[android] add api to enable/disable tile prefetching

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

@@ -99,6 +99,7 @@ public final class MapboxMap {
     setDebugActive(options.getDebugActive());
     setApiBaseUrl(options);
     setStyleUrl(options);
+    setPrefetchesTiles(options);
   }
 
   /**
@@ -247,6 +248,38 @@ public final class MapboxMap {
     nativeMapView.setTransitionDelay(delayMs);
   }
 
+  /**
+   * Sets tile pre-fetching from MapboxOptions.
+   *
+   * @param options the options object
+   */
+  private void setPrefetchesTiles(@NonNull MapboxMapOptions options) {
+    setPrefetchesTiles(options.getPrefetchesTiles());
+  }
+
+  /**
+   * Enable or disable tile pre-fetching. Pre-fetching makes sure that a low-resolution
+   * tile is rendered as soon as possible at the expense of a little bandwidth.
+   *
+   * @param enable true to enable
+   */
+  @UiThread
+  public void setPrefetchesTiles(boolean enable) {
+    nativeMapView.setPrefetchesTiles(enable);
+  }
+
+  /**
+   * Check whether tile pre-fetching is enabled or not.
+   *
+   * @return true if enabled
+   *
+   * @see MapboxMap#setPrefetchesTiles(boolean)
+   */
+  @UiThread
+  public boolean getPrefetchesTiles() {
+    return nativeMapView.getPrefetchesTiles();
+  }
+
   /**
    * Retrieve all the layers in the style
    *

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

@@ -80,6 +80,7 @@ public class MapboxMapOptions implements Parcelable {
   private int myLocationAccuracyTintColor;
   private int myLocationAccuracyAlpha;
   private float myLocationAccuracyThreshold;
+  private boolean prefetchesTiles = true;
 
   private String apiBaseUrl;
 
@@ -154,6 +155,7 @@ public class MapboxMapOptions implements Parcelable {
     style = in.readString();
     apiBaseUrl = in.readString();
     textureMode = in.readByte() != 0;
+    prefetchesTiles = in.readByte() != 0;
   }
 
   static Bitmap getBitmapFromDrawable(Drawable drawable) {
@@ -297,6 +299,8 @@ public class MapboxMapOptions implements Parcelable {
         typedArray.getFloat(R.styleable.mapbox_MapView_mapbox_myLocationAccuracyThreshold, 0));
       mapboxMapOptions.textureMode(
         typedArray.getBoolean(R.styleable.mapbox_MapView_mapbox_renderTextureMode, false));
+      mapboxMapOptions.setPrefetchesTiles(
+        typedArray.getBoolean(R.styleable.mapbox_MapView_mapbox_enableTilePrefetch, true));
     } finally {
       typedArray.recycle();
     }
@@ -711,6 +715,30 @@ public class MapboxMapOptions implements Parcelable {
     return this;
   }
 
+  /**
+   * Enable tile pre-fetching. Loads tiles at a lower zoom-level to pre-render
+   * a low resolution preview while more detailed tiles are loaded.
+   *
+   * Enabled by default
+   *
+   * @param enable true to enable
+   *
+   * @return This
+   */
+  public MapboxMapOptions setPrefetchesTiles(boolean enable) {
+    this.prefetchesTiles = enable;
+    return this;
+  }
+
+  /**
+   * Check whether tile pre-fetching is enabled.
+   *
+   * @return true if enabled
+   */
+  public boolean getPrefetchesTiles() {
+    return prefetchesTiles;
+  }
+
   /**
    * Get the current configured API endpoint base URL.
    *
@@ -1094,6 +1122,7 @@ public class MapboxMapOptions implements Parcelable {
     dest.writeString(style);
     dest.writeString(apiBaseUrl);
     dest.writeByte((byte) (textureMode ? 1 : 0));
+    dest.writeByte((byte) (prefetchesTiles ? 1 : 0));
   }
 
   @Override
@@ -1217,6 +1246,9 @@ public class MapboxMapOptions implements Parcelable {
     if (apiBaseUrl != null ? !apiBaseUrl.equals(options.apiBaseUrl) : options.apiBaseUrl != null) {
       return false;
     }
+    if (prefetchesTiles != options.prefetchesTiles) {
+      return false;
+    }
     return false;
   }
 
@@ -1263,6 +1295,7 @@ public class MapboxMapOptions implements Parcelable {
     result = 31 * result + (apiBaseUrl != null ? apiBaseUrl.hashCode() : 0);
     result = 31 * result + (textureMode ? 1 : 0);
     result = 31 * result + (style != null ? style.hashCode() : 0);
+    result = 31 * result + (prefetchesTiles ? 1 : 0);
     return result;
   }
 }

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

@@ -638,6 +638,20 @@ final class NativeMapView {
     return nativeGetCameraPosition();
   }
 
+  public void setPrefetchesTiles(boolean enable) {
+    if (isDestroyedOn("setPrefetchesTiles")) {
+      return;
+    }
+    nativeSetPrefetchesTiles(enable);
+  }
+
+  public boolean getPrefetchesTiles() {
+    if (isDestroyedOn("getPrefetchesTiles")) {
+      return false;
+    }
+    return nativeGetPrefetchesTiles();
+  }
+
   // Runtime style Api
 
   public long getTransitionDuration() {
@@ -1072,6 +1086,10 @@ final class NativeMapView {
 
   private native Light nativeGetLight();
 
+  private native void nativeSetPrefetchesTiles(boolean enable);
+
+  private native boolean nativeGetPrefetchesTiles();
+
   int getWidth() {
     if (isDestroyedOn("")) {
       return 0;

platform/android/MapboxGLAndroidSDK/src/main/res/values/attrs.xml

@@ -117,6 +117,8 @@
         <!-- Deprecated to use TextureView-->
         <attr name="mapbox_renderTextureMode" format="boolean"/>
 
+        <attr name="mapbox_enableTilePrefetch" format="boolean"/>
+
     </declare-styleable>
 
     <declare-styleable name="mapbox_BubbleLayout">

platform/android/MapboxGLAndroidSDK/src/test/java/com/mapbox/mapboxsdk/maps/MapboxMapOptionsTest.java

@@ -186,5 +186,15 @@ public class MapboxMapOptionsTest {
     assertEquals(Color.BLUE, new MapboxMapOptions()
       .myLocationBackgroundTintColor(Color.BLUE).getMyLocationBackgroundTintColor());
   }
+
+  @Test
+  public void testPrefetchesTiles() {
+    // Default value
+    assertTrue(new MapboxMapOptions().getPrefetchesTiles());
+
+    // Check mutations
+    assertTrue(new MapboxMapOptions().setPrefetchesTiles(true).getPrefetchesTiles());
+    assertFalse(new MapboxMapOptions().setPrefetchesTiles(false).getPrefetchesTiles());
+  }
 }
 

platform/android/MapboxGLAndroidSDKTestApp/src/androidTest/java/com/mapbox/mapboxsdk/maps/MapboxMapTest.java

@@ -779,6 +779,22 @@ public class MapboxMapTest extends BaseActivityTest {
     }));
   }
 
+  // Tile pre-fetching
+
+  @Test
+  public void testTilePrefetch() {
+    validateTestSetup();
+    onView(withId(R.id.mapView)).perform(new MapboxMapAction(new InvokeViewAction() {
+      @Override
+      public void onViewAction(UiController uiController, View view) {
+        mapboxMap.setPrefetchesTiles(true);
+        assertTrue(mapboxMap.getPrefetchesTiles());
+        mapboxMap.setPrefetchesTiles(false);
+        assertFalse(mapboxMap.getPrefetchesTiles());
+      }
+    }));
+  }
+
   private class MapboxMapAction implements ViewAction {
 
     private InvokeViewAction invokeViewAction;

platform/android/src/native_map_view.cpp

@@ -1037,6 +1037,15 @@ void NativeMapView::removeImage(JNIEnv& env, jni::String name) {
     map->getStyle().removeImage(jni::Make<std::string>(env, name));
 }
 
+
+void NativeMapView::setPrefetchesTiles(JNIEnv&, jni::jboolean enable) {
+    map->setPrefetchZoomDelta(enable ? util::DEFAULT_PREFETCH_ZOOM_DELTA : uint8_t(0));
+}
+
+jni::jboolean NativeMapView::getPrefetchesTiles(JNIEnv&) {
+    return jni::jboolean(map->getPrefetchZoomDelta() > 0);
+}
+
 // Private methods //
 
 void NativeMapView::_initializeDisplay() {
@@ -1537,7 +1546,9 @@ void NativeMapView::registerNative(jni::JNIEnv& env) {
             METHOD(&NativeMapView::removeSource, "nativeRemoveSource"),
             METHOD(&NativeMapView::addImage, "nativeAddImage"),
             METHOD(&NativeMapView::removeImage, "nativeRemoveImage"),
-            METHOD(&NativeMapView::setLatLngBounds, "nativeSetLatLngBounds")
+            METHOD(&NativeMapView::setLatLngBounds, "nativeSetLatLngBounds"),
+            METHOD(&NativeMapView::setPrefetchesTiles, "nativeSetPrefetchesTiles"),
+            METHOD(&NativeMapView::getPrefetchesTiles, "nativeGetPrefetchesTiles")
     );
 }
 

platform/android/src/native_map_view.hpp

@@ -255,6 +255,10 @@ public:
 
     void removeImage(JNIEnv&, jni::String);
 
+    void setPrefetchesTiles(JNIEnv&, jni::jboolean);
+
+    jni::jboolean getPrefetchesTiles(JNIEnv&);
+
 protected:
     // mbgl::RendererBackend //