[英]java clear a JPanel with a transparent background
我一直在尝试创建一个屏幕保护程序。 本质上,屏幕上有多个圆圈。 但是,当我使背景透明时,不能再使用clearRect()了,因为这将迫使背景变为白色。 有什么方法可以在保持背景透明的同时清除已经绘制的圆圈?
class ScreenSaver extends JPanel implements ActionListener {
static Timer t;
Ball b[];
int size = 5;
ScreenSaver() {
Random rnd = new Random();
b = new Ball[size];
for (int i = 0; i < size; i++) {
int x = rnd.nextInt(1400)+100;
int y = rnd.nextInt(700)+100;
int r = rnd.nextInt(40)+11;
Color c = new Color(rnd.nextInt(256), rnd.nextInt(256), rnd.nextInt(256));
int dx = rnd.nextInt(20)-10;
if (dx == 0)
dx++;
int dy = rnd.nextInt(20)-10;
if (dy == 0)
dy++;
b[i] = new Ball(x, y, r, c, incR, incG, incB, dx, dy);
}
}
public void actionPerformed(ActionEvent e) {
repaint();
}
public void paintComponent(Graphics g) {
//g.clearRect(0, 0, 1600, 900);
for (int i = 0; i < size; i++) {
if (b[i].x + b[i].r+b[i].dx >= 1600)
b[i].dx *= -1;
if (b[i].x - b[i].r+b[i].dx <= 0)
b[i].dx *= -1;
if (b[i].y + b[i].r+b[i].dy >= 900)
b[i].dy *= -1;
if (b[i].y - b[i].r+b[i].dy <= 0)
b[i].dy *= -1;
b[i].x += b[i].dx;
b[i].y += b[i].dy;
g.fillOval(b[i].x-b[i].r, b[i].y-b[i].r, b[i].r*2, b[i].r*2);
}
}
}
class Painter extends JFrame{
Painter() {
ScreenSaver mySS = new ScreenSaver();
mySS.setBackground(new Color(0, 0, 0, 0)); //setting the JPanel transparent
add(mySS);
ScreenSaver.t = new Timer(100, mySS);
ScreenSaver.t.start();
setTitle("My Screen Saver");
setExtendedState(JFrame.MAXIMIZED_BOTH);
setLocationRelativeTo(null);
setUndecorated(true);
setBackground(new Color(0, 0, 0, 0)); //setting the JFrame transparent
setVisible(true);
}
}
不要在Swing组件中使用基于Alpha的颜色,而只需使用setOpaque(false)
更改
mySS.setBackground(new Color(0, 0, 0, 0));
至
mySS.setOpaque(false)
Swing仅知道如何绘制不透明或透明组件(通过opaque
属性)
作为个人喜好,您还应该super.paintComponent
任何自定义绘画之前调用super.paintComponent
,因为paintComponent
确实应该对状态做出假设。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.