我正在为JPanel中的BufferedImage实现我自己的双缓冲，这样我就可以在BufferedImage中显示鼠标位置，而无需在mousemovement上重新将每个对象重新渲染到它上面。当父JFrame中的JMenu打开时，BufferedImage将重新绘制在JMenu之上。
这个类不完整，只有必要的方法，
public class Foo extends JPanel implements ComponentListener {
BufferedImage bufferedImage;
long mousePosX;
long mousePoxY;
protected void paintComponent(Graphics g) {
paintComponent(g, this.xform);
}
protected void paintComponent(Graphics graphics, XFormPixel xformIn) {
bufferedImage = new BufferedImage(this.getWidth(),this.getHeight(),BufferedImage.TYPE_INT_RGB);
Graphics g = bufferedImage.getGraphics();
super.paintComponent(g);
//Draw lots of stuff to graphics
if(drawMouseLocation) {
int width = this.getWidth();
int height = this.getHeight();
Color origColor = g.getColor();
g.setColor(textColor);
if (cursorLocation != null) {
g.drawString("X: "+mousePosX + " Y: " + mousePosY);
}
}
g.setColor(origColor);
graphics.drawImage(bufferedImage,0,0,null);
}
public void drawMouseLocation() {
int width = this.getWidth();
int height = this.getHeight();
Image image = bufferedImage;
Graphics graphics = this.getGraphics();
Graphics g = image.getGraphics();
Color origColor = g.getColor();
g.setColor(textColor);
if (cursorLocation != null) {
g.drawString("X: "+mousePosX + " Y: " + mousePosY);
}
g.setColor(origColor);
graphics.drawImage(image,0,0,this);
}
}
还有其他办法吗？
另一个可能的交易破坏者是，当初始化Foo JPanel时，它有一个黑色边框，但是当绘制图像以显示鼠标定位时，边框会消失。我假设调用一个repaint（）或父母的东西将修复这两个问题，但它也会调用孩子的重绘，我试图避免。
编辑1： 这是请求的可运行代码。在创建它时，我无法使双缓冲工作正常，所以当鼠标移动时我也遇到了鼠标位置闪烁的问题。
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
public class DrawingTestFrame extends JFrame {
private static final long serialVersionUID = 1L;
public static void main(String[] args) {
new DrawingTestFrame();
}
public DrawingTestFrame() {
init();
}
public void init() {
JMenuBar menuBar = new JMenuBar();
setJMenuBar(menuBar);
JMenu dropMenu = new JMenu("Drop This");
dropMenu.add(needs);
dropMenu.add(to);
dropMenu.add(overlap);
menuBar.add(dropMenu);
DrawingTest test = new DrawingTest();
setTitle("Drawing Test");
add(test);
setMinimumSize(new Dimension(550,270));
pack();
setVisible(true);
}
public static Action needs = new AbstractAction("Needs") {
private static final long serialVersionUID = 1L;
public void actionPerformed(ActionEvent ae) {}};
public static Action to = new AbstractAction("To") {
private static final long serialVersionUID = 1L;
public void actionPerformed(ActionEvent ae) {}};
public static Action overlap = new AbstractAction("Overlap") {
private static final long serialVersionUID = 1L;
public void actionPerformed(ActionEvent ae) {}};
}
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
public class DrawingTest extends JPanel implements MouseListener {
private static final long serialVersionUID = 1L;
public Component parent;
private Point mouseLocation;
private BufferedImage bufferedImage;
public DrawingTest() {
init();
}
public void init() {
this.setPreferredSize(new Dimension(100, 100));
this.setBorder(BorderFactory.createLineBorder(Color.BLACK));
this.addMouseListener(this);
this.addMouseMotionListener(new MouseMotionListener() {
public void mouseDragged(MouseEvent e) {
mouseLocation = MouseInfo.getPointerInfo().getLocation();
DrawingTest.this.repaint();
}
public void mouseMoved(MouseEvent e) {
mouseLocation = MouseInfo.getPointerInfo().getLocation();
DrawingTest.this.drawLocation();
}
});
this.setVisible(true);
}
public void mouseClicked(MouseEvent e) {
mouseLocation = MouseInfo.getPointerInfo().getLocation();
this.repaint();
}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
protected void paintComponent(Graphics graphics) {
bufferedImage = new
BufferedImage(this.getWidth(),this.getHeight(),BufferedImage.TYPE_INT_RGB);
Graphics2D g = bufferedImage.createGraphics();
super.paintComponent(g);
g.setColor(Color.red);
g.drawRect(10,10,110,110);
graphics.drawImage(bufferedImage,0,0,null);
if (mouseLocation != null) {
graphics.drawString("X: " + mouseLocation.getX() +
" Y: " + mouseLocation.getY(), this.getWidth()/2 - 50, this.getHeight()-10);
}
}
protected void drawLocation() {
this.getGraphics().drawImage(bufferedImage, 0,0,null);
this.getGraphics().setColor(Color.green);
if (mouseLocation != null) {
this.getGraphics().drawString("X: " + mouseLocation.getX() +
" Y: " + mouseLocation.getY(), this.getWidth()/2 - 50, this.getHeight()-10);
}
}
}
谢谢！
答案 0 :(得分：1)
问题是你通过在组件上调用getGraphics（）来获取Graphics对象，这是你不应该这样做的。你为什么要做这个自制的双缓冲，你在哪里读到这是实现它的方法？我想看看那个教程。如果这是我的申请，我要么：
例如，此代码显示了两种技术：
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;
@SuppressWarnings("serial")
public class DrawingTestFrame2 {
private static void createAndShowGui() {
JFrame frame = new JFrame("DrawingTestFrame2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DrawingTest2 drawingTest = new DrawingTest2();
frame.getContentPane().add(drawingTest);
frame.setJMenuBar(drawingTest.createMenuBar());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
class DrawingTest2 extends JPanel {
private static final int PREF_W = 500;
private static final int PREF_H = 300;
private static final int RECT_W = 100;
private static final int RECT_H = 20;
public static final Rectangle BOTTOM_RECT = new Rectangle(PREF_W/2 - RECT_W/2, PREF_H - RECT_H,
RECT_W, RECT_H);
private String[] menuItemStrings = {"One", "Two", "Three"};
public Point mouseLocation;
private BufferedImage bufferedImage = new BufferedImage(PREF_W, PREF_H,
BufferedImage.TYPE_INT_ARGB);
private JLabel mousePositionLabel = new JLabel("", SwingConstants.RIGHT);
public DrawingTest2() {
MouseAdapter mouseAdapter = new MyMouseAdapter();
addMouseListener(mouseAdapter);
addMouseMotionListener(mouseAdapter);
mousePositionLabel.setForeground(Color.gray);
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 1;
gbc.gridy = 1;
gbc.gridwidth = 1;
gbc.gridheight = 1;
gbc.weightx = 1.0;
gbc.weighty = 1.0;
gbc.anchor = GridBagConstraints.SOUTHEAST;
add(mousePositionLabel, gbc);
Graphics2D g2 = bufferedImage.createGraphics();
g2.setPaint(new GradientPaint(0, 0, Color.yellow, 40, 40, Color.green, true));
g2.fillRect(0, 0, PREF_W, PREF_H);
g2.dispose();
g2 = bufferedImage.createGraphics();
g2.setColor(Color.red);
g2.setStroke(new BasicStroke(3f));
g2.drawRect(10, 10, 110, 110);
g2.dispose();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (bufferedImage != null) {
g.drawImage(bufferedImage, 0, 0, this);
}
if (mouseLocation != null) {
g.drawString("X: " + mouseLocation.getX() + " Y: "
+ mouseLocation.getY(), this.getWidth() / 2 - 50,
this.getHeight() - 10);
}
}
public JMenuBar createMenuBar() {
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("Menu");
for (int i = 0; i < menuItemStrings .length; i++) {
menu.add(new JMenuItem(menuItemStrings[i]));
}
menuBar.add(menu );
return menuBar;
}
class MyMouseAdapter extends MouseAdapter {
@Override
public void mouseMoved(MouseEvent mEvt) {
mouseLocation = mEvt.getLocationOnScreen();
repaint(BOTTOM_RECT);
String mousePosStr = String.format("x:%d y:%d", mouseLocation.x, mouseLocation.y);
mousePositionLabel.setText(mousePosStr);
}
}
}
答案 1 :(得分：0)
有一个名为DisplayJAI的类。 这可以显示PlanarImage（您可以使用PlanarImage来包装BufferedImage）。 它扩展了JPanel，并且已经为您提供了所需的所有鼠标监听器。 你不需要覆盖油漆或做任何事情。