在Fragment 中拦截返回键

代码如下：

 class XXXFrgmt : Fragment() {

     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
         ...
         return v
     }
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         listenerBackKey()
     }

     fun listenerBackKey(){
         view!!.isFocusableInTouchMode = true
         view!!.requestFocus()
         view!!.setOnKeyListener(View.OnKeyListener { view, i, keyEvent ->
             if (keyEvent.action == KeyEvent.ACTION_UP && i == KeyEvent.KEYCODE_BACK) {
                 if (::callback.isInitialized){
                     callback.invoke(results)
                 }
             }
             false
         })
     }

     override fun onDestroyView() {
         super.onDestroyView()
     }

     override fun onActivityCreated(savedInstanceState: Bundle?) {
         super.onActivityCreated(savedInstanceState)
     }

     override fun onPause() {
         super.onPause()
     }

     override fun onStop() {
         super.onStop()
     }

     override fun onResume() {
         super.onResume()
     }

 }

要求：

　　这个Fragment要是add或者replace 主布局R.id.main的fragment,子fragment不可以 ，如,viewpager里的fragment则不可以.

　　view!! 是

      /**
      * Get the root view for the fragment's layout (the one returned by {@link #onCreateView}),
      * if provided.
      *
      * @return The fragment's root view, or null if it has no layout.
      */
     @Nullable
     public View getView() {
         return mView;
     }