使用Java制作简易的画板教程

//图形接口package Cbs;//图形集合public interface NetJavaShape {public abstract void draw();
}//直线类package Cbs;import java.awt.Color;import java.awt.Graphics;import Cbs.NetJavaShape;public class ImpLine implements NetJavaShape{
    Graphics g;int x1, y1,x2, y2;
    Color c;public ImpLine(Graphics g,int x1,int y1,int x2,int y2,Color c){this.g=g;this.c=c;this.x1=x1;this.y1=y1;this.x2=x2;this.y2=y2;
    }public void draw() {
        g.setColor(c);
        g.drawLine(x1, y1, x2, y2);
    }

}//DrawListener类package Cbs;import java.awt.Color;import java.awt.Graphics;import java.util.List;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.MouseEvent;import java.awt.event.MouseListener;import java.awt.event.MouseMotionListener;import java.util.ArrayList;import Cbs.NetJavaShape;import javax.swing.JButton;public class DrawListener implements ActionListener, MouseListener,
        MouseMotionListener {private Color color=Color.BLACK;//颜色属性,初始值为黑色private Graphics g;//画笔属性private String str;//保存按钮上的字符串，区分不同的按钮private int x1,y1,x2,y2;//(x1,y1),(x2,y2)分别为鼠标的按下和释放时的坐标private JButton nowColor;//当前颜色按钮//保存图形对象的集合private List<NetJavaShape> shapesArray = new ArrayList<NetJavaShape>();//图形private NetJavaShape shape;//在draw类中获取集合public List<NetJavaShape> getShapesArray() {return shapesArray;
    }//获取Draw类的画笔对象public void setG(Graphics g) {this.g = g;
    }//获取当前颜色按钮public void setNowColor(JButton nowColor) {this.nowColor = nowColor;
    }


    @Override//鼠标拖动的方法public void mouseDragged(MouseEvent e) {//画曲线的方法if ("画曲线".equals(str)) {int x, y;
            x = e.getX();
            y = e.getY();//实例化对象，曲线也是直线画的所以不同新建一个曲线类了shape=new ImpLine(g,x,y,x1,y1,color);//调用画图方法            shape.draw();//将图形存入集合中            shapesArray.add(shape);//            g.drawLine(x, y, x1, y1);x1 = x;
            y1 = y;
        }
    }

    @Override//鼠标移动方法public void mouseMoved(MouseEvent e) {

    }

    @Override//鼠标单击方法public void mouseClicked(MouseEvent e) {

    }

    @Override//鼠标按下方法public void mousePressed(MouseEvent e) {
        
        g.setColor(color);//改变画笔的颜色        
        x1=e.getX();//获取按下时鼠标的x坐标y1=e.getY();//获取按下时鼠标的y坐标    }

    @Override//鼠标释放方法public void mouseReleased(MouseEvent e) {
        x2=e.getX();//获取释放时鼠标的x坐标y2=e.getY();//获取释放时鼠标的y坐标//画直线的方法if ("画直线".equals(str)) {//实例化对象，shape=new ImpLine(g,x1,y1,x2,y2,color);//调用画图方法            shape.draw();//将图形存入集合中            shapesArray.add(shape);//            g.drawLine(x1, y1, x2, y2);        }
    }

    @Override//鼠标进入方法public void mouseEntered(MouseEvent e) {

    }

    @Override//鼠标退出方法public void mouseExited(MouseEvent e) {

    }

    @Override//处理按钮上的鼠标点击动作public void actionPerformed(ActionEvent e) {        if ("".equals(e.getActionCommand())) {
            JButton jb = (JButton) e.getSource();
            color = jb.getBackground();
            nowColor.setBackground(color);//处理当前颜色} else {
            str = e.getActionCommand();
        }
    }

}//draw类package Cbs;import java.awt.Color;import java.awt.Dimension;import java.awt.FlowLayout;import java.awt.Graphics;import java.awt.GridLayout;import java.util.ArrayList;import java.util.List;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;/**
 * Draw类，用于界面的初始化
 * @author CBS */@SuppressWarnings("serial")public class Draw extends JFrame {private DrawListener dl;private Graphics g;//保存图形对象的集合private List<NetJavaShape> shapesArray = new ArrayList<NetJavaShape>();// 界面初始化方法public void showUI() {
        setTitle("画图");//窗体名称setSize(1200, 900);//窗体大小setDefaultCloseOperation(3);
        setLocationRelativeTo(null);//窗体居中FlowLayout layout = new FlowLayout(FlowLayout.LEFT);//流式布局左对齐setLayout(layout);//窗体使用流式布局管理器this.setResizable(false);//窗体大小不变        //使用数组保存按钮名String buttonName[] = { "画直线", "画椭圆", "画曲线", "多边形",     "橡皮擦", "拖动线","三角形", "画球形", "笔刷", "喷枪", "色子", "立体矩形", "立体圆", "立体三角","迭代分形", "现代分形", "枫叶", "画树", "mandelbrot集", "L-System", "迭代画线","迭代三角形", "谢尔宾斯基地毯", "画字符", "清空","吸管" ,"矩形","五角星","多线","字符"};
        JPanel jp1=new JPanel(new GridLayout(15, 2,10,10));//用于保存图形按钮，使用网格布局jp1.setPreferredSize(new Dimension(200, 800));        //实例化DrawListener对象dl=new DrawListener();//循环为按钮面板添加按钮for (int i = 0; i < buttonName.length; i++) {
            JButton jbutton = new JButton(buttonName[i]);
            jbutton.addActionListener(dl);//为按钮添加监听            jp1.add(jbutton);
        }
        
        JPanel jp2=new JPanel();//画布面板jp2.setPreferredSize(new Dimension(970, 800));
        jp2.setBackground(Color.WHITE);        // 定义Color数组，用来存储按钮上要显示的颜色信息Color[] colorArray = { Color.BLUE, Color.GREEN, Color.RED, Color.BLACK,Color.ORANGE,Color.PINK,Color.CYAN,Color.MAGENTA,Color.DARK_GRAY,Color.GRAY,Color.LIGHT_GRAY,Color.YELLOW};//用于保存颜色按钮的面板JPanel jp3=new JPanel(new GridLayout(1,colorArray.length,3,3));// 循环遍历colorArray数组，根据数组中的元素来实例化按钮对象for (int i = 0; i < colorArray.length; i++) {
            JButton button = new JButton();
            button.setBackground(colorArray[i]);
            button.setPreferredSize(new Dimension(30, 30));
            button.addActionListener(dl);//为按钮添加监听            jp3.add(button);
        }//将面板添加到主窗体this.add(jp1);this.add(jp2);this.add(jp3);//添加按钮，作为当前颜色JButton nowColor=new JButton();
        nowColor.setPreferredSize(new Dimension(40,40));
        nowColor.setBackground(Color.BLACK);//默认黑色        add(nowColor);//设置窗体的组件可见，如果为FALSE就看不到任何组件setVisible(true);    //获取画笔对象g=jp2.getGraphics();
        dl.setG(g);
        dl.setNowColor(nowColor);//获取保存的集合shapesArray=dl.getShapesArray();//为面板添加鼠标监听，用于绘制图形        jp2.addMouseListener(dl);
        jp2.addMouseMotionListener(dl);
    }
    @Override//重写paint方法public void paint(Graphics g) {//调用父类的paint方法，绘制界面上的组件super.paint(g);//foreach遍历集合for (NetJavaShape l : shapesArray) {
            l.draw();
        }
    }

}