Use a single base class for all app types

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
     ######################################################################
@@ -206,14 +202,15 @@ def create_app_commands(self):
         self.interface.commands.add(
             # About should be the last item in the menu, in a section on its own.
             Command(
-                lambda _: self.interface.about(),
+                self.interface._menu_about,
                 f"About {self.interface.formal_name}",
                 section=sys.maxsize,
             ),
         )
 
     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()

changes/1870.feature.rst

@@ -0,0 +1 @@
+Apps can now create a main window that does not have a menu bar.

changes/2209.feature.rst

@@ -0,0 +1 @@
+The API for document-based apps has been finalized.

changes/2209.removal.rst

@@ -0,0 +1 @@
+The separate ``toga.DocumentApp`` base class is no longer required. All uses of ``toga.DocumentApp`` can be replaced with ``toga.App`.