“简单”是主观的
“最大”的问题是试图弄清楚这幅画应该出现在“哪里”。
图标和翻转图标由 UI 委托绘制。这有点痛苦，因为您真的不想为您可能想要使用的每一种可能的外观和感觉设计一个 UI 委托。
因此，您需要自己接管很多功能。
以下方法基本上使用委托模式来卸载“正常”和“翻转”图标的混合并icon相应地设置按钮的属性（这是作弊）
基本功能是由 Swing 控制的，有关更多详细信息Timer，请参阅如何使用 Swing 计时器。
它是基于时间的，也就是说，它在指定的时间段内运行，而不是运行直到达到一个值。这通常会产生更好的动画效果。
import java.awt.AlphaComposite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ButtonModel;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class JavaApplication155 {
public static void main(String[] args) {
new JavaApplication155();
}
public JavaApplication155() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
}
public class TestPane extends JPanel {
public TestPane() throws IOException {
JButton btn = new JButton();
BufferedImage cat = ImageIO.read(getClass().getResource("cat.png"));
BufferedImage dog = ImageIO.read(getClass().getResource("dog.png"));
btn.setIcon(new ImageIcon(cat));
btn.setRolloverEnabled(true);
RolloverAnimator animator = new RolloverAnimator(btn, cat, dog);
setLayout(new GridBagLayout());
add(btn);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
public class RolloverAnimator {
private JButton btn;
private BufferedImage normalImage;
private BufferedImage rolloverImage;
private double progress;
private Timer timer;
private int totalAnimationTime = 300;
private int animationTime = totalAnimationTime;
private Long startedAt = null;
private boolean wasRolledOver = false;
public RolloverAnimator(JButton btn, BufferedImage normalImage, BufferedImage rolloverImage) {
this.btn = btn;
this.normalImage = normalImage;
this.rolloverImage = rolloverImage;
ButtonModel model = btn.getModel();
model.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
if (model.isArmed()) {
return;
}
if (model.isRollover() && !wasRolledOver) {
wasRolledOver = true;
prepare();
} else if (!model.isRollover() && wasRolledOver) {
wasRolledOver = false;
prepare();
}
}
});
timer = new Timer(5, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (startedAt == null) {
startedAt = System.currentTimeMillis();
}
long duration = System.currentTimeMillis() - startedAt;
progress = (double) duration / (double) animationTime;
if (progress > 1.0) {
progress = 1.0;
startedAt = null;
timer.stop();
}
BufferedImage target = transition(normalImage, rolloverImage, progress);
btn.setIcon(new ImageIcon(target));
if (!timer.isRunning()) {
progress = 0.0;
}
}
});
}
protected void prepare() {
if (timer.isRunning()) {
timer.stop();
animationTime = (int) ((double) totalAnimationTime * progress);
startedAt = System.currentTimeMillis() - (totalAnimationTime - (long)animationTime);
} else {
animationTime = totalAnimationTime;
startedAt = null;
}
progress = 0.0;
timer.start();
}
public BufferedImage transition(BufferedImage from, BufferedImage to, double progress) {
int width = Math.max(from.getWidth(), to.getWidth());
int height = Math.max(from.getHeight(), to.getHeight());
BufferedImage target = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = target.createGraphics();
float normalAlpha = wasRolledOver ? 1.0f - (float) progress : (float) progress;
float rollOverAlpha = wasRolledOver ? (float) progress : 1.0f - (float) progress;
g2d.setComposite(AlphaComposite.SrcOver.derive(normalAlpha));
draw(from, target, g2d);
g2d.setComposite(AlphaComposite.SrcOver.derive(rollOverAlpha));
draw(to, target, g2d);
g2d.dispose();
return target;
}
protected void draw(BufferedImage img, BufferedImage on, Graphics2D g2d) {
int xPos = (img.getWidth() - on.getWidth()) / 2;
int yPos = (img.getHeight() - on.getHeight()) / 2;
g2d.drawImage(img, xPos, yPos, btn);
}
}
}