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2020-05-13 00:41
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Java语言怎么实现一个简单的画图板的功能呢,要支持鼠标的操作并且保存图片

Java语言怎么实现一个简单的画图板的功能呢,要支持鼠标的操作并且保存图片

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  • Z_墨脱 2020-05-13 09:01
    已采纳

    一、画图板界面实现

    所需用到的主要API类:JFrame,JButton,FlowLayout,Graphics以及一些相关的类;

    先创建窗体,设置相关属性,再添加按钮。

    import java.awt.Color;
    import java.awt.Dimension;
    import java.awt.FlowLayout;
    import java.awt.Graphics;
    import java.awt.Graphics2D;

    import javax.swing.JButton;
    import javax.swing.JFrame;

    public class Draw extends JFrame{

    public static void main(String args[]){
        Draw dr = new Draw();
        dr.showdraw();
    }
    public void showdraw(){
        //继承后JFrame后无需实例化
        this.setTitle("画图板");
        this.setSize(700,500);
        //frame.setResizable(false);
        this.setDefaultCloseOperation(3);
        this.setLocationRelativeTo(null);
        FlowLayout f1 = new FlowLayout();
        this.setLayout(f1);
            //实例化监听器
        DrawListener lis = new DrawListener();
        //创建图形按钮和颜色按钮
        String[] array ={"Line","Pencil","Rect","Oval","RoundRect","fillRect",
                "fillArc","fillOval","Text","Image","Triangle","Polygon"};
        for(int i=0 ; i<array.length ;i++){
            JButton button = new JButton(array[i]);
            this.add(button);
            button.addActionListener(lis);
        }
        Color[] colorArray ={Color.black,Color.blue,
                Color.green,Color.red};
        for(int i=0 ; i<colorArray.length ; i++){
            JButton button = new JButton();
            button.setBackground(colorArray[i]);
            button.setPreferredSize(new Dimension(30,30));//设置按钮大小
            this.add(button);
            button.addActionListener(lis);
        }
        this.setVisible(true);  //setVisible设置窗体可见,放在所有组件后
    
        Graphics g = this.getGraphics();
        this.addMouseListener(lis);//用this指代frame可能出错
        this.addMouseMotionListener(lis);
    
        lis.setG(g);
    

    }

    二、监听类的实现

    所需用到的主要API类:MouseAdapter,BasicStroke,Color,Graphics,JButton以及相关的类。以及ActionListener接口

    监听按钮上对应的图形或颜色,并根据得到的内容实现对应的操作,具体的画图在Shape类中实现

    import java.awt.BasicStroke;
    import java.awt.Color;
    import java.awt.Font;
    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.awt.Image;
    import java.awt.RenderingHints;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.awt.event.MouseAdapter;
    import java.awt.event.MouseEvent;

    import javax.swing.ImageIcon;
    import javax.swing.JButton;

    //先继承类,后继承接口
    public class DrawListener extends MouseAdapter implements ActionListener{

    private int x1, y1, x2, y2,x3,y3,sx,sy,ex,ey;
    private Graphics2D g2;
    private String str = "Line";
    private Color color;
    private int flag = 1;//用于标记是否是第一次画线
    
    public void setG(Graphics g){
        g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);// 设置画笔开启抗锯齿
    
    }
    
    public void actionPerformed(ActionEvent e){
        JButton button = (JButton) e.getSource();//getSource返回事件源类型,也可以用getActionCommand返回String类型
    
        if(button.getText() != "")//如果为图形按钮
            str = button.getText();
    
        else{
            color = button.getBackground();
            System.out.println("color"+color);
        }
    }
    
    public void mouseClicked(MouseEvent e){
        System.out.println("点击");//按下和释放要在同一位置才是点击
        x2 = e.getX();
    

                y2 = e.getY();
       

        //画空心矩形
        if(str.equals("Rect")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"Rect");
        s.draw(g2);
        }
        //画填充矩形
        if(str.equals("fillRect")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"fillRect");
        s.draw(g2);
        }
        //画圆角矩形
        if(str.equals("RoundRect")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"fillRect");
        s.draw(g2);
        }
        //画空心圆
        if(str.equals("Oval")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"Oval");
        s.draw(g2);
        }
        //画填充圆
        if(str.equals("fillOval")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"fillOval");
        s.draw(g2);
        }
        //画填充弧
        if(str.equals("fillArc")){
        Shape s = new Shape(x2,y2,80,80,color,
    new BasicStroke(1),"fillArc");
        s.draw(g2);
        }
        //画图片
        if(str.equals("Image")){
        //先用ImageIcon设置路径,再获取图片(绝对路径)
        ImageIcon icon = new ImageIcon("C:\Users\lenovo\Desktop\background1.jpg");
        Image img = icon.getImage();
        Shape s = new Shape(x2,y2,200,150,
    img,"Image");
        s.draw(g2);
        }
        //画文本
        if(str.equals("Text")){
        String text = "Hello World";
        Font font = new Font("华文行楷", Font.BOLD + Font.ITALIC, 26);//字体,粗体,斜体,大小
        g2.setFont(font);
        Shape s = new Shape(x2,y2,text,"Text");
        s.draw(g2);
        }
        //画任意多边形
        if(str.equals("Polygon")){
        if(flag == 2){
        Shape s = new Shape(ex,ey,x2,y2,color,
        new BasicStroke(1),"Line");
        s.draw(g2);
        ex = x2;
        ey = y2;
        }
        //如果与起点较近或鼠标双击,则闭合多边形
        if((Math.abs(sx-x2)<10 && Math.abs(sy-y2)<10)
        ||(e.getClickCount()==2)){
        Shape s = new Shape(sx,sy,x2,y2,color,
        new BasicStroke(1),"Line");
        s.draw(g2);
        flag = 1;
        }
        }
       }

        public void mousePressed(MouseEvent e){
        x1 = e.getX();
        y1 = e.getY();
        g2.setColor(color);
        if(flag == 1){
        sx = x1;
        sy = y1;
        }
        }

        public void mouseReleased(MouseEvent e){
        x2 = e.getX();
        y2 = e.getY();
       

        //画直线
        if(str.equals("Line")){
        Shape s = new Shape(x1,y1,x2,y2,color,
        new BasicStroke(1),"Line");
        s.draw(g2);
        }
        //画任意多边形
        if(str.equals("Polygon")){
        if(flag == 1){
        Shape s = new Shape(x1,y1,x2,y2,color,
        new BasicStroke(1),"Line");
        s.draw(g2);
        ex = x2;
        ey = y2;
        flag = 2;
        }
        }
        //画等腰三角形
        if(str.equals("Triangle")){
        Shape s = new Shape(x1,y1,x2,y2,color,
    new BasicStroke(1),"Triangle");
        s.draw(g2);
        }
        }

        public void mouseDragged(MouseEvent e){
        x3 = e.getX();
        y3 = e.getY();
       

        //画曲线
        if(str.equals("Pencil")){
        Shape s = new Shape(x1, y1, x3, y3, color,
        new BasicStroke(10),"Pencil");
        s.draw(g2);
       
        x1 = x3;
        y1 = y3;
        }
        }
    }

    三、实现画图形的Shape类

    需要定义多个构造方法,传递不同图形需要的参数值,再进行绘制

    import java.awt.Color;
    import java.awt.Graphics2D;
    import java.awt.Image;
    import java.awt.Stroke;

    public class Shape {
    public int x1,x2,y1,y2;
    public Stroke stroke;
    public Color color;
    public String type;
    public Image img;
    public String text;

    public Shape(int x1,int y1,int x2,int y2,Color color,
            Stroke stroke,String type){
        this.x1=x1;
        this.y1=y1;
        this.x2=x2;
        this.y2=y2;
        this.color=color;
        this.stroke=stroke;
        this.type=type;
    }
    
    public Shape(int x1,int y1,int x2,int y2,
            Image img,String type){
        this.x1=x1;
        this.y1=y1;
        this.x2=x2;
        this.y2=y2;
        this.img=img;
        this.type=type;
    }
    
    public Shape(int x1,int y1,
            String text,String type){
        this.x1=x1;
        this.y1=y1;
        this.text=text;
        this.type=type;
    }
    
    public void draw(Graphics2D g){
    
        if(type.equals("Line") || type.equals("Pencil")){
            g.setColor(color);
            g.setStroke(stroke);
            g.drawLine(x1, y1, x2, y2);
        }
        else if(type.equals("Image")){
            g.drawImage(img,x1,y1,x2,y2,null);
        }
        else if(type.equals("Rect")){
            g.setColor(color);
            g.setStroke(stroke);
            g.drawRect(x1, y1, x2, y2);
        }
        else if(type.equals("Oval")){
            g.setColor(color);
            g.setStroke(stroke);
            g.drawOval(x1, y1, x2, y2);
        }
        else if(type.equals("fillRect")){
            g.setColor(color);
            g.setStroke(stroke);
            g.fillRect(x1, y1, x2, y2);
        }
        else if(type.equals("RoundRect")){
            g.setColor(color);
            g.setStroke(stroke);
            g.drawRoundRect(x1, y1, x2, y2, 10, 10);
        }
        else if(type.equals("fillOval")){
            g.setColor(color);
            g.setStroke(stroke);
            g.fillOval(x1, y1, x2, y2);
        }
        else if(type.equals("fillArc")){
            g.setColor(color);
            g.setStroke(stroke);
            g.fillArc(x1, y1, x2, y2,0,-90);
        }
        else if(type.equals("Text")){
            g.drawString(text, x1, y1);
        }
        else if(type.equals("Triangle")){
            g.setColor(color);
            g.setStroke(stroke);
            g.drawLine(x1,y1,x2,y2);
          g.drawLine(2*x1-x2, y2, x2, y2);
          g.drawLine(x1,y1,2*x1-x2, y2);
        }
    }
    

    }

    四、画图板的重绘

    在实现以上类后,已经可以实现点击对应按钮,画出对应的图形和颜色,但是一旦窗体改变,画的图形就会消失。这是因为图形没有被储存,一旦窗体改变后就生成了一个新窗体,旧的图形不会在新窗体上显示,因此需要保存图形数据,并在新窗体上重绘。

    //draw类

            lis.setArray(shapeArray);//增加对图形数组的监听

    public Shape[] shapeArray = new Shape[1000];//储存图形的数组
    public void paint(Graphics g){
        super.paint(g);//super为父类
        System.out.println("绘制了");
        Graphics2D g2 = (Graphics2D) g;
        for(int i=0 ; i<shapeArray.length ; i++){
            Shape s = shapeArray[i];
            if(s != null)
                s.draw(g2);
        }
    
    }
    

    //drawListener类,增加图形数组,并收集数据

            private Shape[] array;

    private int index=0;
    

            public void setArray(Shape[] array){
    this.array = array;
    }

            //以画空心矩形为例
        if(str.equals("Rect")){
        Shape s = new Shape(x2,y2,80,40,color,
    new BasicStroke(1),"Rect");
        s.draw(g2);
        if(index<1000)
        array[index++] = s;
        }

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