ios - 具有自动布局的 UITableView 中的动态单元格高度

Question

我一直在努力得到这个教程dynamic-cell-height现在在 ios8 中工作了几天，不知道发生了什么。它适用于 iphone 上的 ios7，它适用于 iPAD 上的 ios7 和 ios8，但不适用于 ios8 上的任何 iphone。

我认为问题在于如何以及何时在单元格中创建标签。

我在 Controller 中有以下代码:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    self.dbManager = [[DBManager alloc] initWithDatabaseFilename:@"tomhaisdb.sql"];

    [self loadData];

}

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [self deselectAllRows];
}

-(void)deselectAllRows{
    for (NSIndexPath * indexPath in [self.tableView indexPathsForSelectedRows]) {
        [self.tableView deselectRowAtIndexPath:indexPath animated:NO];
    }
}

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

-(void)loadData {
    NSString *query = @"select * from favourites";

    if (self.favourites != nil) {
        self.favourites = nil;
    }

    self.favourites = [[NSArray alloc] initWithArray:[self.dbManager loadDataFromDB:query]];

   /* [self reloadDataWithCompletions:^{
         self.tableView.backgroundColor = [UIColor colorWithRed:28.0f/255.0f green:30.0f/255.0f blue:35.0f/255.0f alpha:1];
    }];*/
    [self reloadTableViewContent];
}

- (void)reloadTableViewContent {
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.tableView reloadData];
        [self.tableView scrollRectToVisible:CGRectMake(0, 0, 1, 1) animated:NO];
    });
}

/*-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
    return 1;
}*/

#pragma mark - UITableViewDataSource

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    NSLog(@"Number of rows: %d", self.favourites.count);
    return self.favourites.count;
}


-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
    return [self basicCellAtIndexPath:indexPath];
}

-(favouritedCell *)basicCellAtIndexPath:(NSIndexPath *)indexPath {
    favouritedCell *cell = [self.tableView dequeueReusableCellWithIdentifier:@"favouriteCell" forIndexPath:indexPath];
    [self configureBasicCell:cell atIndexPath:indexPath];
    return cell;
}

-(void)configureBasicCell:(favouritedCell *)cell atIndexPath:(NSIndexPath *)indexPath{
    NSInteger indexOfTomhaisText = [self.dbManager.arrColumnNames indexOfObject:@"tomhaisText"];
    NSString *tomhaisText = [[self.favourites objectAtIndex:indexPath.row] objectAtIndex:indexOfTomhaisText];
    [self setTomhaisForCell:cell item:tomhaisText];
    [self setAnswerForCell:cell item:tomhaisText]; // change this later
}

-(void)setTomhaisForCell:(favouritedCell *)cell item:(NSString *)item{
    [cell.favouriteText setText:item];
}

-(void)setAnswerForCell:(favouritedCell *)cell item:(NSString *)item{
    [cell.answer setText:item];
}

#pragma mark - UITableViewDelegate

-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
   /* if ([[[UIDevice currentDevice]systemVersion]floatValue] >= 8.0) {
        return UITableViewAutomaticDimension;
    }
    else{*/
        return [self heightForFavouriteCellAtIndexPath:indexPath];
    /*}*/

}

-(CGFloat)heightForFavouriteCellAtIndexPath:(NSIndexPath *)indexPath{
    static favouritedCell *sizingCell = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sizingCell = [self.tableView dequeueReusableCellWithIdentifier:@"favouriteCell"];
    });

    [self configureBasicCell:sizingCell atIndexPath:indexPath];
    return [self calculateHeightForConfiguredSizingCell:sizingCell];
}

-(CGFloat)calculateHeightForConfiguredSizingCell:(UITableViewCell *)sizingCell{
    sizingCell.bounds = CGRectMake(0.0f, 0.0f, CGRectGetWidth(self.tableView.frame), CGRectGetHeight(sizingCell.bounds));
    NSLog(@"Bounds before Layout %@", NSStringFromCGRect(sizingCell.bounds));
     NSLog(@"Content View before Layout %@", NSStringFromCGRect(sizingCell.contentView.bounds));
    [sizingCell setNeedsLayout];
    [sizingCell layoutIfNeeded];

    CGSize size = [sizingCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
    NSLog(@"Bounds after layout %@", NSStringFromCGRect(sizingCell.bounds));
    NSLog(@"Content View before Layout %@", NSStringFromCGRect(sizingCell.contentView.bounds));
    return size.height + 1.0f;
}

-(CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath{
    return 155.0f;
}

在单元格使用的自定义标签中，我有以下内容:

    @implementation favouriteLabel

- (void)setBounds:(CGRect)bounds {
    [super setBounds:bounds];

    // If this is a multiline label, need to make sure
    // preferredMaxLayoutWidth always matches the frame width
    // (i.e. orientation change can mess this up)

    if (self.numberOfLines == 0 && bounds.size.width != self.preferredMaxLayoutWidth) {
        self.preferredMaxLayoutWidth = self.bounds.size.width;
        NSLog(@"Label Bounds before update constraints %@", NSStringFromCGRect(self.bounds));
        [self setNeedsUpdateConstraints];
        NSLog(@"Label Bounds after update constraints %@", NSStringFromCGRect(self.bounds));
    }
}

@end

我认为我的问题在于创建标签时的原因是因为在 ios 7 中我得到如下输出:

2015-06-01 20:07:10.563 Facts[63322:607] Label Bounds before update constraints {{0, 0}, {216, 2}}
2015-06-01 20:07:10.563 Facts[63322:607] Label Bounds after update constraints {{0, 0}, {216, 2}}
2015-06-01 20:07:10.563 Facts[63322:607] Label Bounds before update constraints {{0, 0}, {217, 40}}
2015-06-01 20:07:10.563 Facts[63322:607] Label Bounds after update constraints {{0, 0}, {217, 40}}
>2015-06-01 20:07:10.564 Facts[63322:607] Bounds after layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.564 Facts[63322:607] Content View before Layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.564 Facts[63322:607] Bounds before Layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.564 Facts[63322:607] Content View before Layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.565 Facts[63322:607] Bounds after layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.565 Facts[63322:607] Content View before Layout {{0, 0}, {256, 82}}
2015-06-01 20:07:10.569 Facts[63322:607] Label Bounds before update constraints {{0, 0}, {216, 74.5}}
2015-06-01 20:07:10.569 Facts[63322:607] Label Bounds after update constraints {{0, 0}, {216, 74.5}}
2015-06-01 20:07:10.569 Facts[63322:607] Label Bounds before update constraints {{0, 0}, {217, 40}}
2015-06-01 20:07:10.570 Facts[63322:607] Label Bounds after update constraints {{0, 0}, {217, 40}}

但是在ios8中输出是不同的。

2015-06-01 20:18:06.049 Facts[63396:81689795] Bounds before Layout {{0, 0}, {256, 44}}
2015-06-01 20:18:06.049 Facts[63396:81689795] Content View before Layout {{0, 0}, {320, 44}}
2015-06-01 20:18:06.131 Facts[63396:81689795] Label Bounds before update constraints {{0, 0}, {216, 0}}
2015-06-01 20:18:06.131 Facts[63396:81689795] Label Bounds after update constraints {{0, 0}, {216, 0}}
2015-06-01 20:18:06.131 Facts[63396:81689795] Label Bounds before update constraints {{0, 0}, {217, 4.5}}
2015-06-01 20:18:06.131 Facts[63396:81689795] Label Bounds after update constraints {{0, 0}, {217, 4.5}}

在ios7中，标签似乎是先创建的，然后是单元格边界，然后再次调整标签的大小。但在 ios8 中，我们首先看到内容 View 输出，然后才看到标签的输出。

很抱歉我无法更好地解释它。对我来说，ios 如何制作它的表格有点神秘，所以我真的很困惑为什么它在 ios7 中工作而不是在 ios8 中工作

非常感谢任何帮助。我已经在这里写下了这个问题:Dynamic Cell Height autolayout IOS但我想我在这个问题上引入了关于自动布局的转移注意力。

Answer 1

答案标签的框架错位了。由于没有为 anyXany 安装标签，因此在 Interface Builder 中看不到警告。

因为约束不等于预期高度，所以自动布局无法正确解决 iOS 8 的单元格高度。

快速修复是勾选 anyXany 的已安装框。你会看到警告出现。选择 Answer 标签，选择 Editor->AutoLayout Issues->Update Frames，一切顺利!

更新:

最初显示标签而不需要重新加载的原因是因为勾选了 anyXany 框。 Apple 看到安装了约束，并且初始高度是正确的，无需重新加载或滚动。

如果未勾选此框，则在布局过程中添加约束的时间太晚，导致标签无法具有正确的初始高度。

我建议保留安装单元格的标签(对于任何尺寸类别)，因为单元格的约束不会根据特征而改变。

(虽然 tableView 约束确实发生了变化，但单元格的约束不应该是有条件的。如果有一个单元格，它将始终具有相同的约束，无论大小类别如何。)