layoutIfNeeded 就这样把我害惨

在我的项目里面,我自定义了一个cell,然后用masonry进行约束,tableview的cell自适应label的高度

cell里面:

#import "MedicalRecordCell.h"
@interface MedicalRecordCell ()

@property (weak, nonatomic) UILabel *fieldnameLabel;
@property (weak, nonatomic) UILabel *uomLabel;
@property (weak, nonatomic) UILabel *valueLabel;
@property (weak, nonatomic) UIView *lineView;
@end

static CGFloat const margin = 10;
@implementation MedicalRecordCell

- (instancetype)initWithReuseIdentifier:(NSString *)reuseIdentifier
{
    if (self = [super initWithStyle:UITableViewCellStyleDefault reuseIdentifier:reuseIdentifier]) {
        
        UILabel *fieldnameLabel = [UILabel label];
        fieldnameLabel.textColor = [UIColor darkGrayColor];
        fieldnameLabel.font = [UIFont boldSystemFontOfSize:17];
        fieldnameLabel.textAlignment = NSTextAlignmentLeft;
        fieldnameLabel.backgroundColor = RANDOMCOLOR(0.6);
        [self.contentView addSubview:fieldnameLabel];
        self.fieldnameLabel = fieldnameLabel;
        
        UILabel *uonLabel = [UILabel label];
        [self.contentView addSubview:uonLabel];
        self.uomLabel = uonLabel;
        
        UILabel *valueLabel = [UILabel label];
        valueLabel.backgroundColor = RANDOMCOLOR(0.6);
        valueLabel.textAlignment = NSTextAlignmentRight;
        valueLabel.numberOfLines = 0;
        valueLabel.font = [UIFont systemFontOfSize:15];
        [self.contentView addSubview:valueLabel];
        self.valueLabel = valueLabel;
        
        UIView *lineView = [UIView new];
        lineView.backgroundColor = CELLLINE_COLOR;
        [self.contentView addSubview:lineView];
        self.lineView = lineView;
        
        [self setViewAutoLayout];
    }
    
    return self;
    
}

- (void)setViewAutoLayout
{
    [self.fieldnameLabel mas_makeConstraints:^(MASConstraintMaker *make) {
        
        make.left.mas_equalTo(self.contentView).offset(margin);
        make.top.mas_equalTo(self.contentView).offset(margin);
        
    }];
    [self.valueLabel mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.mas_equalTo(self.fieldnameLabel.mas_right).offset(margin);
        make.right.mas_equalTo(self.uomLabel.mas_left).offset(-margin);
        make.top.mas_equalTo(self.contentView).offset(margin);
        make.bottom.mas_equalTo(self.contentView).offset(-margin);
    }];
    [self.uomLabel mas_makeConstraints:^(MASConstraintMaker *make) {
        make.right.equalTo(self.contentView).offset(-margin);
        make.width.offset(40);
        make.height.offset(40);
        make.centerY.equalTo(self.contentView);
    }];
    [self.lineView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.right.bottom.equalTo(self.contentView);
        make.height.offset(1);
    }];
}
- (void)setMedicalrecordSectionModel:(MedicalrecordSectionModel *)medicalrecordSectionModel
{
    _medicalrecordSectionModel = medicalrecordSectionModel;
    
    self.fieldnameLabel.text = [NSString stringWithFormat:@"%@ :",medicalrecordSectionModel.fieldname];
    self.uomLabel.text = medicalrecordSectionModel.uom;
    self.valueLabel.text = medicalrecordSectionModel.value;
    if ([medicalrecordSectionModel.metatype isEqualToString:@"radio"]) {
        NSArray *options = [medicalrecordSectionModel.metatextassemble componentsSeparatedByString:@"|"];
        NSInteger value = [medicalrecordSectionModel.value integerValue];
        if(value) self.valueLabel.text = options[value - 1];
    }
    
}

@end

控制器设置tableview自适应

 self.tableView.rowHeight = UITableViewAutomaticDimension;
 self.tableView.estimatedRowHeight = 44;

然而,不管是上面那样把约束写在初始化话方法里,还是我原先的把约束写在layoutSubviews里,都不能让内容正常的显示

你看看,你看看,真是可怜,tableview来回滚动的时候还偶尔会显示正常,反正就是看他心情来显示...

后来我解决的办法就是cell里面用模型赋值之后调用了一下layoutIfNeeded  没想到竟然就解决了这个问题

别人是这么说滴:

-layoutIfNeeded方法：如果，有需要刷新的标记，立即调用layoutSubviews进行布局（如果没有标记，不会调用layoutSubviews）
如果要立即刷新，要先调用[view setNeedsLayout]，把标记设为需要布局，然后马上调用[view layoutIfNeeded]，实现布局
在视图第一次显示之前，标记总是“需要刷新”的，可以直接调用[view layoutIfNeeded]

- (void)setMedicalrecordSectionModel:(MedicalrecordSectionModel *)medicalrecordSectionModel
{
    _medicalrecordSectionModel = medicalrecordSectionModel;
    
    self.fieldnameLabel.text = [NSString stringWithFormat:@"%@ :",medicalrecordSectionModel.fieldname];
    self.uomLabel.text = medicalrecordSectionModel.uom;
    self.valueLabel.text = medicalrecordSectionModel.value;
    if ([medicalrecordSectionModel.metatype isEqualToString:@"radio"]) {
        NSArray *options = [medicalrecordSectionModel.metatextassemble componentsSeparatedByString:@"|"];
        NSInteger value = [medicalrecordSectionModel.value integerValue];
        if(value) self.valueLabel.text = options[value - 1];
    }
    [self layoutIfNeeded];
    
}

这样基本是可以正常显示了,但是cell的高度一直是以 valueLabel 底部约束. 那么,有个问题就出现了 ,如果 模型value没有值就会导致label没有高度,回事cell成一坨坨的哦,所以这里要给label一个默认值,让其有高度就可以了