使用自定义 Java class 绘图背景而非对象的已编译处理代码

Question

此代码可以正确编译，然后运行但是我的 Circle 对象在调用 draw 方法时没有显示在屏幕上，它有一个包含对 Processing 中 ellipse 方法的调用的 draw 方法.我对此感到困惑，因为我可以更改背景的颜色并看到该更改得到反映，但没有别的。第一个 class 是一个抽象的父对象，代表要绘制的更复杂的对象，而 Circle class 只代表一个二维形状，主要用于我测试在 Eclipse 和自定义中使用处理 java classes。最后是本例中的驱动程序或草图，Bounce，它应该在屏幕上放置一个 Circle 对象。

//Name: CelestialBody

//Models generic space objects
//For ex. - Stars
//          Planets
//          Asteroids
//          Moons
//          Etc.

import processing.core.*;

public abstract class CelestialBody {
//constants
static final float c = 299792458; //speed of light in vacuum in meters per second


//object variables
String name; //name of object

float volume; //volume in cubic meters
float area; //area in square meters
float density; //density in kilograms per cubic meters
float mass; //mass in kilograms

float distanceM; //distance in meters
float distanceKM; // distance in kilometers

float xPos; //x coordinate (meters relative to origin)
float xVel; //velocity vector on x-axis in meters per second

float yPos; //y coordinate (meters relative to origin)
float yVel; //velocity vector on y-axis in meters per second

float zPos; //z coordinate (meters relative to origin)
float zVel; //velocity vector on z-axis in meters per second

PVector location= new PVector(); //location stored in vector object
PVector velocity= new PVector(); //velocity vector

PApplet parent;
//constructor
public CelestialBody(PApplet p, String name, float volume, float area, float density, float mass, 
    float x, float xVel, float y, float yVel, float z, float zVel)
    {
    parent=p;

    this.name=name;

    this.volume=volume;
    this.area=area;
    this.density=density;
    this.mass=mass;


    xPos=x;
    this.xVel=xVel;
    yPos=y;
    this.yVel=yVel;
    zPos=z;
    this.zVel=zVel;

    location.set(xPos,yPos,zVel);
    velocity.set(xVel,yVel,zVel);
}
}

//Name: Circle



//Models generic circle from 
//CelestialBody Class for the sake of 
// drawing practice even though this class
//is way simpler by nature and is
//not at all related to real objects

import processing.core.PApplet;

public class Circle extends CelestialBody{
//object variables
float radius; //radius in meters
float diameter; //diameter in meters
PApplet parent;

//constructor
public Circle(PApplet p,String name, float mass, float x, float xVel, float y, float yVel, float radius){
    super(p,name,0,0,0,mass,x,xVel,y,yVel,0,0);
    parent=p;
    this.radius=radius;
    diameter = radius * 2;
    area=(float)(Math.PI*Math.pow(radius,2));
}

public void drawCircle() {
    //shift x and y by the radius of the circle in order to correctly center it
    parent.ellipse(location.x - radius,location.y - radius,diameter,diameter);

}
}

//Name: Bounce

//Draws bouncing ball in box

import processing.core.PApplet;

public class Bounce extends PApplet {
public static void main(String args[]) {
    PApplet.main(new String[] { "--present", "Bounce" });
  }

public void settings() {
    size(displayWidth,displayHeight);
}

public void setup(){
    background(100,150,150);
}

public void draw() {
    Circle circ = new Circle (this,"ball",150,0,10,0,10,150);
    fill(0);
    stroke(0);
    circ.drawCircle();

    circ.location.x=circ.location.x+circ.velocity.x;
    circ.location.y=circ.location.y+circ.velocity.y;

    if (circ.location.x>width||circ.location.x<0){
        circ.velocity.x=circ.velocity.x*-1;
    }
    if (circ.location.y>width||circ.location.y<0){
        circ.velocity.y=circ.velocity.y*-1;
    }   
    }

    }

Answer 1

你这里发生了一些事情。

首先，请注意您总是从 draw() 函数中初始化一个 Circle 对象。然后将 10 添加到 x 和 y 位置，因此您的 Circle 始终位于 10, 10.

位置

要解决这个问题，请尝试将 circ 变量的声明移动到草图级别。

你也画错了圆。您的圈子总是以其实际位置的 upper-left 结束。由于 10,10 的 upper-left 位置在 window 的边界之外，这就是为什么你永远看不到它的原因。

要解决此问题，请修改您的 drawCircle() 代码以在正确的位置绘制椭圆。尝试将圆圈的位置更改为 mouseX, mouseY 以了解我的意思。

最后，您并不是每帧都重新绘制背景，所以您最终得到的是 "trail" 个圆圈，而不是一个圆圈。如果这不是您想要的，请尝试在 draw() 函数中添加对 background() 的调用。

使用自定义 Java class 绘图背景而非对象的已编译处理代码

Compiled Processing code using custom Java class drawing background but not object

java

runtime

drawing

processing