当我加载一个UIView时,我如何在iPhone SDK上设置UITextField的最大字符数?
当前回答
有通用的解决方案设置最大长度在Swift。 通过IBInspectable,你可以在Xcode属性检查器中添加新的属性。
import UIKit
private var maxLengths = [UITextField: Int]()
extension UITextField {
@IBInspectable var maxLength: Int {
get {
guard let length = maxLengths[self]
else {
return Int.max
}
return length
}
set {
maxLengths[self] = newValue
addTarget(
self,
action: Selector("limitLength:"),
forControlEvents: UIControlEvents.EditingChanged
)
}
}
func limitLength(textField: UITextField) {
guard let prospectiveText = textField.text
where prospectiveText.characters.count > maxLength else {
return
}
let selection = selectedTextRange
text = prospectiveText.substringWithRange(
Range<String.Index>(prospectiveText.startIndex ..< prospectiveText.startIndex.advancedBy(maxLength))
)
selectedTextRange = selection
}
}
其他回答
你不能直接这样做- UITextField没有maxLength属性,但你可以设置UITextField的委托,然后使用:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
斯威夫特4
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
guard let text = textField.text else { return true }
let newLength = text.count + string.count - range.length
return newLength <= 10
}
我模拟实际的字符串替换,计算未来字符串的长度:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
if([newString length] > maxLength)
return NO;
return YES;
}
我发现这个方法又快又简单
- (IBAction)backgroundClick:(id)sender {
if (mytext.length <= 7) {
[mytext resignFirstResponder];
} else {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Too Big"
message:@"Please Shorten Name"
delegate:nil
cancelButtonTitle:@"Cancel"
otherButtonTitles:nil];
[alert show];
[alert release];
}
}
斯威夫特4
import UIKit
private var kAssociationKeyMaxLength: Int = 0
extension UITextField {
@IBInspectable var maxLength: Int {
get {
if let length = objc_getAssociatedObject(self, &kAssociationKeyMaxLength) as? Int {
return length
} else {
return Int.max
}
}
set {
objc_setAssociatedObject(self, &kAssociationKeyMaxLength, newValue, .OBJC_ASSOCIATION_RETAIN)
addTarget(self, action: #selector(checkMaxLength), for: .editingChanged)
}
}
@objc func checkMaxLength(textField: UITextField) {
guard let prospectiveText = self.text,
prospectiveText.count > maxLength
else {
return
}
let selection = selectedTextRange
let indexEndOfText = prospectiveText.index(prospectiveText.startIndex, offsetBy: maxLength)
let substring = prospectiveText[..<indexEndOfText]
text = String(substring)
selectedTextRange = selection
}
}
编辑:内存泄漏问题修复。
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