java - 用 Java Applet 制作一条蛇

Question

所以我试图重现这个图形程序 here对于我的 java 类。

这是我到目前为止所想到的:

import processing.core.PApplet;

public class Assignment09b extends PApplet {

// Create arrays to stort the x & y values of the mouse
int [] xArray = new int [100];
int [] yArray = new int [100];

public void setup(){
    //Runs at 60Fps

    size(500, 500);
}

public void draw(){
    //Changes the background each frame
    background(0);

    //Stores the x&y values of the mouse in the arrays
    for (int i = 0; i < xArray.length; i++){
        xArray[i] = this.mouseX;
        yArray[i] = this.mouseY;
    }

    //SHOULD print out the snake using series of ellipses
    for (int i = 0; i < xArray.length; i++){

        //Generates a random color each time
        fill(random(255), random(255), random(255));
        ellipse(xArray[i], yArray[i], 25, 25);
    }

}
   }

对于问题可能是什么，我有一些想法:

1. 因为我处于一个循环中，它只是很快地生成一个椭圆，但我不知道如何让它同时生成它们
2. 这可能是帧速率的问题？
3. 我是一个无能的程序员:/

请大家给我一些建议，告诉我我可能做错了什么或根本没有做错。谢谢!

Answer 1

问题是您在此处同时设置所有值:

//Stores the x&y values of the mouse in the arrays
    for (int i = 0; i < xArray.length; i++){
        xArray[i] = this.mouseX;
        yArray[i] = this.mouseY;
    }

您只想更新数组中的 1 个元素，并将其他元素移动 1:“最旧的”值消失，新值进入。您可以手动使用反向 for 循环(从数组末尾开始)到前面(第一个元素除外)或使用 arrayCopy :

private void updateArrays(int x,int y){
  arrayCopy(xArray, 0, xArray, 1, xArray.length-1);//shift all elements backwards by 1
  arrayCopy(yArray, 0, yArray, 1, yArray.length-1);//so x at index 99 goes 98, 98 to 97, etc. excepting index 0
  xArray[0] = x;//finally add the newest value 
  yArray[0] = y;//at the start of the array (so in the next loop it gets shifted over by 1) like the above values
}

完整列表:

import processing.core.PApplet;

public class Assignment09b extends PApplet {
  // Create arrays to stort the x & y values of the mouse
  int [] xArray = new int [100];
  int [] yArray = new int [100];

  public void setup(){
      //Runs at 60Fps

      size(500, 500);
  }

  public void draw(){
      //Changes the background each frame
      background(0);

      updateArrays(mouseX,mouseY);

      //SHOULD print out the snake using series of ellipses
      for (int i = 0; i < xArray.length; i++){

          //Generates a random color each time
          fill(random(255), random(255), random(255));
          ellipse(xArray[i], yArray[i], 25, 25);
      }

  }

  private void updateArrays(int x,int y){
    arrayCopy(xArray, 0, xArray, 1, xArray.length-1);//shift all elements backwards by 1
    arrayCopy(yArray, 0, yArray, 1, yArray.length-1);//so x at index 99 goes 98, 98 to 97, etc. excepting index 0
    xArray[0] = x;//finally add the newest value 
    yArray[0] = y;//at the start of the array (so in the next loop it gets shifted over by 1) like the above values
  }
}

因为这是一个练习，所以我建议更多地使用 for 循环和数组。这是你最终会经常使用并且值得练习/掌握窍门的东西。祝你好运!

var xArray = new Array(100);
var yArray = new Array(100);

function setup(){
  createCanvas(500, 500);
}

function draw(){
    //Changes the background each frame
    background(0);

    updateArrays(mouseX,mouseY);

    //SHOULD print out the snake using series of ellipses
    for (var i = 0; i < xArray.length; i++){

        //Generates a random color each time
        fill(random(255), random(255), random(255));
        ellipse(xArray[i], yArray[i], 25, 25);
    }

}

function updateArrays(x,y){
  arrayCopy(xArray, 0, xArray, 1, xArray.length-1);//shift all elements backwards by 1
  arrayCopy(yArray, 0, yArray, 1, yArray.length-1);//so x at index 99 goes 98, 98 to 97, etc. excepting index 0
  xArray[0] = x;//finally add the newest value 
  yArray[0] = y;//at the start of the array (so in the next loop it gets shifted over by 1) like the above values
}

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