[TIMOB-19919] separates event and callback for onBackPressed

android/titanium/src/java/org/appcelerator/titanium/TiBaseActivity.java

@@ -689,13 +689,18 @@ public void onBackPressed()
 
 		TiWindowProxy topWindow = topWindowOnStack();
 
-		// Prevent default Android behavior for "back" press
-		// if the top window has a listener to handle the event.
 		if (topWindow != null && topWindow.hasListeners(TiC.EVENT_ANDROID_BACK)) {
 			topWindow.fireEvent(TiC.EVENT_ANDROID_BACK, null);
-
+		}
+
+		// Override default Android behavior for "back" press
+		// if the top window has a callback to handle the event.
+		if (topWindow != null && topWindow.hasProperty(TiC.PROPERTY_ON_BACK)) {
+			KrollFunction onBackCallback = (KrollFunction) topWindow.getProperty(TiC.PROPERTY_ON_BACK);
+			onBackCallback.callAsync(activityProxy.getKrollObject(), new Object[] {});
+
 		} else {
-			// If event is not handled by any listeners allow default behavior.
+			// If event is not handled by custom callback allow default behavior.
 			super.onBackPressed();
 		}
 	}

android/titanium/src/java/org/appcelerator/titanium/TiC.java

@@ -1750,7 +1750,12 @@ public class TiC
 	 * @module.api
 	 */
 	public static final String PROPERTY_OKID = "okid";
-
+
+	/**
+	 * @module.api
+	 */
+	public static final String PROPERTY_ON_BACK = "onBack";
+
 	/**
 	 * @module.api
 	 */

android/titanium/src/java/org/appcelerator/titanium/proxy/TiWindowProxy.java

@@ -33,6 +33,7 @@
 @Kroll.proxy(propertyAccessors={
 	TiC.PROPERTY_EXIT_ON_CLOSE,
 	TiC.PROPERTY_FULLSCREEN,
+	TiC.PROPERTY_ON_BACK,
 	TiC.PROPERTY_TITLE,
 	TiC.PROPERTY_TITLEID,
 	TiC.PROPERTY_WINDOW_SOFT_INPUT_MODE

apidoc/Titanium/UI/Window.yml

@@ -151,17 +151,6 @@ events:
         This event is fired when the current window's activity detects
         a back button press by the user to navigate back.
 
-        By default this event would trigger the current activity to be finished
-        and removed from the task stack. Subscribing to this event with a listener
-        will prevent the default behavior. To finish the activity from your listener
-        just call the *close* method of the window.
-
-        This event replaces the android:back event. Some behavior
-        changes may exist such as the event no longer firing when the
-        user dismisses the keyboard with the back button or when the
-        user closes a full-screen video which is embedded in a web view
-        with the back button.
-
     since: '3.0.0'
 
   - name: androidcamera
@@ -517,7 +506,16 @@ properties:
         `backgroundColor` property as well, unless you want the window to be completely
         transparent.
     type: Number
-
+
+  - name: onBack
+    summary: |
+        Callback function that overrides the default behavior when the user presses the **Back** 
+        button.
+    description: |
+        This was separated from the <Ti.UI.Window.androidback> event. You need to define this
+        callback if you explicitly want to override the back button behavior.
+    type: Callback<Object>
+
   - name: orientationModes
     summary: |
         Array of supported orientation modes, specified using the orientation