类型Main必须实现继承的抽象方法textwatcher . bepreview extchanged (charSequence,int,int)

I'm trying to add a TextWatcher editbox.afterTextChanged listenering to my "Main" activity where I have already used an onFocusListener. I receive this error message on the line where I declare the Main class:I'm trying to add a TextWatcher editbox.afterTe