test_tree_icon.py

import toga

class StartApp(toga.App):
    def startup(self):
        self.main_window = toga.MainWindow(self.name)
        self.main_window.app = self

        self.tree = toga.Tree(['Navigate'])
        self.root_one_id = self.tree.insert(None, None, 'root')

        self.root_two_id = self.tree.insert(None, None, 'inner_root')
        self.sub_root_two_id = self.tree.insert(self.root_two_id, None,
                                            'inner_root2')

        button_f = toga.Button('Set Icon Root 1',
                                on_press=self.callbackIconOne)
        button_s = toga.Button('Set Icon Root 2',
                                on_press=self.callbackIconTwo)
        button_t = toga.Button('Set Icon Sub Root 2',
                                on_press=self.callbackIconThree)
        button_all = toga.Button('Set Icon Tree',
                                on_press=self.callbackIconAll)

        self.box = toga.Box()
        self.box.add(button_f)
        self.box.add(button_s)
        self.box.add(button_t)
        self.box.add(button_all)

        container = toga.SplitContainer()
        container.content = [self.tree, self.box]

        self.main_window.content = container
        self.main_window.show()

    def callbackIconOne(self, event):
        self.tree.set_icon('icon.png', self.root_one_id)

    def callbackIconTwo(self, event):
        self.tree.set_icon('icon.png', self.root_two_id)

    def callbackIconThree(self, event):
        self.tree.set_icon('icon.png', self.sub_root_two_id)

    def callbackIconAll(self, event):
        self.tree.set_icon('icon.png')

def main():
    app = StartApp('Tree Test', 'org.pybee.test')
    app.main_loop()

if __name__ == '__main__':
    main()