如何使用pygame在屏幕上拖动图像

Question

我希望能够通过鼠标单击图像来抓取图像，然后将其拖动到屏幕上的某个位置。当鼠标按钮被释放时，它将被丢弃。图像是我想用作精灵的太空飞船，并且有多个宇宙飞船。这是一个战舰游戏，这是游戏的一部分，你将你的船拖到板上所需的位置。我正在使用python 3.3.2和pygame和windows 10.感谢您的帮助！以下是我到目前为止的情况：

def instructions_screen():

    intro = True

    while intro:
        for event in pygame.event.get():
            if event.type ==QUIT:
                pygame.screen.quit()
                exit()

        screen.blit(background, (0, 0))
        largeText = pygame.font.Font('SF Distant Galaxy.ttf',36)
        TextSurf, TextRect = text_objects("Instructions:", largeText)
        TextRect.center = ((display_width/2), (75))

        screen.blit(instruction_text, (280, 120))

        button("Back",0,670,200,50,light_grey,white,"Back_instructions")


        screen.blit(TextSurf, TextRect)
        pygame.display.update()
        clock.tick(30)


def ship_select_screen():
    top_margin = 120
    left_margin = 390

    intro = True

    while intro:
        for event in pygame.event.get():
            if event.type == QUIT:
                pygame.screen.quit()
                exit()

        screen.blit(background, (0, 0))
        largeText = pygame.font.Font('SF Distant Galaxy.ttf',36)
        TextSurf, TextRect = text_objects("Ship selection:", largeText)
        TextRect.center = ((display_width/2), (75))
        screen.blit(TextSurf, TextRect)        
        largeText = pygame.font.Font('SF Distant Galaxy.ttf',36)
        TextSurf, TextRect = text_objects("Ships to place:", largeText)
        TextRect.center = ((200), (150))

        button("Back",0,670,200,50,light_grey,white,"Back_instructions")

    #width and height of each grid location
        WIDTH = 40
        HEIGHT = 40
        #margin between each cell
        MARGIN = 10
        #colours:
        BLACK = (0, 0, 0)
        WHITE = (255, 255, 255)
        GREEN = (0, 255, 0)
        RED = (255, 0, 0)
        # Create a 2 dimensional array.
        grid = []
        for row in range(10):
            # Add an empty array that will hold each cell
            # in this row
            grid.append([])
            for column in range(10):
                grid[row].append(0)  # Append a cell

        while True:
            #draw the grid
            for row in range(10):
                for column in range(10):
                    colour = WHITE
                    if grid[row][column] == 1:
                        colour = GREEN
                    pygame.draw.rect(screen,
                                     colour,
                                     [(((MARGIN + WIDTH) * column) + left_margin),
                                      (((MARGIN + HEIGHT) * row) + top_margin),
                                      WIDTH,
                                      HEIGHT])

            for event in pygame.event.get():
                pos = pygame.mouse.get_pos()
                if event.type == QUIT:
                    exit()
                elif event.type == pygame.MOUSEBUTTONDOWN and pos[0] > 390 and pos[0] < 890 and pos[1] > 120 and pos[1] < 620:
                    column = (pos[0]-left_margin) // (WIDTH + MARGIN)
                    row = (pos[1]-top_margin) // (HEIGHT + MARGIN)
                    # Set that location to zero
                    grid[row][column] = 1
                    print("Click ", pos, "Grid coordinates: ", row, column)
                    print(grid)

            global mouse_button_down
            mouse_button_down = pygame.mouse.get_pressed()


            global mouse_pos
            mouse_pos = pygame.mouse.get_pos()

            global aircraft_x
            aircraft_x = 70

            global aircraft_y
            aircraft_y = 185


            aircraft_carrier()



            screen.blit(TextSurf, TextRect)
            pygame.display.update()
            clock.tick(15)




    button("Back",0,670,200,50,light_grey,white,"Back_game")


def aircraft_carrier():
    global aircraft_x
    global aircraft_y
    global mouse_button_down
    global mouse_pos

    running = True

    while running:
        if mouse_button_down[0] == True and mouse_pos[0] > abs(aircraft_x - aircraft_x) + 250 and mouse_pos[1] > aircraft_y and mouse_pos[1] < aircraft_y + 40:
            print("Running!")
            aircraft_x = (aircraft_x + abs(aircraft_x - mouse_pos[0]))
            aircraft_y = (aircraft_y + abs(aircraft_y - mouse_pos[1]))
            screen.blit(aircraft_carrier_sprite, (aircraft_x, aircraft_y))

        elif mouse_button_down[0] != True:
            running = False

        pygame.display.update()
        clock.tick(30)