the question is similar on Where should I call Rest API in fragment
but i want to discuss about the right on code.
i have call an api from oncreateView()
for example
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
GlobalScope.launch {
showHomeViewModel("someState")
}
}
in function showHomeViewModel() i have defined condition for adapter
private suspend fun showHomeViewModel(state: String) {
withContext(Dispatchers.Main) {
viewModel.liveData().observe(viewLifecycleOwner, observer)
if(adapter.itemCount == 0) callApi() else Log.d(TAG_LOG, "nothing todo")
}
}
so its calling if the data == 0
but i have searchView component , when i navigate to other fragment and back to first fragment , the observer is null...
private val observer =
Observer<MutableList<DataItem>> { item ->
Log.d(TAG_LOG, "observer data $item") // always null if i have ever navigate to other fragment
if (item != null)
adapter.setData(item)
binding.progress.gone()
}
the problem is solve when i remove the condition adapter.itemCount == 0.
but the lifecycle my device always call api when screen or fragment appear.
before i always put the callApi from onResume(), but in my course should i put to the onCreateView and other explain should in onViewCreate() but the main problem is , **its good the code if i use the condition adapter.itemCount == 0 ? to perform searachView , where i defined on viewModel for search (liveData) **
i was tried to from adapter Filterable to perform search but its not work with liveData, so i use my viewModel instead of filterable.
Related
I am observing a list in firestore using LiveData . This observations is dependent on another authentication LiveData.
Should i remove the old LiveData observer before creating the new one? What will happen if i don't?
Currently i am removing the observer using next code but i can simplify it greatly if i won't need to since i do the same all over my code
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
...
//Authentication observer which is the ItemAuto dependent
viewModel.auth.observe(viewLifecycleOwner, Observer {auth ->
updateUserItemAutoLiveData(auth)
})
}
private fun updateUserItemAutoLiveData(auth: Auth) {
if (!auth.uid.isNullOrEmpty()) {
removeUserItemAutoObservers()
itemAutoLiveDate = viewModel.getUserItemAutoLiveData(auth.uid)
itemAutoLiveDate!!.observe(viewLifecycleOwner, Observer {
if (it != null) {
if (it.data != null) {
itemAutoCompleteAdapter.submitItemAuto(it)
}
}
})
} else {
removeUserItemAutoObservers()
}
}
private fun removeUserItemAutoObservers() {
if (itemAutoLiveDate != null && itemAutoLiveDate!!.hasObservers()) {
itemAutoLiveDate!!.removeObservers(this)
}
}
ps: i am using Doug Stevenson tutorial which is great!
If you are using observe method, LiveData will be automatically cleared in onDestroy state.
Observers are bound to Lifecycle objects and clean up after themselves
when their associated lifecycle is destroyed.
More information can be found here
You need to remove livedata manually only if you use observeForever method. The reason why you need to remove it manually is because when you use observeForever method, you don't specify the lifecycle of it.
I'm using Navigation Components, I have Fragment A and Fragment B, from Fragment A I send an object to Fragment B with safe args and navigate to it.
override fun onSelectableItemClick(position:Int,product:Product) {
val action = StoreFragmentDirections.actionNavigationStoreToOptionsSelectFragment(product,position)
findNavController().navigate(action)
}
Now, after some logic in my Fragment B , I want to deliver that data to Fragment A again, which I use
btn_add_to_cart.setOnClickListener {button ->
findNavController().previousBackStackEntry?.savedStateHandle?.set("optionList",Pair(result,product_position))
findNavController().popBackStack()
}
Then in Fragment A, I catch up this data with
findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<Pair<MutableList<ProductOptions>,Int>>("optionList")
?.observe(viewLifecycleOwner, Observer {
storeAdapter.updateProductOptions(it.second,it.first)
})
Now, this is working fine, but if I go from Fragment A to Fragment B and press the back button, the observer above fires again duplicating my current data, is there a way to just fire this observer when I only press the btn_add_to_cart button from Fragment B ?
You use this extenstion:
fun <T> Fragment.getResult(key: String = "key") =
findNavController().currentBackStackEntry?.savedStateHandle?.get<T>(key)
fun <T> Fragment.getResultLiveData(key: String = "key"): MutableLiveData<T>? {
viewLifecycleOwner.lifecycle.addObserver(LifecycleEventObserver { _, event ->
if (event == Lifecycle.Event.ON_DESTROY) {
findNavController().previousBackStackEntry?.savedStateHandle?.remove<T>(key)
}
})
return findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<T>(key)
}
fun <T> Fragment.setResult(key: String = "key", result: T) {
findNavController().previousBackStackEntry?.savedStateHandle?.set(key, result)
}
Example:
FragmentA -> FragmentB
Fragment B need to set the result of the TestModel.class
ResultTestModel.class
data class ResultTestModel(val id:String?, val name:String?)
Fragment A:
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// ...
getNavigationResultLiveData<PassengerFragmentResultNavigationModel>(
"UNIQUE_KEY")?.observe(viewLifecycleOwner) { result ->
Log.i("-->","${result.id} and ${result.name}")
}
//...
}
Fragment B: set data and call popBackStack.
ResultTestModel(id = "xyz", name = "Rasoul")
setNavigationResult(key = "UNIQUE_KEY", result = resultNavigation)
findNavController().popBackStack()
Facing same issue
Resolve this by removing old data from savedStateHandle live data
Inside Fragment B :
button?.setOnClickListener {
findNavController().previousBackStackEntry?.savedStateHandle?.set(key, data)
findNavController().popBackStack()
}
Inside Fragment A:
Here is key to remove the old data by using live data remove method and it should be after view created like in onViewCreated method of fragment
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<String>(key)?.observe(viewLifecycleOwner) {
result(it)
findNavController().currentBackStackEntry?.savedStateHandle?.remove<String>(key)
}
}
Update :
I have created Extension for this for better usage
fun <T> Fragment.setBackStackData(key: String, data: T, doBack: Boolean = false) {
findNavController().previousBackStackEntry?.savedStateHandle?.set(key, data)
if (doBack)
findNavController().popBackStack()
}
fun <T> Fragment.getBackStackData(key: String, singleCall : Boolean= true , result: (T) -> (Unit)) {
findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<T>(key)
?.observe(viewLifecycleOwner) {
result(it)
//if not removed then when click back without set data it will return previous data
if(singleCall) findNavController().currentBackStackEntry?.savedStateHandle?.remove<T>(key)
}
}
Calling inside fragment be like
While setting data in fragment B
var user : User = User(data) // Make sure this is parcelable or serializable
setBackStackData("key",user,true)
While getting data inside fragment A
getBackStackData<User>("key",true) { it ->
}
Thanks to This Guy
It is not clear from your code where your last piece of code is called - where you add an Observer to LiveData. I am guessing it is inside one of the methods onResume() or onViewStateRestored() or any other lifecycle callback which is called again whenever you return to Fragment A from Fragment B. If that is the case, then you are adding a new observer to the LiveData and any observer of a LiveData receives an instant update for the current value.
Move that piece of code to one of the callbacks methods which is called only once during the lifecycle of a fragment.
https://stackoverflow.com/a/66111168/8354145
This answer should help in this case. Use SingleLiveEvent.
Otherwise in these cases, maybe using a shared view model (might be scoped to the nav graph) however you won't need to use savedStateHandle.
edit: 2020.4.12 correct typo from Button.performClick() to button.performClick()
I am writing an app which should display a splash page/fragment for a
few seconds at start then display the next fragment in the navgraph. There are seven fragments in the navgraph which I can navigate around those fragments just fine.
The issue is with the splash fragment, I can only get the splash fragment to display/inflate when the button.onClickListener is set to accept a manual user
input -> click. (vs using button.performClick())
The desired end result is to display a fragment layout consisting of an image view and a text view for a few seconds at app start before displaying the next fragment layout in the navgraph, without having the user to click or press anything.
I have tried using threadsleep, a runnable with a handler, and even a while loop with performClick(). None of which have yielded acceptable results. The closest I have come to getting the desired result is the following:
class SplashFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater,
rootContainer: ViewGroup?,
savedInstanceState: Bundle?): View {
return inflater.inflater(R.layout.fragment_splash, rootContainer, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
button.setOnClickListener {
updateABode()
}
// pizzaLoop initialized to give about 4 seconds delay
val pizzaLoop = 1500000000
while (pizzaLoop > 0) {
pizzaLoop--
if (pizzaLoop == 0) {
button.performClick()
}
}
private fun updateABode {
val ABode = "A" // hard coded for testing purposes
when (ABode) {
"B" -> // for testing purposes only -- does nothing
"A" -> findNavController().navigate(R.id.action_splashFragment_to_firmwareFragment)
}
}
}
With the pizzaLoop installed, the splash fragment will not inflate, but I do see the delay via the firmware screen update. (intially all I get is a white blank screen then subsequent calls to the SplashFragment class show nothing but the firmwareFragment screen (next in the navgraph) -- and the pizzaLoop delay is noticable).
When I comment out the pizzaLoop then the splash fragment displays as intended but I have to click the button to bring up the next fragment in the navgraph (the rest of the navgraph works fine).
It's like the button.performClick() method is preventing the inflation of the splash fragment.
EDIT: 2020.4.12 TO PROPERLY POST SOLUTION.
class SplashFragment : Fragment() {
private val handler: Handler = Handler()
private val updateRunnable: Runnable = Runnable { updateABode() }
override fun onCreateView(inflater: LayoutInflater,
rootContainer: ViewGroup?,
savedInstanceState: Bundle?): View {
return inflater.inflater(R.layout.fragment_splash, rootContainer, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
button.setOnClickListener {
handler.removeCallbacks(updateRunnable)
}
handler.postDelayed(updateRunnable, 4000)
}
private fun updateABode {
val ABode = "A" // hard coded for testing purposes
when (ABode) {
"B" -> // for testing purposes only -- does nothing
"A" -> findNavController().navigate(R.id.action_splashFragment_to_firmwareFragment)
}
}
}
I have an activity using fragments. To communicate from the fragment to the activity, I use interfaces. Here is the simplified code:
Activity:
class HomeActivity : AppCompatActivity(), DiaryFragment.IAddEntryClickedListener, DiaryFragment.IDeleteClickedListener {
override fun onAddEntryClicked() {
//DO something
}
override fun onEntryDeleteClicked(isDeleteSet: Boolean) {
//Do something
}
private val diaryFragment: DiaryFragment = DiaryFragment()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_home)
diaryFragment.setOnEntryClickedListener(this)
diaryFragment.setOnDeleteClickedListener(this)
supportFragmentManager.beginTransaction().replace(R.id.content_frame, diaryFragment)
}
}
The fragment:
class DiaryFragment: Fragment() {
private var onEntryClickedListener: IAddEntryClickedListener? = null
private var onDeleteClickedListener: IDeleteClickedListener? = null
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view: View = inflater.inflate(R.layout.fragment_diary, container, false)
//Some user interaction
onDeleteClickedListener!!.onEntryDeleteClicked()
onDeleteClickedListener!!.onEntryDeleteClicked()
return view
}
interface IAddEntryClickedListener {
fun onAddEntryClicked()
}
interface IDeleteClickedListener {
fun onEntryDeleteClicked()
}
fun setOnEntryClickedListener(listener: IAddEntryClickedListener) {
onEntryClickedListener = listener
}
fun setOnDeleteClickedListener(listener: IDeleteClickedListener) {
onDeleteClickedListener = listener
}
}
This works, but when the fragment is active and the orientation changes from portrait to landscape or otherwise, the listeners are null. I can't put them to the savedInstanceState, or can I somehow? Or is there another way to solve that problem?
Your Problem:
When you switch orientation, the system saves and restores the state of fragments for you. However, you are not accounting for this in your code and you are actually ending up with two (!!) instances of the fragment - one that the system restores (WITHOUT the listeners) and the one you create yourself. When you observe that the fragment's listeners are null, it's because the instance that has been restored for you has not has its listeners reset.
The Solution
First, read the docs on how you should structure your code.
Then update your code to something like this:
class HomeActivity : AppCompatActivity(), DiaryFragment.IAddEntryClickedListener, DiaryFragment.IDeleteClickedListener {
override fun onAddEntryClicked() {
//DO something
}
override fun onEntryDeleteClicked(isDeleteSet: Boolean) {
//Do something
}
// DO NOT create new instance - only if starting from scratch
private lateinit val diaryFragment: DiaryFragment
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_home)
// Null state bundle means fresh activity - create the fragment
if (savedInstanceState == null) {
diaryFragment = DiaryFragment()
supportFragmentManager.beginTransaction().replace(R.id.content_frame, diaryFragment)
}
else { // We are being restarted from state - the system will have
// restored the fragment for us, just find the reference
diaryFragment = supportFragmentManager().findFragment(R.id.content_frame)
}
// Now you can access the ONE fragment and set the listener on it
diaryFragment.setOnEntryClickedListener(this)
diaryFragment.setOnDeleteClickedListener(this)
}
}
Hope that helps!
the short answer without you rewriting your code is you have to restore listeners on activiy resume, and you "should" remove them when you detect activity losing focus. The activity view is completely destroyed and redrawn on rotate so naturally there will be no events on brand new objects.
When you rotate, "onDestroy" is called before anything else happens. When it's being rebuilt, "onCreate" is called. (see https://developer.android.com/guide/topics/resources/runtime-changes)
One of the reasons it's done this way is there is nothing forcing you to even use the same layout after rotating. There could be different controls.
All you really need to do is make sure that your event hooks are assigned in OnCreate.
See this question's answers for an example of event assigning in oncreate.
onSaveInstanceState not working
I'm starting bottomSheetDialogFragment from a fragment A.
I want to select the date from that bottomSheetDialogFragment then set it in the fragment A.
The select date is already done, I just want to get it in the fragment A to set it in some fields.
How can I get the value?
Any suggestions how to do it?
Create an interface class like this
public interface CustomInterface {
public void callbackMethod(String date);
}
Implement this interface in your Activity or Fragment. and make an object of this Interface.
private CustomInterface callback;
Initialize it in onCreate or onCreateView
callback=this;
Now pass this callback in your BottomSheetDialogFragment constructor when you call it.
yourBottomSheetObject = new YourBottomSheet(callback);
yourBottomSheetObject.show(getSupportFragmentManager()," string");
Now in your BottomSheetFragment's constructor
private CustomInterface callback;
public SelectStartTimeSheet(CustomInterface callback){
this.callback=callback;
}
And at last use this callback object to set your date
callback.callbackMethod("your date");
and yout will recieve this date in your Fragment or Your Activity in callbackMethod function.
override the constructor of a fragment is a bad practice as the document said:
Every fragment must have an
* empty constructor, so it can be instantiated when restoring its
* activity's state.
if you using another constructor that passing a callback as the param, when the fragment is resotored by the framework, your app crash
the recommend way is using viewModel and livedata.
Android navigation architecture component
eg:
Suppose you open Fragment B from Fragment A using navController.
and you want some data from fragment B to Fragment A.
class B :BottomSheetDialogFragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val root = inflater.inflate(R.layout.your_layout, container, false)
root.sampleButton.setOnClickListener {
val navController = findNavController()
navController.previousBackStackEntry?.savedStateHandle?.set("your_key", "your_value")
dismiss()
}
}
and in your Fragment A:
findNavController().currentBackStackEntry?.savedStateHandle?.getLiveData<String>("your_key")
?.observe(viewLifecycleOwner) {
if (it == "your_value") {
//your code
}
}
you can use do as below:
Select Account Fragment code
class SelectAccountFragment(val clickListener: OnOptionCLickListener) : BottomSheetDialogFragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.bottom_fragment_accounts, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val list = DataProcessorApp(context).allUsers
val rvAccounts = view.findViewById<RecyclerView>(R.id.rvAccounts)
rvAccounts.layoutManager = LinearLayoutManager(context)
rvAccounts.adapter = AccountsAdapter(context, list)
Log.e(tag,"Accounts "+list.size);
tvAccountAdd.setOnClickListener {
val intent = Intent(context,LoginActivity::class.java)
startActivity(intent)
}
tvManageAccounts.setOnClickListener {
Log.e(tag,"Manage Click")
clickListener.onManageClick()
}
}
interface OnOptionCLickListener{
fun onManageClick()
}
}
Now show and get call back into another fragment /activity as below
SelectAccountFragment accountFragment = new SelectAccountFragment(() -> {
//get fragment by tag and dismiss it
BottomSheetDialogFragment fragment = (BottomSheetDialogFragment) getChildFragmentManager().findFragmentByTag(SelectAccountFragment.class.getSimpleName();
if (fragment!=null){
fragment.dismiss();
}
});
accountFragment.show(getChildFragmentManager(),SelectAccountFragment.class.getSimpleName());
If you are using BottomSheetDialogFragment , since it's a fragment, you should create your interface and bind to it at onAttach lifecycle method of the fragment , doing the appropriate cast of activity reference to your listener/callback type.
Implement this interface in your activity and dispatch change when someone click in a item of fragment's inner recyclerview, for instance
It's a well known pattern and are explained better at here
One big advice is rethink your app architecture, since the best approach is to always pass primitive/simple/tiny data between Android components through Bundle, and your components are able to retrieve the required state with their dependencies later on.
For example, you should never pass along large Objects like Bitmaps, Data Classes , DTO's or View References.
first there is some serialization process going on regarding Parcel which impacts in app responsiveness
second it can lead you to TransactionTooLarge type of error.
Hope that helps!
You can also use LocalBroadcastManager. And as hglf said, it is better to keep the empty constructor for your fragment and use newInstance(Type value) instead to instantiate your fragment if you still want to use the interface callBack way.
You can use the benefit of Navigation library:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val navController = findNavController();
// After a configuration change or process death, the currentBackStackEntry
// points to the dialog destination, so you must use getBackStackEntry()
// with the specific ID of your destination to ensure we always
// get the right NavBackStackEntry
val navBackStackEntry = navController.getBackStackEntry(R.id.your_fragment)
// Create our observer and add it to the NavBackStackEntry's lifecycle
val observer = LifecycleEventObserver { _, event ->
if (event == Lifecycle.Event.ON_RESUME
&& navBackStackEntry.savedStateHandle.contains("key")) {
val result = navBackStackEntry.savedStateHandle.get<String>("key");
// Do something with the result
}
}
navBackStackEntry.lifecycle.addObserver(observer)
// As addObserver() does not automatically remove the observer, we
// call removeObserver() manually when the view lifecycle is destroyed
viewLifecycleOwner.lifecycle.addObserver(LifecycleEventObserver { _, event ->
if (event == Lifecycle.Event.ON_DESTROY) {
navBackStackEntry.lifecycle.removeObserver(observer)
}
})
}
For more info, read the document.
The accepted answer is wrong.
What you can do is just user Fragment A's childFragmentManager when calling show().
like this:
val childFragmentManager = fragmentA.childFragmentManager
bottomSheetDialogFragment.show(childFragmentManager, "dialog")