Apply the workaround for Samsung devices only when strictly needed

Since Samsung firmware may have been fixed and accept more than 4 values
in getRotationMatrixFromVector(), truncate the size of the rotation
vector only when this is strictly needed.

1 files changed, 23 insertions, 5 deletions

diff --git a/main/src/cgeo/geocaching/sensors/RotationProvider.java b/main/src/cgeo/geocaching/sensors/RotationProvider.java
index 59be8f1..d0db113 100644
--- a/main/src/cgeo/geocaching/sensors/RotationProvider.java
+++ b/main/src/cgeo/geocaching/sensors/RotationProvider.java
@@ -18,6 +18,18 @@ import android.hardware.SensorManager;
 
 public class RotationProvider {
 
+    /**
+     * On some Samsung devices, {@link SensorManager#getRotationMatrixFromVector} throws an exception if the rotation
+     * vector has more than 4 elements.
+     * <p/>
+     * This will be detected and remembered after the first occurrence of the exception. Concurrent access
+     * is not a problem as this variable can only go from {@code false} to {@code true} and being {@code false}
+     * instead of {@code true} is innocuous and will be changed immediately when needed.
+     *
+     * @see <a href="http://stackoverflow.com/a/22138449">this Stack Overflow answer</a>
+     */
+    private static boolean isTruncationNeeded = false;
+
     private RotationProvider() {
         // Utility class, not to be instantiated
     }
@@ -43,14 +55,20 @@ public class RotationProvider {
 
                     @Override
                     public void onSensorChanged(final SensorEvent event) {
-                        // On some Samsung devices, SensorManager#getRotationMatrixFromVector throws an exception if the rotation
-                        // vector has more than 4 elements. Since only the four first elements are used, we can truncate the vector
-                        // without losing precision.
-                        if (event.values.length > 4) {
+                        if (isTruncationNeeded) {
+                            // Since only the four first elements are used (and accepted), we truncate the vector.
                             System.arraycopy(event.values, 0, values, 0, 4);
                             SensorManager.getRotationMatrixFromVector(rotationMatrix, values);
                         } else {
-                            SensorManager.getRotationMatrixFromVector(rotationMatrix, event.values);
+                            try {
+                                SensorManager.getRotationMatrixFromVector(rotationMatrix, event.values);
+                            } catch (final IllegalArgumentException ignored) {
+                                Log.d("installing workaround for mismatched number of values in rotation vector");
+                                // Install workaround and retry
+                                isTruncationNeeded = true;
+                                onSensorChanged(event);
+                                return;
+                            }
                         }
                         SensorManager.getOrientation(rotationMatrix, orientation);
                         subscriber.onNext((float) (orientation[0] * 180 / Math.PI));