Call arbitrary Android intents and get result back

src/android/toga_android/app.py

@@ -5,13 +5,18 @@
 from .libs.activity import IPythonApp, MainActivity
 from .window import Window
 
+import asyncio
+
 
 # `MainWindow` is defined here in `app.py`, not `window.py`, to mollify the test suite.
 class MainWindow(Window):
     pass
 
 
 class TogaApp(IPythonApp):
+    last_intent_requestcode = -1  # always increment before using it for invoking new Intents
+    running_intents = {}          # dictionary for currently running Intents
+
     def __init__(self, app):
         super().__init__()
         self._interface = app
@@ -39,6 +44,25 @@ def onDestroy(self):
     def onRestart(self):
         print("Toga app: onRestart")
 
+    def onActivityResult(self, requestCode, resultCode, resultData):
+        """
+        Callback method, called from MainActivity when an Intent ends
+
+        :param int requestCode: The integer request code originally supplied to startActivityForResult(),
+                                allowing you to identify who this result came from.
+        :param int resultCode: The integer result code returned by the child activity through its setResult().
+        :param Intent resultData: An Intent, which can return result data to the caller (various data can be attached
+                                  to Intent "extras").
+        """
+        print("Toga app: onActivityResult, requestCode={0}, resultData={1}".format(requestCode, resultData))
+        try:
+            # remove Intent from the list of running Intents,
+            # and set the result of the intent.
+            result_future = self.running_intents.pop(requestCode)
+            result_future.set_result({"resultCode": resultCode, "resultData": resultData})
+        except KeyError:
+            print("No intent matching request code {requestCode}")
+
     @property
     def native(self):
         # We access `MainActivity.singletonThis` freshly each time, rather than
@@ -92,3 +116,25 @@ def set_on_exit(self, value):
 
     def add_background_task(self, handler):
         self.loop.call_soon(wrapped_handler(self, handler), self)
+
+    async def intent_result(self, intent):
+        """
+        Calls an Intent and waits for its result.
+
+        A RuntimeError will be raised when the Intent cannot be invoked.
+
+        :param Intent intent: The Intent to call
+        :returns: A Dictionary containing "resultCode" (int) and "resultData" (Intent or None)
+        :rtype: dict
+        """
+        if intent.resolveActivity(self.native.getPackageManager()) is None:
+            raise RuntimeError('No appropriate Activity found to handle this intent.')
+        self._listener.last_intent_requestcode += 1
+        code = self._listener.last_intent_requestcode
+
+        result_future = asyncio.Future()
+        self._listener.running_intents[code] = result_future
+
+        self.native.startActivityForResult(intent, code)
+        await result_future
+        return result_future.result()

src/android/toga_android/libs/android.py

@@ -1,6 +1,7 @@
 from rubicon.java import JavaClass, JavaInterface
 
 Color = JavaClass("android/graphics/Color")
+Intent = JavaClass("android/content/Intent")
 MotionEvent = JavaClass("android/view/MotionEvent")
 PorterDuff__Mode = JavaClass("android/graphics/PorterDuff$Mode")
 View__OnTouchListener = JavaInterface("android/view/View$OnTouchListener")