以下内容适用于UITextField和UITextView。
文本字段文本的最开始：
let startPosition: UITextPosition = textField.beginningOfDocument
文本字段文本的末尾：
let endPosition: UITextPosition = textField.endOfDocument
当前选择的范围：
let selectedRange: UITextRange? = textField.selectedTextRange
if let selectedRange = textField.selectedTextRange {
let cursorPosition = textField.offset(from: textField.beginningOfDocument, to: selectedRange.start)
print("\(cursorPosition)")
}
为了设置位置，所有这些方法实际上都是使用相同的开始值和结束值来设置范围。
let newPosition = textField.beginningOfDocument
textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
let newPosition = textField.endOfDocument
textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
// only if there is a currently selected range
if let selectedRange = textField.selectedTextRange {
// and only if the new position is valid
if let newPosition = textField.position(from: selectedRange.start, offset: -1) {
// set the new position
textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
}
}
从头开始，向右移动5个字符。
let arbitraryValue: Int = 5
if let newPosition = textField.position(from: textField.beginningOfDocument, offset: arbitraryValue) {
textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
}
textField.selectedTextRange = textField.textRange(from: textField.beginningOfDocument, to: textField.endOfDocument)
// Range: 3 to 7
let startPosition = textField.position(from: textField.beginningOfDocument, offset: 3)
let endPosition = textField.position(from: textField.beginningOfDocument, offset: 7)
if startPosition != nil && endPosition != nil {
textField.selectedTextRange = textField.textRange(from: startPosition!, to: endPosition!)
}
textField.insertText("Hello")
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