当窗口背景的不透明度为非零时，JComponent repaint()失败。

Question

我已经在这个问题上卡了一天了。我想动态更新一个叫 BufferedImage 绘制在一个透明无边框的窗口之上。但是，当窗口背景的alpha值被设置为除full之外的任何其他值时，repaint()就会停止工作(1.0f);

我试过了 image_canvas.setOpaque(false)但这并没有解决这个问题。

请告诉我，如果有人能找到一个解决办法，让组件的 repaint() 在透明背景上工作。

下面的代码可以重现这个问题。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Window;
import java.awt.image.BufferedImage;
import javax.swing.JComponent;

public class Dynamic_Buffered_Image2 {

    static Window win;
    static JComponent image_canvas;
    static BufferedImage my_image;

public static void main(String[] args) throws InterruptedException {
    // Create a test BufferedImage:
    my_image = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
    for (int i = 0; i < 100; i++)
        my_image.setRGB(i, i, Color.BLUE.getRGB());

    // Create display window:
    create_win();

    // Modify the BufferedImage dynamically:
    for (int i = 0; i < my_image.getWidth(); i++) {
        for (int j = 0; j < my_image.getHeight(); j++) {
            my_image.setRGB(i, j, Color.red.getRGB());
            Thread.sleep(10);
            win.repaint();
        }
    }
}

private static void create_win() {
    win = new Window(null);
    win.setSize(150, 150);
    image_canvas = new JComponent() {
        private static final long serialVersionUID = 1L;

        protected void paintComponent(Graphics g) {
            g.drawImage(my_image, 0, 0, null);
        }
    };
    win.add(image_canvas);
    win.setBackground(new Color(0, 0, 0, 1.0f)); // Any opacity other than 1.0f breaks repaint()??? (no red lines)
    win.setVisible(true);
}

}

Answer 1

我做了两个改动。

//win.repaint();
image_canvas.repaint();

我做了两处改动：

image_canvas.setOpaque(true); // added
win.add(image_canvas);