[Android] Fix handling of back navigation when targeting API level 36

platform/android/java/lib/src/main/java/org/godotengine/godot/Godot.kt

@@ -122,6 +122,15 @@ class Godot private constructor(val context: Context) {
 		internal fun isEditorBuild() = BuildConfig.FLAVOR == EDITOR_FLAVOR
 	}
 
+	/**
+	 * Describes the engine current run status.
+	 */
+	enum class RunStatus {
+		INITIALIZING,
+		STARTED,
+		TERMINATING
+	}
+
 	private val mSensorManager: SensorManager? by lazy { context.getSystemService(Context.SENSOR_SERVICE) as? SensorManager }
 	private val mClipboard: ClipboardManager? by lazy { context.getSystemService(Context.CLIPBOARD_SERVICE) as? ClipboardManager }
 	private val vibratorService: Vibrator? by lazy { context.getSystemService(Context.VIBRATOR_SERVICE) as? Vibrator }
@@ -185,9 +194,11 @@ class Godot private constructor(val context: Context) {
 	private var resumed = false
 
 	/**
-	 * Tracks whether [onGodotSetupCompleted] fired.
+	 * Tracks the engine's run status.
 	 */
-	private val godotMainLoopStarted = AtomicBoolean(false)
+	private val _runStatus = AtomicReference<RunStatus>(RunStatus.INITIALIZING)
+	val runStatus: RunStatus
+		get() = _runStatus.get()
 
 	val io = GodotIO(this)
 
@@ -697,7 +708,7 @@ class Godot private constructor(val context: Context) {
 	}
 
 	private fun registerSensorsIfNeeded() {
-		if (!resumed || !godotMainLoopStarted.get()) {
+		if (!resumed || runStatus != RunStatus.STARTED) {
 			return
 		}
 
@@ -858,7 +869,7 @@ class Godot private constructor(val context: Context) {
 	 */
 	private fun onGodotMainLoopStarted() {
 		Log.v(TAG, "OnGodotMainLoopStarted")
-		godotMainLoopStarted.set(true)
+		_runStatus.set(RunStatus.STARTED)
 
 		accelerometerEnabled.set(java.lang.Boolean.parseBoolean(GodotLib.getGlobal("input_devices/sensors/enable_accelerometer")))
 		gravityEnabled.set(java.lang.Boolean.parseBoolean(GodotLib.getGlobal("input_devices/sensors/enable_gravity")))
@@ -881,6 +892,11 @@ class Godot private constructor(val context: Context) {
 	@Keep
 	private fun onGodotTerminating() {
 		Log.v(TAG, "OnGodotTerminating")
+		_runStatus.set(RunStatus.TERMINATING)
+
+		for (plugin in pluginRegistry.allPlugins) {
+			plugin.onGodotTerminating()
+		}
 		runOnTerminate.get()?.run()
 	}
 

platform/android/java/lib/src/main/java/org/godotengine/godot/GodotActivity.kt

@@ -41,6 +41,7 @@ import android.os.Bundle
 import android.util.Log
 import android.util.Rational
 import android.view.View
+import androidx.activity.addCallback
 import androidx.annotation.CallSuper
 import androidx.annotation.LayoutRes
 import androidx.fragment.app.FragmentActivity
@@ -54,7 +55,7 @@ import java.util.concurrent.atomic.AtomicReference
 /**
  * Base abstract activity for Android apps intending to use Godot as the primary screen.
  *
- * Also a reference implementation for how to setup and use the [GodotFragment] fragment
+ * Also a reference implementation for how to set up and use the [GodotFragment] fragment
  * within an Android app.
  */
 abstract class GodotActivity : FragmentActivity(), GodotHost, PictureInPictureProvider {
@@ -133,6 +134,9 @@ abstract class GodotActivity : FragmentActivity(), GodotHost, PictureInPicturePr
 
 		setContentView(getGodotAppLayout())
 
+		// Register `OnBackPressedCallback` for the Godot fragment.
+		onBackPressedDispatcher.addCallback { godotFragment?.onBackPressed() }
+
 		handleStartIntent(intent, true)
 
 		val currentFragment = supportFragmentManager.findFragmentById(R.id.godot_fragment_container)
@@ -283,10 +287,6 @@ abstract class GodotActivity : FragmentActivity(), GodotHost, PictureInPicturePr
 		}
 	}
 
-	override fun onBackPressed() {
-		godotFragment?.onBackPressed() ?: super.onBackPressed()
-	}
-
 	override fun getActivity(): Activity? {
 		return this
 	}

platform/android/java/lib/src/main/java/org/godotengine/godot/plugin/GodotPlugin.java

@@ -235,6 +235,11 @@ public abstract class GodotPlugin {
 	 */
 	public void onGodotMainLoopStarted() {}
 
+	/**
+	 * Invoked on the render thread when the Godot engine is terminating.
+	 */
+	public void onGodotTerminating() {}
+
 	/**
 	 * When using the OpenGL renderer, this is invoked once per frame on the GL thread after the
 	 * frame is drawn.
@@ -414,7 +419,7 @@ public abstract class GodotPlugin {
 				Object signalArg = signalArgs[i];
 				if (signalArg != null && !signalParamTypes[i].isInstance(signalArg)) {
 					throw new IllegalArgumentException(
-							"Invalid type for argument #" + i + ". Should be of type " + signalParamTypes[i].getName());
+							"Invalid type for argument #" + i + ". Should be of type '" + signalParamTypes[i].getName() + "' but is of type '" + signalArg.getClass().getName() + "'.");
 				}
 			}