MapSnapshotter callback is not always invoked

[fdermishin-radargeo]

Platform: Android
Mapbox SDK version: 5.5.2, 6.0.0-beta.6

Steps to trigger behavior

There is a simple layout containing button and imageView. Clicking on button starts MapSnapshotter.

import android.graphics.Color
import android.graphics.drawable.ColorDrawable
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import com.mapbox.mapboxsdk.Mapbox
import com.mapbox.mapboxsdk.camera.CameraPosition
import com.mapbox.mapboxsdk.geometry.LatLng
import com.mapbox.mapboxsdk.snapshotter.MapSnapshotter
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        Mapbox.getInstance(this, "XXXXXX")
    }

    fun onButtonClick(button: View) {
        val location = LatLng(52 + Math.random(), 13 + Math.random())
        val width = imageView.width
        val height = imageView.height

        val cameraPosition = CameraPosition.Builder()
                .target(location)
                .zoom(12.0)
                .build()
        val options = MapSnapshotter.Options(width, height)
                .withCameraPosition(cameraPosition)

        imageView.setImageDrawable(null)
        MapSnapshotter(this, options).start({ snapshot ->
            imageView.setImageBitmap(snapshot.bitmap)
        }, {
            imageView.setImageDrawable(ColorDrawable(Color.RED))
        })
    }
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onButtonClick"
        android:text="Button"
        app:layout_constraintBottom_toTopOf="@id/imageView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="200dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/button"
        app:srcCompat="@android:color/darker_gray" />
</android.support.constraint.ConstraintLayout>

Expected behavior

After each press imageView displays either a map snapshot or it becomes red.

Actual behavior

Sometimes neither SnapshotReadyCallback nor ErrorHandler is called, so imageView remains blank.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[LukasPaczos]

After re-introduction of a MapSnapshotter test in #15121 and error logging in #15141, we're seeing tests timing out (30 seconds without a snapshot being delivered), even though there's no error emitted from core.

Example builds:

• https://circleci.com/gh/mapbox/mapbox-gl-native/302017
• https://circleci.com/gh/mapbox/mapbox-gl-native/302007

/cc @tobrun @tmpsantos

[chloekraw]

cc @alexshalamov

[brandikun]

I am also using snapshotter in kotlin for Android and it typically takes about 3 tries before I can get the callback to fire. No crash, no error emitted.

[tobrun]

We were able to boil this down to the Snapshotter object being garbage collected before returning the result, solution is to retain the snapshotter instance (eg. scope it to the hosting class).