Java swing，需要使用鼠标绘制矩形而不会丢失具有重叠的先前矩形

Question

在我扩展了JLabel的此类中，我需要能够使用鼠标左键单击，然后向下和/或向右拖动以创建矩形，并能够重复该过程以绘制多个矩形而不会丢失任何先前的矩形和用于重叠的绘图框，以及能够找到所有像这样的矩形并集而成的矩形

我的当前代码已尽可能多地从“ 执行自定义绘画 ”的Java演示中改编而来，由于使用repaint方法更新JLabel的方式，该程序的行为似乎很奇怪，但是我不知道如何解决它

JLabel类

import javax.swing.*;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class JLabelx extends JLabel {
    private int squareX = 0;
    private int squareY = 0;
    private int squareW = 0;
    private int squareH = 0;

public JLabelx() {

    addMouseListener(new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            squareX = e.getX();
            squareY = e.getY();
            //set coordinates of next rectangle 
        }
    });

    addMouseMotionListener(new MouseAdapter() {
        public void mouseDragged(MouseEvent e) {

            newDraw(e.getX(),e.getY());
            //find length and width of next rectangle
        }
    });

    }
protected void newDraw(int x, int y) {
    int OFFSET = 1;
    if ((squareX!=x) || (squareY!=y)) {
    //  repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
        squareW=x-squareX;
        squareH=y-squareY;
        repaint(squareX,squareY,squareW+OFFSET,squareH+OFFSET);
    } 
}
protected void paintComponent(Graphics g) {
    super.paintComponents(g);       

    g.setColor(Color.GREEN);
    g.fillRect(squareX,squareY,squareW,squareH);
    g.setColor(Color.BLACK);
    g.drawRect(squareX,squareY,squareW,squareH);

    }
}

还给了我一个类似于java.awt.Rectangle的Rectangle类，该类具有一些方法，这些方法可以找到由重叠构成的矩形和由所有矩形的并集构成的矩形，但是我不知道如何用鼠标移动，然后在此JLabel中绘制它们

public class Rectangle {
private int x,y,width,height;

public Rectangle(int x,int y,int width,int height)
{
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
}

public Rectangle(Rectangle a)
{
    this.x = a.x;
    this.y = a.y;
    this.width = a.width;
    this.height = a.height;
}

public String toString()
{
    return "Start: ("+x+","+y+"), Width: "+width+", Height: "+height+"\n";
}

public int getX()
{
    return x;
}

public int getY()
{
    return y;
}

public int getWidth()
{
    return width;
}

public int getHeight()
{
    return height;
}

public void setX(int x)
{
    this.x = x;
}

public void setY(int y)
{
    this.y = y;
}

public void setWidth(int width)
{
    this.width = width;
}

public void setHeight(int height)
{
    this.height = height;
}

public int area()
{
    return width*height;
}

public boolean overlaps(Rectangle a)
{
    if ((x>a.x+a.width) || (a.x>x+width) || (y>a.y+a.height) || (a.y>y+height))
    {
        return false;
    }
    return true;
}

public Rectangle intersect(Rectangle a)
{
    if (!overlaps(a))
        return null;

    int left,right,top,bottom;

    if (x<a.x)
        left = a.x;
    else
        left = x;

    if (y<a.y)
        bottom = a.y;
    else
        bottom = y;

    if ((x+width)<(a.x+a.width))
        right = x+width;
    else
        right = a.x+a.width;

    if ((y+height)<(a.y+a.height))
        top = y+height;
    else
        top = a.y+a.height;

    return new Rectangle(left,bottom,right-left,top-bottom);
}

public Rectangle union(Rectangle a)
{
    int left,right,top,bottom;

    if (x<a.x)
        left = x;
    else
        left = a.x;

    if (y<a.y)
        bottom = y;
    else
        bottom = a.y;

    if ((x+width)<(a.x+a.width))
        right = a.x+a.width;
    else
        right = x+width;

    if ((y+height)<(a.y+a.height))
        top = a.y+a.height;
    else
        top = y+height;

    return new Rectangle(left,bottom,right-left,top-bottom);
    }


 }

Answer 1

不知道为什么要扩展JLabel以进行自定义绘制。 本教程向您展示了如何使用JPanel。

有关进行增量绘画的两种常用方法，请查看“ 自定义绘画方法” ：

1. 使用列表来跟踪矩形（这可能是您想要的，因为您希望能够测试交叉点。
2. 使用BufferedImage。