我已经制作了一个可以允许用户绘制屏幕截图的工具。这是我的代码:
package GUI.Views;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
public class Canvas extends JPanel {
public static int radius = 5;
public class DrawPointListener extends MouseInputAdapter{
private void draw(Point p, int radius){
Graphics2D g2 = (Graphics2D)getGraphics();
int x = (int)p.getX() - radius/2;
int y = (int)p.getY() - radius/2;
g2.fillOval(x, y, radius, radius);
}
@Override
public void mousePressed(MouseEvent e) {
draw(e.getPoint(), radius);
}
@Override
public void mouseDragged(MouseEvent e) {
draw(e.getPoint(), radius);
}
}
private BufferedImage screenShot;
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(this.screenShot, 0, 0, null);
}
public Canvas() {
this.setVisible(true);
this.screenShot = getScreenShot();
this.setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));
DrawPointListener drawListener = new DrawPointListener();
this.addMouseListener(drawListener);
this.addMouseMotionListener(drawListener);
}
private BufferedImage getScreenShot() {
try {
return new Robot().createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
} catch (AWTException e) {
System.out.println("Error");
return null;
}
}
public static void main(String[] args) {
JFrame f = new JFrame();
Canvas canvas = new Canvas();
f.setUndecorated(true);
f.add(canvas);
f.setExtendedState(JFrame.MAXIMIZED_BOTH);
f.setVisible(true);
}
}
当您尝试"draw"
在屏幕上缓慢运行时,代码可以正常工作,但是当您快速移动鼠标时,您会看到这些点不是连续的,如下所示:
我认为是因为存在时间间隔。Listener
我该如何改善?
您无法更改监听器的时间间隔。您不能保证为每个像素生成一个事件。
因此,您无需绘制单个点,而是需要在当前点和上一个点之间绘制一条线。
就像是:
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
class DrawingPanel extends JPanel
{
private ArrayList<ArrayList<Point>> previous = new ArrayList<ArrayList<Point>>();
private ArrayList<Point> current = new ArrayList<Point>();
private BasicStroke basicStroke;
public DrawingPanel(int strokeSize)
{
basicStroke = new BasicStroke(strokeSize, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
MouseAdapter ma = new MouseAdapter()
{
@Override
public void mousePressed(MouseEvent e)
{
current.add( new Point(e.getX(), e.getY()) );
}
@Override
public void mouseDragged(MouseEvent e)
{
current.add( new Point(e.getX(), e.getY()) );
repaint();
}
@Override
public void mouseReleased(MouseEvent e)
{
if (current.size() > 1)
{
previous.add( current );
}
current = new ArrayList<Point>();
}
};
addMouseMotionListener( ma );
addMouseListener( ma );
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setStroke( basicStroke );
// Paint lines from previous drags
for (int i = 0; i < previous.size(); i++)
{
drawLines(g, previous.get(i));
}
// Paint line from current drag
drawLines(g, current);
}
private void drawLines(Graphics g, ArrayList<Point> points)
{
for (int i = 0; i < points.size() - 1; i++)
{
int x = (int) points.get(i).getX();
int y = (int) points.get(i).getY();
int x2 = (int) points.get(i + 1).getX();
int y2 = (int) points.get(i + 1).getY();
g.drawLine(x, y, x2, y2);
}
}
private static void createAndShowGUI()
{
JFrame frame = new JFrame("Drawing Panel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new DrawingPanel(15));
frame.setSize(400, 400);
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args) throws Exception
{
EventQueue.invokeLater( () -> createAndShowGUI() );
/*
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
*/
}
}
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