java - 如何获取两点之间的距离并沿线移动一个点到达另一点

Question

我正在尝试将一个点(100,100)移动到另一个点(450,500)。为此，我通过减去:int dx = x2 - x1，然后减去:int dy = y2 - y1来获得点之间的距离。我得到 dy (dy/100) * 1; 的 1% 和 dx (dx/100) * 1; 的 1%。然后，我将 x1 和 y1 中各值的 1% 添加到沿 JFrame 移动该点以到达第二个点。

出于某种原因，当我在 tick() 方法中移动该点时，它会错过第二个点。我尝试了多种不同的方法来实现这一目标。我认为这是数学计算错误，或者我正在做一些根本错误的事情。

这是我的代码:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;

import javax.swing.JFrame;


public class Distance extends JFrame implements Runnable {

    private int x1, y1;
    private int x2, y2;
    private int width, height;

    private int dx, dy;

    public Distance() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(850, 600);
        setResizable(false);
        setLocationRelativeTo(null);
        setVisible(true);

        init();
    }

    private void init() {
        x1 = y1 = 100;
        x2 = 450;
        y2 = 500;
        width = height = 20;

        dx = x2 - x1;
        dy = y2 - y1;

        Thread thread = new Thread(this);
        thread.start();
    }

    @Override
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        g.fillOval(x1, y1, width, height);
        g.fillOval(x2, y2, width, height);
        repaint();
    }

    private void tick() {
        int moveX = (dx / 100) * 1;
        int moveY = (dy / 100) * 1;
        x1 += moveX;
        y1 += moveY;
    }

    @Override
    public void run() {
        while(true) {
            try {
                tick();
                Thread.sleep(100);
            } catch(InterruptedException e) {
                e.printStackTrace();
            }
        } 
    }

    public static void main(String[] args) {
        new Distance();
    }
}

Answer 1

您应该使用double而不是int，否则，您将失去精度。

由于 fillOval 仅接受 int 作为参数，因此您必须对它们进行强制转换，但不用担心，它不会影响渲染。

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;


public class Distance extends JFrame implements Runnable {

    private double x1, y1;
    private double x2, y2;
    private double width, height;

    private double dx, dy;

    public Distance() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(850, 600);
        setResizable(false);
        setLocationRelativeTo(null);
        setVisible(true);

        init();
    }

    private void init() {
        x1 = y1 = 100;
        x2 = 450;
        y2 = 500;
        width = height = 20;

        dx = x2 - x1;
        dy = y2 - y1;

        Thread thread = new Thread(this);
        thread.start();
    }

    @Override
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        g.fillOval((int)x1, (int)y1, (int)width, (int)height);
        g.fillOval((int)x2, (int)y2, (int)width, (int)height);
        repaint();
    }

    private void tick() {
        double moveX = (dx / 100) * 1;
        double moveY = (dy / 100) * 1;
        x1 += moveX;
        y1 += moveY;
    }

    @Override
    public void run() {
        while(true) {
            try {
                tick();
                Thread.sleep(100);
            } catch(InterruptedException e) {
                e.printStackTrace();
            }
        } 
    }

    public static void main(String[] args) {
        new Distance();
    }
}