如何使用动态单元格高度和自动布局以编程方式创建非常基本的UITableView？

Question

请注意:我知道在类似的行上有很多例子.我正在寻找最基本的解决方案,只需要最少的设置.

我试图自己创造一个,我知道我离开了..

    #import "ViewController.h"

    @interface ViewController () <UITableViewDataSource, UITableViewDelegate>

    @property(strong, nonatomic) UITableView *tableView;
    @property(strong, nonatomic) NSMutableArray *dataArray;
    @property (strong, nonatomic) UITableViewCell *customCell;

    @end

    @implementation ViewController

    - (void)viewDidLoad {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.
        self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) style:UITableViewStylePlain];
        [self.tableView setDataSource:self];
        [self.tableView setDelegate:self];
        [self.tableView setShowsVerticalScrollIndicator:NO];
        self.tableView.translatesAutoresizingMaskIntoConstraints = NO;
        self.tableView.rowHeight = UITableViewAutomaticDimension;
        [self.view addSubview:self.tableView];

        self.dataArray = [@[@"For the past 33 years, I have looked in the mirror every morning and asked myself: 'If today were the last day of my life, would I want to do what I am about to do today?' And whenever the answer has been 'No' for too many days in a row, I know I need to change something. -Steve Jobs",
                         @"Be a yardstick of quality. Some people aren't used to an environment where excellence is expected. - Steve Jobs",
                         @"Innovation distinguishes between a leader and a follower. -Steve Jobs"] mutableCopy];


    }

    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }

    - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

        return [self.dataArray count];
    }

    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
        NSString *cellIdentifier = @"CustomCell";
        UITableViewCell *cell = (UITableViewCell *)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];

        if (cell == nil)
        {
            cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
        }

        cell.backgroundColor = [UIColor colorWithRed:249.0/255 green:237.0/255 blue:224.0/255 alpha:1.0];

        int dataIndex = (int) indexPath.row % [self.dataArray count];
        cell.textLabel.text = self.dataArray[dataIndex];
        cell.textLabel.numberOfLines = 0;
        cell.textLabel.lineBreakMode = NSLineBreakByWordWrapping;

        NSDictionary *views = @{@"label":cell.textLabel};
        NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[label]|"
                                                                       options:0
                                                                       metrics:nil
                                                                         views:views];
        [cell.contentView addConstraints:constraints];

        constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[label]|"
                                                              options: 0
                                                              metrics:nil
                                                                views:views];
        [cell.contentView addConstraints:constraints];

        return cell;

    }

    - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
        // Calculate a height based on a cell
        if(!self.customCell) {
            self.customCell = [self.tableView dequeueReusableCellWithIdentifier:@"CustomCell"];
        }

        // Configure the cell
        int dataIndex = (int) indexPath.row % [self.dataArray count];
        self.customCell.textLabel.text = self.dataArray[dataIndex];

        // auto layout

        NSDictionary *views = @{@"label":self.customCell.textLabel};
        NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[label]|"
                                                                       options:0
                                                                       metrics:nil
                                                                         views:views];
        [self.customCell.contentView addConstraints:constraints];

        constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[label]|"
                                                              options: 0
                                                              metrics:nil
                                                                views:views];
        [self.customCell.contentView addConstraints:constraints];

        // Layout the cell

        [self.customCell layoutIfNeeded];

        // Get the height for the cell

        CGFloat height = [self.customCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

        // Padding of 1 point (cell separator)
        CGFloat separatorHeight = 1;

        return height + separatorHeight;
    }

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

        return 140;

    }


    @end

Answer 1

经过大量的例子后,我终于明白了什么是错的.它是其中一个缺少线条会扰乱整个代码的东西之一.对我来说是,

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.

我得到了解决由于在意见惊人的答案之一在这里.虽然在答案中给出的示例代码中,上面的代码行在函数cellForRowAtIndexPath而不是heightForRowAtIndexPath中.但我的代码无法以这种方式运行.

所以,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,棘手的部分是在两个地方,首先设置约束.第二,实现方法heightForRowAtIndexPath和cellForRowAtIndexPath.