[android] Introduce a getDatabasePath() method that enables switching storage paths

Fixes #5589

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/constants/MapboxConstants.java

@@ -30,6 +30,16 @@ public class MapboxConstants {
      */
     public static final String KEY_META_DATA_STAGING_ACCESS_TOKEN = "com.mapbox.TestEventsAccessToken";
 
+    /**
+     * Key used to switch storage to external in AndroidManifest.xml
+     */
+    public final static String KEY_META_DATA_SET_STORAGE_EXTERNAL = "com.mapbox.SetStorageExternal";
+
+    /**
+     * Default value for KEY_META_DATA_SET_STORAGE_EXTERNAL (default is internal storage)
+     */
+    public final static boolean DEFAULT_SET_STORAGE_EXTERNAL = false;
+
     /**
      * Default animation time
      */

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/NativeMapView.java

@@ -15,6 +15,7 @@ import com.mapbox.mapboxsdk.geometry.LatLng;
 import com.mapbox.mapboxsdk.geometry.LatLngBounds;
 import com.mapbox.mapboxsdk.geometry.ProjectedMeters;
 import com.mapbox.mapboxsdk.layers.CustomLayer;
+import com.mapbox.mapboxsdk.offline.OfflineManager;
 
 import java.util.List;
 
@@ -51,7 +52,7 @@ final class NativeMapView {
 
     public NativeMapView(MapView mapView) {
         Context context = mapView.getContext();
-        String dataPath = context.getFilesDir().getAbsolutePath();
+        String dataPath = OfflineManager.getDatabasePath(context);
 
         // With the availability of offline, we're unifying the ambient (cache) and the offline
         // databases to be in the same folder, outside cache, to avoid automatic deletion from

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

@@ -1,11 +1,17 @@
 package com.mapbox.mapboxsdk.offline;
 
 import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.os.Environment;
 import android.os.Handler;
 import android.os.Looper;
 import android.support.annotation.NonNull;
 import android.util.Log;
+
 import com.mapbox.mapboxsdk.MapboxAccountManager;
+import com.mapbox.mapboxsdk.constants.MapboxConstants;
+
 import java.io.File;
 
 /**
@@ -88,7 +94,7 @@ public class OfflineManager {
 
     private OfflineManager(Context context) {
         // Get a pointer to the DefaultFileSource instance
-        String assetRoot = context.getFilesDir().getAbsolutePath();
+        String assetRoot = getDatabasePath(context);
         String cachePath = assetRoot  + File.separator + DATABASE_NAME;
         mDefaultFileSourcePtr = createDefaultFileSource(cachePath, assetRoot, DEFAULT_MAX_CACHE_SIZE);
 
@@ -100,6 +106,61 @@ public class OfflineManager {
         deleteAmbientDatabase(context);
     }
 
+    public static String getDatabasePath(Context context) {
+        // Default value
+        boolean setStorageExternal = MapboxConstants.DEFAULT_SET_STORAGE_EXTERNAL;
+
+        try {
+            // Try getting a custom value from the app Manifest
+            ApplicationInfo appInfo = context.getPackageManager().getApplicationInfo(
+                    context.getPackageName(), PackageManager.GET_META_DATA);
+            setStorageExternal = appInfo.metaData.getBoolean(
+                    MapboxConstants.KEY_META_DATA_SET_STORAGE_EXTERNAL,
+                    MapboxConstants.DEFAULT_SET_STORAGE_EXTERNAL);
+        } catch (PackageManager.NameNotFoundException e) {
+            Log.e(LOG_TAG, "Failed to read the package metadata: " + e.getMessage());
+        } catch (Exception e) {
+            Log.e(LOG_TAG, "Failed to read the storage key: " + e.getMessage());
+        }
+
+        String databasePath = null;
+        if (setStorageExternal && isExternalStorageReadable()) {
+            try {
+                // Try getting the external storage path
+                databasePath = context.getExternalFilesDir(null).getAbsolutePath();
+            } catch (NullPointerException e) {
+                Log.e(LOG_TAG, "Failed to obtain the external storage path: " + e.getMessage());
+            }
+        }
+
+        if (databasePath == null) {
+            // Default to internal storage
+            databasePath = context.getFilesDir().getAbsolutePath();
+        }
+
+        return databasePath;
+    }
+
+    /**
+     *  Checks if external storage is available to at least read. In order for this to work, make
+     *  sure you include <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
+     *  (or WRITE_EXTERNAL_STORAGE) for API level < 18 in your app Manifest.
+     *
+     *  Code from https://developer.android.com/guide/topics/data/data-storage.html#filesExternal
+     */
+    public static boolean isExternalStorageReadable() {
+        String state = Environment.getExternalStorageState();
+        if (Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
+            return true;
+        }
+
+        Log.w(LOG_TAG, "External storage was requested but it isn't readable. For API level < 18"
+                + " make sure you've requested READ_EXTERNAL_STORAGE or WRITE_EXTERNAL_STORAGE"
+                + " permissions in your app Manifest (defaulting to internal storage).");
+
+        return false;
+    }
+
     private void deleteAmbientDatabase(final Context context) {
         // Delete the file in a separate thread to avoid affecting the UI
         new Thread(new Runnable() {