自定义键盘：获取所选文本

Question

From my Custom Keyboard I would like to know if the user has selected something in their text (and the range of it). Following the documentation I thought I can utilize the callbacks provided by the UITextInputDelegate protocol:

• selectionWillChange(textInput: UITextInput)
• selectionDidChange(textInput: UITextInput)
• textWillChange(textInput: UITextInput)
• textDidChange(textInput: UITextInput)

However, the selectionWill/DidChange callbacks are never called. If I change the selection in my text, the other callbacks are triggered ( textWill/DidChange ) instead. As this is already odd, the problem I have is that the textInput param is always nil. But I need it, as I would like to access selectedTextRange to solve my problem.

Any ideas how to retrieve the currently selected text and/or its range within a custom keyboard implementation?

Answer 1

If I'm not completely wrong, this is impossible. (You're referring to an own keyboard app on iOS 8; not an implementation of your own keyboard in your own app, right?)

Your keyboard has no access to the text actually written by the user, because the UITextView is in an completely different app.

Source: https://developer.apple.com/library/ios/documentation/General/Conceptual/ExtensibilityPG/Keyboard.html - "System Keyboard Features Unavailable to Custom Keyboards", paragraph 7

Because a custom keyboard can draw only within the primary view of its UIInputViewController object, it cannot select text. Text selection is under the control of the app that is using the keyboard. If that app provides an editing menu interface (such as for Cut, Copy, and Paste), the keyboard has no access to it. A custom keyboard cannot offer inline autocorrection controls near the insertion point.

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If you are referring to your own implementation in your own app: have you selected the correct class as textfield delegate in your IB? Have you added UITextInputDelegate to the class's (do you write it like this in English?) header file? Then your delegate methods should be called... Also some example code could be useful ;)