Can I avoid `!!` everywhere when I'm using Android View Binding with Kotlin?-CodePudding

I'm playing around with Kotlin on Android and one thing makes me confused.

When I converted few Fragments from Java to Kotlin I got this:

class XFragment : Fragment() {
    
    private var binding: FragmentXBinding? = null

    override fun onCreateView(inflater: LayoutInflater,
                          container: ViewGroup?, savedInstanceState: Bundle?): View? {
        binding = FragmentUhfReadBinding.inflate(inflater, container, false)
        return binding!!.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        binding!!.slPower.addOnChangeListener(this)
        binding!!.btnClearTagList.setOnClickListener(this)
    }

    // ...

    private fun updateUi(){
        binding!!.someTextView.text = getSomeTextViewText()
        binding!!.someSlider.value = getSomeSliderValue()
    }

}

I can't make binding non-nullable, because it has to be initialized after XFragment class constructor, in onCreateView() or later.

So with this approach it has to be nullable and I have to put !! everywhere.

Is there some way to avoid these !!?

CodePudding user response：

The official documentation suggests this strategy:

private var _binding: FragmentXBinding? = null

// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!

Ultimately, it becomes just like requireActivity() and requireContext(). You just need to remember not to use it in a callback that might get called outside the view lifecycle.

Note, you can create your view using the super-constructor layout parameter and then bind to the pre-existing view in onViewCreated. Then you might not even need to have it in a property. I rarely need to do anything with it outside onViewCreated() and functions directly called by it:

class XFragment : Fragment(R.layout.fragment_x) {

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        val binding = FragmentXBinding.bind(view)
        binding.slPower.addOnChangeListener(this)
        binding.btnClearTagList.setOnClickListener(this)
    }

}