当我将鼠标悬停在pygame上时，为什么我的按钮不会更改颜色？

Question

我是pygame的新手，一直在尝试创建带有一些按钮的简单界面。当鼠标悬停在按钮上时，我无法更改按钮的颜色。

我已经成功创建了按钮，但是无法使其与鼠标交互。该代码使用一个绿色按钮实例创建一个按钮对象。当鼠标悬停在鼠标上时，应该将按钮从绿色更改为红色。

import pygame

pygame.init()

display_width = 1200
display_height = 600

black = (0, 0, 0)
white = (255, 255, 255)
red = (255, 0, 0)
green = (0, 255, 0)

StartScreen = pygame.display.set_mode((display_width, display_height))
pygame.display.set_caption('Log In')
clock = pygame.time.Clock()

StartScreen.fill(white)

class Buttons():
    def __init__(self, color, x, y, width, height, text=''):
        self.color = color
        self.x = int(x)
        self.y = int(y)
        self.w = int(width)
        self.h = int(height)
        self.text = text


    def Draw(self, StartScreen, outline=None):
        if outline:
            pygame.draw.rect(StartScreen, outline, (float(self.x-2), float(self.y-2), float(self.w+4), float(self.h+4)), 0)

        pygame.draw.rect(StartScreen, self.color, (self.x, self.y, self.w, self.h), 0)

        if self.text != '':
            font = pygame.font.SysFont('comicsans', 20)
            text = font.render(self.text, 1, black)
            StartScreen.blit(text, (self.x + (self.w/2 - text.get_width()/2), self.y + (self.h/2 - text.get_height()/2)))


    def MouseOver(self, pos):
        if pos[0] > self.x and pos[0] < self.x + self.w:
            if pos[1] > self.y and pos[1] < self.y + self.h:
                return True

        return False

def redrawWindow():
    StartScreen.fill(white)
    GrnBut.Draw(StartScreen, black)

run = True

GrnBut = Buttons(green, 150, 200, 90, 100, 'Press')
while run:
    redrawWindow()
    pygame.display.update()

    for event in pygame.event.get():
        pos = pygame.mouse.get_pos()

        Exit = False
        while not Exit:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    print(event)
                    pygame.quit()
                    quit()

        if event.type == pygame.MOUSEBUTTONDOWN:
            if GrnBut.MouseOver(pos):
                print("Clicked")

        if event.type == pygame.MOUSEMOTION:
            if GrnBut.MouseOver(pos):
                GrnBut.color = red
            else:
                GrnBut.color = green

Answer 1

您的主要问题是在事件循环中有一个嵌套的事件循环：

while run:         # outer loop
    redrawWindow()
    pygame.display.update()

    for event in pygame.event.get():
        pos = pygame.mouse.get_pos()

        Exit = False
        while not Exit:       # inner loop
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    print(event)
                    pygame.quit()
                    quit()

当执行到达这个内循环，没有redrawWindow()或者GrnBut.MouseOver(pos)是以后再调用。

摆脱它：

while run:
    redrawWindow()
    pygame.display.update()

    for event in pygame.event.get():
        pos = pygame.mouse.get_pos()

        if event.type == pygame.QUIT:
            print(event)
            pygame.quit()
            quit()

您可以使用pygame的某些功能（例如Sprite和Rect类）来改进您的代码。

这是一个示例，说明如何创建Button支持更多，不同按钮的类的更多“异性恋”版本：

import pygame

pygame.init()

display_width = 1200
display_height = 600

# use python style variable names (lowercase)
screen = pygame.display.set_mode((display_width, display_height))
pygame.display.set_caption('Log In')
clock = pygame.time.Clock()

# load the font only once instead of every frame
font = pygame.font.SysFont('comicsans', 20)

# class name should be singular
class Button(pygame.sprite.Sprite):
    # 1) no need to have 4 parameters for position and size, use pygame.Rect instead
    # 2) let the Button itself handle which color it is
    # 3) give a callback function to the button so it can handle the click itself 
    def __init__(self, color, color_hover, rect, callback, text='', outline=None):
        super().__init__()
        self.text = text
        # a temporary Rect to store the size of the button
        tmp_rect = pygame.Rect(0, 0, *rect.size)

        # create two Surfaces here, one the normal state, and one for the hovering state
        # we create the Surfaces here once, so we can simple blit them and dont have
        # to render the text and outline again every frame
        self.org = self._create_image(color, outline, text, tmp_rect)
        self.hov = self._create_image(color_hover, outline, text, tmp_rect)

        # in Sprites, the image attribute holds the Surface to be displayed...
        self.image = self.org
        # ...and the rect holds the Rect that defines it position
        self.rect = rect
        self.callback = callback

    def _create_image(self, color, outline, text, rect):
        # function to create the actual surface
        # see how we can make use of Rect's virtual attributes like 'size'
        img = pygame.Surface(rect.size)
        if outline:
            # here we can make good use of Rect's functions again
            # first, fill the Surface in the outline color
            # then fill a rectangular area in the actual color
            # 'inflate' is used to 'shrink' the rect
            img.fill(outline)
            img.fill(color, rect.inflate(-4, -4))
        else:
            img.fill(color)

        # render the text once here instead of every frame
        if text != '':
            text_surf = font.render(text, 1, pygame.Color('black'))
            # again, see how easy it is to center stuff using Rect's attributes like 'center'
            text_rect = text_surf.get_rect(center=rect.center)
            img.blit(text_surf, text_rect)
        return img

    def update(self, events):
        # here we handle all the logic of the Button
        pos = pygame.mouse.get_pos()
        hit = self.rect.collidepoint(pos)
        # if the mouse in inside the Rect (again, see how the Rect class
        # does all the calculation for use), use the 'hov' image instead of 'org'
        self.image = self.hov if hit else self.org
        for event in events:
            # the Button checks for events itself.
            # if this Button is clicked, it runs the callback function
            if event.type == pygame.MOUSEBUTTONDOWN and hit:
                self.callback(self)

run = True

# we store all Sprites in a Group, so we can easily
# call the 'update' and 'draw' functions of the Buttons
# in the main loop
sprites = pygame.sprite.Group()
sprites.add(Button(pygame.Color('green'), 
                   pygame.Color('red'), 
                   pygame.Rect(150, 200, 90, 100), 
                   lambda b: print(f"Button '{b.text}' was clicked"),
                   'Press',
                   pygame.Color('black')))

sprites.add(Button(pygame.Color('dodgerblue'), 
                   pygame.Color('lightgreen'), 
                   pygame.Rect(300, 200, 90, 100), 
                   lambda b: print(f"Click me again!"),
                   'Another'))

while run:
    events = pygame.event.get()
    for event in events:
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()

    # update all sprites
    # it now doesn't matter if we have one or 200 Buttons
    sprites.update(events)
    # clear the screen
    screen.fill(pygame.Color('white'))
    # draw all sprites/Buttons
    sprites.draw(screen)
    pygame.display.update()
    # limit framerate to 60 FPS
    clock.tick(60)