simpleanimation.py

import sys
import pygame

from utils import Timer


class SimpleAnimation(object):
    """ A simple animation. Scrolls cyclically through a list of
        images, drawing them onto the screen in the same posision.    
    """
    def __init__(self, screen, pos, images, scroll_period, duration=-1):
        """ Create an animation.        
            
            screen: The screen to which the animation will be drawn
            pos: Position on the screen
            images: 
                A list of surface objects to cyclically scroll through
            scroll_period: 
                Scrolling period (in ms)
            duration:
                Duration of the animation (in ms). If -1, the 
                animation will have indefinite duration.
        """
	print "starting animation."
        self.screen = screen
        self.images = images
        self.pos = pos
        self.img_ptr = 0
        self.active = True
        self.duration = duration
        
        self.scroll_timer = Timer(scroll_period, self._advance_img)
        self.active_timer = Timer(duration, self._inactivate, True)
    
    def is_active(self):
        """ Is the animation active ?
        
            An animation is active from the moment of its creation
            and until the duration has passed.
        """
        return self.active
    
    def update(self, time_passed):
        """ Update the animation's state.
        
            time_passed:
                The time passed (in ms) since the previous update.
        """
        for timer in [self.scroll_timer, self.active_timer]:
            timer.update(time_passed)

    def draw(self):
        """ Draw the animation onto the screen.
        """
        if self.active:
            cur_img = self.images[self.img_ptr]
            self.draw_rect = cur_img.get_rect().move(self.pos)
            self.screen.blit(cur_img, self.draw_rect)
            
    def _inactivate(self):
        if self.duration >= 0:
            self.active = False
    
    def _advance_img(self):
        self.img_ptr = (self.img_ptr + 1) % len(self.images)

class start():
	if __name__ == "__main__":
	    print "initializing"
	    pygame.init()
	    screen = pygame.display.set_mode((300, 300), 0, 32)

	    clock = pygame.time.Clock()
	    explosion_img = pygame.image.load('images/explosion1.png').convert_alpha()
	    images = [explosion_img, pygame.transform.rotate(explosion_img, 90)]

	    expl = SimpleAnimation(screen, (100, 100), images, 100, 2120)

	    while True:
		time_passed = clock.tick(50)
		
		screen.fill((0, 0, 0))
		
		for event in pygame.event.get():
		    if event.type == pygame.QUIT:
			sys.exit()
		
		expl.update(time_passed)
		expl.draw()
		
		pygame.display.flip()

go = start()