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Hacking Swing: Translucent Windows
Pages: 1, 2, 3
Additionally, any user action that would change the screen will probably create lots of events, not just one. It's just the last event that should trigger updateBackground( ), not the first. To handle all these issues, the code creates a thread that watches for repaint requests and only processes a new screenshot if it hasn't already been done in the last 1,000 milliseconds. If the user generates events continuously for five seconds (searching for that lost browser window, for example), then only when everything else has settled down for a second will the refresh actually happen. This ensures that users won't have a window disappear out from under them while they are moving things around.
Another annoyance is that the window still has its border, which sort of ruins the effect of having a transparent background. Unfortunately, removing the borders with setUndecorated(true) would also remove the titlebar and window controls. This probably isn't too much of a problem, though, because the types of applications that typically use shaped windows usually have draggable backgrounds [Hack #34].
Here's a simple test program to put this into action:
public static void main(String[] args) {
JFrame frame = new JFrame("Transparent Window");
frame.setUndecorated(true);
TransparentBackground bg = new TransparentBackground(frame);
bg.snapBackground( );
bg.setLayout(new BorderLayout( ));
JPanel panel = new JPanel( ) {
public void paintComponent(Graphics g) {
g.setColor(Color.blue);
Image img = new ImageIcon("mp3.png").getImage( );
g.drawImage(img,0,0,null);
}
};
panel.setOpaque(false);
bg.add("Center",panel);
frame.getContentPane( ).add("Center",bg);
frame.pack( );
frame.setSize(200,200);
frame.setLocation(500,500);
frame.show( );
}The code creates a faux MP3 player interface using a JPanel subclass and a PNG image with transparency. Note the call to frame.setUndecorated(true), which turns off the border and titlebar. The call to panel.setOpaque(false) turns off the default background (usually plain gray), allowing the screenshot background to shine through the transparent parts of the image (Figure 6-2). This produces a window that looks like Figure 6-3—a vision of Java programs to come?
Figure 6-2. Template for an MP3 player
Figure 6-3. Running the MP3 player
Joshua Marinacci is the author of "The Java Sketchbook" column for java.net, covering topics in Java client-side and web development.
Chris Adamson is an author, editor, and developer specializing in iPhone and Mac.
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Showing messages 1 through 7 of 7.
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Problem with multiple monitors
2006-01-03 08:25:37 kennet [Reply | View]
In the original source code for the TransparentBackground (now somewhat rewritten) the Toolkit is asked for screen dimensions. But if one is using two monitors, just one of the monitors dimensions is reported. This makes the image transparent on just one of the monitors. According to http://java.sun.com/j2se/1.4.2/docs/guide/awt/AWTChanges.html#windowCentering this now needs something like
public void updateBackground() {
try {
Robot rbt = new Robot();
background = rbt.createScreenCapture(getTotalScreenBounds());
} catch (Exception ex) {
p(ex.toString());
ex.printStackTrace();
}
}
private Rectangle getTotalScreenBounds(){
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
int w = 0, h = 0;
for(int i = 0; i < ge.getScreenDevices().length; i++){
w += ge.getMaximumWindowBounds().width;
}
h = ge.getMaximumWindowBounds().height;
return new Rectangle(0,0, w, h);
}
In this case I'm presuming that the two monitors are placed beside each other not ontop.
-
Java 5 Problems
2005-12-01 11:15:32 jamescook2 [Reply | View]
It seems that in Java 5 (on Windows) the frame.hide() and frame.show() methods cause a focus lost/gained event to fire creating an infinite loop of flicker. -
Java 5 Problems
2005-12-01 12:07:34 jamescook2 [Reply | View]
Instead of hiding and showing the frame (which caused the focus lost/gain loop in Java5), moving the location of the window to an "offscreen" position seems to fix most problems. Here is some updated code that gets uses this approach.
In addition, this code causes the background area to blur slightly and fade towards white a bit. It's like the effect that you might see in Window's Vista, just not as nice/native. I also get rid of the unnecessary create of Date objects that are in the original code base. Less objects created the better.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
public class TransparentBackground extends JComponent
implements ComponentListener, WindowFocusListener, Runnable {
// constants ---------------------------------------------------------------
// instance ----------------------------------------------------------------
private JFrame _frame;
private BufferedImage _background;
private long _lastUpdate = 0;
private boolean _refreshRequested = true;
private Robot _robot;
private Rectangle _screenRect;
private ConvolveOp _blurOp;
// constructor -------------------------------------------------------------
public TransparentBackground(JFrame frame) {
_frame = frame;
try {
_robot = new Robot();
} catch (AWTException e) {
e.printStackTrace();
return;
}
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
_screenRect = new Rectangle(dim.width, dim.height);
float[] my_kernel = {
0.10f, 0.10f, 0.10f,
0.10f, 0.20f, 0.10f,
0.10f, 0.10f, 0.10f};
_blurOp = new ConvolveOp(new Kernel(3, 3, my_kernel));
updateBackground();
_frame.addComponentListener(this);
_frame.addWindowFocusListener(this);
new Thread(this).start();
}
// protected ---------------------------------------------------------------
protected void updateBackground() {
_background = _robot.createScreenCapture(_screenRect);
}
protected void refresh() {
if (_frame.isVisible() && this.isVisible()) {
repaint();
_refreshRequested = true;
_lastUpdate = System.currentTimeMillis();
}
}
// JComponent --------------------------------------------------------------
protected void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
Point pos = this.getLocationOnScreen();
BufferedImage buf = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB);
buf.getGraphics().drawImage(_background, -pos.x, -pos.y, null);
Image img = _blurOp.filter(buf, null);
g2.drawImage(img, 0, 0, null);
g2.setColor(new Color(255, 255, 255, 192));
g2.fillRect(0, 0, getWidth(), getHeight());
}
// ComponentListener -------------------------------------------------------
public void componentHidden(ComponentEvent e) {
}
public void componentMoved(ComponentEvent e) {
repaint();
}
public void componentResized(ComponentEvent e) {
repaint();
}
public void componentShown(ComponentEvent e) {
repaint();
}
// WindowFocusListener -----------------------------------------------------
public void windowGainedFocus(WindowEvent e) {
refresh();
}
public void windowLostFocus(WindowEvent e) {
refresh();
}
// Runnable ----------------------------------------------------------------
public void run() {
try {
while (true) {
Thread.sleep(100);
long now = System.currentTimeMillis();
if (_refreshRequested && ((now - _lastUpdate) > 1000)) {
if (_frame.isVisible()) {
Point location = _frame.getLocation();
_frame.setLocation(-_frame.getWidth(), -_frame.getHeight());
updateBackground();
_frame.setLocation(location);
refresh();
}
_lastUpdate = now;
_refreshRequested = false;
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
JFrame frame = new JFrame("Transparent Window");
TransparentBackground bg = new TransparentBackground(frame);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(bg);
frame.pack();
frame.setSize(200, 200);
frame.setLocation(500, 500);
frame.setVisible(true);
}
}
-
Nice but the flashing makes it impractical
2005-11-16 08:39:50 AriShap [Reply | View]
The application flashing (hide and show) every time it gains/loses focus is really annoying and makes this scheme not realistic for any real application. I don't understand why we have to hide and show the frame. Why can't we just update the background, and the next time paintComponent is called it will use the new background image? Why do we need to actually hide and show the frame?
There is a minor bug. After launching the app it will flash after 1 second even if you haven't done anything I assume because after the window is painted we get a windowGainedFocus event which causes it to update the background.
-
RE: Nice but the flashing makes it impractical
2005-11-29 15:39:16 dataxpress [Reply | View]
The reason we have to hide() the jframe is so that we can see the background. The method used to capture the screen captures exactly what you see-- if we didn't hide the jframe, it would show up. Instead of hiding the window, you could move it so that it is outside of it's own coordinates, and the move it back-- but this would probably be just as annoying if not more annoying than simply hiding and unhiding it.
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It seems like a nice solution and solves many of the issues with the hack. The only problem here is that you need hardware and software support for it, and the lack of support is getting less and less common.