Java：JFrame使用setBackground实现透明背景的雪花屏保

直接上效果图：

 

Java代码：

import com.sun.awt.AWTUtilities;

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.io.IOException;
import java.io.InputStream;

//这2句是核心
//frame.setBackground(new Color(0,0,0,0));
//pane.setBackground(new Color(0,0,0,0));
//这句写上后没有效果，不知道为什么，jdk1.8
//AWTUtilities.setWindowOpaque(frame, false);

public class t4 {

    public static void main(String[] args) {
        new t4();
    }
    public t4(){
        start();
    }

    public static void start() {
        final JFrame frame = new JFrame();

        frame.setAlwaysOnTop(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setUndecorated(true);
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
        //这句写上后没有效果，不知道为什么，jdk1.8
        //AWTUtilities.setWindowOpaque(frame, false);
        //设置透明背景1，重要
        frame.setBackground(new Color(0,0,0,0));

        final JPanel pane = new JPanel() {

            private int[] snowX = null;
            private int[] snowY = null;
            private int[] angles = null;
            private int count = 50;

            @Override
            public void paint(Graphics g) {
                super.paint(g);
                Rectangle bounds = frame.getBounds();
                if (snowX == null) {

                    snowX = new int[count];
                    for (int i = 0; i < snowX.length; i++) {
                        snowX[i] = getRandomInt(bounds.width);
                    }
                    snowY = new int[count];
                    for (int i = 0; i < snowY.length; i++) {
                        snowY[i] = getRandomInt(bounds.height);
                    }
                    angles = new int[count];
                    for (int i = 0; i < snowY.length; i++) {
                        angles[i] = getRandomInt(360);
                    }
                }

                Graphics2D g2d = (Graphics2D) g;


                InputStream imgIS = this.getClass().getResourceAsStream("snow.png");
                Image image = null;
                try {
                    image = ImageIO.read(imgIS);
                } catch (IOException e) {
                    e.printStackTrace();
                }

                for (int i = 0; i < count; i++) {
                    //snowX[i] += getRandomInt(5) - 3;
                    snowY[i] += 5;
                    angles[i] += i / 5;
                    snowY[i] = snowY[i] > bounds.height ? 0 : snowY[i];
                    angles[i] = angles[i] > 360 ? 0 : angles[i];
                    int x = snowX[i];
                    int y = snowY[i];
                    int angle = angles[i];
                    g2d.translate(x, y);
                    double angleValue = Math.toRadians(angle);
                    g2d.rotate(angleValue);
                    g2d.drawImage(image, 0, 0, null);
                    g2d.rotate(-angleValue);
                    g2d.translate(-x, -y);
                }
            }
        };

        //设置透明背景2，重要
        pane.setBackground(new Color(0,0,0,0));
        //这里不设置了
        //frame.setContentPane(pane);
        frame.setVisible(true);
        Thread thread = new Thread() {
            @Override
            public void run() {
                while (true) {
                    try {
                        //这里设置一次
                        frame.setContentPane(pane);
                        Thread.sleep(10);
                        //然后移除
                        frame.remove(pane);
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                    //然后重画
                    pane.repaint();
                }
            }
        };

        thread.start();
    }



    public static int getRandomInt(int width) {
        int i = 0;
        double d = Math.random() * width;
        i = (int)d;
        return i;
    }
}

需要的雪花图片（应该是没有背景的png才对）：

说明：

直接复制代码就可以用了，本人是jdk1.8的环境，没有问题。