app: add app classe for building application or test

kivy/app.py

@@ -0,0 +1,56 @@
+'''
+App: base class for creating a Kivy application
+
+Example of very simple application with button ::
+
+    from kivy.app import App
+    from kivy.uix.button import Button
+
+    class MyApp(App):
+        def init(self):
+            self.root = Button(label='hello world'))
+
+    MyApp().run()
+'''
+
+from kivy.base import EventLoop, runTouchApp
+from kivy.event import EventDispatcher
+
+class App(EventDispatcher):
+    def __init__(self, **kwargs):
+        super(App, self).__init__()
+        self.register_event_type('on_start')
+        self.register_event_type('on_stop')
+        self.use_default_uxl = kwargs.get('use_default_uxl', True)
+        self.is_build = False
+        self.root = None
+
+    def build(self):
+        '''Initialization of the application, will be called only once.
+        If the build() return a widget, it will be used as the root widget.
+        '''
+        pass
+
+    def run(self):
+        '''Launch the app in standalone mode
+        '''
+        if not self.is_build:
+            self.root = self.build()
+        self.dispatch('on_start')
+        if self.root:
+            runTouchApp(self.root)
+        else:
+            runTouchApp()
+        self.dispatch('on_stop')
+
+    def on_start(self):
+        '''Event called after initialization, and before running the
+        application
+        '''
+        pass
+
+    def on_stop(self):
+        '''Event called after running, before closing the application
+        '''
+        pass
+