In my app I have two activities. The main activity that only has a search button in the Appbar
and a second, searchable, activity. The second activity hold a fragment that fetches the data searched in it's onCreate
call. My problem is that the fragment fetches the data twice. Inspecting the lifecycle of my activities, I concluded that the searchable activity gets paused at some point, which obviously determines the fragment to be recreated. But I have no idea what causes the activity to be paused.
Here are my activities
MainActivity.kt
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
val root = binding.root
setContentView(root)
//Setup the app bar
setSupportActionBar(binding.toolbar);
}
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
return initOptionMenu(menu, this)
}
}
fun initOptionMenu(menu: Menu?, context: AppCompatActivity): Boolean {
val inflater = context.menuInflater;
inflater.inflate(R.menu.app_bar_menu, menu)
// Get the SearchView and set the searchable configuration
val searchManager = context.getSystemService(Context.SEARCH_SERVICE) as SearchManager
(menu?.findItem(R.id.app_bar_search)?.actionView as SearchView).apply {
// Assumes current activity is the searchable activity
setSearchableInfo(searchManager.getSearchableInfo(context.componentName))
setIconifiedByDefault(false) // Do not iconify the widget; expand it by default
}
return true;
}
SearchActivity.kt
class SearchActivity : AppCompatActivity() {
private lateinit var viewBinding: SearchActivityBinding
private var query: String? = ""
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
viewBinding = SearchActivityBinding.inflate(layoutInflater)
val root = viewBinding.root
setContentView(root)
// Setup app bar
supportActionBar?.displayOptions = ActionBar.DISPLAY_SHOW_CUSTOM
supportActionBar?.setCustomView(R.layout.search_app_bar)
supportActionBar?.setDisplayHomeAsUpEnabled(true)
//Get the query string
if (Intent.ACTION_SEARCH == intent.action) {
intent.getStringExtra(SearchManager.QUERY).also {
//Add the query to the appbar
query = it
updateAppBarQuery(it)
}
}
//Instantiate the fragment
if (savedInstanceState == null) {
val fragment = SearchFragment.newInstance();
val bundle = Bundle();
bundle.putString(Intent.ACTION_SEARCH, query)
fragment.arguments = bundle;
supportFragmentManager.beginTransaction()
.replace(R.id.container, fragment)
.commitNow()
}
}
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
return initOptionMenu(menu, this)
}
private fun updateAppBarQuery(q: String?) {
supportActionBar?.customView?.findViewById<TextView>(R.id.query)?.apply {
text = q
}
}
}
As you can see, I am using the built in SearchManger
to handle my search action and switching between activities. I haven't seen anywhere in the docs that during search, my searchable activity might get paused or anything like that. Does anyone have any idea why this happens? Thanks in advance!
edit: Here is my onCreate
method for the SearchFragment
:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val query = arguments?.getString(Intent.ACTION_SEARCH);
//Create observers
val searchResultObserver = Observer<Array<GoodreadsBook>> {
searchResultListViewAdapter.setData(it)
}
viewModel.getSearchResults().observe(this, searchResultObserver)
GlobalScope.launch { //Perform the search
viewModel.search(query)
}
lifecycle.addObserver(SearchFragmentLifecycleObserver())
}
Here, searchResultListViewAdapter
is the adapter for a RecyclerView
and searchResult
is a livedata in the view-model holding the search result
Here is the stack trace for the first call of onCreate()
on SearchFragment
:
And here is for the second call:
Here is the ViewModel
for the SearchFragment
:
class SearchViewModel() : ViewModel() {
private val searchResults: MutableLiveData<Array<GoodreadsBook>> by lazy {
MutableLiveData<Array<GoodreadsBook>>();
}
fun getSearchResults(): LiveData<Array<GoodreadsBook>> {
return searchResults;
}
// TODO: Add pagination
suspend fun search(query: String?) = withContext(Dispatchers.Default) {
val callback: Callback = object : Callback {
override fun onFailure(call: Call, e: IOException) {
// TODO: Display error message
}
override fun onResponse(call: Call, response: Response) {
// TODO: Check res status
val gson = Gson();
val parsedRes = gson.fromJson(
response.body?.charStream(),
Array<GoodreadsBook>::class.java
);
// Create the bitmap from the imageUrl
searchResults.postValue(parsedRes)
}
}
launch { searchBook(query, callback) }
}
}
I made some changes to the app since posted this and right now the search doesn't work for some reason in the main branch. This ViewModel
it's from a branch closer to the time I posted this. Here is the current ViewModel
, although the problem is present in this variant as well:
class SearchViewModel(private val savedStateHandle: SavedStateHandle) : ViewModel() {
// private val searchResults: MutableLiveData<Array<GoodreadsBook>> by lazy {
//// MutableLiveData<Array<GoodreadsBook>>();
//// }
companion object {
private const val SEARCH_RESULTS = "searchResults"
}
fun getSearchResults(): LiveData<Array<GoodreadsBook>> =
savedStateHandle.getLiveData<Array<GoodreadsBook>>(SEARCH_RESULTS)
// TODO: Add pagination
fun search(query: String?) {
val searchResults = savedStateHandle.getLiveData<Array<GoodreadsBook>>(SEARCH_RESULTS)
if (searchResults.value == null)
viewModelScope.launch {
withContext(Dispatchers.Default) {
//Handle the API response
val callback: Callback = object : Callback {
override fun onFailure(call: Call, e: IOException) {
// TODO: Display error message
}
override fun onResponse(call: Call, response: Response) {
// TODO: Check res status
val gson = Gson();
val parsedRes = gson.fromJson(
response.body?.charStream(),
Array<GoodreadsBook>::class.java
);
searchResults.postValue(parsedRes)
}
}
launch { searchBook(query, callback) }
}
}
}
}
The searchBook
function just performs the HTTP request to the API, all the data manipulation is handled in the viewModel
try this way
Fragment sf = SearchFragment.newInstance();
Bundle args = new Bundle();
args.putString(Intent.ACTION_SEARCH, query);
sf.setArguments(args);
getFragmentManager().beginTransaction()
.replace(R.id.fragmentContainer, sf).addToBackStack(null).commit();
Use SaveStateHandle in your ViewModel to persist the loaded data, and don't use GlobalContext to do the fetching, encapsulate the fetching in VieModel. GlobalContext should only be used for fire and forget actions, which are not bound the any views or lifecycle.
How your SearchViewModel could look like:
@Parcelize
class SearchResult(
//fields ...
) : Parcelable
class SearchViewModel(private val savedStateHandle: SavedStateHandle) : ViewModel() {
private var isLoading : Boolean = false
fun searchLiveData() : LiveData<SearchResult> = savedStateHandle.getLiveData<SearchResult>(EXTRA_SEARCH)
fun fetchSearchResultIfNotLoaded() { //do this in onCreate
val liveData = savedStateHandle.getLiveData<SearchResult>(EXTRA_SEARCH)
if(liveData.value == null) {
if(isLoading)
return
isLoading = true
viewModelScope.launch {
try {
val result = withContext(Dispatchers.IO) {
//fetching task
SearchResult()
}
liveData.value = result
isLoading = false
}catch (e : Exception) {
//log
isLoading = false
}
}
}
}
companion object {
private const val EXTRA_SEARCH = "EXTRA_SEARCH"
}
}
And in your Search Fragment onCreate
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val searchResultObserver = Observer<Array<GoodreadsBook>> {
searchResultListViewAdapter.setData(it)
}
viewModel.searchLiveData().observe(viewLifeCycleScope, searchResultObserver)
viewModel.fetchSearchResultIfNotLoaded()
}
If your activity is getting paused in between then also onCreate
of your activity should not be called and that's where you are instantiating the fragment.ie Fragment is not created again(view might be created again).
As as you have subscribed live data in onCreate
of Fragment it should also not trigger an update( onChanged() won't be called for liveData ) again.
Just to be sure about live data is not calling onChanged()
again try below (i feel that's the culprit here as i can't see any other update happening)
viewModel.getSearchResults().distinctUntilChanged().observe(viewLifecycleOwner, searchResultObserver)
onActivityCreated
of fragment.( reference )Instead of using globalScope you can use viewModelScope and launch from inside your ViewModel.(just a suggestion for clean code)
And what's SearchFragmentLifecycleObserver
?
PS - If you can share the ViewModel code and how the search callback's are triggering data it will be great.But Current lifecycle should not effect the creation of new fragment.
I think the Android team in charge of the documentation should really do a better job. I went ahead and just removed the SearchManager
from the SearchView
and use the onQueryTextListener
directly, only to see that with this approach I also get my listener called twice. But thanks to this post, I saw that apparently it's a bug with the emulator (or with the way SearchView
handles the submit event). So if I press the OSK enter button everything works as expected.
Thanks everyone for their help!
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