在循环中使用if语句？-处理

Question

可以说我必须在for循环内使用if语句，并且for循环在特定条件下触发，而if语句仅在for循环达到特定阶段时才触发。

例如，条件是一个计数器，该计数器在发生某些事情（例如，球从屏幕上掉下来）时进行计数。每次球越过屏幕时，都会一圈绘制一个圆圈。当第一行中的圆圈到达屏幕的末端时，圆圈开始出现在第一行下方的第二行中。但是第二行对我不起作用，我已经用if语句实现了。

float BallY = 50; // y value of the ball
float BallX = 260; // x value of the ball
float ScoreX = 52;
float ScoreY = 40;
int counter;


void setup()
{
  size(512, 348); //width and height of screen
  counter = 0;
}

void draw()
{
  frameRate(600);
  background(255);
  fill(0);
  ellipse(BallX, BallY, 15, 15); //ball that will fall 
  BallY++; //ball's y value increases each frame
  if (BallY > height) //if ball's y value is greater than the screen
  {
    BallY = 0; //reset the y value of the ball back to 0
    counter++;
  }

  for (int i = 0; i < counter; i++) { 
    ellipse(ScoreX + i * 80, 40, 40, 40); // draw circles in the first row one by one

     if( ScoreX + i * 80 > width) // if the circles cross the width
     {
     i = 0; //reset i to be 0
     ellipse(ScoreX + i * 80, 80, 40, 40); // draw circles in the second row
     }
  }}

if语句仅在第一行的球越过宽度时才触发，但是整个游戏只是停止而不是在该行触发，似乎是问题所在？

Answer 1

初步建议：学习正确的Java编码约定，学习如何缩进代码，以及命名变量。

对您的代码进行轻微的重写应该可以使可读的修正：

int scoreStartX = 52;
int scoreStartY = 40;
int scoreBallSize = 40;
// scorePosX/Y means the position the score-ball should be drawn
scorePosX = scoreStartX;  // scoreStartX/Y = starting position of score balls 
scorePosY = scoreStartY;

for (int i = 0; i < score; i++) { 
    ellipse(scorePosX , scorePosY , scoreBallSize , scoreBallSize);

    // increment the positions, and wrap to next col if over screen width
    scorePosX += scoreBallSize ;


   if( scorePosX  > screenWidth) { // next score ball position is beyond the screen
       scorePosX = scoreStartX;
       scorePosY += scoreBallSize;
   }
}

进一步重构代码以使用诸如Point之类的东西来表示坐标

Point scoreStartPos = new Point(52, 40);
int scoreBallSize = 40;
Point scorePos = new Point(scoreStartPos );

for (int i = 0; i < score; i++) { 
   drawCircle(scorePos, scoreBallSize); // a little helper method makes your code easier to read

    // increment the positions, and wrap to next col if over screen width
    scorePos.translate( +scoreBallSize, 0);


   if( scorePos.getX() > screenWidth) { // next score ball position is beyond the screen
       scorePos.setLocation(scoreStartPoint.getX(),
                            scorePos.getY() + scoreBallSize);
   }
}