AlphaPane.java

package jdepend.framework.ui.dialog;

import java.awt.AlphaComposite;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JComponent;
import javax.swing.Timer;

public abstract class AlphaPane extends JComponent implements ActionListener {

	// 常数定义
	private static final int ANIMATION_FRAMES = 100;
	private static final int ANIMATION_INTERVAL = 10;
	// 帧索引
	private int frameIndex;
	// 时钟
	private Timer timer;

	public void paint(Graphics g) {
		if (isAnimating()) {
			// 根据当前帧显示当前透明度的内容组件
			float alpha = (float) frameIndex / (float) ANIMATION_FRAMES;
			Graphics2D g2d = (Graphics2D) g;
			g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, alpha));
			// Renderer渲染机制
			super.paint(g2d);
		} else {
			// 如果是第一次，启动动画时钟
			frameIndex = 0;
			timer = new Timer(ANIMATION_INTERVAL, this);
			timer.start();
		}
	}

	// 判断当前是否正在进行动画
	private boolean isAnimating() {
		return timer != null && timer.isRunning();
	}

	// 关闭时钟，重新初始化
	protected void closeTimer() {
		if (isAnimating()) {
			timer.stop();
			frameIndex = 0;
			timer = null;
		}
	}

	// 动画时钟处理事件
	public void actionPerformed(ActionEvent e) {
		// 前进一帧
		frameIndex++;
		if (frameIndex >= ANIMATION_FRAMES)
			// 最后一帧，关闭动画
			closeTimer();
		else
			// 更新当前一帧
			repaint();
	}
}