How to focus a JFrame?

问题

I am writing a small game, with one JFrame that holds the main game, and another JFrame that displays the score. the problem is, when I am done constructing them, the score JFrame always ends up focused! I have tried calling scoreDisplay.toFront(), scoreDisplay.requestFocus(), and even:

display.setState(JFrame.ICONIZED);
display.setState(JFrame.NORMAL);

Is there any way to make this work? Thanks in advance, john murano

回答1:

Have you consider setting the score in the same frame as the game frame?

Other possible ( quick and dirty ) option is to create them in reverse order, or at least ( if score depends on game ) display them in reverse order.

score.setVisible( true );
game.setVisible( true );

My guess is that currently they are:

game.setVisible( true );
score.setVisible( true );

回答2:

Call the requestFocus() method.

This is not guaranteed to work, because there are many reasons why an operating system would not allow a frame to have focus. There could be another frame with higher priority in a different application. There are also some linux desktops which (if I recall correctly) do not allow frames to request focus.

To give you a better chance of success, I also recommend calling the toFront() method before requesting focus.

frame.setVisible(true);
frame.toFront();
frame.requestFocus();

Please keep in mind, none of this is guaranteed because frame handling, especially with focus and layering, is very operating system-dependant. So set the frame to visible, move it to the front, and request the focus. Once you give up the EDT, the operating system will likely give the frame the focus. At the very least, the window should be on top.

回答3:

Toggle alwaysOnTop

See here:

http://forums.sun.com/thread.jspa?threadID=5124278

Read about toFront in the API http://java.sun.com/j2se/1.5.0/docs/api/java/awt/Window.html#toFront

Some platforms may not permit this VM to place its Windows above windows of native applications, or Windows of other VMs.

On Windows OS for example toFront causes the icon on the Task Bar to flicker, but the window stays in the back.

The only think that will force the window to front is setAlwaysOnTop.

frame.setAlwaysOnTop(true); 
frame.setAlwaysOnTop(false);

回答4:

The way that I would do is:

 frame.toFront();
 frame.setState(Frame.NORMAL); 

and If you also want have more control on it you should use requestFocuse.

BTW, here is an example : http://coding.derkeiler.com/Archive/Java/comp.lang.java.gui/2006-06/msg00152.html

回答5:

Just add the following line of code above the JOptionPaneMessageDialog code ... this.setAlwaysOnTop(false);

回答6:

frame.setExtendedState( JFrame.MAXIMIZED_BOTH);
frame.setVisible(true);

Try the above..

来源：https://stackoverflow.com/questions/641172/how-to-focus-a-jframe