Java Magazine - May/June 2012

//java architect /

frame.addComponentListener(new ComponentAdapter() { @Override public void componentMoved(ComponentEvent e) { tab.hideTab();

} }); frame.add WindowListener(new WindowAdapter() {

LISTING 7 LISTING 8 LISTING 9 LISTING 10

close the pop-down menu. The code in Listing 7 adds listeners to the main frame to move or hide the pop-down menu as needed.

Remember, when creating this sort of custom window, we must always consider how the user will actually use it.

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@Override public void windowClosed(WindowEvent e) { }

JAVA IN ACTION

Figure 4

class. This lets you merge multiple shapes together. I created the pointy tab shape by merging a triangle with a rounded rectangle. This was far easier than trying to write the Bezier curve code for the shape directly. Then I filled the shape with another nice translucent gradient and added a stroked border to make it stand out.

The pop-down menu looks great and it doesn’t show up in the taskbar, because I used a JWindow—but there is still one problem. If the user chooses an action, the pop-down menu will close, but what happens if the user switches to another application or minimizes the main window? What if the user moves the window? The pop-down menu will still be there, just sort of hanging out in space unattached to anything.

To fix this, I need to add an extra listener for window events. If the window moves, we should move the pop-down menu. If the window is hidden or is no longer the active window, we should

Magnifying Glass

For our final example, let’s build something crazy that simply wasn’t possible before: an onscreen magnifying glass. This is a window that actually has a hole in it. Anything inside the hole will be magnified. To make it look cool, we will use a fully custom window without any window decorations, which means we need another way for the user to move it around.

First, let’s create the cool-looking window. I drew the window using Adobe Photoshop and saved it as a transparent PNG file. See Figure 4.

Again, I’ll create a custom component inside of an alpha channel window. I also set the window to always be on top so that I can use it when interacting with other windows. Listing 8 shows what the code looks like.

Now let’s make the magnification actually work. To capture what’s inside the smaller circle, we will use the java . awt.Robot API. This API was created mainly for doing testing and automation, but it has a very handy screen capture method that lets you specify a small area of the screen to capture. Once we have that small slice of screen, we will draw it blown up by a factor of 8 in the other circular area. Listing 9 shows an

@Override public void windowIconified(WindowEvent e) { } @Override public void windowDeactivated(WindowEvent e) { } }); frame.add(button); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); frame.setSize(300, 100); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

tab.hideTab();

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excerpt of the full code available in the architect.trans-windows-project.zip.

Now we have a magnifying glass, but there are no window decorations, so the user can’t move it. The most natural thing is to let the user click and drag anywhere on the window to move the magnifying glass. We can do this by attaching a mouse listener to the main component. Every time the user drags, we will update the position of the window and then update the screen cap-