Scene transitions

[mrcoxall]

I came back to try this again, just to make sure it is still working before I try it with my students. When I use the current version of the original Pythonista and this: https://gist.github.com/offe/a58d34573d8f5c89743a, the app is just crashing on me now.

Is anyone else having this problem?

[ccc]

Scenes have changed a lot since those posts were written and now multi scene support is builtin.

See: scene.Scene.present_modal_scene() and scene.Scene.presented_scene.

[mrcoxall]

I am having a problem presenting the second scene with the present_modal_scene().
Does anyone have an example of the best practises using this?

This is what I have so far:
(note: I am using a UI.view since I want to place it in the PythonistaAppTemplate and then into Xcode)

# for use with https://github.com/omz/PythonistaAppTemplate

from scene import *
import ui

class FirstScene (Scene):
    def setup(self):
        self.background_color = 'midnightblue'
        self.ship = SpriteNode('spc:PlayerShip1Orange')
        self.ship.position = self.size / 2
        self.add_child(self.ship)

    def touch_began(self, touch):
        # question?
        # how do you get to the second scene? 
        self.present_modal_scene(my_second_scene)
        
class SecondScene (Scene):
    def setup(self):
        self.background_color = '#704414'
        self.ship = SpriteNode('spc:EnemyGreen2')
        self.ship.position = self.size / 2
        self.add_child(self.ship)

    def touch_began(self, touch):
        pass

my_scene = FirstScene()
my_second_scene = SecondScene()
# Instead of...
# run(MyScene())

# ..use:
main_view = ui.View()
scene_view = SceneView(frame=main_view.bounds, flex='WH')
main_view.add_subview(scene_view)
scene_view.scene = my_scene
main_view.present(hide_title_bar=True, animated=False)

[omz]

@mrcoxall Your code works for me, but note that modal scenes don't draw any background (i.e. the background_color attribute is ignored). You might want to use a colored SpriteNode to prevent the first scene from shining through. This behavior is intentional because a common use case for present_modal_scene is to present a menu overlay with transparent background (as in the included game examples).

[mrcoxall]

So omz was correct and the background was the first problem.
When I do it for just a single scene, it all seems to work fine.

My next problem is that I tried to make it move from one scene to a second.
Problem is I am getting a "Value error: inconsistent Node hierarchy", when I try to move from the second scene back to the first one.

The good news is that I placed it in Xcode and the App template works great.
Here is my code:

# for use with https://github.com/omz/PythonistaAppTemplate

from scene import *
import ui

class MainScene (Scene):
    def setup(self):
        # this is the starting scene, for ui.View
        # all other scenes will come from
        
        self.background_color = 'black'
        self.present_modal_scene(first_scene)


class FirstScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ship = SpriteNode('spc:PlayerShip1Orange')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
    
    def update(self):
        pass
    #x, y, z = gravity()
    #pos = self.ship.position
    #pos += (x * 15, y * 15)
    # Don't allow the ship to move beyond the screen bounds:
    #pos.x = max(0, min(self.size.w, pos.x))
    #pos.y = max(0, min(self.size.h, pos.y))
    #self.ship.position = pos
    
    def touch_began(self, touch):
        # question?
        # how do you get to the second scene?
        #self.dismiss_modal_scene()
        self.present_modal_scene(second_scene)
    
    def touch_moved(self, touch):
        pass
    
    def touch_ended(self, touch):
        pass


class SecondScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'green')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ship = SpriteNode('spc:EnemyGreen2')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
    
    def touch_began(self, touch):
        self.present_modal_scene(first_scene)
#pass


main_scene = MainScene()
first_scene = FirstScene()
second_scene = SecondScene()
# Instead of...
# run(MyScene())

# ..use:
main_view = ui.View()
scene_view = SceneView(frame=main_view.bounds, flex='WH')
main_view.add_subview(scene_view)
scene_view.scene = first_scene
main_view.present(hide_title_bar=True, animated=False)

[omz]

@mrcoxall Use dismiss_modal_scene instead of present_modal_scene to get back from the second scene to the first one.

[ccc]

from scene import *


class FirstScene(Scene):
    def setup(self):
        # add white background
        SpriteNode(anchor_point=(0, 0), color='white', parent=self,
                   size=self.size)
        self.ship = SpriteNode('spc:PlayerShip1Orange', parent=self,
                               position=self.size / 2)
    
    def touch_began(self, touch):
        self.present_modal_scene(SecondScene())


class SecondScene(Scene):
    def setup(self):
        # add green background
        SpriteNode(anchor_point=(0, 0), color='green', parent=self,
                   size=self.size)
        self.ship = SpriteNode('spc:EnemyGreen2', parent=self,
                               position=self.size / 2)
    
    def touch_began(self, touch):
        self.dismiss_modal_scene()


if __name__ == '__main__':
    scene_view = SceneView()
    scene_view.scene = FirstScene()
    scene_view.present(hide_title_bar=True, animated=False)

[mrcoxall]

Thanks again to everyone for their help, I am getting close to a "scene solution" I can use.

The problem I have now is, I would like to use a timer, so that after a second it automatically moves to the next scene. I would like to use it for a splash screen at the beginning. Because it is modal though, the scene is still running in the background.

Is there any way to not have it modal or to actually really completely remove the scene, so it is not running and then go to the new one? There will be some scenes I will only ever use once, so removing them from memory would be the best.

# for use with https://github.com/omz/PythonistaAppTemplate

from scene import *
import ui
import time

class FirstScene (Scene):

    # global variable to class
    start_time = None
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        # get starting time
        global start_time
        start_time = time.time() 
        
        self.ship = SpriteNode('spc:PlayerShip1Orange')
        self.ship.position = self.size / 4
        self.add_child(self.ship)
        
    def update(self):
        # move to new scene after 1 second
        # problem is it keeps happening, since it is modal
        # is there a way to actually really dispose 
        # of a scene and then move forward?
        
        current_time = time.time()
        if current_time - start_time > 1:
            #self.present_modal_scene(second_scene)
            pass

    def touch_began(self, touch):
        #self.dismiss_modal_scene()
        #self.present_modal_scene(second_scene)
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        if self.ship.frame.contains_point(touch.location):
            self.present_modal_scene(second_scene)
        
        
class SecondScene (Scene):
	
    # global variable to class
    start_time = None
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'green')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        # get starting time
        global start_time
        start_time = time.time()
        
        self.ship = SpriteNode('spc:EnemyGreen2')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
        
    def update(self):
        # move to new scene after 1 second
        current_time = time.time()
        if current_time - start_time > 1:
            #self.present_modal_scene(second_scene)
            pass

    def touch_began(self, touch):
        
        self.present_modal_scene(main_menu_scene)
    
    
class MainMenuScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'blue')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ace = SpriteNode('card:ClubsA')
        self.ace.position = (683.0, 512.0)
        self.add_child(self.ace)
        
        self.king = SpriteNode('card:ClubsK')
        self.king.position = (683.0, 750.0)
        self.add_child(self.king)
        
        self.queen = SpriteNode('card:ClubsQ')
        self.queen.position = (683.0, 238.0)
        self.add_child(self.queen)
        
    def update(self):
        pass

    def touch_began(self, touch):
        #self.dismiss_modal_scene()
        #self.present_modal_scene(a_scene)
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        # move to new scenes
        if self.ace.frame.contains_point(touch.location):
            self.present_modal_scene(a_scene)
        elif self.king.frame.contains_point(touch.location):
            self.present_modal_scene(b_scene)
        elif self.queen.frame.contains_point(touch.location):
            self.present_modal_scene(c_scene)
        
        
class AScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
         
        self.a_choise = SpriteNode('card:BackBlue1')
        self.a_choise.position = self.size / 2
        self.add_child(self.a_choise)
        
    def update(self):
        pass

    def touch_began(self, touch):
        self.dismiss_modal_scene()
        #self.present_modal_scene(b_scene)
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        pass


class BScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ship = SpriteNode('card:BackGreen1')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
        
    def update(self):
        pass

    def touch_began(self, touch):
        self.dismiss_modal_scene()
        #self.present_modal_scene(c_scene)
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        pass


class CScene (Scene):
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ship = SpriteNode('card:BackRed1')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
        
    def update(self):
        pass

    def touch_began(self, touch):
        self.dismiss_modal_scene()
        #self.present_modal_scene(second_scene)
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        pass


first_scene = FirstScene()
second_scene = SecondScene()
main_menu_scene = MainMenuScene()
a_scene = AScene()
b_scene = BScene()
c_scene = CScene()
# Instead of...
# run(MyScene())

# ..use:
main_view = ui.View()
scene_view = SceneView(frame=main_view.bounds, flex='WH')
main_view.add_subview(scene_view)
scene_view.scene = first_scene
main_view.present(hide_title_bar=True, animated=False)

[mrcoxall]

The following is the best I have been able to come up with as a template for scene management. I have a timer for the fist scene. Unfortunately I cannot get one working for the second.

I am still looking for a "non-modal" way to present a scene or a way to completely remove a scene, so that it is no longer running.
Thanks again for any help.

# for use with https://github.com/omz/PythonistaAppTemplate

from scene import *
import ui
import time

class FirstScene (Scene):

    # global variable to class
    start_time = None
       
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        # get starting time
        global start_time
        start_time = time.time() 
               
        self.ship = SpriteNode('test:Pythonista')
        self.ship.position = self.size / 2
        self.ship.size = self.size
        self.add_child(self.ship)
        
    def update(self):
        # move to new scene after 2 second
        # problem is it keeps happening, since it is modal
        # is there a way to actually really dispose 
        # of a scene and then move forward?
              
        current_time = time.time()
        
        #global scene_moved_away_from
        if current_time - start_time > 2:
            self.present_modal_scene(second_scene)

    def touch_began(self, touch):
        #self.present_modal_scene(second_scene)
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        if self.ship.frame.contains_point(touch.location):
            self.present_modal_scene(second_scene)
        
        
class SecondScene (Scene):

    # global variable to class
    start_time = None
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'green')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        start_time = time.time()
        
        self.ship = SpriteNode('spc:EnemyGreen2')
        self.ship.position = self.size / 2
        self.add_child(self.ship)
        
    def update(self):
        # move to new scene after 2 second
        current_time = time.time()
        
        # have to comment out because get "max recursion error"
        # code keeps reloading first then second scene over and
        # over again, since time has lapsed
        #if current_time - start_time > 2:
            #self.present_modal_scene(second_scene)
            #pass

    def touch_began(self, touch):
        self.pause = True
        self.present_modal_scene(main_menu_scene)
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        pass
    
    
class MainMenuScene (Scene):
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'blue')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.ace = SpriteNode('card:ClubsA')
        self.ace.position = (683.0, 512.0)
        self.add_child(self.ace)
        
        self.king = SpriteNode('card:ClubsK')
        self.king.position = (683.0, 750.0)
        self.add_child(self.king)
        
        self.queen = SpriteNode('card:ClubsQ')
        self.queen.position = (683.0, 238.0)
        self.add_child(self.queen)
        
    def update(self):
        pass

    def touch_began(self, touch):
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        # move to new scenes
        if self.ace.frame.contains_point(touch.location):
            self.present_modal_scene(a_scene)
        elif self.king.frame.contains_point(touch.location):
            self.present_modal_scene(b_scene)
        elif self.queen.frame.contains_point(touch.location):
            self.present_modal_scene(c_scene)
        
        
class AScene (Scene):
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
         
        self.blue_card = SpriteNode('card:BackBlue1')
        self.blue_card.position = self.size / 2
        self.add_child(self.blue_card)
        
    def update(self):
        pass

    def touch_began(self, touch):
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        # moving back to previous scene, so remove modal makes sense
        if self.blue_card.frame.contains_point(touch.location):
            self.dismiss_modal_scene()


class BScene (Scene):
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.green_card = SpriteNode('card:BackGreen1')
        self.green_card.position = self.size / 2
        self.add_child(self.green_card)
        
    def update(self):
        pass

    def touch_began(self, touch):
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        # moving back to previous scene, so remove modal makes sense
        if self.green_card.frame.contains_point(touch.location):
            self.dismiss_modal_scene()


class CScene (Scene):
    
    def setup(self):
        # add background color
        self.background = SpriteNode(color = 'white')
        self.background.size = self.size
        self.background.position = self.size / 2
        self.add_child(self.background)
        
        self.red_card = SpriteNode('card:BackRed1')
        self.red_card.position = self.size / 2
        self.add_child(self.red_card)
        
    def update(self):
        pass

    def touch_began(self, touch):
        pass
        
    def touch_moved(self, touch):
        pass
        
    def touch_ended(self, touch):
        # moving back to previous scene, so remove modal makes sense
        if self.red_card.frame.contains_point(touch.location):
            self.dismiss_modal_scene()


first_scene = FirstScene()
second_scene = SecondScene()
main_menu_scene = MainMenuScene()
a_scene = AScene()
b_scene = BScene()
c_scene = CScene()
# Instead of...
# run(MyScene())

# ..use:
main_view = ui.View()
scene_view = SceneView(frame=main_view.bounds, flex='WH')
main_view.add_subview(scene_view)
scene_view.scene = first_scene
main_view.present(hide_title_bar=True, animated=False)

[ccc]

If you want transitory scenes then create the main scene in your main program but then only create overlaying scenes when you actually need them. That is, do not create scenes in your main() if you want them to be transitory.

• Try creating sceneA inside the body of the MainScene class.
• Try creating sceneB inside the body of the sceneA class.
• Try creating sceneC inside the body of the sceneB class.

As variables like "sceneC" fall out of scope, they can be garbage collected but those scenes that are defined in main() can not be garbage collected until main() ends.

See the code above where FirstScene.touch_begin() creates and displays a SecondScene. Then SecondScene.touch_begin() destroys self to go back to the FirstScene.

[ccc]

My "Pull Request"...

• Uses self.presented_sceneto know if there is a modal scene above self.
• Removes both class variables and global variables -- they are NOT the same thing.
• Does a two second hop from 1st scene to 2nd scene and a two second hop from 2nd scene to 3rd scene without recursion issues.
• Creates scenes on-the-fly when needed to allow them to be garbage collected once they have been closed.
• Adds card_back_colorto allow one scene class to show card backs of different colors.

# for use with https://github.com/omz/PythonistaAppTemplate

from scene import *
import time


class FirstScene(Scene):
    def setup(self):
        # get starting time
        self.start_time = time.time()
        # add background color
        SpriteNode(anchor_point=(0, 0), color='white', parent=self,
                   size=self.size)
        self.ship = SpriteNode('test:Pythonista', anchor_point=(0, 0),
                               parent=self, size=self.size)
        
    def update(self):
        # move to new scene after 2 seconds
        if not self.presented_scene and time.time() - self.start_time > 2:
            self.present_modal_scene(SecondScene())

    def touch_began(self, touch):
        # self.present_modal_scene(SecondScene())
        pass

    def touch_ended(self, touch):
        if self.ship.frame.contains_point(touch.location):
            self.present_modal_scene(SecondScene())
        
        
class SecondScene(Scene):
    def setup(self):
        self.start_time = time.time()
        # add background color
        SpriteNode(anchor_point=(0, 0), color='green', parent=self,
                   size=self.size)
        self.ship = SpriteNode('spc:EnemyGreen2', parent=self,
                               position=self.size/2)
        
    def update(self):
        if not self.presented_scene and time.time() - self.start_time > 2:
            self.present_modal_scene(MainMenuScene())

    def touch_began(self, touch):
        self.present_modal_scene(MainMenuScene())
    

class MainMenuScene (Scene):
    def setup(self):
        # add background color
        SpriteNode(anchor_point=(0, 0), color='blue', parent=self,
                   size=self.size)
        
        self.ace = SpriteNode('card:ClubsA', parent=self, position=(683, 512))
        self.king = SpriteNode('card:ClubsK', parent=self, position=(683, 750))
        self.queen = SpriteNode('card:ClubsQ', parent=self, position=(683, 238))
        
    def touch_ended(self, touch):
        # move to new scenes
        if self.ace.frame.contains_point(touch.location):
            self.present_modal_scene(CardBackScene('blue'))
        elif self.king.frame.contains_point(touch.location):
            self.present_modal_scene(CardBackScene('green'))
        elif self.queen.frame.contains_point(touch.location):
            self.present_modal_scene(CardBackScene('red'))
        
        
class CardBackScene(Scene):
    def __init__(self, card_back_color='blue'):
        Scene.__init__(self)
        self.img_name = 'card:Back{}1'.format(card_back_color.title())

    def setup(self):
        # add background color
        SpriteNode(anchor_point=(0, 0), color='white', parent=self,
                   size=self.size)
        self.card = SpriteNode(self.img_name, parent=self,
                               position=self.size/2)

    def touch_ended(self, touch):
        # moving back to previous scene, so remove modal makes sense
        if self.card.frame.contains_point(touch.location):
            self.dismiss_modal_scene()


main_view = SceneView()
main_view.scene = FirstScene()
main_view.present(hide_title_bar=True, animated=False)

[mrcoxall]

Works great.
Thanks so much.

Patrick

[PeterG]

@ccc, just something I need , very nice indeed! I import a game, that for grand-son and daughter, and run it before the background cardimages are shown, meeaning I am on the way for an 4-level game ...
Next try, just using one of the marvallous available games , as next levels ..
.. Topscore files will be used for further interaction ..

Thanks to your example ... Helps a lot 😊 , happy OpaPeter