在JPanel中创建无数个对象，并通过Java中的PaintComponent绘制它们 [英] Creating endless number of objects in JPanel and draw them through PaintComponent in Java

问题描述

我有一个难题，如何实现应用.我有宽度为288，高度为512的JPanel，然后创建了两个对象(图像)，并使用坐标

I have one dilemma , how to realize application. I have JPanel with width 288 and height 512, then I created two objects ( images ) and drew them through paintComponent using coordinates

 drawImage (Image1,288,128,this) ;
 drawImage (Image2, 288, 384, this);

.它们在X轴上同时递减，当到达x = 144时，应在坐标'(x = 288，y =(int)Math.random()* 512)'处绘制新的(相同)图像，然后开始递减以及第一个应该减少.这个过程应该是无止境的.每个达到x = 144的新对象都应建立新对象.我试图创建ArrayList并在其中添加坐标

. They are decrementing simultaneously in the X axis and when it reaches x = 144 , new (same) images should be drawn at the coordinates ‘( x = 288 , y = (int)Math.random()* 512 )’ and begin decrement as well as first ones should still decrements. And this process should be endless. Every new objects reaching x = 144 should build new ones . I tried to create ArrayList with adding coordinates in it

ArrayList arrayX = new ArrayList(); 
arrayX.add(288)
arrayY.add((int) Math.random()* 512 )

然后通过

array.get()

但是那没有成功. 我看过视频，那里的人是通过数组使用JavaScript的

But that was unsuccessfully. I saw video where man did it using JavaScript through the array

var position = []
position = ({
X : 288
Y : 256
 })

然后通过这样的循环实现

And then implemented through the loop like this

 function draw() {

 for (int i = 0; i < position.length; i++ ){
 cvs.drawImage(Image1,position[i].x , position[i].y)
 cvs.drawImage(Image2,position[i].x , position[i].y + 50)

 position [i] .x - -;
 if(position[i].x == 128)
 position.push({
 X : 288
 Y : Math.floor(Math.random()*512 })
 })
 }
 }

我不知道如何用Java做到这一点. 也许我也应该使用array来保持变量的坐标，或者arraylist，但是以不同的方式.请帮帮我 . 预先感谢

I don’t know how to do this in Java. May be I should use array too to keep variables with coordinates , or arraylist but in different way. Help me please . Thanks in advance

推荐答案

我的答案完全基于 MadProgrammer的答案(实际上是一个全面的教程).
从我在帖子中看到的内容:每个达到x = 144的新对象都应该构建新对象"，我认为所需的实现略有不同:

My answer is complitely based on MadProgrammer's answer (A comprehensive tutorial actually).
From what I read in the post : "Every new objects reaching x = 144 should build new ones", I think the desired implementation is slightly different:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class ImageAnimator {

    public ImageAnimator() {
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Testing");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.add(new AnimationPane());
            frame.pack();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
        });
    }

    public static class Drawable {

        private int x;
        private final int y;
        private static final Image image = image();

        //construct with a random y value
        public Drawable(int x) {
            this(x, -1);
        }

        public Drawable(int x, int y) {
            this.x = x;
            this.y =  y < 0 ? (int) (Math.random() * (512 - 20)) : y;
        }

        public int getX() { return x;  }

        public int getY() { return y; }

        public void update() {  x--; }

        public Image getImage(){  return image; }

        public static Image image() {

            URL url = null;
            try {
                url = new URL("https://dl1.cbsistatic.com/i/r/2017/09/24/b2320b25-27f3-4059-938c-9ee4d4e5cadf/thumbnail/32x32/707de8365496c85e90c975cec8278ff5/iconimg241979.png");
                return ImageIO.read(url);

            } catch ( IOException ex) {
                ex.printStackTrace();
                return null;
            }
        }
    }

    public class AnimationPane extends JPanel {

        private final List<Drawable> drawables;
        private static final int W = 288, H = 512, CYCLE_TIME = 5;

        public AnimationPane() {
            drawables = new ArrayList<>(2);
            drawables.add(new Drawable(W, H/4));
            drawables.add(new Drawable(W, 3*H/4));

            Timer timer = new Timer(CYCLE_TIME, e ->  animate());
            timer.start();
        }

        private void animate() {

          for (Drawable drawable : new ArrayList<>(drawables)) {

              drawable.update();
              if(drawable.getX() == W/2) {
                  drawables.add(new Drawable(W)); //random Y
              }
              if(drawable.getX() <= 0) {
                  drawables.remove(drawable);
              }
          }
          repaint();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(W, H);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            for (Drawable drawable : drawables ) {
                g.drawImage(drawable.getImage(),drawable.getX(), drawable.getY(), null);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(()->new ImageAnimator());
    }
}

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