Add deep linking support to IntentAndroid

Summary:
Add a method to handle URLs registered to the app,

```js
IntentAndroid.getInitialURL(url => {
    if (url) {
        // do stuff
    }
});
```

Refer - http://developer.android.com/training/app-indexing/deep-linking.html#adding-filters

The API cannot be same as the iOS API (i.e. as a constant), as the activity is not availble at the time of module initialization. Moreover, multiple activties can share the same bridge instance, and the activity itself is not a constant. Hence the initialURL can change.
Closes #4320

Reviewed By: svcscm

Differential Revision: D2759667

Pulled By: foghina

fb-gh-sync-id: b725231ae1401fa5565d444eee5a30d303e263ae

Author: satya164

Libraries/Components/Intent/IntentAndroid.android.js

@@ -16,6 +16,26 @@ var invariant = require('invariant');
 /**
  * `IntentAndroid` gives you a general interface to handle external links.
  *
+ * ### Basic Usage
+ *
+ * #### Handling deep links
+ *
+ * If your app was launched from an external url registered to your app you can
+ * access and handle it from any component you want with
+ *
+ * ```
+ * componentDidMount() {
+ *   var url = IntentAndroid.getInitialURL(url => {
+ *     if (url) {
+ *       console.log('Initial url is: ' + url);
+ *     }
+ *   });
+ * }
+ * ```
+ *
+ * NOTE: For instructions on how to add support for deep linking,
+ * refer [Enabling Deep Links for App Content - Add Intent Filters for Your Deep Links](http://developer.android.com/training/app-indexing/deep-linking.html#adding-filters).
+ *
  * #### Opening external links
  *
  * To start the corresponding activity for a link (web URL, email, contact etc.), call
@@ -75,6 +95,20 @@ class IntentAndroid {
     IntentAndroidModule.canOpenURL(url, callback);
   }
 
+  /**
+   * If the app launch was triggered by an app link with {@code Intent.ACTION_VIEW},
+   * it will give the link url, otherwise it will give `null`
+   *
+   * Refer http://developer.android.com/training/app-indexing/deep-linking.html#handling-intents
+   */
+  static getInitialURL(callback: Function) {
+    invariant(
+      typeof callback === 'function',
+      'A valid callback function is required'
+    );
+    IntentAndroidModule.getInitialURL(callback);
+  }
+
   static _validateURL(url: string) {
     invariant(
       typeof url === 'string',

ReactAndroid/src/main/java/com/facebook/react/modules/intent/IntentModule.java

@@ -9,15 +9,15 @@
 
 package com.facebook.react.modules.intent;
 
+import android.app.Activity;
 import android.content.Intent;
 import android.net.Uri;
 
 import com.facebook.react.bridge.Callback;
+import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
 import com.facebook.react.bridge.ReactApplicationContext;
-import com.facebook.react.bridge.ReactContext;
 import com.facebook.react.bridge.ReactContextBaseJavaModule;
 import com.facebook.react.bridge.ReactMethod;
-import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
 
 /**
  * Intent module. Launch other activities or open URLs.
@@ -33,25 +33,58 @@ public String getName() {
     return "IntentAndroid";
   }
 
+  /**
+   * Return the URL the activity was started with
+   *
+   * @param callback a callback which is called with the initial URL
+   */
+  @ReactMethod
+  public void getInitialURL(Callback callback) {
+    try {
+      Activity currentActivity = getCurrentActivity();
+      String initialURL = null;
+
+      if (currentActivity != null) {
+        Intent intent = currentActivity.getIntent();
+        String action = intent.getAction();
+        Uri uri = intent.getData();
+
+        if (Intent.ACTION_VIEW.equals(action) && uri != null) {
+          initialURL = uri.toString();
+        }
+      }
+
+      callback.invoke(initialURL);
+    } catch (Exception e) {
+      throw new JSApplicationIllegalArgumentException(
+          "Could not get the initial URL : " + e.getMessage());
+    }
+  }
+
   /**
    * Starts a corresponding external activity for the given URL.
    *
    * For example, if the URL is "https://www.facebook.com", the system browser will be opened,
    * or the "choose application" dialog will be shown.
    *
-   * @param URL the URL to open
+   * @param url the URL to open
    */
   @ReactMethod
   public void openURL(String url) {
     if (url == null || url.isEmpty()) {
       throw new JSApplicationIllegalArgumentException("Invalid URL: " + url);
     }
+
     try {
+      Activity currentActivity = getCurrentActivity();
       Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
-      // We need Intent.FLAG_ACTIVITY_NEW_TASK since getReactApplicationContext() returns
-      // the ApplicationContext instead of the Activity context.
-      intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
-      getReactApplicationContext().startActivity(intent);
+
+      if (currentActivity != null) {
+        currentActivity.startActivity(intent);
+      } else {
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        getReactApplicationContext().startActivity(intent);
+      }
     } catch (Exception e) {
       throw new JSApplicationIllegalArgumentException(
           "Could not open URL '" + url + "': " + e.getMessage());
@@ -61,21 +94,22 @@ public void openURL(String url) {
   /**
    * Determine whether or not an installed app can handle a given URL.
    *
-   * @param URL the URL to open
-   * @param promise a promise that is always resolved with a boolean argument
+   * @param url the URL to open
+   * @param callback a callback that is always called with a boolean argument
    */
   @ReactMethod
   public void canOpenURL(String url, Callback callback) {
     if (url == null || url.isEmpty()) {
       throw new JSApplicationIllegalArgumentException("Invalid URL: " + url);
     }
+
     try {
       Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
       // We need Intent.FLAG_ACTIVITY_NEW_TASK since getReactApplicationContext() returns
       // the ApplicationContext instead of the Activity context.
       intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
       boolean canOpen =
-          intent.resolveActivity(this.getReactApplicationContext().getPackageManager()) != null;
+          intent.resolveActivity(getReactApplicationContext().getPackageManager()) != null;
       callback.invoke(canOpen);
     } catch (Exception e) {
       throw new JSApplicationIllegalArgumentException(