feat(Leanplum): Adds getDeviceId method. (#118)

Author: Enuviel

AndroidSDK/src/com/leanplum/Leanplum.java

@@ -295,6 +295,20 @@ public static void setDeviceId(String deviceId) {
     userSpecifiedDeviceId = true;
   }
 
+  /**
+   * Gets the deviceId in the current Leanplum session. This should only be called after
+   * {@link Leanplum#start}.
+   *
+   * @return String Returns the deviceId in the current Leanplum session.
+   */
+  public static String getDeviceId() {
+    if (!LeanplumInternal.hasCalledStart()) {
+      Log.e("Leanplum.start() must be called before calling getDeviceId.");
+      return null;
+    }
+    return Request.deviceId();
+  }
+
   /**
    * Sets the application context. This should be the first call to Leanplum.
    */

AndroidSDKTests/src/test/java/com/leanplum/LeanplumTest.java

@@ -1213,4 +1213,17 @@ public void variablesChanged() {
     handlers = CollectionUtil.uncheckedCast(TestClassUtil.getField(Leanplum.class, "onceNoDownloadsHandlers"));
     assertEquals(0, handlers.size());
   }
+
+  /**
+   * Test for {@link Leanplum#getDeviceId()}.
+   */
+  @Test
+  public void testGetDeviceId() {
+    String deviceId = Leanplum.getDeviceId();
+    assertNull(deviceId);
+    Leanplum.start(mContext);
+    assertTrue(Leanplum.hasStarted());
+    deviceId = Leanplum.getDeviceId();
+    assertNotNull(deviceId);
+  }
 }