我最初是在尋找一個庫來為java制作“鼠標書寫”或“手寫”簽名。我沒有找到任何東西，所以我只是想讓用戶在 JPanel 上的畫布上繪制，然后他可以選擇保存它、重新繪制它或取消簽名。我遇到的問題是，當我嘗試將繪制的內容保存在畫布中時，我得到一個空的 .jpeg到目前為止我的代碼：import javax.swing.*;import java.awt.*;import java.awt.event.*;import java.awt.image.BufferedImage;import java.awt.*;import java.awt.event.*;import javax.swing.*;import javax.swing.colorchooser.*;import javax.swing.event.*;import java.awt.geom.Line2D;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.util.logging.Logger;import javax.imageio.ImageIO;public class AES_Encryption extends JFrame implements ActionListener{public BufferedImage image = new BufferedImage(500, 500, BufferedImage.TYPE_INT_RGB);//JPanel canvas = new JPanel(); JPanel buttonPanel = new JPanel(); Point lastPos = null; Point startPos = null; Point finishPos = null; Graphics g; JButton save = new JButton("Save"); JButton cancel = new JButton("Cancel"); JButton clear = new JButton("Clear"); JPanel canvas = new JPanel(); int changer = 1; String path=""; public AES_Encryption () { setLocation(100,100); setSize(600,500); setTitle("ENCODE SECTION"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); canvas.setBackground(Color.WHITE); clear.addActionListener(this); clear.setActionCommand("clear"); save.addActionListener(this); save.setActionCommand("Save"); cancel.addActionListener(this); cancel.setActionCommand("Cancel");
1 回答
揚帆大魚
TA貢獻1799條經驗 獲得超9個贊
創建線的坐標時，將它們保存在列表中。
List<Point> points = new ArrayList<>(); // instance field.
canvas.addMouseMotionListener(new MouseMotionListener () {
public void mouseDragged (MouseEvent m) {
Point p = m.getPoint() ;
if (changer==1){
g.drawLine(lastPos.x, lastPos.y, p.x, p.y) ;
points.add(lastPos);// add it here.
}
lastPos = p ;
}
public void mouseMoved (MouseEvent m) {}
});
這是一個例子。您需要確定放置points.add()代碼的位置。在這里查看繪畫示例
編輯：
這是如何在窗口中繪圖的示例。不要在繪畫環境之外使用圖形上下文，例如paintor paintComponent（例外情況是buffered images,etc 不在 之內繪畫EDT）。
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class ExampleDrawDemo extends JPanel {
int WIDTH = 600;
int HEIGHT = 500;
JFrame frame = new JFrame();
List<Line> lines;
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new ExampleDrawDemo().start());
}
public void start() {
Random r = new Random();
Color[] color = {
Color.RED, Color.BLUE, Color.GREEN, Color.MAGENTA, Color.ORANGE,
Color.CYAN
};
// generate some lines.
lines = IntStream.range(0, 100).mapToObj(
i -> new Line(r, color[r.nextInt(color.length)])).collect(
Collectors.toList());
setPreferredSize(new Dimension(600, 500));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(this);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
// smooth lines
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// line thickness
g2d.setStroke(new BasicStroke(2));
for (Line line : lines) {
g2d.setColor(line.color);
g2d.drawLine(line.start.x, line.start.y, line.end.x, line.end.y);
}
g2d.dispose();
}
class Line {
Point start;
Point end;
Color color;
public Line(Random r, Color color) {
this.color = color;
start = new Point(r.nextInt(WIDTH), r.nextInt(HEIGHT));
end = new Point(r.nextInt(WIDTH), r.nextInt(HEIGHT));
}
}
}
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