python - 为什么Processing.py 跳过数组的倒数第二项？

Question

我一直在处理中制作一种抽象艺术风格的东西。左键单击放置一个点，再次单击会生成一条随机线，右键单击会生成一个新点。

当我使用向上和向下箭头选择笔颜色时，问题就出现了。当我使用这些键时，会跳过倒数第二个项目(黑色或粉色)。代码附后。

def setup():
    size(750, 750)
    background(255)
    global clicks
    global selector
    global fillcolors
    fillcolors = [0x80FFFFFF, 0x80000000, 0x80FF0000, 0x8000FF00, 0x800000FF, 0x80FFFF00, 0x80FF00FF, 0x8000FFFF]
    selector = 1
    clicks = 0
    ellipseMode(CENTER)
    fill(255, 255, 255, 128)

def draw():
    ellipse(50, 50, 50, 50)

def mousePressed():
    global x
    global y
    global clicks
    if (mouseButton == LEFT) and (clicks == 0):
        x = mouseX
        y = mouseY
        clicks = 1
    if (mouseButton == LEFT) and (0 < clicks < 11):
        line(x, y, x+random(-300, 300), y+random(-300, 300))
        clicks += 1
    if (mouseButton == LEFT) and (clicks == 11):
        wide = random(300)
        clicks = 1
        line(x, y, x+random(-300, 300), y+random(-300, 300))
        ellipse(x, y, wide, wide)
    if mouseButton == RIGHT:
        clicks = 0

def keyPressed():              # this is the color selector area.
    global selector
    global fillcolors
    global clicks
    clicks = 0
    if key != CODED:
        background(255)
    elif key == CODED:
        if keyCode == UP:
            if selector < 8:                  # something in here is causing the second-to-last item of the array to be skipped.
                fill(fillcolors[selector])
                selector += 1
            if selector == 7:
                fill(fillcolors[selector])
                selector = 0
        if keyCode == DOWN:
            if selector > 0:
                fill(fillcolors[selector])
                selector -= 1
            if selector == 0:
                fill(fillcolors[selector])
                selector = 7

Answer 1

您的第一个if在每种情况下都会影响您的第二个。对于 UP ，如果selector是6，就变成7，然后匹配selector == 7 ;对于 DOWN ，如果selector为1，则变为0，然后匹配selector == 0 .

使用elif使它们独一无二:

if selector < 8:
    fill(fillcolors[selector])
    selector += 1
<b>el</b>if selector == 7:
    fill(fillcolors[selector])
    selector = 0

if selector > 0:
    fill(fillcolors[selector])
    selector -= 1
<b>el</b>if selector == 0:
    fill(fillcolors[selector])
    selector = 7

你的第一个条件可能应该是 if selector < 7而不是8 .