Java transparent window

Question

I am trying to create a round window that follows the mouse and skips clicks in the underlying windows.

I did this with Python and Qt (see the Python overlay window ), but then I switched to Java and Swing. However, I cannot make the window transparent. I tried this method , but it does not work, however I think that my system supports transparency, because if I run Screencast-O-Matic (which is in Java), the rectangle is actually transparent.

How can I achieve something like this? (I'm on Linux KDE4)

Answer 1

Why the Java tutorial How to create a transparent and formatted Windows does not work? Are you using the latest version of Java 6 or Java 7? The May / June issue of Java Magazine was a tutorial on formatted and transparent windows requiring java 7. You will probably need to register a Java log to read it. See if you can run it on your system:

import java.awt.*; //Graphics2D, LinearGradientPaint, Point, Window, Window.Type; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.SwingUtilities; /** * From JavaMagazine May/June 2012 * @author josh */ public class ShapedAboutWindowDemo { /** * @param args the command line arguments */ public static void main(String[] args) { //switch to the right thread SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame frame = new JFrame("About box"); //turn of window decorations frame.setUndecorated(true); //turn off the background frame.setBackground(new Color(0,0,0,0)); frame.setContentPane(new AboutComponent()); frame.pack(); //size the window frame.setSize(500, 200); frame.setVisible(true); //center on screen frame.setLocationRelativeTo(null); } } ); } private static class AboutComponent extends JComponent { public void paintComponent(Graphics graphics) { Graphics2D g = (Graphics2D) graphics; //create a translucent gradient Color[] colors = new Color[]{ new Color(0,0,0,0) ,new Color(0.3f,0.3f,0.3f,1f) ,new Color(0.3f,0.3f,0.3f,1f) ,new Color(0,0,0,0)}; float[] stops = new float[]{0,0.2f,0.8f,1f}; LinearGradientPaint paint = new LinearGradientPaint( new Point(0,0), new Point(500,0), stops,colors); //fill a rect then paint with text g.setPaint(paint); g.fillRect(0, 0, 500, 200); g.setPaint(Color.WHITE); g.drawString("My Killer App", 200, 100); } } } 

Answer 2

If you use Java 6, you need to use the AWTUtilities private API. Check out the Java SE 6 Update 10 API for more details.

Example

It's a bit quick hack, but it gets the idea through

 public class TransparentWindow { /** * @param args the command line arguments */ public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { MyFrame frame = new MyFrame(); frame.setUndecorated(true); String version = System.getProperty("java.version"); if (version.startsWith("1.7")) { GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment(); GraphicsDevice graphicsDevice = ge.getDefaultScreenDevice(); System.out.println("Transparent from under Java 7"); /* This won't run under Java 6, uncomment if you are using Java 7 System.out.println("isPerPixelAlphaTranslucent = " + graphicsDevice.isWindowTranslucencySupported(GraphicsDevice.WindowTranslucency.PERPIXEL_TRANSLUCENT)); System.out.println("isPerPixelAlphaTransparent = " + graphicsDevice.isWindowTranslucencySupported(GraphicsDevice.WindowTranslucency.PERPIXEL_TRANSPARENT)); System.out.println("isPerPixelAlphaTranslucent = " + graphicsDevice.isWindowTranslucencySupported(GraphicsDevice.WindowTranslucency.TRANSLUCENT)); */ frame.setBackground(new Color(0, 0, 0, 0)); } else if (version.startsWith("1.6")) { System.out.println("Transparent from under Java 6"); System.out.println("isPerPixelAlphaSupported = " + supportsPerAlphaPixel()); setOpaque(frame, false); } frame.setSize(400, 400); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public static class MyFrame extends JFrame { public MyFrame() throws HeadlessException { setContentPane(new MyContentPane()); setDefaultCloseOperation(EXIT_ON_CLOSE); addMouseListener(new MouseAdapter() { @Override public void mouseClicked(MouseEvent e) { if (e.getClickCount() == 2) { dispose(); } } }); } } public static class MyContentPane extends JPanel { public MyContentPane() { setLayout(new GridBagLayout()); add(new JLabel("Hello, I'm a transparent frame under Java " + System.getProperty("java.version"))); setOpaque(false); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g.create(); g2d.setColor(Color.BLUE); g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f)); g2d.fillRoundRect(0, 0, getWidth() - 1, getHeight() - 1, 20, 20); } } public static boolean supportsPerAlphaPixel() { boolean support = false; try { Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities"); support = true; } catch (Exception exp) { } return support; } public static void setOpaque(Window window, boolean opaque) { try { Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities"); if (awtUtilsClass != null) { Method method = awtUtilsClass.getMethod("setWindowOpaque", Window.class, boolean.class); method.invoke(null, window, opaque); // com.sun.awt.AWTUtilities.setWindowOpaque(this, opaque); // ((JComponent) window.getContentPane()).setOpaque(opaque); } } catch (Exception exp) { } } public static void setOpacity(Window window, float opacity) { try { Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities"); if (awtUtilsClass != null) { Method method = awtUtilsClass.getMethod("setWindowOpacity", Window.class, float.class); method.invoke(null, window, opacity); } } catch (Exception exp) { exp.printStackTrace(); } } public static float getOpacity(Window window) { float opacity = 1f; try { Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities"); if (awtUtilsClass != null) { Method method = awtUtilsClass.getMethod("getWindowOpacity", Window.class); Object value = method.invoke(null, window); if (value != null && value instanceof Float) { opacity = ((Float) value).floatValue(); } } } catch (Exception exp) { exp.printStackTrace(); } return opacity; } } 

On Windows 7, it produces

In Java 6

In Java 7

Answer 3

I think this will work, I already tried to do it. To make a JFrame or window transparent, you first need to select the Undecorated(true) frame. Here is a sample code:

 import javax.swing.*; import com.sun.awt.AWTUtilities; import java.awt.Color; class transFrame { private JFrame f=new JFrame(); private JLabel msg=new JLabel("Hello I'm a Transparent Window"); transFrame() { f.setBounds(400,150,500,500); f.setLayout(null); f.setUndecorated(true); // Undecorates the Window f.setBackground(new Color(0,0,0,25)); // fourth index decides the opacity f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); msg.setBounds(150,250,300,25); f.add(msg); f.setVisible(true); } public static void main(String[] args) { new transFrame(); } } 

The only problem is you need to add your own code to close and collapse using the buttons.

Answer 4

If you want to do it yourself, without using an external library, you can start a thread that executes:

• set the transparent window invisible
• take a screenshot of the desktop
• put this screenshot as the background image of your window.

Or you can use JavaFX