如何在设置其值后在UITextField中移动光标

Question

任何人都可以帮助我:我需要实现UITextField输入数字.此数字应始终为十进制格式,包含4个位置,例如12.3456或12.3400.所以我创建NSNumberFormatter了帮助我小数位.

我正在设置UITextField值

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string 方法.我处理输入,使用格式化程序,最后调用[textField setText: myFormattedValue];

这工作正常,但此调用也将光标移动到我的字段的末尾.这是不需要的.例如,我的字段中有12.3400,光标位于最开头,用户类型编号为1.结果值为112.3400,但光标在末尾移动.我希望在用户期望时(在最近添加的数字1之后)以光标结束.有一些关于设置游标的主题,TextView但这是UITextField.我也尝试捕获selectedTextRange该字段,它正确地保存了光标位置但是在setText方法调用之后,这会自动更改并且原点UITextRange丢失(更改为当前).希望我的解释清楚.

请在这件事上给予我帮助.非常感谢你.

编辑:最后,我决定在整个编辑后切换功能改变格式,并且工作得很好.我通过添加选择器完成了它forControlEvents:UIControlEventEditingDidEnd.

Answer 1

后UITextField.text属性更改,以以往任何引用UITextPosition或UITextRange之后您设置文本属性,用旧的文本关联的对象将被设置为零.在设置text属性之前,您需要存储操作之后文本偏移量.

这对我有用(注意,如果从下面的示例中删除t中的任何字符,则必须测试cursorOffset是否为<textField.text.length):

- (BOOL) textField:(UITextField *) textField shouldChangeCharactersInRange:(NSRange) range replacementString:(NSString *) string

{
    UITextPosition *beginning = textField.beginningOfDocument;
    UITextPosition *start = [textField positionFromPosition:beginning offset:range.location];
    UITextPosition *end = [textField positionFromPosition:start offset:range.length];
    UITextRange *textRange = [textField textRangeFromPosition:start toPosition:end];

    // this will be the new cursor location after insert/paste/typing
    NSInteger cursorOffset = [textField offsetFromPosition:beginning toPosition:start] + string.length; 

    // now apply the text changes that were typed or pasted in to the text field
    [textField replaceRange:textRange withText:string];

    // now go modify the text in interesting ways doing our post processing of what was typed...
    NSMutableString *t = [textField.text mutableCopy];
    t = [t upperCaseString];
    // ... etc

    // now update the text field and reposition the cursor afterwards
    textField.text = t;
    UITextPosition *newCursorPosition = [textField positionFromPosition:textField.beginningOfDocument offset:cursorOffset];
    UITextRange *newSelectedRange = [textField textRangeFromPosition:newCursorPosition toPosition:newCursorPosition];
    [textField setSelectedTextRange:newSelectedRange];

    return NO;
}

Answer 2

这是快速版本：

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let beginning = textField.beginningOfDocument
    let start = textField.positionFromPosition(beginning, offset:range.location)
    let end = textField.positionFromPosition(start!, offset:range.length)
    let textRange = textField.textRangeFromPosition(start!, toPosition:end!)
    let cursorOffset = textField.offsetFromPosition(beginning, toPosition:start!) + string.characters.count

// just used same text, use whatever you want :)
    textField.text = (textField.text! as NSString).stringByReplacingCharactersInRange(range, withString: string)

    let newCursorPosition = textField.positionFromPosition(textField.beginningOfDocument, offset:cursorOffset)
    let newSelectedRange = textField.textRangeFromPosition(newCursorPosition!, toPosition:newCursorPosition!)
    textField.selectedTextRange = newSelectedRange

    return false
}

Answer 3

实际上对我有用的非常简单，只需使用dispatch main async：

DispatchQueue.main.async(execute: {
  textField.selectedTextRange = textField.textRange(from: start, to: end)
})

Answer 4

实现此答案中描述的代码：将光标移动到 UITextField 的开头

NSRange beginningRange = NSMakeRange(0, 0);
NSRange currentRange = [textField selectedRange];
if(!NSEqualRanges(beginningRange, currentRange))
{
    [textField setSelectedRange:beginningRange];
}

编辑：从这个答案来看，如果您使用的是 iOS 5 或更高版本，您似乎可以将此代码与 UITextField 一起使用。否则，您需要使用 UITextView 来代替。