Getting and Setting Cursor Position of UITextField and UITextView in Swift

问题:

I've been experimenting with UITextField and how to work with it's cursor position. I've found a number of relation Objective-C answers, as in

• Getting the cursor position of UITextField in ios
• Control cursor position in UITextField
• UITextField get currently edited word

But since I am working with Swift, I wanted to learn how to get the current cursor location and also set it in Swift.

The answer below is the the result of my experimentation and translation from Objective-C.

回答1:

This answer has been updated for Swift 3

The following content applies to both UITextField and UITextView.

Useful information

The very beginning of the text field text:

let startPosition: UITextPosition = textField.beginningOfDocument

The very end of the text field text:

let endPosition: UITextPosition = textField.endOfDocument

The currently selected range:

let selectedRange: UITextRange? = textField.selectedTextRange

Get cursor position

if let selectedRange = textField.selectedTextRange {      let cursorPosition = textField.offset(from: textField.beginningOfDocument, to: selectedRange.start)      print("\(cursorPosition)") }

Set cursor position

In order to set the position, all of these methods are actually setting a range with the same start and end values.

To the beginning

let newPosition = textField.beginningOfDocument textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)

To the end

let newPosition = textField.endOfDocument textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)

To one position to the left of the current cursor position

// 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)     } }

To an arbitrary position

Start at the beginning and move 5 characters to the right.

let arbitraryValue: Int = 5 if let newPosition = textField.position(from: textField.beginningOfDocument, offset: arbitraryValue) {      textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition) }

Related

Select all text

textField.selectedTextRange = textField.textRange(from: textField.beginningOfDocument, to: textField.endOfDocument)

Select a range of text

// 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!) }

Insert text at the current cursor position

textField.insertText("Hello")

Notes

• Use textField.becomeFirstResponder() to give focus to the text field and make the keyboard appear.

• See this answer for how to get the text at some range.

See also

• How to Create a Range in Swift

回答2:

in my case I had to use DispatchQueue:

func textViewDidBeginEditing(_ textView: UITextView) {     DispatchQueue.main.async{       textField.selectedTextRange = ...    } }

nothing else from this and other threads worked.

PS: I double checked which thread did textViewDidBeginEditing was running on, and it was main thread, as all UI should run on, so not sure why that little delay using main.asynch worked.

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