有没有办法更改 iOS 8 上 UIAlertController 内显示的消息的对齐方式？
我相信访问子视图并更改 UILabel 已不再可能。
我已成功使用以下内容来对齐和设置 UIAlertControllers 文本的样式：
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")
如果您使用
"attributedTitle""attributedMessage"上面的代码在 Swift 3 中仍然有效，但代码必须稍作修改：
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")
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")
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = alignment
let messageText = NSAttributedString(
string: "message",
attributes: [
NSAttributedString.Key.paragraphStyle: paragraphStyle,
NSAttributedString.Key.foregroundColor : UIColor.primaryText,
NSAttributedString.Key.font : UIFont(name: "name", size: size)
]
)
myAlert.setValue(messageText, forKey: "attributedMessage")
使用以下代码
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];
我采纳了@Amos的答案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")
}
}
然后您可以简单地设置对齐值：
myAlert.setMessageAlignment(.left)导航到子视图树，直到到达标题和消息的 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，您可能想为其创建一个类别
@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;
Swift 4.2 + 多行字符串换行缩进
let paragraphStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
paragraphStyle.headIndent = 14
let messageText = NSMutableAttributedString(
string: "... multiline string need linebreak indentation ...",
attributes: [
NSAttributedString.Key.paragraphStyle: paragraphStyle,
NSAttributedString.Key.font: UIFont.systemFont(ofSize: 12),
NSAttributedString.Key.foregroundColor: UIColor.gray
]
)
alert.setValue(messageText, forKey: "attributedMessage")
以下方法将设置文本对齐方式，同时保留默认字体大小。
static void makeAlertControllerLeftAligned( UIAlertController* avc )
{
NSMutableParagraphStyle *paraStyle = [[[NSMutableParagraphStyle alloc] init] autorelease];
paraStyle.alignment = NSTextAlignmentLeft;
NSMutableAttributedString *atrStr =
[[[NSMutableAttributedString alloc] initWithString:avc.message attributes:@{
NSParagraphStyleAttributeName:paraStyle,
NSFontAttributeName: [UIFont preferredFontForTextStyle: UIFontTextStyleFootnote],
}]
autorelease];
[avc setValue:atrStr forKey:@"attributedMessage"];
}
此属性公开文本字段，因此可能用于配置它们：
文本字段
警报显示的文本字段数组。 （只读）
声明
环球银行金融电信协会
var textFields: [AnyObject]? { get }目标-C
@property(nonatomic, readonly) NSArray *textFields讨论
用这个 属性来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的顺序排列 控制器。此顺序也对应于它们的顺序 显示在警报中。
注意：尽管它说属性是
readonly我注意到有些答案使用了私有 API，这是不安全的。我有一个更安全、更简单的方法来实现同样的目标。这是代码：
extension UIAlertController {
func demo() {
title = "My Title"
message = "My subtitle\nsecond line\nthird line"
customMessageLabel { label in
label.textAlignment = .left
}
}
func customMessageLabel(config: (UILabel) -> Void) {
let originMessage = self.message
let secret = UUID().uuidString
self.message = secret
if let messageLabel = findMessageLabel(in: view, secret: secret) {
config(messageLabel)
}
self.message = originMessage
}
@discardableResult
private func findMessageLabel(in targetView: UIView, secret: String) -> UILabel? {
if let label = targetView as? UILabel, label.text == secret {
return label
} else {
for subview in targetView.subviews {
if let label = findMessageLabel(in: subview, secret: secret) {
return label
}
}
return nil
}
}
}
yourAlertController.messageLabel.textAlignment = NSTextAlignmentLeft;