textField就是单行文本,多行的话,用textView吧
你用textview就可以了
-(void)viewDidLoad{[[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(textChange)name:UITextFieldTextDidChangeNotificationobject:_textF];}-(void)textChange{_btn.enabled=self.textF.text.length>0;}