Why is it that my fragment returns a blank screen whenever I use savedInstanceState with it? I've already included the relevant savedInstanceStatecode in my activity, but the associated fragment still doesn't appear at all.
class MyActivity : AppCompatActivity() {
private var mCurrentValue: Boolean = false
private var mTwoPane: Boolean = false
private var activityRecreated: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
val mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
mCurrentValue = mSharedPreferences.getBoolean("preference_a", false)
when {
mCurrentValue -> setTheme(R.style.MyDarkTheme)
else -> setTheme(R.style.MyLightTheme)
}
super.onCreate(savedInstanceState)
activityRecreated = savedInstanceState != null
setContentView(R.layout.md)
}
override fun onStart() {
super.onStart()
setContentView(R.layout.md)
mTwoPane = findViewById<View>(R.id.detail_container) != null
val mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
val mNewValue = mSharedPreferences.getBoolean("preference_a", false)
when {
mCurrentValue != mNewValue -> recreate()
}
val mToolbar = findViewById<Toolbar>(R.id.my_toolbar)
setSupportActionBar(mToolbar)
if (activityRecreated) {
val newFragment = MyFragment()
val transaction = supportFragmentManager.beginTransaction()
transaction.replace(R.id.master_container, newFragment)
transaction.commit()
}
}
}
There are a few problems here.
You should be setting your content view in onCreate(), not onStart(). onStart() can be invoked multiple times for the same Activity instance. For instance, if you start your Activity, press the Home button, and then resume your app, you'll go through onPause(), onStop(), then onStart(), onResume(). You only need to initialize your view when the Activity is created.
Your logic to display the Fragment only executes if the Activity is being recreated. I think you likely meant the inverse. You could simply change that to be if (!activityRecreated) but I would instead suggest cleaning this up by moving your view initialization entirely into onCreate() like so, and only checking if the theme state has changed in onStart():
class MyActivity : AppCompatActivity() {
private val useDarkTheme: Boolean = false
private var twoPane: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
useDarkTheme = shouldUseDarkTheme()
setTheme(if (useDarkTheme) R.style.MyDarkTheme else R.style.MyLightTheme)
super.onCreate(savedInstanceState)
setContentView(R.layout.md)
// savedInstanceState will be null only the first time the Activity is created
if (savedInstanceState == null) {
supportFragmentManager.beginTransaction()
.replace(R.id.master_container, MyFragment())
.commit()
}
twoPane = findViewById<View>(R.id.detail_container) != null
setSupportActionBar(findViewById(R.id.my_toolbar))
}
override fun onStart() {
super.onStart()
if (useDarkTheme != shouldUseDarkTheme()) {
recreate()
}
}
private fun shouldUseDarkTheme(): Boolean =
PreferenceManager.getDefaultSharedPreferences(this).getBoolean("preference_a", false)
}
Related
I am making a simple app in kotlin and would like to add an additional option for night mode like this
example from Material Files app
I was thinking of adding a style and applying it programmatically, But I don't know how to do it properly.
Here's my code:
MainActivity
override fun onCreate(savedInstanceState: Bundle?) {
WindowCompat.setDecorFitsSystemWindows(window, false)
super.onCreate(savedInstanceState)
//It is called after super.onCreate because otherwise isNightMode does not return the correct value
when (ThemeHelper.nightModeChoice(this)) {
"nightModeFollowSystem" -> AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM)
"nightModeOn" -> AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES)
"nightModeOff" -> AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO)
}
override fun onResume() {
super.onResume()
//If MainActivity is recreated return to SettingsFragment to have a nice animation
if (intent.extras != null) {
if (intent.extras!!.getBoolean("TEMA_CAMBIATO")) {
intent.putExtra("TEMA_CAMBIATO", false)
navController.navigate(R.id.SettingsFragment)
}
}
}
ThemeHelper,
this part is a bit messy, but it serves to prevent the activity from being recreated unnecessarily.
object ThemeHelper {
private fun isNightMode(context: Context): Boolean {
return context.resources.configuration.uiMode.and(Configuration.UI_MODE_NIGHT_MASK) == Configuration.UI_MODE_NIGHT_YES
}
fun nightModeChoice(context: Context): String? {
val prefs = PreferenceManager.getDefaultSharedPreferences(context)
return prefs.getString("modTema", "nightModeFollowSystem")
}
fun recreate(context: Context, activity: Activity) {
var flag = true
if (isNightMode(context) && nightModeChoice(context) == "nightModeOn") {
Log.d("THEME_HELPER", "Non c'è bisogno di aggiornare")
flag = false
}
if (!isNightMode(context) && nightModeChoice(context) == "nightModeOff") {
Log.d("THEME_HELPER", "Non c'è bisogno di aggiornare")
flag = false
}
if (flag) {
val intent = activity.intent
intent?.putExtra("TEMA_CAMBIATO", true)
activity.finish()
activity.overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out)
activity.startActivity(intent)
}
}
}
SettingsFragment
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
PreferenceManager.getDefaultSharedPreferences(requireContext()).registerOnSharedPreferenceChangeListener(this)
}
override fun onDestroyView() {
super.onDestroyView()
PreferenceManager.getDefaultSharedPreferences(requireContext()).unregisterOnSharedPreferenceChangeListener(this)
}
override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences?, key: String?) {
if (isAdded) {
if (key == "modTema") {
ThemeHelper.recreate(requireContext(), requireActivity())
}
}
}
I solved in this way btw:
ThemeHelper
fun applyAmoled(context: Context, view: View){
val prefs = PreferenceManager.getDefaultSharedPreferences(context)
if (prefs.getBoolean("modAmoled", false) && isNightMode(context)){
view.setBackgroundColor(Color.BLACK)
}
}
MainActivity after super.onCreate
ThemeHelper.applyAmoled(this, findViewById(R.id.content_main))
It's not the best solution but it works, I just need to recreate activity when needed
So I have my settings activity set up with my < PreferenceScreen > for choosing the app settings.
What I want to do is have my changes do immediate effect, and not on app restart.
Naturally I wanted to use OnSharedPreferenceChangeListener , but if I try to put a Log in onSharedPreferenceChanged, it never procs on changed selection. My plan was to recreate() on preference changed, so my preference apply function would proc on onCreate() with that recreate().
The problem is, as previously stated that onSharedPreferenceChanged never procs.
I tried registering the listener as it was stated somewhere, but it didn't help.
Can anyone help me?
class SettingsActivity : AppCompatActivity(),
PreferenceFragmentCompat.OnPreferenceStartFragmentCallback,
SharedPreferences.OnSharedPreferenceChangeListener {
val Tag = "My Activity:"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val prefMen = SharedPreferencesManager(this)
prefMen.loadTheme()
setContentView(R.layout.activity_settings)
if (savedInstanceState == null) {
supportFragmentManager.beginTransaction()
.replace(R.id.content_preference, MainPreference()).commit()
} else {
title = savedInstanceState.getCharSequence(TAG_TITLE)
}
supportFragmentManager.addOnBackStackChangedListener {
if (supportFragmentManager.backStackEntryCount == 0) {
setTitle("Settings")
}
}
setUpToolbar()
}
override fun onStart() {
super.onStart()
getPreferences(MODE_PRIVATE).unregisterOnSharedPreferenceChangeListener(this)
}
override fun onDestroy() {
super.onDestroy()
getPreferences(MODE_PRIVATE).unregisterOnSharedPreferenceChangeListener(this)
}
override fun onSaveInstanceState(outState: Bundle, outPersistentState: PersistableBundle) {
super.onSaveInstanceState(outState, outPersistentState)
outState.putCharSequence(TAG_TITLE, title)
}
override fun onSupportNavigateUp(): Boolean {
if (supportFragmentManager.popBackStackImmediate()) {
return true
}
return super.onSupportNavigateUp()
}
private fun setUpToolbar() {
supportActionBar?.setTitle("Settings")
supportActionBar?.setDisplayHomeAsUpEnabled(true)
supportActionBar?.setDisplayShowHomeEnabled(true)
}
class MainPreference : PreferenceFragmentCompat() {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
setPreferencesFromResource(R.xml.preferences, rootKey)
}
}
override fun onPreferenceStartFragment(
caller: PreferenceFragmentCompat?,
pref: Preference?
): Boolean {
val args = pref?.extras
val fragment = pref?.fragment?.let {
supportFragmentManager.fragmentFactory.instantiate(
classLoader,
it
).apply {
arguments = args
setTargetFragment(caller, 0)
}
}
fragment?.let {
supportFragmentManager.beginTransaction().replace(R.id.content_preference, it)
.addToBackStack(null).commit()
}
title = pref?.title
return true
}
companion object {
private val TAG_TITLE = "PREFERENCE_ACTIVITY"
}
override fun onSharedPreferenceChanged(sharedPreferences: SharedPreferences?, key: String?) {
recreate()
}
}
I see two mistakes. The first is that you never register your listener. You have called unregisterOnSharedPreferenceChangeListener() in your onStart() instead of registerOnSharedPreferenceChangeListener().
Secondly, you are not listening to the same SharedPreferences as the settings Fragment is using. PreferenceFragmentCompat by default uses the default shared preferences of the whole application. But you are listening to preferences retrieved with Activity.getPreferences(), which are not the default preferences, but rather a SharedPreferences instance that is named after the Activity.
So you should switch to using default shared preferences, because the private shared preferences of the Activity will not be as easy to get a reference to in other activities.
I would also register in onCreate() instead of onStart() so you aren't registering multiple times. I don't know if that really matters, but the documentation doesn't specify what happens when you repeatedly register the same listener. Maybe it would fire the callback repeatedly, which could end up wasting your time hunting the bug later.
override fun onCreate() {
// ...
PreferenceManager.getDefaultSharedPreferences(this)
.registerOnSharedPreferenceChangeListener(this)
}
override fun onDestroy() {
super.onDestroy()
PreferenceManager.getDefaultSharedPreferences(this)
.unregisterOnSharedPreferenceChangeListener(this)
}
It is possible to specify the SharedPreferences that will be used by PreferenceFragmentCompat, but the default preferences are the easiest to use for settings that you want to access from across your application.
I want to use a DropDownPreference for my settings page but despite looking all over the internet, there doesn't seem to be any decent tutorial on how to do this. Does anyone know what should go in the onPreferenceChange method? I previously used a RadioButton but now want to use a DropDownPreference for easier implementation and maintenance.
Activity
class SettingsActivity : AppCompatActivity(), FragmentSettings.PreferenceXchangeListener {
private var mCurrentValue: Boolean = false // False is the default value
override fun onCreate(savedInstanceState: Bundle?) {
val mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
mCurrentValue = mSharedPreferences.getBoolean("preference_dark", false)
if (mCurrentValue) {
setTheme(R.style.MyDarkSettingsTheme)
} else {
setTheme(R.style.MyLightSettingsTheme)
}
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_settings)
val viewllSettingsContainer = settings_container
val root = viewllSettingsContainer.rootView
if (mCurrentValue) {
root.setBackgroundColor(Color.BLACK)
} else {
root.setBackgroundColor(Color.WHITE)
}
val settingsFragment = FragmentSettings()
supportFragmentManager
.beginTransaction()
.replace(R.id.settings_container, settingsFragment)
.commit()
}
override fun onXchange(value:Boolean) {
when {
mCurrentValue != value -> {
mCurrentValue = value
recreate()
}
}
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
android.R.id.home -> {
val intent = parentActivityIntent
intent?.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION)
onBackPressed()
true
}
else ->
super.onOptionsItemSelected(item)
}
}
}
Fragment
class SettingsFragment : PreferenceFragmentCompat(), Preference.OnPreferenceChangeListener,
Preference.OnPreferenceClickListener {
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
addPreferencesFromResource(R.xml.app_preferences)
}
}
I think you're over-complicating it. There is no need to involve the fragment in listening to changes to a preference it won't be handling and passing that back to the activity. You can register a preference change listener for all preferences in your Activity and respond accordingly there.
class SettingsActivity : AppCompatActivity(),
SharedPreferences.OnSharedPreferenceChangeListener {
override fun onCreate(savedInstanceState: Bundle?) {
val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
sharedPreferences.registerOnSharedPreferenceChangeListener(this)
//...
}
override fun onDestroy() {
val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this)
sharedPreferences.unregisterOnSharedPreferenceChangeListener(this)
//...
super.onDestroy()
}
override fun onSharedPreferenceChanged(_: SharedPreferences, key: String) {
when (key){
"preference_dark" -> recreate()
}
}
}
I have a fragment class that contains a ViewPager with two sites. These sites contain a few widgets like CheckBoxes and I want them to stay checked when the orientation changes.
MainFragment:
class StatsFragment: Fragment() {
private val fragmentStatsCat = StatsCategoryFragment()
private val fragmentStatsMon = StatsMonthFragment()
private lateinit var pager: ViewPager
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view: View = inflater.inflate(R.layout.fragment_stats, container, false)
pager = view.findViewById(R.id.stats_container)
val pagerAdapter = StatsScreenSlidePagerAdapter(childFragmentManager)
pager.adapter = pagerAdapter
return view
}
private inner class StatsScreenSlidePagerAdapter(fm: FragmentManager): FragmentStatePagerAdapter(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
override fun getItem(position: Int): Fragment {
return if (position == 0) {
fragmentStatsCat
} else {
fragmentStatsMon
}
}
override fun getCount(): Int = 2
override fun saveState(): Parcelable? {
return null
}
}
}
One of the ViewPagerFragments:
class StatsMonthFragment: Fragment() {
companion object {
private const val CHECKBOX_KEY = "isChecked"
private const val CATEGORY_KEY = "category"
}
private lateinit var btnPrevCat: ImageButton
private lateinit var btnNextCat: ImageButton
private lateinit var cbAllCats: CheckBox
private lateinit var categories: List<Category>
private var i: Int = 0
private var isCbChecked: Boolean? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if(savedInstanceState != null) {
i = savedInstanceState.getInt(CATEGORY_KEY)
isCbChecked = savedInstanceState.getBoolean(CHECKBOX_KEY)
}
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_stats_months, container, false)
btnNextCat = view.findViewById(R.id.btn_next_cat)
btnPrevCat = view.findViewById(R.id.btn_prev_cat)
cbAllCats = view.findViewById(R.id.cb_all_cats)
categories = DatabaseInitializer.getInstance().getAllCategories(AppDatabase.getInstance(context).categoryDao())
if(isCbChecked == null || isCbChecked!!) {
val initFragment = StatsSelectedFilterFragment() //This is just a fragment with a TextView; I use fragments for that for the CustomAnimations
initFragment.setText(categories[i].cat_name)
childFragmentManager.beginTransaction().add(R.id.container_stats_categories, initFragment).commit()
} else {
val fragment = StatsSelectedFilterFragment()
fragment.setText(getString(R.string.all_categories))
childFragmentManager.beginTransaction()
.replace(R.id.container_stats_categories, fragment)
.commit()
}
btnNextCat.setOnClickListener {
val fragment = StatsSelectedFilterFragment()
fragment.setText(categories[i].cat_name)
childFragmentManager.beginTransaction()
.setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left)
.replace(R.id.container_stats_categories, fragment)
.commit()
}
btnPrevCat.setOnClickListener {
val fragment = StatsSelectedFilterFragment()
fragment.setText(categories[i].cat_name)
childFragmentManager.beginTransaction()
.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right)
.replace(R.id.container_stats_categories, fragment)
.commit()
}
cbAllCats.setOnCheckedChangeListener{_,checked->
if(checked) {
val fragment = StatsSelectedFilterFragment()
fragment.setText(getString(R.string.all_categories))
childFragmentManager.beginTransaction()
.replace(R.id.container_stats_categories, fragment)
.commit()
} else {
val fragment = StatsSelectedFilterFragment()
fragment.setText(categories[i].cat_name)
childFragmentManager.beginTransaction()
.replace(R.id.container_stats_categories, fragment)
.commit()
}
}
return view
}
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
val isAllCatsChecked = cbAllCats.isChecked
outState.putBoolean(CHECKBOX_KEY, isAllCatsChecked)
outState.putInt(CATEGORY_KEY, i)
}
}
Now on every screen rotation, the fragment gets recreated twice, first with savedInstanceState != null and then with savedInstanceState == null, which means that I don't have access to the old settings in the Fragments. As I know, it is because the fragment gets recreated, and then the MainFragment containing the viewpager gets also recreated, which means that the fragments within the viewPager get created a second time. I have tried something like this in the MainFragment:
private lateinit var fragmentStatsCat: StatsCategoryFragment
private lateinit var fragmentStatsMon: StatsMonthFragment
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if(savedInstanceState == null) {
fragmentStatsMon = StatsMonthFragment()
fragmentStatsCat = StatsCategoryFragment()
} else {
//Finding old fragments
}
}
Maybe this would solve the problem (I am not sure), but I don't know how I can find the fragments, as they are inside a ViewPager.
EDIT
I have now found a solution to find the fragments when the activity is recreated:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if(savedInstanceState == null)
{
fragmentStatsMon = StatsMonthFragment()
fragmentStatsCat = StatsCategoryFragment()
} else {
fragmentStatsMon = childFragmentManager.getFragment(savedInstanceState, FRAG_MONTH_TAG) as StatsMonthFragment
fragmentStatsCat = childFragmentManager.getFragment(savedInstanceState, FRAG_CAT_TAG) as StatsCategoryFragment
}
}
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
childFragmentManager.putFragment(outState, FRAG_CAT_TAG, fragmentStatsCat)
childFragmentManager.putFragment(outState, FRAG_MONTH_TAG, fragmentStatsMon)
}
This puts a reference in the Bundle with which I can get the fragment afterwards. But now, I have another problem. When the activity is recreated, it throws the following exception:
java.lang.IllegalStateException: Fragment already added: StatsCategoryFragment{f06ec65 (a1991f39-3af4-4a74-9aeb-79274beae04a) id=0x7f09014a}
I don't know how to solve that because I don't really manually add the fragments. Also, I don't really get it because the viewpager and the adapter also get recreated, don't they? So why are the fragments still attached to the adapter?
I also don't know in which line of code this happens, I could neither find it out in the logcat nor by debugging.
Put this line in AndroidManifest.xml in the entry of your Activity in which you are loading your Fragments:
android:configChanges="layoutDirection|keyboardHidden|orientation|screenSize"
By this, Data will not be reset when your Fragment is recreated by any condition.
Example:
<activity
android:name=".activity.MainActivity"
android:configChanges="layoutDirection|keyboardHidden|orientation|screenSize"
android:label="#string/app_name"></activity>
Check out this similar question
https://www.google.com/url?sa=t&source=web&rct=j&url=https://stackoverflow.com/questions/15313598/once-for-all-how-to-correctly-save-instance-state-of-fragments-in-back-stack&ved=2ahUKEwja6rasobzjAhVh1uAKHRakDXIQFjAAegQIBhAB&usg=AOvVaw0Hg_vwSnBayxV1EJfKOUZk
Guess I'm missing something obvious here but... I'm storing data in uiModel in the DiaryViewModel class, and since I use architecture components I'm expecting the data to be retained through screen rotation - but it doesn't. I'm blind to why.
Here's a stripped down fragment
class DiaryFragment: Fragment() {
private lateinit var viewModel: DiaryViewModel
override onCreateView(...) {
viewModel = ViewModelProviders.of(this).get(DiaryViewModel::class.java)
viewModel.getModel().observe(this, Observer<DiaryUIModel> { uiModel ->
render(uiModel)
})
}
}
And the corresponding view model.
class DiaryViewModel: ViewModel() {
private var uiModel: MutableLiveData<DiaryUIModel>? = null
fun getModel(): LiveData<DiaryUIModel> {
if (uiModel == null) {
uiModel = MutableLiveData<DiaryUIModel>()
uiModel?.value = DiaryUIModel()
}
return uiModel as MutableLiveData<DiaryUIModel>
}
}
Can any one see what's missing in this simple example? Right now, uiModel is set to null when rotating the screen.
The issue was with how the activity was handling the fragment creation. MainActivity was always creating a new fragment per rotation, as in
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
supportFragmentManager
.beginTransaction()
.replace(overlay.id, DiaryFragment.newInstance())
.commit()
}
But of course, it works much better when checking if we have a saved instance, as in
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
if (savedInstanceState == null) {
supportFragmentManager
.beginTransaction()
.replace(overlay.id, DiaryFragment.newInstance())
.commit()
}
}