this ar app doesn't work properly on API 23.
and I need some support I want to make an AR app in flutter but I can't get resources for it that how to create my custom model so can you please help me?

.add doesn't exist in latest.

Also Running this now I get it to start but crashes immediately:
E/AndroidRuntime( 7204): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sheep_herder_ar/com.google.ar.core.InstallActivity}: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState
E/AndroidRuntime( 7204): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)

Getting the following error message in the console:
Launching lib/main.dart on Nokia 8 1 in debug mode... Initializing gradle... 1.6s Resolving dependencies... 2.8s Running Gradle task 'assembleDebug'... Running Gradle task 'assembleDebug'... Done 3.9s Built build\app\outputs\apk\debug\app-debug.apk. I/Filament(32511): FEngine (64 bits) created at 0x7441400000 (threading is enabled) D/Filament(32511): Using ASurfaceTexture D/Filament(32511): FEngine resolved backend: OpenGL I/SceneView(32511): Optional library com.google.ar.sceneform.animation not present. Sceneform animation disabled I/DecorView(32511): It non-support bigbang I/PhoneWindow(32511): generateLayout isLightNavi false, Visibility: 0 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): arScenViewInit I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): name: [yatd]nm_t[vjxuy I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): shape: dartType: ArCoreSphere I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): radius: 0.2 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): size: [x=0.0, y=0.0, z=0.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): height: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): material: color: -10011977 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): argb: [255, 103, 58, 183] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): metallic: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): reflectance: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): position: [x=0.0, y=0.0, z=-1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): name: [yatd]nm_t[vjxuy I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): shape: dartType: ArCoreSphere I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): radius: 0.2 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): size: [x=0.0, y=0.0, z=0.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): height: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): material: color: -10011977 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): argb: [255, 103, 58, 183] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): metallic: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): reflectance: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): position: [x=0.0, y=0.0, z=-1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): name: [gpdlnxua\_upkpw I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): shape: dartType: ArCoreCube I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): radius: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): size: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): height: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): material: color: -1499549 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): argb: [255, 233, 30, 99] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): metallic: 1.0 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): reflectance: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): position: [x=-0.5, y=-0.5, z=-3.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): name: [gpdlnxua\_upkpw I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): shape: dartType: ArCoreCube I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): radius: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): size: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): height: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): material: color: -1499549 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): argb: [255, 233, 30, 99] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): metallic: 1.0 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): reflectance: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): position: [x=-0.5, y=-0.5, z=-3.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): name: wwmufjcephkh\ttj I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): shape: dartType: ArCoreCylinder I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): radius: 0.3 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): size: [x=0.0, y=0.0, z=0.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): height: 0.4 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): material: color: -11751600 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): argb: [255, 76, 175, 80] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): metallic: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): reflectance: 1.0 I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): position: [x=0.0, y=-2.5, z=-3.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): dartType: ArCoreNode I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): name: wwmufjcephkh\ttj I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): shape: dartType: ArCoreCylinder I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): radius: 0.3 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): size: [x=0.0, y=0.0, z=0.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): height: 0.4 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): material: color: -11751600 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): argb: [255, 76, 175, 80] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): texture: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): metallic: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): roughness: null I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): reflectance: 1.0 I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): position: [x=0.0, y=-2.5, z=-3.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): scale: [x=1.0, y=1.0, z=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.NodeFactory(32511): rotation: [x=0.0, y=0.0, z=0.0, w=1.0] I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): onActivityPaused I/com.difrancescogianmarco.arcore_flutter_plugin.RenderableCustomFactory(32511): material not null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addNodeToSceneWithGeometry: NOT PARENT_NODE_NAME I/com.difrancescogianmarco.arcore_flutter_plugin.RenderableCustomFactory(32511): material not null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addNodeToSceneWithGeometry: NOT PARENT_NODE_NAME I/com.difrancescogianmarco.arcore_flutter_plugin.RenderableCustomFactory(32511): material not null I/com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView(32511): addNodeToSceneWithGeometry: NOT PARENT_NODE_NAME W/ActivityThread(32511): handleWindowVisibility: no activity for token android.os.BinderProxy@9dcadac D/AndroidRuntime(32511): Shutting down VM E/AndroidRuntime(32511): FATAL EXCEPTION: main E/AndroidRuntime(32511): Process: com.example.flutter_ar, PID: 32511 E/AndroidRuntime(32511): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.flutter_ar/com.google.ar.core.InstallActivity}: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState E/AndroidRuntime(32511): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2928) E/AndroidRuntime(32511): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3063) E/AndroidRuntime(32511): at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) E/AndroidRuntime(32511): at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) E/AndroidRuntime(32511): at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) E/AndroidRuntime(32511): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1823) E/AndroidRuntime(32511): at android.os.Handler.dispatchMessage(Handler.java:107) E/AndroidRuntime(32511): at android.os.Looper.loop(Looper.java:198) E/AndroidRuntime(32511): at android.app.ActivityThread.main(ActivityThread.java:6729) E/AndroidRuntime(32511): at java.lang.reflect.Method.invoke(Native Method) E/AndroidRuntime(32511): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) E/AndroidRuntime(32511): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:876) E/AndroidRuntime(32511): Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState E/AndroidRuntime(32511): at com.difrancescogianmarco.arcore_flutter_plugin.ArCoreView$setupLifeCycle$1.onActivityCreated(Unknown Source:7) E/AndroidRuntime(32511): at android.app.Application.dispatchActivityCreated(Application.java:220) E/AndroidRuntime(32511): at android.app.Activity.onCreate(Activity.java:1048) E/AndroidRuntime(32511): at com.google.ar.core.InstallActivity.onCreate(InstallActivity.java:4) E/AndroidRuntime(32511): at android.app.Activity.performCreate(Activity.java:7136) E/AndroidRuntime(32511): at android.app.Activity.performCreate(Activity.java:7127) E/AndroidRuntime(32511): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272) E/AndroidRuntime(32511): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2908) E/AndroidRuntime(32511): ... 11 more Syncing files to device Nokia 8 1... 1,536ms

hi there! thanks for your good tutorial on youtube... can you record a video about loading 3d models (gltf , glb , etc ...) with arcore flutter for android or tell me some sources? thanks a lot for answer and helping.