我之前发布了这段代码,得到了一个非常好的答案,但不是一个有效的答案。有人可以告诉我如何更改我的代码,以解决这个问题吗?这将运行并编译。它应该在一条线的顶部绘制一条线,而是在前一条线下绘制。我尝试过使用Collections.reverse(segments);但它没有处理零元素。我也尝试过更改为segments.add(new Segment());但我不确定要在MouseMotionListener中更改什么才能使其相应地工作。任何帮助都会很棒!谢谢! :)
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
public class SimplePaint extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
JButton action = new JButton();
JButton red = new JButton();
JButton blue = new JButton();
JButton yellow = new JButton();
Color initial = Color.MAGENTA;
JButton thin = new JButton();
JButton medium = new JButton();
JButton thick = new JButton();
Stroke stroke = new BasicStroke(3);
private static ArrayList<Point> points = new ArrayList<Point>();
JButton erase = new JButton();
JButton drawing = new JButton();
Point start = null;
Point end = null;
Line2D draw = new Line2D.Float();
JPanel panel = new JPanel();
private class Segment {
private final List<Point> points = new ArrayList<Point>();
private final Color color = initial;
private final Stroke stroke = SimplePaint.this.stroke;
}
private final List<Segment> segments = new ArrayList<>();
public SimplePaint() {
getContentPane().add(panel);
setSize(450, 450);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
design();
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
segments.add(0, new Segment());
}
});
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
segments.get(0).points.add(e.getPoint());
repaint();
}
});
addMouseMotionListener(new MouseMotionAdapter(){
@Override
public void mouseDragged(MouseEvent e){
points.add(e.getPoint());
repaint();
}
});
blue.addActionListener(this);
red.addActionListener(this);
yellow.addActionListener(this);
thin.addActionListener(this);
medium.addActionListener(this);
thick.addActionListener(this);
erase.addActionListener(this);
drawing.addActionListener(this);
}
public void design() {
panel.setBackground(Color.BLACK);
blue.setBackground(Color.BLUE);
blue.setPreferredSize(new Dimension(50, 25));
panel.add(blue);
red.setBackground(Color.RED);
red.setPreferredSize(new Dimension(50, 25));
panel.add(red);
yellow.setBackground(Color.yellow);
yellow.setPreferredSize(new Dimension(50, 25));
panel.add(yellow);
thin.setText("Thin");
panel.add(thin);
medium.setText("Medium");
panel.add(medium);
thick.setText("Thick");
panel.add(thick);
erase.setText("Erase");
panel.add(erase);
drawing.setText("Draw");
panel.add(drawing);
}
public void actionPerformed(ActionEvent e) {
if(e.getSource() == blue){
initial = Color.BLUE;
}else if(e.getSource() == red){
initial = Color.RED;
}else if(e.getSource() == yellow){
initial = Color.YELLOW;
}else if(e.getSource() == thin){
stroke = new BasicStroke(1);
}else if(e.getSource() == medium){
stroke = new BasicStroke(5);
}else if(e.getSource() == thick){
stroke = new BasicStroke(10);
}else if(e.getSource() == erase){
initial = Color.WHITE;
stroke = new BasicStroke(15);
}
//repaint();
}
@Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2 = (Graphics2D) g;
int x1, y1, x2, y2;
for (Segment segment : segments) {
g2.setColor(segment.color);
g2.setStroke(segment.stroke);
for (int p = 0; p < segment.points.size() - 1; p++) {
x1 = segment.points.get(p).x;
y1 = segment.points.get(p).y;
x2 = segment.points.get(p + 1).x;
y2 = segment.points.get(p + 1).y;
g2.drawLine(x1, y1, x2, y2);
}
}
g2.dispose();
}
public static void main(String []args){
SimplePaint s = new SimplePaint();
s.setVisible(true);
}
}
答案 0 :(得分:1)
要解决您的问题,您需要添加到List
的末尾而不是开头:
addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
segments.add(new Segment());
}
});
addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent e) {
segments.get(segments.size() - 1).points.add(e.getPoint());
repaint();
}
});
此外,第二个mouseDragged()
实现似乎是多余的,如果删除它,它仍然按预期运行。
// Can be removed
addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent e) {
points.add(e.getPoint());
repaint();
}
});
此外,您应该使用JComponent
或JPanel
绘制草图,@Override
paintComponent()
而不是paint()
。这将有助于(或应该完全)消除您看到的闪烁。加上javax.swing.Timer
到repaint()
,而不是拖动,可以快速更新(并且不必要)。
最后,您应该使用SwingUtilities.invokeLater(Runnable doRun)
确保您的GUI在事件派发线程上运行,因为Swing objects are not thread safe。
e.g。
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
SimplePaint s = new SimplePaint();
s.setVisible(true);
}
});
}