viewBinding not making any changes inside fragment-CodePudding

My Goal

I am trying to access the widget that was created inside my fragment using viewBinding.

What I have done / Info about my app

The language I am using is kotlin.
I have already added the code below into gradle:

buildFeatures{ dataBinding = true viewBinding = true }
I have tested binding.aTextView.setText("Code working.") inside my main activity and it works.

What's the problem

I have tested the setText code inside activity and it works. The problem right now is the same code when I move into the fragment it wouldn't work. And I am sure that the code has been executed as I putted a toast above it and the toast executed successfully which mean it should have at least reached that point before but not sure due to what reason there wasn't any changes.

My mainActivity Code:

class MainProgramActivity : AppCompatActivity() {
lateinit var binding: ActivityMainProgramBinding

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = ActivityMainProgramBinding.inflate(layoutInflater)
    setContentView(binding.root)
    replaceFragment(FragmentMainPage())
}
private fun replaceFragment(fragment: Fragment){
    val fragmentManager = supportFragmentManager
    val fragmentTransaction = fragmentManager.beginTransaction()
    fragmentTransaction.replace(R.id.fragmentContainerView,fragment)
    fragmentTransaction.commit()
}

}

My fragment code:

class FragmentMainPage : Fragment(R.layout.fragment_main_page) {

lateinit var binding: FragmentMainPageBinding

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    Toast.makeText(getActivity(),"Text!",Toast.LENGTH_SHORT).show();
    binding = FragmentMainPageBinding.inflate(layoutInflater)
    binding.aTextView.setText("Code working") //<-- I want this code to make changes towards the textView
    return super.onCreateView(inflater, container, savedInstanceState)
}

}

The aTextView itself is empty at the beginning, the expected result will be the aTextView to show "Code working".

CodePudding user response：

I see two problems with your code. First, exactly what Michael pointed out. You're returning the super method when you should be returning the View you just created (binding.root). Second, you're currenly leaking your fragment. When you viewbind a fragment, you are supposed to set the variable to null in onDestroyView(), as per defined in the documentation.

class FragmentMainPage : Fragment(R.layout.fragment_main_page) {

  private var _binding: FragmentMainPageBinding? = null
  private val binding get() = _binding!! // non-null variable in order to avoid having safe calls everywhere

  // create the view through binding
  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View? {
    _binding = FragmentMainPageBinding.inflate(layoutInflater, container, false)
    return binding.root
  }

  // view already created, do whatever with it
  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    binding.aTextView.setText("Code working")
  }

  // clear the binding in order to avoid memory leaks
  override fun onDestroyView() {
    super.onDestroyView()
    _binding = null
  }
}