I need to know the size of a Button (or any other view).
But none of the procedures in lifecycle (onCreate, onStart, OnResume) seem to know it, as the Button seems not yet to be initialized!
...
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
private var servOffset: Int=0 // Value depends on Layout/Orientation and Device
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
btPunkte.setOnClickListener { doPunkt(true) }
servOffset = btPR1.width/2 // 'btPR1' is a Button in 'Layout activity_main.*'
//ToDo: Doesn't work! = remains 0
}
override fun onResume() {
super.onResume()
// ToDo: unsolved! When do I get the size??
// onStart (or onResume) are invoked correctly, but don't know the value!
// ?? Button doesn't yet exist in Livecycle?!
servOffset = btPR1.width/2 // //ToDo: Still doesn't work!
anzeigeAktualisieren()
}
private fun anzeigeAktualisieren() {
// If ... move Button
btPR1.x += servOffset //ToDo: unsolved offset remains 0 ?!
}
private fun doPunkt(links:Boolean) {
anzeigeAktualisieren()
...
}
...
}
I did find "When are views drawn", and several other threads, but they didn't help me solve my problem.
You can try using viewTreeObserver.
val vto = button.viewTreeObserver
vto.addOnGlobalLayoutListener {
Log.e("Show me width", button.width.toString())
}
It is working, but it can and WILL be called several times!!!
Other option is to use Handler and postDelayed
Handler().postDelayed({
Log.e("Show me width2", button.width.toString())
}, 1000)
Yes, this is very bad practice, but it can save you in stupid situation :)
Good luck!
Related
When the button is clicked, data is received from the API, after which the Observer is fired, however, even with removeObservers, it is called twice.
Without removeObservers it triggers more than 2 times.
MainActivity
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
TestApiAppTheme {
Surface() {
TextInfo()
}
}
}
}
#Preview
#Composable
fun TextInfo() {
val viewModel = ViewModelProvider(this).get(MainViewModel::class.java)
var txt = remember {
mutableStateOf(0)
}
viewModel.serverInfoResponse.removeObservers(this)
viewModel.serverInfoResponse.observe(this) {
txt.value = it.players
Toast.makeText(this, "${it.players} -", Toast.LENGTH_SHORT).show()
}
Column() {
Text(
text = txt.value.toString(),
)
Button(onClick = {
viewModel.getServerInfo()
visible = true
}) {
Text("Update")
}
}
}}
ViewModel
var serverInfoResponse = MutableLiveData<ServerInfo>()
fun getServerInfo() {
viewModelScope.launch {
val apiService = ApiService.getInstance()
val info = apiService.getInfo()
serverInfoResponse.value = info
}
}
A composable function can be called multiple times, whenever the it observes changes removeObserver() and observe() should not be called directly but, rather in some effect.
The extension function observeAsState() does all work to subscribe and correctly unsubscribe for you.
Composable functions can get called many times although the compiler tries to reduce how often.
You should not have side effects in them such as adding and removing the observer. Since LiveData sends the last item out to new subscribers, every time this function composes you get the value again.
The correct way to consume live data is to convert it to a state. https://developer.android.com/reference/kotlin/androidx/compose/runtime/livedata/package-summary
But then you still have problems with showing the toast too often. For that you will need something like a LaunchEffect to make sure you only show a toast once. Might want to consider if you really need a toast or if a compose type UI would be better.
I'm working on a news app and I want my layout to become invisible when a user saves an article. Can anyone please tell me the right way to write this code?
2 things to note:
-when I run the app,the layout is visible in the "saved fragment"
but then when I add "hideSavedMessage" right next to the code that updates the recyclerView and I run the app, the layout becomes invisible.
I want the layout to be invisible only when the user saves an article.
PS: I know how the visible and invisible mode works. I have used it before. My major problem is not knowing the right place to write the code. And by layout, I mean the text view and image view that appears on the screen. I would appreciate any contributions. Thank you.
Here's my code
class SavedFragment : Fragment(R.layout.fragment_saved) {
lateinit var viewModel: NewsViewModel
lateinit var newsAdapter: SavedAdapter
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel = (activity as NewsActivity).viewModel
setupRecyclerView()
newsAdapter.setOnItemClickListener {
val bundle = Bundle().apply {
putSerializable("article", it)
}
findNavController().navigate(
R.id.action_savedFragment_to_savedArticleFragment,
bundle
)
}
val itemTouchHelperCallback = object : ItemTouchHelper.SimpleCallback(
ItemTouchHelper.UP or ItemTouchHelper.DOWN,
ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
) {
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val position =
viewHolder.adapterPosition//get position of item we deleted so that we swipe to left or right
val article =
newsAdapter.differ.currentList[position]//from news adapter at the index of the position
viewModel.deleteArticle(article)
Snackbar.make(view, "Successfully deleted article", Snackbar.LENGTH_LONG)
.apply {
setAction("Undo") {
viewModel.saveArticle(article); hideSavedMessage()
}
show()
}
val isAtLastItem = position <= 0
val shouldUpdateLayout = isAtLastItem
if (shouldUpdateLayout) {
showSavedMessage()
}
}
}
ItemTouchHelper(itemTouchHelperCallback).apply {
attachToRecyclerView(rvSavedNews)
}
viewModel.getSavedNews().observe(viewLifecycleOwner, Observer { articles ->
newsAdapter.differ.submitList(articles)
})
}
private fun setupRecyclerView() {
newsAdapter = SavedAdapter()
rvSavedNews.apply {
adapter = newsAdapter
layoutManager = LinearLayoutManager(activity)
}
}
private fun hideSavedMessage() {
savedMessage.visibility = View.INVISIBLE
isArticleAdded = false
}
private fun showSavedMessage() {
savedMessage.visibility = View.VISIBLE
}
}
The problem is that code inside observer runs even at the beginning - when you run your app, right? If I understand your problem, you just have to manage to make the fun hideSavedMessage() not be running for the first time. You could for example instantiate a boolean in onCreate() and set it to false. Then, inside the observer, you could run the hideSavedMessage() only if that boolean is true - you would set it as true at the end of the observer. I hope you understand.
I have been reading the different answers here on stackoverflow and on this blog post and tried to implement their solutions but I am still getting the error. The code is from a yt tutorial. I hope someone can help me. Thanks
Error E/RecyclerView: No adapter attached; skipping layout
My Adapter
This is my Main Activity
class MainActivity : AppCompatActivity(), IDrinkLoadListener {
lateinit var drinkLoadListener: IDrinkLoadListener
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
init()
loadDrinkFromFirebase()
}
private fun loadDrinkFromFirebase() {
val drinkModels : MutableList<DrinkModel> = ArrayList()
FirebaseDatabase.getInstance()
.getReference("Drink")
.addListenerForSingleValueEvent(object: ValueEventListener{
override fun onDataChange(snapshot: DataSnapshot) {
if(snapshot.exists()) {
for (drinkSnapshot in snapshot.children) {
val drinkModel = drinkSnapshot.getValue(DrinkModel::class.java)
drinkModel!!.key = drinkSnapshot.key
drinkModels.add(drinkModel)
}
drinkLoadListener.onDrinkLoadSuccess(drinkModels)
} else
drinkLoadListener.onDrinkLoadFailed("Drink items not exist")
}
override fun onCancelled(error: DatabaseError) {
drinkLoadListener.onDrinkLoadFailed(error.message)
}
})
}
private fun init() {
drinkLoadListener = this
val gridLayoutManager = GridLayoutManager(this, 2)
recycler_drink.layoutManager = gridLayoutManager
recycler_drink.addItemDecoration(SpaceItemDecoration())
}
override fun onDrinkLoadSuccess(drinkModelList: List<DrinkModel>?) {
val adapter = MyDrinkAdapter(this,drinkModelList!!)
recycler_drink.adapter = adapter
}
override fun onDrinkLoadFailed(message: String?) {
Snackbar.make(mainLayout,message!!,Snackbar.LENGTH_LONG).show()
}
}
class SpaceItemDecoration : RecyclerView.ItemDecoration() {
override fun getItemOffsets(
outRect: Rect,
view: View,
parent: RecyclerView,
state: RecyclerView.State
) {
if(parent.getChildLayoutPosition(view) % 2 != 0)
{
outRect.top= 25
outRect.bottom= -25
}else outRect.top = 0
}
}
Thanks in advance!!!
That happens because the adapter is attached to the recycler after an asynchronous operation on onDrinkLoadSuccess
You can attach the adapter to the recycler during onCreate and then the onDrinkLoadSuccess update it with the data.
The ListAdapter class has a submit method for it. If you are using plain recycler is usually something like this:
Recycler ... {
private val dataList = mutableListOf()
fun update(list: List<YourType>) {
dataList.clear()
dataList.addAll(list)
notifyDataDetChanged() //important updates the UI
}
}
There are more specific updates methods like notifyItemRangeChanged, etc.
Also there are helpers for finding difference in the data sets DiffUtil.ItemCallback
class DialFragment: DialogFragment() {
private lateinit var image001: ImageView
private val caller = object: FingerprintManager.AuthenticationCallback() {
override fun onAuthenticationError(errorCode: Int, errString: CharSequence?) {
super.onAuthenticationError(errorCode, errString)
listener.onDialClick(errString.toString(), "2")
dismiss()
}
override fun onAuthenticationSucceeded(result: FingerprintManager.AuthenticationResult?) {
super.onAuthenticationSucceeded(result)
listener.onDialClick("yes","1")
var avp = image001.drawable as AnimatedVectorDrawable
avp.start()
dismiss()
}
override fun onAuthenticationFailed() {
super.onAuthenticationFailed()
listener.onDialClick("no","3")
dismiss()
}
The animation called by avp.start() is not beeing shown, the dialog fragment directly dismisses after succesfull authentification. if i omit the dismiss()-Call below then it works properly. My question is why is this and how to fix it? And yes, i know FingerprintManager-API is deprecated, i am running this for test purposes.
dismiss() immediately ends the life of your DialogFragment, so it will have no more opportunity to show you any animations in the Fragment. You should dismiss after a delay (however long the animation is).
override fun onAuthenticationSucceeded(result: FingerprintManager.AuthenticationResult?) {
super.onAuthenticationSucceeded(result)
listener.onDialClick("yes","1")
var avp = image001.drawable as AnimatedVectorDrawable
avp.start()
activity?.runOnUiThread(300L) { // put however long your animation takes
dismiss()
}
}
When you press the button to open a separate input window, there is a function to display the results toast.
class MainActivity : AppCompatActivity() {
val disposable = CompositeDisposable()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
button.setOnClickListener {
val f = TestPopup()
usingRxJava(f)
//usingLiveData(f)
}
}
private fun usingRxJava(f: TestPopup) {
val subject = SingleSubject.create<String>()
f.show(supportFragmentManager, "TAG")
button.post {
f.dialog.setOnDismissListener {
val str = f.arguments?.getString(TestPopup.TEST_KEY) ?: ""
subject.onSuccess(str)
}
}
subject.subscribe({
Toast.makeText(this, "Accept : $it", Toast.LENGTH_SHORT).show()
}, {
}).addTo(disposable)
}
private fun usingLiveData(f: TestPopup) {
val liveData = MutableLiveData<String>()
f.show(supportFragmentManager, "TAG")
button.post {
f.dialog.setOnDismissListener {
val str = f.arguments?.getString(TestPopup.TEST_KEY) ?: ""
liveData.postValue(str)
}
}
liveData.observe(this, Observer {
Toast.makeText(this, "Accept : $it", Toast.LENGTH_SHORT).show()
})
}
override fun onDestroy() {
disposable.dispose()
super.onDestroy()
}
}
DialogFragment
class TestPopup : DialogFragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.dialog_test, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
button_test.setOnClickListener {
val arg = Bundle()
arg.putString(TEST_KEY, edit_test.text.toString())
arguments = arg
dismiss()
}
}
companion object {
const val TEST_KEY = "KEY"
}
}
(Sample Project Url : https://github.com/heukhyeon/DialogObserverPattern )
This sample code works in normal cases. However, the toast does not float after the following procedure.
Developer Option - Dont'keep activities enable
Open TestPopup, and enter your text. (Do not press OK button)
Press the home button to move the app to the background
The app is killed by the system.
Reactivate the app (Like clicking on an app in the apps list)
In this case, the text I entered remains on the screen, but nothing happens when I press the OK button.
Of course I know this happens because at the end of the activity the observe relationship between the activity and the Dialog is over.
Most of the code uses the implementation of the callback interface for that Dialog in the Activity to handle that case.
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
button_test.setOnClickListener {
val input = edit_test.text.toString()
(activity as MyListener).inputComplete(input)
dismiss()
}
}
class MainActivity : AppCompatActivity(), TestPopup.MyListener {
override fun inputComplete(input: String) {
Toast.makeText(this, "Accept : $input", Toast.LENGTH_SHORT).show()
}
}
But I think it's a way that doesn't match the Observer pattern, and I want to implement it using the Observer pattern as much as possible.
I'm thinking of getting a Fragment from the FragmentManager and subscribing again at onCreate, but I think there's a better way.
Can someone help me?
Your understanding of the problem is correct, except that the problem happens with any configuration changes, including screen rotation. You can reproduce issue without using the developer mode. Try this for example:
Open TestPopup, and enter your text. (Do not press OK button)
Rotate screen
See toast message not popping up.
Also note that your "observer pattern" implementation is not a proper observer pattern. Observer pattern has a subject and an observer. In your implementation, the activity is acting as both the subject and the observer. The dialog is not taking any part in this observer pattern, and using .setOnDismissListener is just another form of a listener pattern.
In order to implement observer pattern between the Fragment(the subject) and the Activity(the observer), the Activity needs to get the reference of the Fragment using the FragmentManager as you suggested. I suggest to use view model and establish observer pattern between view layer and view model layer instead.
RxJava example:
//MainViewModel.kt
class MainViewModel: ViewModel() {
val dialogText = PublishProcessor.create<String>()
fun postNewDialogText(text: String) {
dialogText.onNext(text)
}
}
// Activity
val disposable = CompositeDisposable()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
viewModel.dialogText.subscribe {
Toast.makeText(this, "Accept : $it", Toast.LENGTH_SHORT).show()
}.addTo(disposable)
button.setOnClickListener {
TestPopup().show(supportFragmentManager, "TAG")
// usingRxJava(f)
// usingLiveData(f)
}
}
override fun onDestroy() {
disposable.dispose()
super.onDestroy()
}
// Dialog Fragment
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
// Important!! use activity when getting the viewmodel.
val viewModel = ViewModelProviders.of(requireActivity()).get(MainViewModel::class.java)
button_test.setOnClickListener {
viewModel.postNewDialogText(edit_test.text.toString())
dismiss()
}
}