Use ?. (and ?.let) safe operators instead of !!

This PR prevents potential NPEs, and follows Kotlin conventions more closely
by replacing the unsafe !! operator with safe ?. (or ?.let) (usually
!! would only be used very rarely, and with a good reason - there is one
place left in this PR where !! makes sense), and by replacing Java style
'if (x != null)' with Kotlin's '?.'

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

@@ -396,16 +396,19 @@ class Godot(private val context: Context) : SensorEventListener {
 			}
 
 			if (host == primaryHost) {
-				renderView!!.startRenderer()
+				renderView?.startRenderer()
 			}
-			val view: View = renderView!!.view
+
+			renderView?.let {
 				containerLayout?.addView(
-					view,
+					it.view,
 					ViewGroup.LayoutParams(
 							ViewGroup.LayoutParams.MATCH_PARENT,
 							ViewGroup.LayoutParams.MATCH_PARENT
 					)
 				)
+			}
+
 			editText.setView(renderView)
 			io?.setEdit(editText)
 
@@ -448,20 +451,23 @@ class Godot(private val context: Context) : SensorEventListener {
 				})
 			} else {
 				// Infer the virtual keyboard height using visible area.
-				view.viewTreeObserver.addOnGlobalLayoutListener(object : OnGlobalLayoutListener {
+				renderView?.view?.viewTreeObserver?.addOnGlobalLayoutListener(object : OnGlobalLayoutListener {
 					// Don't allocate a new Rect every time the callback is called.
 					val visibleSize = Rect()
 					override fun onGlobalLayout() {
-						val surfaceView = renderView!!.view
+						renderView?.let {
+							val surfaceView = it.view
+
 							surfaceView.getWindowVisibleDisplayFrame(visibleSize)
 							val keyboardHeight = surfaceView.height - visibleSize.bottom
 							GodotLib.setVirtualKeyboardHeight(keyboardHeight)
 						}
+					}
 				})
 			}
 
 			if (host == primaryHost) {
-				renderView!!.queueOnRenderThread {
+				renderView?.queueOnRenderThread {
 					for (plugin in pluginRegistry.allPlugins) {
 						plugin.onRegisterPluginWithGodotNative()
 					}
@@ -495,7 +501,7 @@ class Godot(private val context: Context) : SensorEventListener {
 			return
 		}
 
-		renderView!!.onActivityStarted()
+		renderView?.onActivityStarted()
 	}
 
 	fun onResume(host: GodotHost) {
@@ -503,7 +509,7 @@ class Godot(private val context: Context) : SensorEventListener {
 			return
 		}
 
-		renderView!!.onActivityResumed()
+		renderView?.onActivityResumed()
 		if (mAccelerometer != null) {
 			mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_GAME)
 		}
@@ -535,7 +541,7 @@ class Godot(private val context: Context) : SensorEventListener {
 			return
 		}
 
-		renderView!!.onActivityPaused()
+		renderView?.onActivityPaused()
 		mSensorManager.unregisterListener(this)
 		for (plugin in pluginRegistry.allPlugins) {
 			plugin.onMainPause()
@@ -547,7 +553,7 @@ class Godot(private val context: Context) : SensorEventListener {
 			return
 		}
 
-		renderView!!.onActivityStopped()
+		renderView?.onActivityStopped()
 	}
 
 	fun onDestroy(primaryHost: GodotHost) {
@@ -569,7 +575,7 @@ class Godot(private val context: Context) : SensorEventListener {
 	 * Configuration change callback
 	*/
 	fun onConfigurationChanged(newConfig: Configuration) {
-		var newDarkMode = newConfig.uiMode?.and(Configuration.UI_MODE_NIGHT_MASK) == Configuration.UI_MODE_NIGHT_YES
+		val newDarkMode = newConfig.uiMode.and(Configuration.UI_MODE_NIGHT_MASK) == Configuration.UI_MODE_NIGHT_YES
 		if (darkMode != newDarkMode) {
 			darkMode = newDarkMode
 			GodotLib.onNightModeChanged()
@@ -686,9 +692,7 @@ class Godot(private val context: Context) : SensorEventListener {
 	 * This must be called after the render thread has started.
 	 */
 	fun runOnRenderThread(action: Runnable) {
-		if (renderView != null) {
+		renderView?.queueOnRenderThread(action)
-			renderView!!.queueOnRenderThread(action)
-		}
 	}
 
 	/**
@@ -765,7 +769,7 @@ class Godot(private val context: Context) : SensorEventListener {
 		return mClipboard.hasPrimaryClip()
 	}
 
-	fun getClipboard(): String? {
+	fun getClipboard(): String {
 		val clipData = mClipboard.primaryClip ?: return ""
 		val text = clipData.getItemAt(0).text ?: return ""
 		return text.toString()
@@ -782,15 +786,14 @@ class Godot(private val context: Context) : SensorEventListener {
 
 	@Keep
 	private fun forceQuit(instanceId: Int): Boolean {
-		if (primaryHost == null) {
+		primaryHost?.let {
-			return false
+			if (instanceId == 0) {
-		}
+				it.onGodotForceQuit(this)
-		return if (instanceId == 0) {
+				return true
-			primaryHost!!.onGodotForceQuit(this)
-			true
 			} else {
-			primaryHost!!.onGodotForceQuit(instanceId)
+				return it.onGodotForceQuit(instanceId)
 			}
+		} ?: return false
 	}
 
 	fun onBackPressed(host: GodotHost) {
@@ -804,14 +807,14 @@ class Godot(private val context: Context) : SensorEventListener {
 				shouldQuit = false
 			}
 		}
-		if (shouldQuit && renderView != null) {
+		if (shouldQuit) {
-			renderView!!.queueOnRenderThread { GodotLib.back() }
+			renderView?.queueOnRenderThread { GodotLib.back() }
 		}
 	}
 
 	private fun getRotatedValues(values: FloatArray?): FloatArray? {
 		if (values == null || values.size != 3) {
-			return values
+			return null
 		}
 		val display =
 			(requireActivity().getSystemService(Context.WINDOW_SERVICE) as WindowManager).defaultDisplay
@@ -848,39 +851,43 @@ class Godot(private val context: Context) : SensorEventListener {
 		}
 		when (event.sensor.type) {
 			Sensor.TYPE_ACCELEROMETER -> {
-				val rotatedValues = getRotatedValues(event.values)
+				getRotatedValues(event.values)?.let { rotatedValues ->
-				renderView!!.queueOnRenderThread {
+					renderView?.queueOnRenderThread {
 						GodotLib.accelerometer(
-						-rotatedValues!![0], -rotatedValues[1], -rotatedValues[2]
+							-rotatedValues[0], -rotatedValues[1], -rotatedValues[2]
 						)
 					}
 				}
+			}
 			Sensor.TYPE_GRAVITY -> {
-				val rotatedValues = getRotatedValues(event.values)
+				getRotatedValues(event.values)?.let { rotatedValues ->
-				renderView!!.queueOnRenderThread {
+					renderView?.queueOnRenderThread {
 						GodotLib.gravity(
-						-rotatedValues!![0], -rotatedValues[1], -rotatedValues[2]
+							-rotatedValues[0], -rotatedValues[1], -rotatedValues[2]
 						)
 					}
 				}
+			}
 			Sensor.TYPE_MAGNETIC_FIELD -> {
-				val rotatedValues = getRotatedValues(event.values)
+				getRotatedValues(event.values)?.let { rotatedValues ->
-				renderView!!.queueOnRenderThread {
+					renderView?.queueOnRenderThread {
 						GodotLib.magnetometer(
-						-rotatedValues!![0], -rotatedValues[1], -rotatedValues[2]
+							-rotatedValues[0], -rotatedValues[1], -rotatedValues[2]
 						)
 					}
 				}
+			}
 			Sensor.TYPE_GYROSCOPE -> {
-				val rotatedValues = getRotatedValues(event.values)
+				getRotatedValues(event.values)?.let { rotatedValues ->
-				renderView!!.queueOnRenderThread {
+					renderView?.queueOnRenderThread {
 						GodotLib.gyroscope(
-						rotatedValues!![0], rotatedValues[1], rotatedValues[2]
+							rotatedValues[0], rotatedValues[1], rotatedValues[2]
 						)
 					}
 				}
 			}
 		}
+	}
 
 	override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {}
 
@@ -1039,7 +1046,7 @@ class Godot(private val context: Context) : SensorEventListener {
 
 	@Keep
 	private fun initInputDevices() {
-		renderView!!.initInputDevices()
+		renderView?.initInputDevices()
 	}
 
 	@Keep

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

@@ -83,8 +83,9 @@ abstract class GodotActivity : FragmentActivity(), GodotHost {
 	override fun onDestroy() {
 		Log.v(TAG, "Destroying Godot app...")
 		super.onDestroy()
-		if (godotFragment != null) {
+
-			terminateGodotInstance(godotFragment!!.godot)
+		godotFragment?.let {
+			terminateGodotInstance(it.godot)
 		}
 	}
 
@@ -93,15 +94,18 @@ abstract class GodotActivity : FragmentActivity(), GodotHost {
 	}
 
 	private fun terminateGodotInstance(instance: Godot) {
-		if (godotFragment != null && instance === godotFragment!!.godot) {
+		godotFragment?.let {
+			if (instance === it.godot) {
 				Log.v(TAG, "Force quitting Godot instance")
 				ProcessPhoenix.forceQuit(this)
 			}
 		}
+	}
 
 	override fun onGodotRestartRequested(instance: Godot) {
 		runOnUiThread {
-			if (godotFragment != null && instance === godotFragment!!.godot) {
+			godotFragment?.let {
+				if (instance === it.godot) {
 					// It's very hard to properly de-initialize Godot on Android to restart the game
 					// from scratch. Therefore, we need to kill the whole app process and relaunch it.
 					//
@@ -112,6 +116,7 @@ abstract class GodotActivity : FragmentActivity(), GodotHost {
 				}
 			}
 		}
+	}
 
 	override fun onNewIntent(newIntent: Intent) {
 		super.onNewIntent(newIntent)

platform/android/java/lib/src/org/godotengine/godot/io/file/FileAccessHandler.kt

@@ -56,7 +56,9 @@ class FileAccessHandler(val context: Context) {
 			}
 
 			return try {
-				DataAccess.fileExists(storageScope, context, path!!)
+				path?.let {
+					DataAccess.fileExists(storageScope, context, it)
+				} ?: false
 			} catch (e: SecurityException) {
 				false
 			}
@@ -69,20 +71,22 @@ class FileAccessHandler(val context: Context) {
 			}
 
 			return try {
-				DataAccess.removeFile(storageScope, context, path!!)
+				path?.let {
+					DataAccess.removeFile(storageScope, context, it)
+				} ?: false
 			} catch (e: Exception) {
 				false
 			}
 		}
 
-		internal fun renameFile(context: Context, storageScopeIdentifier: StorageScope.Identifier, from: String?, to: String?): Boolean {
+		internal fun renameFile(context: Context, storageScopeIdentifier: StorageScope.Identifier, from: String, to: String): Boolean {
 			val storageScope = storageScopeIdentifier.identifyStorageScope(from)
 			if (storageScope == StorageScope.UNKNOWN) {
 				return false
 			}
 
 			return try {
-				DataAccess.renameFile(storageScope, context, from!!, to!!)
+				DataAccess.renameFile(storageScope, context, from, to)
 			} catch (e: Exception) {
 				false
 			}
@@ -106,16 +110,18 @@ class FileAccessHandler(val context: Context) {
 			return INVALID_FILE_ID
 		}
 
-		try {
+		return try {
-			val dataAccess = DataAccess.generateDataAccess(storageScope, context, path!!, accessFlag) ?: return INVALID_FILE_ID
+			path?.let {
+				val dataAccess = DataAccess.generateDataAccess(storageScope, context, it, accessFlag) ?: return INVALID_FILE_ID
 
 				files.put(++lastFileId, dataAccess)
-			return lastFileId
+				lastFileId
+			} ?: INVALID_FILE_ID
 		} catch (e: FileNotFoundException) {
-			return FILE_NOT_FOUND_ERROR_ID
+			FILE_NOT_FOUND_ERROR_ID
 		} catch (e: Exception) {
 			Log.w(TAG, "Error while opening $path", e)
-			return INVALID_FILE_ID
+			INVALID_FILE_ID
 		}
 	}
 
@@ -176,7 +182,9 @@ class FileAccessHandler(val context: Context) {
 		}
 
 		return try {
-			DataAccess.fileLastModified(storageScope, context, filepath!!)
+			filepath?.let {
+				DataAccess.fileLastModified(storageScope, context, it)
+			} ?: 0L
 		} catch (e: SecurityException) {
 			0L
 		}