Develop Reference

Setting setOnClickListener using bindings android kotlin

I have been doing a tutorial that is a bit out of date and uses synthetics rather than bindings. I am trying to use bindins. I am trying to set up a listener in a fragment (AddEditFragment.kt). It's using a callback to MainActivity.onSaveClicked.
In AddEditFragment I use an import for the binding
import com.funkytwig.tasktimer.databinding.FragmentAddEditBinding
I have a lateinit on the first line of the class defenition
class AddEditFragment : Fragment() {
private lateinit var binding: FragmentAddEditBinding
I am initializing the bunding in onActivityCreated and setting up the listner. I can use findViewById to get the ID
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
val addEditSave = view?.findViewById(R.id.addEditSave) as Button
addEditSave.setOnClickListener { listener?.onSaveClicked() }
}
And this works fine but if I try to use the binding
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
binding.addEditSave.setOnClickListener { listener?.onSaveClicked() }
}
The code does not show any errrors but it does not seem to create the listner. I have a Log.d in the onSaveClicked callback function and when I use the first (findViewById) version of the function it works (it calles onSaveClicked) but with the second version (using bindings) onSaveClicked does not get called when I click the Button.
I Cant figre out why the second version does not work, I thought the two versions of onActivityCreated should do the same thing.
The interface in AddEditFragment.kt is
interface OnSaveClicked {
fun onSaveClicked()
}

In fragment you should add your view in onCreateView or in OnViewCreated not in onActivityCreated
Please refer link for more details.
private var _binding: FragmentAddEditBinding? = null
// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentAddEditBinding.inflate(inflater, container, false)
val view = binding.root
binding.addEditSave.setOnClickListener { listener?.onSaveClicked() }
return view
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}

OK, thanks for all the help. turned out I was doing the inflate wrong.
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
Log.d(TAG, "onCreateView")
binding = FragmentAddEditBinding.inflate(layoutInflater, container, false)
return binding.root
}
I was doing
binding = FragmentAddEditBinding.inflate(layoutInflater)
I missed out on the last 2 args as I was taking the code from the inflate when I am in an Activity, not a Fragment. I think it is to do with the layout effecticly being in the parent.

viewBinding not making any changes inside fragment

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".

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
}
}

Jetpack Compose In Fragment doesn't recompose on popbackstack

I'm using the jetpack navigation component here, not the Compose Navigation Component since there are some areas in my app I cannot convert yet.
The issue I'm running into is:
Fragment A starts and contains a ComposeView in it's xml. Fragment A opens Fragment B. But, when you return to Fragment A, the ComposeView is empty and doesn't show anything.
Is this a bug? Is this known? Am I just doing something wrong? I looked into setting the view composition strategy and tried each option and none of them worked.

I found the answer. I had a BaseFragment:
abstract class BaseFragment : Fragment() {
private var hasInitializedRootView = false
private var rootView: View? = null
protected abstract val layoutId: Int
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return getPersistentView(inflater, container, savedInstanceState, layoutId)
}
private fun getPersistentView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?, layout: Int): View? {
if (rootView == null) {
// Inflate the layout for this fragment
rootView = inflater?.inflate(layout, container, false)
} else {
// Do not inflate the layout again.
// The returned View of onCreateView will be added into the fragment.
// However it is not allowed to be added twice even if the parent is same.
// So we must remove rootView from the existing parent view group
// (it will be added back).
(rootView?.parent as? ViewGroup)?.removeView(rootView)
}
return rootView
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
if (!hasInitializedRootView) {
hasInitializedRootView = true
viewCreated(view, savedInstanceState)
}
}
abstract fun viewCreated(view: View, savedInstanceState: Bundle?)
}
What would happen is that onCreateView wouldn't be called as wanted and the composition wouldn't restart. Changing to using a normal Fragment fixed this perfectly.

Different ways to use Fragments

I am developing an app with Firebase. But whenever I use the onViewCreated method, the button does not respond to any clicks. But when I use the onCreateView, it works.
Here is my LoginFragment (Button does not respond to clicks):
class LoginFragment : Fragment(R.layout.fragment_login) {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val binding = FragmentLoginBinding.inflate(layoutInflater)
binding.buttonGoogleSignin.setOnClickListener {
toast("THIS IS NOT WORKING")
Authentication.getInstance().signIn(context!!, getString(R.string.default_web_client_id)) {
startActivityForResult(mGoogleClient.signInIntent, RC_GOOGLE_SIGN_IN)
}
}
}
}
In this code, my button responds to clicks:
class LoginFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInFlater,
container: ViewGroup?,
savedInstanceState: Bundle?
) {
val view = inflater.inflate(R.layout.fragment_login, container, false)
val binding = FragmentLoginBinding.bind(view)
binding.buttonGoogleSignin.setOnClickListener {
toast("THIS IS WORKING")
Authentication.getInstance().signIn(context!!, getString(R.string.default_web_client_id)) {
startActivityForResult(mGoogleClient.signInIntent, RC_GOOGLE_SIGN_IN)
}
}
return view
}
}
Can someone explain to me why the first approach did not work?

The problem is in the fact that in onViewCreated you are creating a binding object with FragmentLoginBinding.inflate(layoutInflater) but you are not connecting that binding to the view, so whatever you do with that object will not have effect on the view.
FragmentLoginBinding.inflate(layoutInflater) creates a new binding object and also inflate a new view to which it is connected. But you are not using that view in your fragment, so using that method is not the correct choice.
So you can do something like:
val binding = FragmentLoginBinding.bind(getView())
inside onViewCreated if you really want, and that will create a binding with the view you have in your fragment.
Said that, creating the binding already in onCreateView is actually recommended by the Android documentation.

Trouble with NavController inside OnBackPressedCallback

I am getting a does not have a NavController set error inside a OnBackPressedCallback. Here is the code
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
fragmentView = inflater.inflate(R.layout.patient_info_fragment, container, false)
if(Utils.connectedToInternet()){
fragmentView.pastScreeningsButton.visibility = View.GONE
}
requireActivity().onBackPressedDispatcher.addCallback(object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
Navigation.findNavController(fragmentView).navigate(R.id.action_patientInfoFragment_to_patientsList)
}
})
setHasOptionsMenu(true)
return fragmentView
}
I am only getting this error when I come back into the fragment where this is implemented.
I have android:name="androidx.navigation.fragment.NavHostFragment" in the home fragment.
To clarify, I am using Navigation controller to do all my Navigation around my app and it works just fine. I only get this error inside this OnBackPressedCallback and only when the user navigates back into the fragment where this is implemented.
Let me know if you need to see any more of my code.

You might run into an issue with leaks of old instances of your fragment. Also it's not a good practice to store the created view within another variable like fragmentView. All in all your onCreateView implementation is doing too many things unrelated to its purpose.
I'd suggest to split up the functionality into relevant life-cycle methods and use the fragment.view directly within your callback. To not run into an issue with unattached views, you then bind and unbind the callback with the life-cycle.
class PatientInfoFragment: Fragment() {
private val callback = object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
Navigation.findNavController(view).navigate(R.id.action_patientInfoFragment_to_patientsList)
}
}
override fun onCreate(
savedInstanceState: Bundle?
) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View = inflater.inflate(R.layout.patient_info_fragment, container, false)
override fun onViewCreated(
view: View,
savedInstanceState: Bundle?
) {
if(Utils.connectedToInternet()){
view.pastScreeningsButton.visibility = View.GONE
}
}
override fun onStart() {
super.onStart()
requireActivity().onBackPressedDispatcher.addCallback(callback)
}
override fun onStop() {
callback.remove()
super.onStop()
}
}
The callback life-cycle binding can be bound with the fragment as lifecycle owner calling the other addCallback(LifecycleOwner, OnBackPressedCallback).
Additionally you could have a look into Android KTX and Kotlin Android Extensions to simplify your implementation.

Move your code in the onViewCreated and pass the view that is provided by the overriden method:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
requireActivity().onBackPressedDispatcher.addCallback(object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
Navigation.findNavController(view).navigate(R.id.action_patientInfoFragment_to_patientsList)
}
})
}
If that also doesn't work, replace the .navigate() with popBastack(R.id.framgment_where_you_want to go, false), in case your previous fragment stays on the backStack