[Android] Allow to start a native fragment via Navigator.startNative().

* Introduces NativeScreenFactory for android.support.v4.app.Fragment.
* Changes NavigatorModule.pushNative() to check for native screen availability.
* Adds Native2Fragment to example app to show case usage of the new api.
* ReactNavigationCoordinator throws exceptions early if no activity where registered.

example/android/app/src/main/java/com/airbnb/android/react/navigation/example/MainActivity.java

@@ -3,12 +3,13 @@
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 
-import com.airbnb.android.react.navigation.ScreenCoordinatorLayout;
 import com.airbnb.android.react.navigation.ReactAwareActivity;
 import com.airbnb.android.react.navigation.ScreenCoordinator;
 import com.airbnb.android.react.navigation.ScreenCoordinatorComponent;
+import com.airbnb.android.react.navigation.ScreenCoordinatorLayout;
 
 public class MainActivity extends ReactAwareActivity implements ScreenCoordinatorComponent {
+
   private static final String TAG = MainActivity.class.getSimpleName();
 
   private ScreenCoordinator screenCoordinator;
@@ -19,12 +20,25 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
     setContentView(R.layout.activity_main);
     ScreenCoordinatorLayout container = (ScreenCoordinatorLayout) findViewById(R.id.content);
     screenCoordinator = new ScreenCoordinator(this, container, savedInstanceState);
+    screenCoordinator.registerScreen("NativeFragment2", Native2Fragment.FACTORY);
 
     if (savedInstanceState == null) {
       screenCoordinator.presentScreen(MainFragment.newInstance());
     }
   }
 
+  @Override
+  protected void onResume() {
+    super.onResume();
+    screenCoordinator.onResume();
+  }
+
+  @Override
+  protected void onPause() {
+    screenCoordinator.onPause();
+    super.onPause();
+  }
+
   @Override
   public ScreenCoordinator getScreenCoordinator() {
     return screenCoordinator;

example/android/app/src/main/java/com/airbnb/android/react/navigation/example/MainApplication.java

@@ -1,6 +1,7 @@
 package com.airbnb.android.react.navigation.example;
 
 import android.app.Application;
+
 import com.airbnb.android.react.navigation.NativeNavigationPackage;
 import com.airbnb.android.react.navigation.ReactNavigationCoordinator;
 import com.facebook.react.ReactApplication;
@@ -22,7 +23,7 @@ public boolean getUseDeveloperSupport() {
 
     @Override
     protected List<ReactPackage> getPackages() {
-      return Arrays.<ReactPackage>asList(
+      return Arrays.asList(
           new MainReactPackage(),
           new NativeNavigationPackage()
       );
@@ -48,5 +49,4 @@ public void onCreate() {
     coordinator.injectReactInstanceManager(mReactNativeHost.getReactInstanceManager());
     coordinator.start(this);
   }
-
 }

example/android/app/src/main/java/com/airbnb/android/react/navigation/example/Native2Fragment.java

@@ -0,0 +1,46 @@
+package com.airbnb.android.react.navigation.example;
+
+
+import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.support.v4.app.Fragment;
+import android.support.v7.app.AppCompatActivity;
+import android.support.v7.widget.Toolbar;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.airbnb.android.react.navigation.NativeScreenFactory;
+
+public class Native2Fragment extends Fragment {
+  static final NativeScreenFactory FACTORY = new NativeScreenFactory() {
+    @NonNull
+    @Override
+    public Fragment newScreen(@Nullable Bundle props) {
+      return new Native2Fragment();
+    }
+  };
+
+  @Nullable
+  @Override
+  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
+    return inflater.inflate(R.layout.fragment_native_2, container, false);
+  }
+
+  @Override
+  public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+    super.onViewCreated(view, savedInstanceState);
+
+    Toolbar toolbar = (Toolbar) view.findViewById(R.id.toolbar);
+    ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);
+    toolbar.setTitle("Native Fragment");
+    toolbar.setNavigationIcon(R.drawable.n2_ic_arrow_back_white);
+    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
+      @Override
+      public void onClick(View v) {
+        getActivity().onBackPressed();
+      }
+    });
+  }
+}

example/android/app/src/main/res/layout/fragment_native_2.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="@android:color/white"
+    android:orientation="vertical">
+
+    <android.support.v7.widget.Toolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="@color/color_primary"
+        android:minHeight="?attr/actionBarSize"
+        app:theme="@style/ToolbarTheme" />
+
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_gravity="center"
+        android:gravity="center"
+        android:text="Second Native Fragment" />
+</LinearLayout>

example/screens/NavigationExampleScreen.js

@@ -56,6 +56,10 @@ export default class NavigationExampleScreen extends Component {
           title="Navigation bar customisation"
           onPress={() => Navigator.push('NavigationBar')}
         />
+        <Row
+          title="Start Native Screen 2"
+          onPress={() => Navigator.push('NativeFragment2')}
+        />
       </Screen>
     );
   }

lib/android/src/main/java/com/airbnb/android/react/navigation/NativeScreenFactory.java

@@ -0,0 +1,14 @@
+package com.airbnb.android.react.navigation;
+
+import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.support.v4.app.Fragment;
+
+public interface NativeScreenFactory {
+  /**
+   * Creates a new {@linkplain Fragment native screen} with {@code props}.
+   */
+  @NonNull
+  Fragment newScreen(@Nullable Bundle props);
+}

lib/android/src/main/java/com/airbnb/android/react/navigation/NavigatorModule.java

@@ -18,8 +18,8 @@
 import java.util.Map;
 
 import static com.airbnb.android.react.navigation.ReactNativeIntents.EXTRA_IS_DISMISS;
-import static com.airbnb.android.react.navigation.ScreenCoordinator.EXTRA_PAYLOAD;
 import static com.airbnb.android.react.navigation.ReactNativeUtils.VERSION_CONSTANT_KEY;
+import static com.airbnb.android.react.navigation.ScreenCoordinator.EXTRA_PAYLOAD;
 
 class NavigatorModule extends ReactContextBaseJavaModule {
   private static final int VERSION = 2;
@@ -79,7 +79,8 @@ public void signalFirstRenderComplete(String id) {
     final ReactInterface component = coordinator.componentFromId(id);
     if (component != null) {
       handler.post(new Runnable() {
-        @Override public void run() {
+        @Override
+        public void run() {
           component.signalFirstRenderComplete();
         }
       });
@@ -113,8 +114,13 @@ public void pushNative(String name, ReadableMap props, ReadableMap options, Prom
     if (activity == null) {
       return;
     }
-    Intent intent = coordinator.intentForKey(activity.getBaseContext(), name, props);
-    startActivityWithPromise(activity, intent, promise, options);
+
+    boolean startedFragment = coordinator.startFragmentForKey(name, props, options);
+
+    if (!startedFragment) {
+      Intent intent = coordinator.intentForKey(activity.getBaseContext(), name, props);
+      startActivityWithPromise(activity, intent, promise, options);
+    }
   }
 
   @SuppressWarnings("UnusedParameters")

lib/android/src/main/java/com/airbnb/android/react/navigation/ReactNavigationCoordinator.java

@@ -8,7 +8,10 @@
 import android.os.Handler;
 import android.os.Looper;
 import android.provider.Settings;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.widget.Toast;
+
 import com.facebook.react.ReactInstanceManager;
 import com.facebook.react.bridge.ReactContext;
 import com.facebook.react.bridge.ReadableMap;
@@ -49,6 +52,7 @@ public class ReactNavigationCoordinator {
   private boolean isSuccessfullyInitialized = false;
   private static final int APP_INITIALIZE_TOAST_DELAY = 3000;
 
+  @Nullable ScreenCoordinator screenCoordinator;
 
   private ReactNavigationCoordinator() {
   }
@@ -71,6 +75,7 @@ public void onReactContextInitialized(ReactContext context) {
         }
       });
   }
+
   public void injectImplementation(NavigationImplementation implementation) {
     if (this.navigationImplementation != null) {
       // TODO: throw error. can only initialize once.
@@ -125,12 +130,17 @@ public void unregisterComponent(String name) {
    *
    * @see ReactExposedActivityParams#toIntent(Context, ReadableMap)
    */
-  Intent intentForKey(Context context, String key, ReadableMap arguments) {
+  @NonNull Intent intentForKey(Context context, String key, ReadableMap arguments) {
+    if (exposedActivities == null) {
+      throw new IllegalArgumentException("No Activities registered.");
+    }
+
     for (ReactExposedActivityParams exposedActivity : exposedActivities) {
       if (exposedActivity.key().equals(key)) {
         return exposedActivity.toIntent(context, arguments);
       }
     }
+
     throw new IllegalArgumentException(
         String.format("Tried to push Activity with key '%s', but it could not be found", key));
   }
@@ -202,4 +212,11 @@ public void run() {
       }
     }, APP_INITIALIZE_TOAST_DELAY);
   }
+
+  boolean startFragmentForKey(String name, ReadableMap props, ReadableMap options) {
+    if (screenCoordinator == null) {
+      throw new IllegalStateException("screenCoordinator == null");
+    }
+    return screenCoordinator.pushNativeScreen(name, ConversionUtil.toBundle(props), ConversionUtil.toBundle(options));
+  }
 }

lib/android/src/main/java/com/airbnb/android/react/navigation/ScreenCoordinator.java

@@ -6,6 +6,8 @@
 import android.os.Build;
 import android.os.Bundle;
 import android.support.annotation.AnimRes;
+import android.support.annotation.CallSuper;
+import android.support.annotation.CheckResult;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.support.v4.app.Fragment;
@@ -24,6 +26,7 @@
 import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.common.MapBuilder;
 
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Stack;
 
@@ -34,9 +37,10 @@
  */
 public class ScreenCoordinator {
   private static final String TAG = ScreenCoordinator.class.getSimpleName();
-  static final String EXTRA_PAYLOAD = "payload";
   private static final String TRANSITION_GROUP = "transitionGroup";
 
+  static final String EXTRA_PAYLOAD = "payload";
+
   enum PresentAnimation {
     Modal(R.anim.slide_up, R.anim.delay, R.anim.delay, R.anim.slide_down),
     Push(R.anim.slide_in_right, R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_out_right),
@@ -61,6 +65,7 @@ enum PresentAnimation {
   private ReactNavigationCoordinator reactNavigationCoordinator = ReactNavigationCoordinator.sharedInstance;
 
   private int stackId = 0;
+
   /**
    * When we dismiss a back stack, the fragment manager would normally execute the latest fragment's
    * pop exit animation. However, if we present A as a modal, push, B, then dismiss(), the latest
@@ -69,6 +74,8 @@ enum PresentAnimation {
    */
   @AnimRes private int nextPopExitAnim;
 
+  private Map<String, NativeScreenFactory> factories = new LinkedHashMap<>();
+
   public ScreenCoordinator(AppCompatActivity activity, ScreenCoordinatorLayout container,
       @Nullable Bundle savedInstanceState) {
     this.activity = activity;
@@ -81,6 +88,38 @@ void onSaveInstanceState(Bundle outState) {
     // TODO
   }
 
+  @CallSuper
+  public void onResume() {
+    reactNavigationCoordinator.screenCoordinator = this;
+  }
+
+  @CallSuper
+  public void onPause() {
+    reactNavigationCoordinator.screenCoordinator = null;
+  }
+
+  /**
+   * Register a {@linkplain NativeScreenFactory} for {@code moduleName}.
+   */
+  public void registerScreen(String moduleName, @NonNull NativeScreenFactory nativeScreenFactory) {
+    factories.put(moduleName, nativeScreenFactory);
+  }
+
+  /**
+   * Will try to push a native screen if a {@link NativeScreenFactory factory} is available for {@code moduleName}. Will return {@code true} if a screen was
+   * pushed, otherwise false.
+   */
+  @CheckResult
+  boolean pushNativeScreen(String moduleName, @Nullable Bundle props, @Nullable Bundle options) {
+    NativeScreenFactory nativeScreenFactory = factories.get(moduleName);
+    if (nativeScreenFactory != null) {
+      pushScreen(nativeScreenFactory.newScreen(props), options);
+      return true;
+    }
+
+    return false;
+  }
+
   public void pushScreen(String moduleName) {
     pushScreen(moduleName, null, null);
   }