Add steps for closing ML Kit detector handles when the fragment is de…

…stroyed

translate/starter/app/src/main/java/com/google/mlkit/codelab/translate/analyzer/TextAnalyzer.kt

@@ -23,6 +23,7 @@ import android.util.Log
 import android.widget.Toast
 import androidx.camera.core.ImageAnalysis
 import androidx.camera.core.ImageProxy
+import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.MutableLiveData
 import com.google.android.gms.tasks.Task
 import com.google.mlkit.common.MlKitException
@@ -38,12 +39,15 @@ import java.lang.Exception
  */
 class TextAnalyzer(
     private val context: Context,
+    private val lifecycle: Lifecycle,
     private val result: MutableLiveData<String>,
     private val imageCropPercentages: MutableLiveData<Pair<Int, Int>>
 ) : ImageAnalysis.Analyzer {
 
     // TODO: Instantiate TextRecognition detector
 
+    // TODO: Add lifecycle observer to properly close ML Kit detectors
+
     @androidx.camera.core.ExperimentalGetImage
     override fun analyze(imageProxy: ImageProxy) {
         val mediaImage = imageProxy.image ?: return

translate/starter/app/src/main/java/com/google/mlkit/codelab/translate/main/MainFragment.kt

@@ -42,6 +42,7 @@ import androidx.lifecycle.Observer
 import com.google.mlkit.codelab.translate.R
 import com.google.mlkit.codelab.translate.analyzer.TextAnalyzer
 import com.google.mlkit.codelab.translate.util.Language
+import com.google.mlkit.codelab.translate.util.ScopedExecutor
 import kotlinx.android.synthetic.main.main_fragment.*
 import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
@@ -83,6 +84,8 @@ class MainFragment : Fragment() {
     /** Blocking camera operations are performed using this executor */
     private lateinit var cameraExecutor: ExecutorService
 
+    private lateinit var scopedExecutor: ScopedExecutor
+
     override fun onCreateView(
         inflater: LayoutInflater, container: ViewGroup?,
         savedInstanceState: Bundle?
@@ -95,6 +98,7 @@ class MainFragment : Fragment() {
 
         // Shut down our background executor
         cameraExecutor.shutdown()
+        scopedExecutor.shutdown()
     }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
@@ -105,6 +109,7 @@ class MainFragment : Fragment() {
 
         // Initialize our background executor
         cameraExecutor = Executors.newSingleThreadExecutor()
+        scopedExecutor = ScopedExecutor(cameraExecutor)
 
         // Request camera permissions
         if (allPermissionsGranted()) {
@@ -228,6 +233,7 @@ class MainFragment : Fragment() {
                     cameraExecutor
                     , TextAnalyzer(
                         requireContext(),
+                        lifecycle,
                         viewModel.sourceText,
                         viewModel.imageCropPercentages
                     )

translate/starter/app/src/main/java/com/google/mlkit/codelab/translate/main/MainViewModel.kt

@@ -78,6 +78,10 @@ class MainViewModel(application: Application) : AndroidViewModel(application) {
         result
     }
 
+    override fun onCleared() {
+        // TODO Shut down ML Kit clients.
+    }
+
     private fun translate(): Task<String> {
         // TODO
         return Tasks.forResult("") // replace this with your code

translate/starter/app/src/main/java/com/google/mlkit/codelab/translate/util/ScopedExecutor.kt

@@ -0,0 +1,19 @@
+package com.google.mlkit.codelab.translate.util
+
+import java.util.concurrent.Executor
+import java.util.concurrent.atomic.AtomicBoolean
+
+class ScopedExecutor(private val executor: Executor) : Executor {
+
+    private val isShutdown = AtomicBoolean()
+
+    fun shutdown() {
+        isShutdown.set(true)
+    }
+
+    override fun execute(command: Runnable) {
+        executor.execute {
+            if (!isShutdown.get()) command.run()
+        }
+    }
+}