Shooting games lesson 1-2: using sprites

Pygame The first 1-2 course ： Use sprites

This is us. “ Use Pygame Develop games ” Tutorial Series No 2 part . You should start with The first 1 Part of it ： introduction

What is the spirit ？

sprite Is a computer graphics term , Refers to any object that can be moved on the screen . When you play any 2D In the game , All the objects you see on the screen are sprites . Elves can be animated , They can be controlled by the player , They can even interact with each other .

We will be in the game cycle to update and draw Part is responsible for updating and drawing sprites . But you can probably imagine , If your game has a lot of sprites , Then these parts of the game cycle may become very long and complex . Fortunately, ,Pygame There is a good solution to this ： Spirit group .

The elves group is just a collection of elves , You can perform all operations on them at the same time . Let's create a sprite group to save all the sprites in the game ：

 clock = pygame.time.Clock()
 all_sprites = pygame.sprite.Group()
 

Now? , We can take advantage of this group by adding the following to the loop ：

    # Update
    all_sprites.update()

    # Draw / render
    screen.fill(BLACK)
    all_sprites.draw(screen)
 

Now? , For every sprite we create , We just need to make sure to add it to all_sprites In the sprite group , It will automatically draw on the screen , And update each time through the cycle .

Create an elf

Now we are going to make our first elf . stay Pygame in , Elves are object . It is a convenient way to group data and code into a single entity . It may be a little confusing at first , But fortunately ,Pygame Elves are a good way to practice objects and get used to the way they work .

We first define our new elves ：

class Player(pygame.sprite.Sprite):

class tell Python We are defining a new class , It will be the player spirit , The type is pygame.sprite.Sprite, That means it will be based on Pygame Predefined Sprite class

We are class The first code in the definition is __init__() Special functions , It defines what code will run whenever a new object of this type is created . Every Pygame Sprite There must also be two properties ： One image And a rect ：`

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 50))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
 

first line pygame.sprite.Sprite.__init__(self) yes Pygame Necessary , It runs Built in Sprint class Initializers . Next , We define image attribute , ad locum , We're just creating one Surface, It is 50 x 50 Square and use GREEN Fill it with color . later , We will learn how to use image Create elves , For example, characters or spaceships , But now a square of fixed size is enough .

Next , We must define the spirit rect , It is “ rectangular ” Abbreviation . stay Pygame in , Rectangles are everywhere , To track the coordinates of the object .get_rect() Command calculation image The rectangular .

We can use rect Put the genie anywhere on the screen . Let the genie appear in the middle of the screen from the beginning ：

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 50))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.rect.center = (WIDTH / 2, HEIGHT / 2)
 

Now we have defined Player spirit , We need to create Player Class example Come on “ Generate ” it . We also need to ensure that sprite Add to all_sprites In the group ：

all_sprites = pygame.sprite.Group()
player = Player()
all_sprites.add(player)
 

Now? , If you run the program , You will see a green square in the center of the screen . Continue and add WIDTH``HEIGHT Set up , So that you will have enough space for the genie to move in the next step .

The spirit movement

please remember , In the game cycle , We have all_sprites.update() . This means for each sprite in the Group ,Pygame Will find a update() Function and run it . therefore , Let our elves move , We just need to define its update rules ：

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 50))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.rect.center = (WIDTH / 2, HEIGHT / 2)

    def update(self):
        self.rect.x += 5

 

This means that every time you go through the game cycle , We will all be elves x Coordinates increase 5 Pixel . Keep running it , You will see the spirit disappear on the right side of the screen ：

Let's solve this problem by making the spirit move around - Whenever it reaches the right side of the screen , We will all move it to the left . We can do this by rect Use a convenient “ Handle ” To do this easily ：

therefore , If rect The left edge of leaves the screen , We set the right edge to 0：

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((50, 50))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.rect.center = (WIDTH / 2, HEIGHT / 2)

    def update(self):
        self.rect.x += 5
        if self.rect.left > WIDTH:
            self.rect.right = 0
 

Now we can see that the genie will appear around the screen ：

This will be done in this lesson . Continue to try to - Please note that , You are in the spirit update() Anything put into the method will happen at every frame . Try to make the spirit move up and down （ change y coordinate ） Or let it bounce off the wall （ When the rectangle reaches the edge, reverse the direction ）.

In the next tutorial , We will show you how to use art for elves - Change it from a normal square to an animated character .