[android] #3891 - make reason a more idiomatic ErrorReason Android In…

…tDef and remove unnecessary constructor

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/offline/OfflineRegionError.java

@@ -1,18 +1,29 @@
 package com.mapbox.mapboxsdk.offline;
 
+import android.support.annotation.IntDef;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
 /**
  * An Offline Region error
  */
 public class OfflineRegionError {
 
  /**
- * Success = 1
- * NotFound = 2
- * Server = 3
- * Connection = 4
- * Other = 6
+ * Error code, self-explanatory.
  */
- private int reason;
+ @IntDef({REASON_SUCCESS, REASON_NOT_FOUND, REASON_SERVER, REASON_CONNECTION, REASON_OTHER})
+ @Retention(RetentionPolicy.SOURCE)
+ public @interface ErrorReason {}
+
+ public static final int REASON_SUCCESS = 1;
+ public static final int REASON_NOT_FOUND = 2;
+ public static final int REASON_SERVER = 3;
+ public static final int REASON_CONNECTION = 4;
+ public static final int REASON_OTHER = 6;
+
+ private @ErrorReason int reason;
 
  /**
  /* An error message from the request handler, e.g. a server message or a system message
@@ -28,16 +39,11 @@ private OfflineRegionError() {
  // For JNI use only
  }
 
- public OfflineRegionError(int reason, String message) {
- this.reason = reason;
- this.message = message;
- }
-
  /*
  * Getters
  */
 
- public int getReason() {
+ public @ErrorReason int getReason() {
  return reason;
  }