java AWT 简易绘图

 1 package io.guanghe;
 2 
 3 import java.awt.*;
 4 import java.awt.event.*;
 5 import java.awt.image.BufferedImage;
 6 
 7 public class DrawImage {
 8     private Frame frame = new Frame("光何绘图");
 9     private final int AREA_WIDTH = 500;
10     private final int AREA_HEIGHT = 400;
11     private PopupMenu colorMenu = new PopupMenu();
12     private MenuItem redItem = new MenuItem("red");
13     private MenuItem greenItem = new MenuItem("green");
14     private MenuItem blueItem = new MenuItem("blue");
15     private Color forceColor = Color.BLACK;
16     BufferedImage image = new BufferedImage(AREA_WIDTH, AREA_HEIGHT, BufferedImage.TYPE_INT_RGB);
17     Graphics g = image.getGraphics();
18     private class MyCanvas extends Canvas {
19         @Override
20         public void paint(Graphics g) {
21             g.drawImage(image, 0, 0, null);
22         }
23     }
24     MyCanvas canvas = new MyCanvas();
25     private int preX = -1;
26     private int preY = -1;
27 
28     public void init() {
29         frame.addWindowListener(new WindowAdapter() {
30             @Override
31             public void windowClosing(WindowEvent e) {
32                 System.exit(0);
33             }
34         });
35         ActionListener listener = e -> {
36             String actionCommand = e.getActionCommand();
37             switch(actionCommand) {
38                 case "red":
39                     forceColor = Color.RED;
40                     break;
41                 case "green":
42                     forceColor = Color.GREEN;
43                     break;
44                 case "blue":
45                     forceColor = Color.BLUE;
46                     break;
47             }
48         };
49         redItem.addActionListener(listener);
50         greenItem.addActionListener(listener);
51         blueItem.addActionListener(listener);
52         colorMenu.add(redItem);
53         colorMenu.add(greenItem);
54         colorMenu.add(blueItem);
55         canvas.add(colorMenu);
56         canvas.addMouseListener(new MouseAdapter() {
57             @Override
58             public void mouseReleased(MouseEvent e) {
59                 if(e.isPopupTrigger()) {
60                     colorMenu.show(canvas, e.getX(), e.getY());
61                 }
62                 preX = -1;
63                 preY = -1;
64             }
65         });
66         g.setColor(Color.WHITE);
67         g.fillRect(0, 0, AREA_WIDTH, AREA_HEIGHT);
68         canvas.addMouseMotionListener(new MouseMotionAdapter() {
69             @Override
70             public void mouseDragged(MouseEvent e) {
71                 if(preX > 0 && preY > 0) {
72                     g.setColor(forceColor);
73                     g.drawLine(preX, preY, e.getX(), e.getY());
74                 }
75                 preX = e.getX();
76                 preY = e.getY();
77                 canvas.repaint();
78             }
79         });
80         canvas.setPreferredSize(new Dimension(AREA_WIDTH, AREA_HEIGHT));
81         frame.add(canvas);
82         frame.pack();
83         frame.setVisible(true);
84     }
85 
86     public static void main(String[] args) {
87         new DrawImage().init();
88     }
89 }