我希望绘制并重新绘制JPanel，它可以与图像一起旋转90度。 最初的绘画不会引起任何问题。当我尝试重绘（）面板时，它不会立即执行此操作，而是等待第二次重绘（）。
我的第二个问题是，当我按照下面的代码说明我的面板垂直时，它根本不会重新绘制。我至少看不到图像红色，黄色或绿色，但图像“光”仍然存在。
感谢您抽出宝贵时间阅读本文。
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
if(vertical){
g2d.translate(this.getWidth() / 2, this.getHeight() / 2);
g2d.rotate(-Math.PI / 2);
g2d.translate(-img_light.getWidth(null) / 2, -img_light.getHeight(null) / 2);
g2d.drawImage(img_light, 0, 0, this);
if(showRed){
g2d.translate(-img_red.getWidth(null) / 2, -img_red.getHeight(null) / 2);
g2d.drawImage(img_red, 0, 0, null);
}
if(showYellow){
g2d.translate(-img_yellow.getWidth(null) / 2, -img_yellow.getHeight(null) / 2);
g2d.drawImage(img_yellow, 0, 0, null);
}
if(showGreen){
g2d.translate(-img_green.getWidth(null) / 2, -img_green.getHeight(null) / 2);
g2d.drawImage(img_green, 0, 0, null);
}
}else{
g2d.drawImage(img_light, 0, 0, this);
if(showRed){
g2d.drawImage(img_red, 0, 0, null);
}
if(showYellow){
g2d.drawImage(img_yellow, 0, 0, null);
}
if(showGreen){
g2d.drawImage(img_green, 0, 0, null);
}
}
}
答案 0 :(得分：2)
查看教程Graphics2D和两个关于Graphics2d#rotate()的方法
那么你应该如此能够
代码（由@CtrAltDelete初始???）
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.Timer;
import javax.swing.filechooser.*;
public class RotatableImageComponent extends JComponent {
private static final long serialVersionUID = 1L;
private Image image;
private double angle = 0;
private MyObservable myObservable;
public RotatableImageComponent() {
myObservable = new MyObservable();
}
public RotatableImageComponent(Image image) {
this();
this.image = image;
}
public Image getImage() {
return image;
}
public void setImage(Image image) {
this.image = image;
}
public double getAngle() {
return angle;
}
public void setAngle(double angle) {
if (angle == this.angle) {
return;
}
this.angle = angle;
double circle = Math.PI * 2;
while (angle < 0) {
angle += circle;
}
while (angle > circle) {
angle -= circle;
}
if (myObservable != null) {
myObservable.setChanged();
myObservable.notifyObservers(this);
}
repaint();
}
/**
* In the rotation events sent to the listener(s), the second argument
* (the value) will be a reference to the RotatableImageComponent. One then
* should call getAngle() to get the new value.
* @param o
*/
public void addRotationListener(Observer o) {
myObservable.addObserver(o);
}
public void removeRotationListener(Observer o) {
myObservable.deleteObserver(o);
}
public void rotateClockwise(double rotation) {
setAngle(getAngle() + rotation);
}
public void rotateCounterClockwise(double rotation) {
//setAngle(getAngle() - rotation);
rotateClockwise(-rotation);
}
@Override
public void paintComponent(Graphics g) {
if (image == null) {
super.paintComponent(g);
return;
}
Graphics2D g2 = (Graphics2D) g;
AffineTransform trans = AffineTransform.getTranslateInstance(getWidth() / 2, getHeight() / 2);
trans.rotate(angle);
trans.translate(-image.getWidth(null) / 2, -image.getHeight(null) / 2);
g2.transform(trans);
g2.drawImage(image, 0, 0, null);
}
@Override
public Dimension getPreferredSize() {
if (image == null) {
return super.getPreferredSize();
}
int wid = image.getWidth(null);
int ht = image.getHeight(null);
int dist = (int) Math.ceil(Math.sqrt(wid * wid + ht * ht));
return new Dimension(dist, dist);
}
public static class TimedRotation {
private RotatableImageComponent comp;
private long totalTime, startTime;
private double toRotate, startRotation;
private int interval;
public Timer myTimer;
private myAction mAction;
public TimedRotation(RotatableImageComponent comp, double toRotate, long totalTime, int interval) {
//super(interval, new myAction());
this.comp = comp;
this.totalTime = totalTime;
this.toRotate = toRotate;
this.startRotation = comp.getAngle();
this.interval = interval;
}
public void start() {
if (mAction == null) {
mAction = new myAction();
}
if (myTimer == null) {
myTimer = new Timer(interval, new myAction());
myTimer.setRepeats(true);
} else {
myTimer.setDelay(interval);
}
myTimer.start();
startTime = System.currentTimeMillis();
}
public void stop() {
myTimer.stop();
}
private class myAction implements ActionListener {
@Override
public void actionPerformed(ActionEvent ae) {
long now = System.currentTimeMillis();
if (totalTime <= (now - startTime)) {
comp.setAngle(startRotation + toRotate);
stop();
return;
}
double percent = (double) (now - startTime) / totalTime;
double rotation = toRotate * percent;
comp.setAngle(startRotation + rotation);
}
}
}
private class MyObservable extends Observable {
@Override
protected void setChanged() {
super.setChanged();
}
}
public static class RotationKeys extends KeyAdapter {
private RotatableImageComponent comp;
private double rotationAmt;
public RotationKeys(RotatableImageComponent comp, double rotationAmt) {
this.comp = comp;
this.rotationAmt = rotationAmt;
}
public RotationKeys(RotatableImageComponent comp) {
this(comp, Math.PI / 90);
}
@Override
public void keyPressed(KeyEvent ke) {
if (ke.getKeyCode() == KeyEvent.VK_LEFT) {
comp.rotateCounterClockwise(rotationAmt);
} else if (ke.getKeyCode() == KeyEvent.VK_RIGHT) {
comp.rotateClockwise(rotationAmt);
}
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
try {
FileFilter filter = new FileNameExtensionFilter("JPEG file", "jpg", "jpeg");
JFileChooser chooser = new JFileChooser();
chooser.addChoosableFileFilter(filter);
if (chooser.showSaveDialog(null) == JFileChooser.APPROVE_OPTION) {
File f = chooser.getSelectedFile();
BufferedImage im = ImageIO.read(f);
final RotatableImageComponent c = new RotatableImageComponent(im);
c.addRotationListener(new Observer() {
@Override
public void update(Observable arg0, Object arg1) {
System.out.println("Angle changed: " + ((RotatableImageComponent) arg1).getAngle());
}
});
JPanel controls = new JPanel(new FlowLayout());
final JTextField rotation = new JTextField();
rotation.setText("30");
controls.add(new JLabel("Rotation(degrees)"));
controls.add(rotation);
final JTextField time = new JTextField();
time.setText("1000");
time.setColumns(6);
rotation.setColumns(7);
controls.add(new JLabel("Time(millis)"));
controls.add(time);
JButton go = new JButton("Go");
go.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
TimedRotation tr = new TimedRotation(c,
Double.parseDouble(rotation.getText()) / 180 * Math.PI,
Integer.parseInt(time.getText()), 50);
tr.start();
}
});
controls.add(go);
RotationKeys keys = new RotationKeys(c);
c.addKeyListener(keys);
c.setFocusable(true);
JFrame jf1 = new JFrame();
jf1.getContentPane().add(c);
JFrame jf2 = new JFrame();
jf2.getContentPane().add(controls);
jf1.pack();
jf2.pack();
jf1.setLocation(100, 100);
jf2.setLocation(400, 100);
jf1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf2.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
jf1.setVisible(true);
jf2.setVisible(true);
}
} catch (Throwable t) {
t.printStackTrace();
}
}
});
}
}