Prevent default style reload when string style json was set

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

@@ -103,7 +103,7 @@ void initialise(@NonNull Context context, @NonNull MapboxMapOptions options) {
    */
   void onStart() {
     nativeMapView.update();
-    if (TextUtils.isEmpty(nativeMapView.getStyleUrl())) {
+    if (TextUtils.isEmpty(nativeMapView.getStyleUrl()) && TextUtils.isEmpty(nativeMapView.getStyleJson())) {
       // if user hasn't loaded a Style yet
       nativeMapView.setStyleUrl(Style.MAPBOX_STREETS);
     }

platform/android/MapboxGLAndroidSDKTestApp/src/androidTest/java/com/mapbox/mapboxsdk/testapp/style/StyleLoaderTest.java

@@ -0,0 +1,77 @@
+package com.mapbox.mapboxsdk.testapp.style;
+
+
+import android.support.test.espresso.UiController;
+
+import com.mapbox.mapboxsdk.maps.MapView;
+import com.mapbox.mapboxsdk.maps.MapboxMap;
+import com.mapbox.mapboxsdk.testapp.R;
+import com.mapbox.mapboxsdk.testapp.action.MapboxMapAction;
+import com.mapbox.mapboxsdk.testapp.activity.BaseActivityTest;
+import com.mapbox.mapboxsdk.testapp.activity.espresso.EspressoTestActivity;
+import com.mapbox.mapboxsdk.testapp.utils.ResourceUtils;
+
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static com.mapbox.mapboxsdk.testapp.action.MapboxMapAction.invoke;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests around style loading
+ */
+public class StyleLoaderTest extends BaseActivityTest {
+
+
+  @Override
+  protected Class getActivityClass() {
+    return EspressoTestActivity.class;
+  }
+
+  @Test
+  public void testSetGetStyleJsonString() throws Exception {
+    validateTestSetup();
+    invoke(mapboxMap, new MapboxMapAction.OnInvokeActionListener() {
+      @Override
+      public void onInvokeAction(UiController uiController, MapboxMap mapboxMap) {
+        try {
+          String expected = ResourceUtils.readRawResource(rule.getActivity(), R.raw.local_style);
+          mapboxMap.setStyleJson(expected);
+          String actual = mapboxMap.getStyleJson();
+          assertEquals("Style json should match", expected, actual);
+        } catch (IOException exception) {
+          exception.printStackTrace();
+        }
+      }
+    });
+  }
+
+  @Test
+  public void testDefaultStyleLoadWithActivityLifecycleChange() throws Exception {
+    validateTestSetup();
+    invoke(mapboxMap, new MapboxMapAction.OnInvokeActionListener() {
+      @Override
+      public void onInvokeAction(UiController uiController, MapboxMap mapboxMap) {
+        try {
+          String expected = ResourceUtils.readRawResource(rule.getActivity(), R.raw.local_style);
+          mapboxMap.setStyleJson(expected);
+
+          // fake activity stop/start
+          MapView mapView = (MapView) rule.getActivity().findViewById(R.id.mapView);
+          mapView.onPause();
+          mapView.onStop();
+
+          mapView.onStart();
+          mapView.onResume();
+
+          String actual = mapboxMap.getStyleJson();
+          assertEquals("Style URL should be empty", "", mapboxMap.getStyleUrl());
+          assertEquals("Style json should match", expected, actual);
+        } catch (IOException exception) {
+          exception.printStackTrace();
+        }
+      }
+    });
+  }
+}