Java实验-Swing 涂鸦板

实验要求：

涂鸦板是一个具有趣味性的小程序，它的实现原理是通过鼠标事件，控制鼠标移动结合画图功能实现。鼠标拖拽才开始绘制，松开鼠标则停止绘制。

代码：

--MyPaint画板类：

package com.junlin.exer6;

import javax.swing.JLabel;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;

public class MyPaint extends JLabel {
    private boolean is_painting = false;  //判断是否正在绘制
    private List<Curve> curves = new ArrayList<>();  //记录绘制过程中所有的曲线

    //记录使用过的线条粗细，主要是为了保留之前绘制的效果，不会让改变线条粗细影响之前的绘制
    private List<Float> lineSizes = new ArrayList<>();

    //同上记录使用过的颜色
    private List<Color> lineColors = new ArrayList<>();
    private Float currentLineSize = 2.0f;  //当前线条的粗细
    private Color currentLineColor = Color.RED;

    public MyPaint(){
        //绑定事件
        MyMouseListener handler = new MyMouseListener();
        this.addMouseListener(handler);
        this.addMouseMotionListener(handler);
    }

    public void setCurrentLineSize(float currentLineSize) {
        this.currentLineSize = currentLineSize;
    }
    public void setCurrentLineColor(Color color) {
        this.currentLineColor = color;
    }

    //下面这个方法在程序运行的时候被一直调用
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int width = getWidth();
        int height = getHeight();
        //this.setOpaque(true);
        //this.setBackground(Color.WHITE);  //为什么这行代码不起作用就是因为没有写上面设置透明度的代码

//        System.out.printf("%d %d\n", width, height);
        g.setColor(Color.WHITE);
        g.fillRect(0,0,width,height);
        //g.setFont(new Font("宋体", Font.BOLD, 200));
        Graphics2D g2 = (Graphics2D)g;  //g是Graphics对象
        g2.setStroke(new BasicStroke(currentLineSize));
        g2.setPaint(currentLineColor);

        //从曲线集合中进行绘制
        for(int i = 0;i < curves.size();i++) {
            Curve curve = curves.get(i);
            g2.setStroke(new BasicStroke(lineSizes.get(i)));
            g2.setPaint(lineColors.get(i));
            if(curve.points.size() >= 2) {
                Point p1 = curve.points.get(0);
                for(int j = 1;j < curve.points.size();j++){
                    Point p2 = curve.points.get(j);
                    g.drawLine(p1.x,p1.y,p2.x,p2.y);
                    p1 = p2;
                }
            }
        }
    }

    //清空画板
    public void clearPaint() {
        this.curves.clear();
        this.lineSizes.clear();
        this.lineColors.clear();
        repaint();
    }


    //监听内部类
    public class MyMouseListener extends MouseAdapter {
        @Override
        public void mousePressed(MouseEvent e) {
            is_painting = true;
            lineSizes.add(currentLineSize);
            lineColors.add(currentLineColor);
            Curve curve = new Curve();
            curve.points = new ArrayList<>();
            curves.add(curve);
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            is_painting = false;
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            //如果表示正在绘制
            if(is_painting) {
                //取出曲线集合中的最后一条曲线（就是当前正在绘制的曲线）
                Curve curve = curves.get(curves.size() - 1);
                curve.points.add(e.getPoint());  //将当前的点加入曲线中
                repaint();   //重新绘制
            }
        }
    }

    //曲线内部类，其属性就是曲线上的点的集合
    public class Curve {
        List<Point> points;
    }
}

MyFrame窗体类:

package com.junlin.exer6;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import java.awt.Color;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;


public class MyFrame extends JFrame {
    public MyFrame(){
        super("涂鸦板");

        JPanel root = new JPanel();
        root.setLayout(null);
        this.add(root);

        //自定义画板控件
        MyPaint paint = new MyPaint();
        paint.setBounds(250,10,600,600);
        root.add(paint);

        //清除画板按钮
        JButton clearBtn = new JButton("清空画板");
        clearBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                paint.clearPaint();
            }
        });
        clearBtn.setBounds(70,40,95,40);
        root.add(clearBtn);

        //文本标签
        JLabel lineSizeLabel = new JLabel("选择线条粗细:");
        lineSizeLabel.setBounds(10,300,100,20);
        lineSizeLabel.setFont(new Font("宋体", Font.BOLD, 14));
        root.add(lineSizeLabel);

        //线条粗细列表
        JComboBox<String> LineTypeField = new JComboBox<>();
        for(int i = 2;i <= 12;i += 2) {
            LineTypeField.addItem(i+"");
        }
        LineTypeField.setBounds(120,300,100,30);
        LineTypeField.addItemListener(new ItemListener() {
            @Override
            public void itemStateChanged(ItemEvent e) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    // 选择的下拉框选项
                    System.out.println(e.getItem() instanceof String);
                    float size = Float.parseFloat(String.valueOf(e.getItem()));
                    paint.setCurrentLineSize(size);
                }
            }
        });
        root.add(LineTypeField);


        //文本控件
        JLabel lineColorLabel = new JLabel("选择线条颜色:");
        lineColorLabel.setBounds(10,200,100,20);
        lineColorLabel.setFont(new Font("宋体", Font.BOLD, 14));
        root.add(lineColorLabel);

        //颜色选择列表
        JComboBox<String> LineColorField = new JComboBox<>();
        LineColorField.addItem("红色");
        LineColorField.addItem("蓝色");
        LineColorField.addItem("粉红色");
        LineColorField.addItem("橙色");
        LineColorField.addItem("绿色");
        LineColorField.setBounds(120,200,100,30);
        LineColorField.addItemListener(new ItemListener() {
            @Override
            public void itemStateChanged(ItemEvent e) {
                if (e.getStateChange() == ItemEvent.SELECTED) {
                    // 选择的下拉框选项
                    Color color;
                    switch (String.valueOf(e.getItem())) {
                        case "红色":
                            color = Color.RED;
                            break;
                        case "蓝色":
                            color = Color.BLUE;
                            break;
                        case "粉红色":
                            color = Color.PINK;
                            break;
                        case "橙色":
                            color = Color.ORANGE;
                            break;
                        case "绿色":
                            color = Color.GREEN;
                            break;
                        default:
                            color = Color.BLACK;
                            break;
                    }
                    paint.setCurrentLineColor(color);
                }
            }
        });
        root.add(LineColorField);

        this.setSize(1000,700);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

--JavaMain主类：

package com.junlin.exer6;

public class JavaMain {
    public static void main(String[] args) {
        new MyFrame();
    }
}