Question

我正试图在我的java窗口上移动一列火车并遇到严重问题。我有一个火车课，我在那里制作了火车，还有一个驾驶课，它应该可以移动火车。我需要让整列火车从右向左移动，直到它“通过”屏幕的左边缘。然后添加一个if语句来更改dx，以便列车在右侧重新启动。以下是我尝试过的但是没有用。谁能帮帮我呢？

public class Driver extends GraphicsProgram
{
    //~ Instance/static variables .............................................

    private static final int N_STEPS = 1000;
    private static final int PAUSE_TIME = 20;
    private static final double TRAIN_LENGTH = 320;

    //~ Constructor ...........................................................

    // ----------------------------------------------------------
    /**
     * The run() method of the Driver Class.
     * Creates an instance of the Train Class.
     * Responsible for animating the train across the screen.
     */
    public void run()
    {
        Train train = new Train(getGCanvas());
        for (int i = 0; i < N_STEPS; i++) {
            train.move(-100, 0);
            pause(PAUSE_TIME);
    }

Answer 1

这是一个用摇摆做的小演示。只需用火车图像替换黑色矩形即可。

诀窍是使用单独的线程（或计时器）来执行动画循环（通常称为game loop）。循环只告诉你的窗口重绘自己，并且在每次重绘时，首先计算动画对象的新位置，然后绘制它们。

import javax.swing.*;
import java.awt.*;

public class TrainDemo {

    public static void main(String[] args) {
        JFrame frame = new JFrame("Train Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(800, 400);
        frame.setLocationRelativeTo(null);
        frame.add(new TrainCanvas());
        frame.setVisible(true);
    }

}

class TrainCanvas extends JComponent {

    private int lastX = 0;

    public TrainCanvas() {
        Thread animationThread = new Thread(new Runnable() {
            public void run() {
                while (true) {
                    repaint();
                    try {Thread.sleep(10);} catch (Exception ex) {}
                }
            }
        });

        animationThread.start();
    }

    public void paintComponent(Graphics g) {
        Graphics2D gg = (Graphics2D) g;

        int w = getWidth();
        int h = getHeight();

        int trainW = 100;
        int trainH = 10;
        int trainSpeed = 3;

        int x = lastX + trainSpeed;

        if (x > w + trainW) {
            x = -trainW;
        }

        gg.setColor(Color.BLACK);
        gg.fillRect(x, h/2 + trainH, trainW, trainH);

        lastX = x;
    }

}

Answer 2

color c = color(0); float x = 0; float y = 100; float speed = 1;
void setup() { size(200,200); }
void draw() { background(255); move(); display(); }
void move() { x = x + speed; if (x > width) { x = 0; } }
void display() { fill(c); rect(x,y,30,10); }

Java在屏幕上移动对象

2 个答案: