UIControlEventEditingChanged being called twice under Chinese or Japanese when click keyboard's confirm button

I notice that the UIControlEventEditingChanged action will be called twice under Chinese or Japanese when click confirm button of the UITextfield's keyboard. While for other languages such as English it only be called once. Could anyone can explain the detail for it?

UIControlEventEditingChanged being called twice under Chinese or Japanese when click keyboard's confirm button
 
 
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