如何使UITableView行高响应用户的首选文本大小（动态类型）？

问题描述

我希望 UITableView 的行高能够响应用户首选文本大小的变化。例如，当首选文本大小增加时，我想将行高增加一个比例。这是我到目前为止所拥有的：

I would like the UITableView's row height to respond to changes in the user's preferred text size. For example, when the preferred text size increases, I would like to increase the row height by a proportional amount. Here's what I have so far:

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

    [self.tableView reloadData];

    // observe when user changes preferred text size
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(preferredContentSizeChanged:) name:UIContentSizeCategoryDidChangeNotification object:nil];
}

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

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellID = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellID forIndexPath:indexPath];

    // leverage Text Kit's Dynamic Type
    cell.textLabel.font = [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];

    cell.textLabel.text = @"All work and no play...";

    return cell;
}

那么计算反映用户首选文本的行高的最佳方法是什么尺寸？

So what's the best way to calculate a row height that reflects the user's preferred text size?

推荐答案

我最近完成了这项工作并发现它非常简单。而不是使用 sizeWithFont：，你应该在iOS 7中使用新的 boundingRectWithSize：options：attributes：context 方法。

I have recently accomplished this and found it to be very simple. Instead of using sizeWithFont: you should use the new boundingRectWithSize:options:attributes:context method in iOS 7.

像往常一样设置表格视图单元格并在文本标签上指定 preferredFontForTextStyle：：

Set up your table view cell as usual and specify the preferredFontForTextStyle: on your text label as such:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:TableViewCellIdentifier forIndexPath:indexPath];

    //set your table view cell content here
    [[cell textLabel] setText:@"Lorem ipsum dolour sit amet."];
    [[cell textLabel] setNumberOfLines:0];
    [[cell textLabel] setLineBreakMode:NSLineBreakByWordWrapping];
    [[cell textLabel] setFont:[UIFont preferredFontForTextStyle:UIFontTextStyleBody]];

    return cell;
}

然后要正确确定文本标签的大小，请评估 boundingRectWithSize：options：attributes：context 计算所需的高度。

Then to correctly determine the size of the text label, evaluate the boundingRectWithSize:options:attributes:context to calculate the required height.

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //add your table view cell content here
    NSString *string = @"Lorem ipsum dolor sit amet.";

    NSDictionary *attributes = @{NSFontAttributeName: [UIFont preferredFontForTextStyle:UIFontTextStyleBody]};

    CGRect frame = [string boundingRectWithSize:CGSizeMake(CGRectGetWidth(tableView.bounds), CGFLOAT_MAX) options:(NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading) attributes:attributes context:nil];

    return ceilf(CGRectGetHeight(frame);
}

您可能还希望将表视图单元格子类化为侦听 UIContentSizeCategoryDidChangeNotification 通知，此时您可以在用户更改Settings.app中的首选项时更新UI。

You may want to subclass your table view cell also to listen for UIContentSizeCategoryDidChangeNotification notifications at which point you can update your UI when the user changes their preferences in Settings.app

- (void)contentSizeCategoryDidChangeNotificationHandler:(NSNotification *)notification
{
    [[self textLabel] setFont:[UIFont preferredFontForTextStyle:UIFontTextStyleBody]];
}

如果您需要在文本标签周围添加额外的填充，可以定义一个常量值，例如

Should you require additional padding around the text label, you can define a constant value such as

static CGFloat const TableViewCellPadding = 10.0;

有了这个，您可以为从 tableView：heightForRowAtIndexPath返回的值添加一个常量值：

With this in place, you can either add a constant value to the value returned from tableView:heightForRowAtIndexPath:

return (ceilf(CGRectGetHeight(frame) + TableViewCellPadding);

或者你可以插入从 boundingRectWithSize返回的帧：options：attributes：context 这样：

Or you could inset the frame returned from boundingRectWithSize:options:attributes:context as such:

CGRect frame = [string boundingRectWithSize:CGSizeMake(CGRectGetWidth(tableView.bounds), CGFLOAT_MAX) options:(NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading) attributes:attributes context:nil];

frame = CGRectInset(frame, 0.0, TableViewCellPadding);

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