333"];
[_tableHeaderView addSubview:titleLab];
UILabel *timeLab = [[UILabel alloc] init];
timeLab.font = [UIFont systemFontOfSize:12];
timeLab.textColor = [UIColor hexStringToColor:@"#999999"];
timeLab.text = [NSString stringWithFormat:@"%@",_headerDataDic[@"online_time"]];
[_tableHeaderView addSubview:timeLab];
UILabel *editorLab = [[UILabel alloc] init];
editorLab.textColor = timeLab.textColor;
editorLab.font = timeLab.font;
editorLab.text = [NSString stringWithFormat:@"%@",_headerDataDic[@"art_author"]];
[_tableHeaderView addSubview:editorLab];
UILabel *clickCountLab = [[UILabel alloc] init];
clickCountLab.font = timeLab.font;
clickCountLab.textColor = timeLab.textColor;
clickCountLab.text = [NSString stringWithFormat:@"%@",_headerDataDic[@"art_click"]];
[_tableHeaderView addSubview:clickCountLab];
UIImageView *clickImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"discover_see"]];
[_tableHeaderView addSubview:clickImageView];
UILabel *thumbUpLab = [[UILabel alloc] init];
thumbUpLab.textColor = timeLab.textColor;
thumbUpLab.font = timeLab.font;
thumbUpLab.text = [NSString stringWithFormat:@"%@",_headerDataDic[@"laud_count"]];
[_tableHeaderView addSubview:thumbUpLab];
_thumbUpCountLab = thumbUpLab;
UIButton *thumbUpBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[thumbUpBtn setImage:[UIImage imageNamed:@"discover_thumbUp"] forState:UIControlStateNormal];
thumbUpBtn.userInteractionEnabled = NO;
[_tableHeaderView addSubview:thumbUpBtn];
UILabel *detailLab = [[UILabel alloc] init];
detailLab.numberOfLines = 0;
[_tableHeaderView addSubview:detailLab];
NSString *detailTextString = [NSString stringWithFormat:@"%@",_headerDataDic[@"art_content"]];
NSString *str = [NSString stringWithFormat:@"<head><style>img{width:%f !important;height:auto}</style></head>%@",self.view.width,detailTextString];
NSMutableAttributedString *attributeString = [[NSMutableAttributedString alloc] initWithData:[str dataUsingEncoding:NSUnicodeStringEncoding] options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType} documentAttributes:nil error:nil];
detailLab.attributedText = attributeString;
UIView *seperatorView = [[UIView alloc] init];
seperatorView.backgroundColor = [UIColor hexStringToColor:@"#f1f2f6"];
[_tableHeaderView addSubview:seperatorView];
UILabel *commentLab = [[UILabel alloc] init];
commentLab.textColor = [UIColor hexStringToColor:@"#333333"];
commentLab.font = [UIFont systemFontOfSize:15];
commentLab.text = @"评论";
[_tableHeaderView addSubview:commentLab];
UILabel *commentCountLab = [[UILabel alloc] init];
commentCountLab.textColor = [UIColor hexStringToColor:@"#999999"];
commentCountLab.text = [NSString stringWithFormat:@"%@条",[NSString stringWithFormat:@"%@",_headerDataDic[@"comm_count"]]];
commentCountLab.font = [UIFont systemFontOfSize:12];
[_tableHeaderView addSubview:commentCountLab];
UIView *bottomSeperatorView = [[UIView alloc] init];
bottomSeperatorView.backgroundColor = [UIColor hexStringToColor:@"#e2e2e2"];
[_tableHeaderView addSubview:bottomSeperatorView];
[titleLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(_tableHeaderView.mas_top).offset(24);
make.left.equalTo(_tableHeaderView.mas_left).offset(15);
make.right.equalTo(_tableHeaderView.mas_right).offset(-15);
}];
[timeLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(titleLab.mas_bottom).offset(15);
make.left.equalTo(titleLab.mas_left);
}];
[clickCountLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(timeLab.mas_centerY);
make.right.equalTo(titleLab.mas_right);
}];
[clickImageView mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(clickCountLab.mas_centerY);
make.right.equalTo(clickCountLab.mas_left).offset(-5);
make.width.height.mas_equalTo(17);
}];
[thumbUpLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(clickCountLab.mas_centerY);
make.right.equalTo(clickImageView.mas_left).offset(-20);
}];
[thumbUpBtn mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(thumbUpLab.mas_centerY);
make.right.equalTo(thumbUpLab.mas_left);
make.width.mas_equalTo(29);
make.height.mas_equalTo(34);
}];
[editorLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(timeLab.mas_centerY);
make.left.equalTo(timeLab.mas_right).offset(20);
}];
[detailLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.right.equalTo(titleLab);
make.top.equalTo(timeLab.mas_bottom).offset(24);
}];
titleLab.preferredMaxLayoutWidth = [UIScreen mainScreen].bounds.size.width - 30;
detailLab.preferredMaxLayoutWidth = [UIScreen mainScreen].bounds.size.width - 30;
[seperatorView mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.right.equalTo(_tableHeaderView);
make.top.equalTo(detailLab.mas_bottom).offset(35);
make.height.mas_equalTo(8);
}];
[commentLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(seperatorView.mas_bottom);
make.left.equalTo(titleLab.mas_left);
make.height.mas_equalTo(44);
}];
[commentCountLab mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.bottom.equalTo(commentLab);
make.left.equalTo(commentLab.mas_right).offset(10);
}];
[bottomSeperatorView mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.right.equalTo(_tableHeaderView);
make.top.equalTo(commentLab.mas_bottom);
make.height.mas_equalTo(1);
make.bottom.equalTo(_tableHeaderView.mas_bottom);
}];
CGFloat height = [_tableHeaderView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
_tableHeaderView.height = height;
}
return _tableHeaderView;
}
注意点：在有label的情况下需要确定label的最大宽度，如下所示：
titleLab.preferredMaxLayoutWidth = [UIScreen mainScreen].bounds.size.width - 30;
detailLab.preferredMaxLayoutWidth = [UIScreen mainScreen].bounds.size.width - 30;
