Catch NotTrackingException when calling HitResult.createAnchor

[DavidWalter]

Hello together, Great project! I like it very much and use it in a current project.

During testing I found that there is the com.google.ar.core.exceptions.NotTrackingException that can occur if createAnchor() is called on a HitResult that is in a scene that is not tracking.

It can be reproduced in the sample-ar-model-viewer with the following steps:

1. Establish tracking and place the robot.
2. Drag the robot and break the tracking.
3. If you then end the drag in the right moment it produces the appended stack-trace.

(I broke the tracking either through blocking the camera with one hand, or by locking the phone and unlocking it again and start dragging right away before the tracking is established)

I would suggest wrapping those calls to the createAnchor() in a try catch mostly because the locations where this happens return an Anchor? anyway, so a try catch does not break any other code but keeps the scene from crashing.

(Tested on Pixel 3a with Android 12)

2022-09-02 14:45:00.639 18540-18540/io.github.sceneview.sample.armodelviewer E/AndroidRuntime: FATAL EXCEPTION: main Process: io.github.sceneview.sample.armodelviewer, PID: 18540 com.google.ar.core.exceptions.NotTrackingException at java.lang.reflect.Constructor.newInstance0(Native Method) at java.lang.reflect.Constructor.newInstance(Constructor.java:343) at com.google.ar.core.Session.throwExceptionFromArStatus(Session.java:14) at com.google.ar.core.HitResult.nativeCreateAnchor(Native Method) at com.google.ar.core.HitResult.createAnchor(HitResult.java:1) at io.github.sceneview.ar.node.ArModelNode.onMoveEnd(ArModelNode.kt:325) at io.github.sceneview.gesture.GestureDetector$moveGestureDetector$1.onMoveEnd(GestureDetector.kt:257) at io.github.sceneview.gesture.MoveGestureDetector.onTouchEvent(MoveGestureDetector.kt:160) at io.github.sceneview.gesture.GestureDetector.onTouchEvent(GestureDetector.kt:328) at io.github.sceneview.SceneView.onTouchEvent(SceneView.kt:546) at android.view.View.dispatchTouchEvent(View.java:14599) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3120) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2801) at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:498) at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1890) at android.app.Activity.dispatchTouchEvent(Activity.java:4199) at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69) at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:456) at android.view.View.dispatchPointerEvent(View.java:14858) at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6446) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:6247) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5725) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5782) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5748) at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5913) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5756) at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5970) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5729) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5782) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5748) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5756) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5729) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8696) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8647) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:8616) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8819) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:259) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:335) at android.os.Looper.loopOnce(Looper.java:161) at android.os.Looper.loop(Looper.java:288) at android.app.ActivityThread.main(ActivityThread.java:7870) 2022-09-02 14:45:00.639 18540-18540/io.github.sceneview.sample.armodelviewer E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) at `com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)

[grassydragon]

Hi! Thank you for the pull request! We'll take this into consideration after the big changes for the version 1.0.0 are merged by Thomas.