做网上水果网站的调查/百度推广怎么弄
基本思想是创建一个足以覆盖组件的矩形,创建一个Ellipse2D作为“洞”或“聚光灯”,并从Rectangle中减去Ellipse2D,以便在其中创建一个洞,然后绘制它.
>你应该避免在可能的情况下覆盖油漆,而是使用paintComponent,油漆链中的油漆往往很高,并且会出现一些最好避免的并发症
>您应该避免在任何paintXxx方法中更改组件或模型的状态.可以出于多种原因调用Paint,其中许多原因都不会实例化.这可能会使您的模型处于不一致状态.相反,你应该使用类似javax.swing.Timer的东西来规范模型何时更新,并简单地调用重绘
>不要在Event Dispatching Thread的上下文中调用Thread.sleep,Threasd.wait或执行任何类型的长时间运行循环或I / O操作. Swing是一个单线程环境.也就是说,UI和事件处理的所有更新都是在单个线程内完成的.如果您执行任何阻止EDT的操作,它将无法处理这些事件并更新UI,直到您停止阻止…
>不要在paintXxx方法中调用重绘或任何可能从内部调用重绘的方法.这会让你的程序陷入死亡之中,看到它消耗你的CPU ……
有关详细信息,请查看…
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Area;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Spotlight {
public static void main(String[] args) {
new Spotlight();
}
public Spotlight() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public static final int RADIUS = 80;
private BufferedImage img;
private Point mousePoint;
public TestPane() {
try {
img = ImageIO.read(new File("C:\\hold\\thumbnails\\Rampage_Small.png"));
} catch (IOException ex) {
Logger.getLogger(Spotlight.class.getName()).log(Level.SEVERE, null, ex);
}
addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseMoved(MouseEvent e) {
mousePoint = e.getPoint();
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
int x = (getWidth() - img.getWidth()) / 2;
int y = (getHeight() - img.getHeight()) / 2;
g2d.drawImage(img, x, y, this);
x = mousePoint == null ? getWidth() / 2 : mousePoint.x;
y = mousePoint == null ? getHeight() / 2 : mousePoint.y;
Rectangle rect = new Rectangle(0, 0, getWidth(), getHeight());
Ellipse2D spot = new Ellipse2D.Float(
(float) x - (RADIUS / 2f),
(float) y - (RADIUS / 2f),
(float) RADIUS,
(float) RADIUS);
Area area = new Area(rect);
area.subtract(new Area(spot));
g2d.setColor(Color.BLACK);
g2d.fill(area);
g2d.dispose();
}
}
}
}