mouseMoved(MouseEvent e) 跟不上程序逻辑

Question

我写了一个无用的程序，在你的鼠标指针上添加了一条红色轨迹。但是，如果鼠标移动得太快，轨迹会失真。我认为我的问题在于我的paintComponent(Graphics g)方法或mouseMoved(MouseEvent e)方法。关于让 Swing 将这条小径画得更顺畅的任何想法？

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.MouseEvent;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.event.MouseInputAdapter;
public class TrailTest {
//needs SwingUtilities.invokeLater but this a test class
public static void main(String[] args) {
JFrame f = new JFrame();
TrailPanel p = new TrailPanel();
p.setOpaque(false);
p.addMouseMotionListener(new MouseInputAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
//can't add enough points? or my rendering policy is bad?
p.put(e.getPoint());
p.repaint();
}
});
f.add(p);
f.setSize(500, 500);
f.setLocationRelativeTo(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
private static class TrailPanel extends JPanel {
private static final long serialVersionUID = 214019134136464119L;
private ConcurrentHashMap<Point, Integer> m;
public TrailPanel() {
m = new ConcurrentHashMap<>();
Thread t = new Thread(() -> {
while (true) {
m.replaceAll((k, v) -> v - 10);
m.entrySet().removeIf(entry -> entry.getValue() < 0);
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
repaint();
}
});
t.start();
}
public void put(Point p) {
m.put(p, 1020);
}
//problem is with the rendering policy????? idk, help :(
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(new BasicStroke(3));
for (Entry<Point, Integer> entry : m.entrySet()) {
Point p = entry.getKey();
try {
g2d.setColor(new Color(255, 0, 0, entry.getValue() / 4));
} catch (IllegalArgumentException ex) {}
g2d.drawArc((int) p.getX(), (int) p.getY(), 1, 1, 0, 360);
}
}
}
}

Answer 1

多亏了安德鲁·汤普森的想法，我让它工作得非常快。我创建了另一个HashMap，它将一个Point映射到另一个Point。然后在我的paintComponent(Graphics g)方法中，我在它们之间画了一条线。这样，点之间的空间就消失了。

注意：解决方案使用LinkedHashMap是因为LinkedHashMap在执行操作时会保留广告顺序。

工作代码：

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.MouseEvent;
import java.util.LinkedHashMap;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.event.MouseInputAdapter;
public class TrailTest {
public static void main(String[] args) {
JFrame f = new JFrame();
TrailPanel p = new TrailPanel();
p.setOpaque(false);
p.addMouseMotionListener(new MouseInputAdapter() {
// must remember to connect the current with the last one
private Point lastPoint = null;
@Override
public void mouseMoved(MouseEvent e) {
final Point mouseLocation = e.getPoint();
if (lastPoint != null) {
p.put(mouseLocation);
p.connect(mouseLocation, lastPoint);
}
lastPoint = mouseLocation;
p.repaint();
}
});
f.add(p);
f.setSize(500, 500);
f.setLocationRelativeTo(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
private static class TrailPanel extends JPanel {
private static final long serialVersionUID = 214019134136464119L;
private ConcurrentHashMap<Point, Integer> points;
private LinkedHashMap<Point, Point> lines;
public TrailPanel() {
points = new ConcurrentHashMap<>();
lines = new LinkedHashMap<>();
Thread t = new Thread(() -> {
while (true) {
points.replaceAll((k, v) -> v - 10);
points.entrySet().removeIf(entry -> entry.getValue() < 0);
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
repaint();
}
});
t.start();
}
public void connect(Point p1, Point p2) {
lines.put(p1, p2);
}
public void put(Point p) {
points.put(p, 1020);
}
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setStroke(new BasicStroke(3));
for (Entry<Point, Integer> entry : points.entrySet()) {
Point p = entry.getKey();
try {
g2d.setColor(new Color(255, 0, 0, entry.getValue() / 4));
} catch (IllegalArgumentException ex) {}
//might want to comment drawArc if you want to make it look better by a liiiiitle.
g2d.drawArc((int) p.getX(), (int) p.getY(), 1, 1, 0, 360);
g2d.drawLine((int) p.getX(), (int) p.getY(), (int) lines.get(p).getX(), (int) lines.get(p).getY());
}
}
}
}