如何以动态单元格高度和自动布局以编程方式创建一个非常基本的UITableView？

因此，在浏览了许多示例之后，我终于明白了哪里出了问题。这是其中缺少一行将整个代码弄乱的那些事情之一。对我来说，

cell.bodyLabel.preferredMaxLayoutWidth = tableView.bounds.size.width;

我们需要在heightForRowAtIndexPath方法中添加它，否则会产生约束错误。

感谢这里对这个惊人答案的评论之一，我找到了解决方案。尽管在答案中给出的示例代码中，上面的代码行在cellForRowAtIndexPath函数中，而不是在heightForRowAtIndexPath函数中。但是我的代码无法那样运行。

因此，基本代码是

// RJCell.h

#import <UIKit/UIKit.h>

@interface RJTableViewCell : UITableViewCell

@property (strong, nonatomic) UILabel *titleLabel;
@property (strong, nonatomic) UILabel *bodyLabel;

@end

// RJCell.m

#import "RJTableViewCell.h"

@interface RJTableViewCell ()

@property (nonatomic, assign) BOOL didSetupConstraints;

@end

@implementation RJTableViewCell

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {
        // Initialization code

        self.titleLabel = [[UILabel alloc] init];
        [self.titleLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
        [self.titleLabel setLineBreakMode:NSLineBreakByTruncatingTail];
        [self.titleLabel setNumberOfLines:1];
        [self.titleLabel setTextAlignment:NSTextAlignmentLeft];
        [self.titleLabel setTextColor:[UIColor blackColor]];
        [self.titleLabel setBackgroundColor:[UIColor clearColor]];
        [self.contentView addSubview:self.titleLabel];

        // Add this label to the button
        self.bodyLabel = [[UILabel alloc] init];
        [self.bodyLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
        [self.bodyLabel setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
        [self.bodyLabel setLineBreakMode:NSLineBreakByTruncatingTail];
        [self.bodyLabel setNumberOfLines:0];
        [self.bodyLabel setTextAlignment:NSTextAlignmentLeft];
        [self.bodyLabel setTextColor:[UIColor darkGrayColor]];
        [self.bodyLabel setBackgroundColor:[UIColor clearColor]];
        [self.contentView addSubview:self.bodyLabel];
    }

    return self;
}

- (void)updateConstraints {
    [super updateConstraints];

    if (self.didSetupConstraints) return;

    // Get the views dictionary
    NSDictionary *viewsDictionary =
        @{
            @"titleLabel" : self.titleLabel,
            @"bodyLabel" : self.bodyLabel
        };

    NSString *format;
    NSArray *constraintsArray;

    //Create the constraints using the visual language format
    format = @"V:|-10-[titleLabel]-10-[bodyLabel]-10-|";
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:nil views:viewsDictionary];
    [self.contentView addConstraints:constraintsArray];

    format = @"|-10-[titleLabel]-10-|";
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:nil views:viewsDictionary];
    [self.contentView addConstraints:constraintsArray];

    format = @"|-10-[bodyLabel]-10-|";
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:nil views:viewsDictionary];
    [self.contentView addConstraints:constraintsArray];

    self.didSetupConstraints = YES;
}

@end

// RJTableViewController.h

#import <UIKit/UIKit.h>

@interface RJTableViewController : UITableViewController

@end

// RJTableViewController.m

#import "RJTableViewController.h"
#import "RJTableViewCell.h"

static NSString *CellIdentifier = @"CellIdentifier";

@interface RJTableViewController ()

@property(strong,nonatomic) NSMutableArray *titleArray;
@property(strong,nonatomic) NSMutableArray *bodyArray;

@end

@implementation RJTableViewController

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
        self.title = @"Table View Controller";
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self.tableView registerClass:[RJTableViewCell class] forCellReuseIdentifier:CellIdentifier];
    self.titleArray = [[UIFont familyNames] mutableCopy];
    for(int i = 0; i < 100; i++) {
        [self.titleArray addObjectsFromArray:[UIFont familyNames]];
    }
    self.bodyArray = [@[@"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",@"Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.",@"Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.",@"Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."] mutableCopy];
}

- (void)contentSizeCategoryChanged:(NSNotification *)notification
{
    [self.tableView reloadData];
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [self.titleArray count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    RJTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    int dataIndex = (int) indexPath.row % [self.bodyArray count];
    cell.titleLabel.text =  self.titleArray[indexPath.row];
    cell.bodyLabel.text = self.bodyArray[dataIndex];

    // Make sure the constraints have been added to this cell, since it may have just been created from scratch
    [cell setNeedsUpdateConstraints];

    return cell;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{

    RJTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    int dataIndex = (int) indexPath.row % [self.bodyArray count];
    cell.titleLabel.text =  self.titleArray[indexPath.row];
    cell.bodyLabel.text = self.bodyArray[dataIndex];

    cell.bodyLabel.preferredMaxLayoutWidth = tableView.bounds.size.width - (20.0 * 2.0f);

    [cell setNeedsUpdateConstraints];
    [cell updateConstraintsIfNeeded];
    [cell.contentView setNeedsLayout];

    [cell.contentView layoutIfNeeded];

    CGFloat height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

    return height;
}

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 200.0f;
}

@end

基本上，棘手的部分在两个地方，首先是设置约束。其次，实现heightForRowAtIndexPath和cellForRowAtIndexPath方法。