lateinit value is always null or not initialized with MapBox - android-fragments

Question

Hello i have an issue with MapBox SDK for android , i use kotlin language in my project and the Viewmap value always came with problem. I'm new in kotlin so maybe i skip something.
i make bottom_navigation_bar so i use fragment to navigate in my application.
my fragment class were i use my variable
package com.example.parky.parky_android
import android.app.Application
import android.content.Context
import android.os.Bundle
import android.support.v4.app.Fragment
import android.support.v7.app.AppCompatActivity
import android.view.ContextThemeWrapper
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.RelativeLayout
import com.mapbox.mapboxsdk.constants.Style
import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.annotations.MarkerOptions;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.maps.MapView;
import com.mapbox.mapboxsdk.maps.MapboxMap;
import com.mapbox.mapboxsdk.maps.OnMapReadyCallback;
class ItemFourFragment : Fragment() {
private lateinit var mapView: MapView
fun onCreate(savedInstanceState: Bundle?, context: Context, inflater: LayoutInflater, container: ViewGroup?) {
super.onCreate(savedInstanceState)
// Mapbox Access token
Mapbox.getInstance(context, getString(R.string.token_mapbox))
val view = inflater.inflate(R.layout.activity_main, container ,false)
mapView = view.findViewById(R.id.mapview)
mapView.onCreate(savedInstanceState)
mapView.getMapAsync({
it.setStyle(Style.SATELLITE)
// Customize map with markers, polylines, etc.
})
}
override fun onStart() {
super.onStart()
mapView.onStart()
}
override fun onResume() {
super.onResume()
mapView.onResume()
}
override fun onPause() {
super.onPause()
mapView.onPause()
}
override fun onStop() {
super.onStop()
mapView.onStop()
}
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
mapView.onSaveInstanceState(outState)
}
override fun onLowMemory() {
super.onLowMemory()
mapView.onLowMemory()
}
override fun onDestroy() {
super.onDestroy()
mapView.onDestroy()
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_item_four, container, false)
}
companion object {
fun newInstance(): ItemFourFragment {
val fragment = ItemFourFragment()
return fragment
}
}
}
And my xml files where i display it :
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:mapbox="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ItemFiveFragment">
<com.mapbox.mapboxsdk.maps.MapView
android:id="#+id/mapview"
android:layout_width="match_parent"
android:layout_height="match_parent"
mapbox:mapbox_cameraTargetLat="41.885"
mapbox:mapbox_cameraTargetLng="-87.679"
mapbox:mapbox_styleUrl="#string/mapbox_style_satellite"
mapbox:mapbox_cameraTilt="20"
mapbox:mapbox_cameraZoom="12"/>
</RelativeLayout>
and finally the log
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.parky.parky_android, PID: 30820
kotlin.UninitializedPropertyAccessException: lateinit property mapView has not been initialized
at com.example.parky.parky_android.ItemFourFragment.onStart(ItemFourFragment.kt:42)
at android.support.v4.app.Fragment.performStart(Fragment.java:2372)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1467)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2245)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:703)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6938)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
Do you have any idea what the problem is ?
Thanks for your time.

Answer 1

So here:
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_item_four, container, false)
}
You're returning a view that will be attached to the Fragment and actually displayed.
Here:
fun onCreate(savedInstanceState: Bundle?, context: Context, inflater: LayoutInflater, container: ViewGroup?) {
super.onCreate(savedInstanceState)
// Mapbox Access token
Mapbox.getInstance(context, getString(R.string.token_mapbox))
val view = inflater.inflate(R.layout.activity_main, container ,false)
mapView = view.findViewById(R.id.mapview)
mapView.onCreate(savedInstanceState)
mapView.getMapAsync({
it.setStyle(Style.SATELLITE)
// Customize map with markers, polylines, etc.
})
}
You're inflating a new view that is never being attached to anything. It's also inflating a separate layout, activity_main.xml, which I assume does not include a MapView.
Instead, you should resolve your MapView within onViewCreated(), after you've returned your inflated view in onCreateView():
override fun onViewCreated(View view, Bundle savedState) {
mapView = view.findViewById(R.id.mapview).apply {
onCreate(savedState)
getMapAsync { map ->
map.setStyle(Style.SATELLITE)
}
}
}
You also should not use lateinit var for this property, as you're not guaranteed to have a view created (e.g. onCreateView() may never be invoked). One instance of this is if your Fragment is on the backstack and not user visible. On a configuration change or recreation of the Activity, the Fragment on the backstack will go through onCreate(), but will not create a view. In this case, you would run into a crash in onStart() attempting to reference mapView that has not been initialized.
Instead, leave it nullable, and perform the operations with mapView?.doThing().