Fix concurrent modification exception for detectors

Author: jush

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog for the Mapbox Gestures for Android
 
+## Main
+* Fix concurrent modification exception for detectors
+
 ## 0.9.1 - November 27, 2023
 Minor release with internal fixes for publishing library
 

library/src/main/java/com/mapbox/android/gestures/AndroidGesturesManager.java

@@ -12,6 +12,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
  * Entry point for all of the detectors. Set listener for gestures you'd like to be notified about
@@ -58,7 +59,7 @@ public class AndroidGesturesManager {
   public static final int GESTURE_TYPE_QUICK_SCALE = 15;
 
   private final List<Set<Integer>> mutuallyExclusiveGestures = new ArrayList<>();
-  private final List<BaseGesture> detectors = new ArrayList<>();
+  private final List<BaseGesture> detectors = new CopyOnWriteArrayList<>();
 
   private final StandardGestureDetector standardGestureDetector;
   private final StandardScaleGestureDetector standardScaleGestureDetector;

library/src/test/java/com/mapbox/android/gestures/AndroidGesturesManagerTest.java

@@ -1,5 +1,11 @@
 package com.mapbox.android.gestures;
 
+import static junit.framework.Assert.assertEquals;
+import static junit.framework.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import android.view.MotionEvent;
+
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -11,9 +17,6 @@
 import java.util.List;
 import java.util.Set;
 
-import static junit.framework.Assert.assertEquals;
-import static junit.framework.Assert.assertNotNull;
-
 @RunWith(RobolectricTestRunner.class)
 public class AndroidGesturesManagerTest {
   private AndroidGesturesManager androidGesturesManager;
@@ -44,9 +47,9 @@ public void setUp() throws Exception {
     mutuallyExclusivesList.add(set3);
 
     androidGesturesManager =
-      new AndroidGesturesManager(
-        RuntimeEnvironment.application.getApplicationContext(),
-        mutuallyExclusivesList, true);
+            new AndroidGesturesManager(
+                    RuntimeEnvironment.application.getApplicationContext(),
+                    mutuallyExclusivesList, true);
   }
 
   @Test
@@ -69,4 +72,21 @@ public void setMutuallyExclusivesTest() throws Exception {
     androidGesturesManager.setMutuallyExclusiveGestures(mutuallyExclusivesList);
     assertEquals(androidGesturesManager.getMutuallyExclusiveGestures(), mutuallyExclusivesList);
   }
+
+  @Test
+  public void onSingleTapModifyDetectorsTest() {
+    final StandardGestureDetector standardGestureDetector = new StandardGestureDetector(RuntimeEnvironment.getApplication().getApplicationContext(), androidGesturesManager);
+
+    androidGesturesManager.setStandardGestureListener(new StandardGestureDetector.SimpleStandardOnGestureListener() {
+      @Override
+      public boolean onDown(MotionEvent e) {
+        androidGesturesManager.getDetectors().add(standardGestureDetector);
+        return true;
+      }
+    });
+
+    MotionEvent downEvent = TestUtils.INSTANCE.getMotionEvent(MotionEvent.ACTION_DOWN, 0, 0, null);
+    androidGesturesManager.onTouchEvent(downEvent);
+    assertTrue(androidGesturesManager.getDetectors().contains(standardGestureDetector));
+  }
 }