UIAlertController文本对齐

Question

有没有办法更改iOS 8上UIAlertController内显示的消息的对齐方式？

我相信不再可能访问子视图并为UILabel更改它.

Answer 1

我成功地使用了以下内容,用于对齐和设计UIAlertControllers的文本:

let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = NSTextAlignment.Left

let messageText = NSMutableAttributedString(
    string: "The message you want to display",
    attributes: [
        NSParagraphStyleAttributeName: paragraphStyle,
        NSFontAttributeName : UIFont.preferredFontForTextStyle(UIFontTextStyleBody),
        NSForegroundColorAttributeName : UIColor.blackColor()
    ]
)

myAlert.setValue(messageText, forKey: "attributedMessage")

如果你使用的话"attributedTitle",你可以用标题做类似的事情,而不是"attributedMessage"

Swift 3更新

以上仍然适用于Swift 3,但代码必须稍微修改为:

let messageText = NSMutableAttributedString(
    string: "The message you want to display",
    attributes: [
        NSParagraphStyleAttributeName: paragraphStyle,
        NSFontAttributeName : UIFont.preferredFont(forTextStyle: UIFontTextStyle.body),
        NSForegroundColorAttributeName : UIColor.black
    ]
)

myAlert.setValue(messageText, forKey: "attributedMessage")

Swift 4更新

let messageText = NSMutableAttributedString(
    string: "The message you want to display",
    attributes: [
        NSAttributedStringKey.paragraphStyle: paragraphStyle,
        NSAttributedStringKey.font: UIFont.preferredFont(forTextStyle: UIFontTextStyle.body),
        NSAttributedStringKey.foregroundColor: UIColor.black
    ]
)

myAlert.setValue(messageText, forKey: "attributedMessage")

Answer 2

使用下面的代码

UIAlertController * alert = [UIAlertController
                                 alertControllerWithTitle:[title lowercaseString]
                                 message:[message lowercaseString]
                                 preferredStyle:UIAlertControllerStyleAlert];

    if (alertStyle == kUIAlertStylePlainText)
    {
        [alert addTextFieldWithConfigurationHandler:^(UITextField *textField) {

        }];
    }

    if (okTitle) {
        UIAlertAction* ok = [UIAlertAction actionWithTitle:[okTitle lowercaseString] style:UIAlertActionStyleDefault
                                                   handler:^(UIAlertAction * action) {
                                                       callback(alert, action, nil);
                                                   }];
        [alert addAction:ok];
    }

    if (cancelTitle) {
        UIAlertAction* cancel = [UIAlertAction actionWithTitle:[cancelTitle lowercaseString] style:UIAlertActionStyleDefault
                                                       handler:^(UIAlertAction * action) {
                                                           callback(alert, nil, action);
                                                       }];
        [alert addAction:cancel];
    }


    NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init];
    paraStyle.alignment = NSTextAlignmentLeft;

    NSMutableAttributedString *atrStr = [[NSMutableAttributedString alloc] initWithString:[message lowercaseString] attributes:@{NSParagraphStyleAttributeName:paraStyle,NSFontAttributeName:[UIFont systemFontOfSize:13.0]}];

    [alert setValue:atrStr forKey:@"attributedMessage"];
    [viewInstance presentViewController:alert animated:YES completion:nil];

Answer 3

导航到子视图树,直到您到达标题和消息的UILabels

NSArray *viewArray = [[[[[[[[[[[[alertController view] subviews] firstObject] subviews] firstObject] subviews] firstObject] subviews] firstObject] subviews] firstObject] subviews];
UILabel *alertTitle = viewArray[0]
UILabel *alertMessage = viewArray[1];
alertMessage.textAlignment = NSTextAlignmentLeft;

但是,您可能希望为其创建一个类别

@interface UIAlertController (ShowMeTheLabels)

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

@end

@implementation UIAlertController (ShowMeTheLabels)
@dynamic titleLabel;
@dynamic messageLabel;

- (NSArray *)viewArray:(UIView *)root {
    NSLog(@"%@", root.subviews);
    static NSArray *_subviews = nil;
    _subviews = nil;
    for (UIView *v in root.subviews) {
        if (_subviews) {
            break;
        }
        if ([v isKindOfClass:[UILabel class]]) {
            _subviews = root.subviews;
            return _subviews;
        }
        [self viewArray:v];
    }
    return _subviews;
}

- (UILabel *)titleLabel {
    return [self viewArray:self.view][0];
}

- (UILabel *)messageLabel {
    return [self viewArray:self.view][1];
}

@end

然后你可以像这样对齐文本

yourAlertController.messageLabel.textAlignment = NSTextAlignmentLeft;

Answer 4

我接受了@Amos的回答并将其变成了一个方便的扩展：

public extension UIAlertController {

    func setMessageAlignment(_ alignment : NSTextAlignment) {
        let paragraphStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
        paragraphStyle.alignment = alignment

        let messageText = NSMutableAttributedString(
            string: self.message ?? "",
            attributes: [
                NSAttributedString.Key.paragraphStyle: paragraphStyle,
                NSAttributedString.Key.font: UIFont.systemFont(ofSize: 12),
                NSAttributedString.Key.foregroundColor: UIColor.gray
            ]
        )

        self.setValue(messageText, forKey: "attributedMessage")
    }
}

然后你可以简单地设置对齐值： myAlert.setMessageAlignment(.left)

Answer 5

此属性公开文本字段，因此可以用于配置它们：

文本字段

警报显示的文本字段数组。（只读）

宣言

迅速

var textFields: [AnyObject]? { get }

目标C

@property(nonatomic, readonly) NSArray *textFields

讨论

使用此属性可以访问警报显示的文本字段。文本字段按照您将其添加到警报控制器的顺序排列。此顺序也对应于它们在警报中显示的顺序。

注意：即使它说属性是readonly，它也会返回一个文本字段对象引用数组，可用于修改控件。