Add Android and iOS implementations of new app/window APIs.

android/src/toga_android/app.py

@@ -9,15 +9,11 @@
 from java import dynamic_proxy
 from org.beeware.android import IPythonApp, MainActivity
 
+import toga
 from toga.command import Command, Group, Separator
 
 from .libs import events
 from .screens import Screen as ScreenImpl
-from .window import Window
-
-
-class MainWindow(Window):
-    _is_main_window = True
 
 
 class TogaApp(dynamic_proxy(IPythonApp)):
@@ -95,6 +91,11 @@ def onOptionsItemSelected(self, menuitem):
             return True
 
     def onPrepareOptionsMenu(self, menu):
+        # If the main window doesn't have a toolbar, there's no preparation required;
+        # this is a simple main window, which can't have commands.
+        if not hasattr(self._impl.interface.main_window, "toolbar"):
+            return False
+
         menu.clear()
         itemid = 1  # 0 is the same as Menu.NONE.
         groupid = 1
@@ -179,6 +180,9 @@ def onPrepareOptionsMenu(self, menu):
 
 
 class App:
+    # Android apps exit when the last window is closed
+    CLOSE_ON_LAST_WINDOW = True
+
     def __init__(self, interface):
         self.interface = interface
         self.interface._impl = self
@@ -190,14 +194,6 @@ def __init__(self, interface):
     def native(self):
         return self._listener.native if self._listener else None
 
-    def create(self):
-        # The `_listener` listens for activity event callbacks. For simplicity,
-        # the app's `.native` is the listener's native Java class.
-        self._listener = TogaApp(self)
-        # Call user code to populate the main window
-        self.interface._startup()
-        self.create_app_commands()
-
     ######################################################################
     # Commands and menus
     ######################################################################
@@ -213,7 +209,8 @@ def create_app_commands(self):
         )
 
     def create_menus(self):
-        self.native.invalidateOptionsMenu()  # Triggers onPrepareOptionsMenu
+        # On Android, menus and toolbars are populated using the same mechanism.
+        self.interface.main_window._impl.create_toolbar()
 
     ######################################################################
     # App lifecycle
@@ -222,16 +219,28 @@ def create_menus(self):
     def exit(self):
         pass  # pragma: no cover
 
+    def finalize(self):
+        self.create_app_commands()
+        self.create_menus()
+
     def main_loop(self):
         # In order to support user asyncio code, start the Python/Android cooperative event loop.
         self.loop.run_forever_cooperatively()
 
-        # On Android, Toga UI integrates automatically into the main Android event loop by virtue
-        # of the Android Activity system.
-        self.create()
+        # On Android, Toga UI integrates automatically into the main Android event loop
+        # by virtue of the Android Activity system. The `_listener` listens for activity
+        # event callbacks. For simplicity, the app's `.native` is the listener's native
+        # Java class.
+        self._listener = TogaApp(self)
+
+        # Call user code to populate the main window
+        self.interface._startup()
 
     def set_main_window(self, window):
-        pass
+        if window is None:
+            raise RuntimeError("Session-based apps are not supported on Android")
+        elif window == toga.App.BACKGROUND:
+            raise RuntimeError("Background apps are not supported on Android")
 
     ######################################################################
     # App resources

android/src/toga_android/factory.py

@@ -1,7 +1,7 @@
 from toga import NotImplementedWarning
 
 from . import dialogs
-from .app import App, MainWindow
+from .app import App
 from .command import Command
 from .fonts import Font
 from .hardware.camera import Camera
@@ -30,7 +30,7 @@
 from .widgets.textinput import TextInput
 from .widgets.timeinput import TimeInput
 from .widgets.webview import WebView
-from .window import Window
+from .window import MainWindow, Window
 
 
 def not_implemented(feature):
@@ -40,7 +40,6 @@ def not_implemented(feature):
 __all__ = [
     "App",
     "Command",
-    "MainWindow",
     "not_implemented",
     # Resources
     "dialogs",
@@ -76,7 +75,9 @@ def not_implemented(feature):
     "TimeInput",
     # "Tree",
     "WebView",
+    # Windows
     "Window",
+    "MainWindow",
 ]
 
 

android/src/toga_android/window.py

@@ -29,19 +29,12 @@ def onGlobalLayout(self):
 
 
 class Window(Container):
-    _is_main_window = False
-
     def __init__(self, interface, title, position, size):
         super().__init__()
         self.interface = interface
         self.interface._impl = self
         self._initial_title = title
 
-        if not self._is_main_window:
-            raise RuntimeError(
-                "Secondary windows cannot be created on mobile platforms"
-            )
-
     ######################################################################
     # Window properties
     ######################################################################
@@ -60,17 +53,27 @@ def close(self):
         pass
 
     def create_toolbar(self):
-        self.app.native.invalidateOptionsMenu()
+        # Simple windows don't have a titlebar
+        pass
+
+    def _configure_titlebar(self):
+        # Simple windows hide the titlebar.
+        self.app.native.getSupportActionBar().hide()
 
     def set_app(self, app):
+        if len(app.interface.windows) > 1:
+            raise RuntimeError("Secondary windows cannot be created on Android")
+
         self.app = app
-        native_parent = app.native.findViewById(R.id.content)
+        native_parent = self.app.native.findViewById(R.id.content)
         self.init_container(native_parent)
         native_parent.getViewTreeObserver().addOnGlobalLayoutListener(
             LayoutListener(self)
         )
         self.set_title(self._initial_title)
 
+        self._configure_titlebar()
+
     def show(self):
         pass
 
@@ -155,3 +158,12 @@ def get_image_data(self):
         stream = ByteArrayOutputStream()
         bitmap.compress(Bitmap.CompressFormat.PNG, 0, stream)
         return bytes(stream.toByteArray())
+
+
+class MainWindow(Window):
+    def _configure_titlebar(self):
+        # The titlebar will be visible by default.
+        pass
+
+    def create_toolbar(self):
+        self.app.native.invalidateOptionsMenu()

cocoa/src/toga_cocoa/app.py

@@ -59,7 +59,7 @@ def applicationSupportsSecureRestorableState_(self, app) -> bool:
     @objc_method
     def applicationOpenUntitledFile_(self, sender) -> bool:
         if self.interface.document_types and self.interface.main_window is None:
-            self.impl.select_file()
+            self.impl._select_file()
             return True
         return False
 
@@ -166,7 +166,7 @@ def new_file_handler(app, **kwargs):
         return new_file_handler
 
     def _menu_open_file(self, app, **kwargs):
-        self.select_file()
+        self._select_file()
 
     def _menu_quit(self, command, **kwargs):
         self.interface.on_exit()
@@ -582,10 +582,7 @@ def get_screens(self):
     # App capabilities
     ######################################################################
 
-    def beep(self):
-        NSBeep()
-
-    def select_file(self, **kwargs):
+    def _select_file(self, **kwargs):
         # FIXME This should be all we need; but for some reason, application types
         # aren't being registered correctly..
         # NSDocumentController.sharedDocumentController().openDocument_(None)
@@ -605,6 +602,9 @@ def select_file(self, **kwargs):
         # print("Untitled File opened?", panel.URLs)
         self.appDelegate.application(None, openFiles=panel.URLs)
 
+    def beep(self):
+        NSBeep()
+
     def show_about_dialog(self):
         options = NSMutableDictionary.alloc().init()
 

iOS/src/toga_iOS/app.py

@@ -3,16 +3,12 @@
 from rubicon.objc import objc_method
 from rubicon.objc.eventloop import EventLoopPolicy, iOSLifecycle
 
+import toga
 from toga_iOS.libs import UIResponder, UIScreen, av_foundation
-from toga_iOS.window import Window
 
 from .screens import Screen as ScreenImpl
 
 
-class MainWindow(Window):
-    _is_main_window = True
-
-
 class PythonAppDelegate(UIResponder):
     @objc_method
     def applicationDidBecomeActive_(self, application) -> None:
@@ -53,6 +49,9 @@ def application_didChangeStatusBarOrientation_(
 
 
 class App:
+    # iOS apps exit when the last window is closed
+    CLOSE_ON_LAST_WINDOW = True
+
     def __init__(self, interface):
         self.interface = interface
         self.interface._impl = self
@@ -66,13 +65,17 @@ def __init__(self, interface):
         self.loop = asyncio.new_event_loop()
 
     def create(self):
-        """Calls the startup method on the interface."""
+        # Call the app's startup method
         self.interface._startup()
 
     ######################################################################
     # Commands and menus
     ######################################################################
 
+    def create_app_commands(self):
+        # No commands on an iOS app (for now)
+        pass
+
     def create_menus(self):
         # No menus on an iOS app (for now)
         pass
@@ -85,6 +88,10 @@ def exit(self):  # pragma: no cover
         # Mobile apps can't be exited, but the entry point needs to exist
         pass
 
+    def finalize(self):
+        self.create_app_commands()
+        self.create_menus()
+
     def main_loop(self):
         # Main loop is non-blocking on iOS. The app loop is integrated with the
         # main iOS event loop, so this call will return; however, it will leave
@@ -93,7 +100,10 @@ def main_loop(self):
         self.loop.run_forever_cooperatively(lifecycle=iOSLifecycle())
 
     def set_main_window(self, window):
-        pass
+        if window is None:
+            raise RuntimeError("Session-based apps are not supported on iOS")
+        elif window == toga.App.BACKGROUND:
+            raise RuntimeError("Background apps are not supported on iOS")
 
     ######################################################################
     # App resources
@@ -111,10 +121,6 @@ def beep(self):
         # sounding like a single strike of a bell.
         av_foundation.AudioServicesPlayAlertSound(1013)
 
-    def open_document(self, fileURL):  # pragma: no cover
-        """Add a new document to this app."""
-        pass
-
     def show_about_dialog(self):
         self.interface.factory.not_implemented("App.show_about_dialog()")
 

iOS/src/toga_iOS/container.py

@@ -124,7 +124,54 @@ def __init__(
         layout_native=None,
         on_refresh=None,
     ):
+        """A bare content container.
+
+        :param content: The widget impl that is the container's initial content.
+        :param layout_native: The native widget that should be used to provide
+            size hints to the layout. This will usually be the container widget
+            itself; however, for widgets like ScrollContainer where the layout
+            needs to be computed based on a different size to what will be
+            rendered, the source of the size can be different.
+        :param on_refresh: The callback to be notified when this container's layout is
+            refreshed.
         """
+        super().__init__(
+            content=content,
+            layout_native=layout_native,
+            on_refresh=on_refresh,
+        )
+
+        # Construct a UIViewController to hold the root content
+        self.controller = UIViewController.alloc().init()
+
+        # Set the controller's view to be the root content widget
+        self.controller.view = self.native
+
+    @property
+    def height(self):
+        return self.layout_native.bounds.size.height - self.top_offset
+
+    @property
+    def top_offset(self):
+        return UIApplication.sharedApplication.statusBarFrame.size.height
+
+    @property
+    def title(self):
+        return self._title
+
+    @title.setter
+    def title(self, value):
+        self._title = value
+
+
+class NavigationContainer(Container):
+    def __init__(
+        self,
+        content=None,
+        layout_native=None,
+        on_refresh=None,
+    ):
+        """A container that provides a navigation bar.
         :param content: The widget impl that is the container's initial content.
         :param layout_native: The native widget that should be used to provide
             size hints to the layout. This will usually be the container widget