Yes, Mike I very much agree! Good info. And Mihai should write a book about it as good as his explanation is ;-)
Very useful! Thank you, Craig On 7/22/10, Mike M. Lin <[email protected]> wrote: > This is great information. I can see how the containing JPanel might > help now -- and I got a little history lesson too ;) > > Thanks so much Michèle and Mihai for your responses. > > Mike > > > On Jul 22, 3:31 am, Mihai DINCA <[email protected]> wrote: >> Hi Mike >> >> You must know that Java Swing is like Kung Fu: it's more than a sport, >> it's a philosophy. And before being able to fully taking advantages of >> its benefits one must learn how to raise bonsais, carry the water and >> wash the windows for at least a couple of years :-) >> >> Now, as far as I know (I must confess I have skipped some windows >> washing classes, not to speak about my bonsais), a JFrame is the parent >> of several embedded containers that allow fancy effects: >> -- The RootPane (use myFrame.getRootPane() to grab it) is a JRootPane >> (derived from Component); its role is to contain the GlassPane and the >> LayeredPane >> -- The LayeredPane (use myFrame.getLayeredPane() or >> myFrame.getRootPane.getLayeredPane()) is a JLayeredPane derived from >> JComponent derived from Container derived from Component; it contains >> several graphical "layers" (in the z-Order) with specific functions; it >> is the container for the frame menu and for the ContentPane >> -- The GlassPane (use myFrame.getGlassPane() or >> myFrame.getRootPane.getGlassPane() or >> myFrame.getRootPane.getLayeredPane.getGlassPane() ...) is an AWT >> Component (or some derived class); it is a transparent layer above the >> Frame contents and allows to add some fancy effects, such as obscuring >> the whole Frame, to display additional fancy messages or controls and to >> intercept user input (for e.g., to display an input aid while typing) >> -- The ContentPane (myFrame.getContentPane() or ...) is an AWT Container >> (or some derived class - in practice it is a JPanel, but you can replace >> it by any AWT Container); it displays (or draws if you prefer) the >> Components of the Frame. >> >> The description of whole structure can be found in the Sun tutorials >> about Swing (I don't have the URL under my hand) but the role of each >> component is not too explicit. >> >> You can (1) directly add the JFrame Components to the ContentPane >> (including specifying its LayoutManager). In fact, the "add" methods of >> the JFrame are overridden so they call the corresponding "add" methods >> of the ContentPane (same for the LayoutManager management methods). >> >> Or you can (2) create your own Container, such as a JPanel, add >> Components to it and replace the ContentPane of your JFrame. >> >> Or you can (3) use your own JPanel to add Components and play with the >> LayoutManager and, in the end, add it to the (ContentPane of the) JFrame. >> >> The simplest ways is to use the first method. However some people prefer >> the methods 2 and 3 for some reasons and consider doing so as a "best >> practice". >> >> One of the reason is that you can work to your JPanel and all the logic >> behind without asking yourself about the final enclosing container. Then >> decide (eventually at execution time) to display it in a JFrame (and let >> the user play with several things on the screen including your JPanel) >> or in a modal JDialog (so to prevent the user to touch anything else as >> long as your JPanel is in sight) or in a JApplet (because the user >> requested your JPanel over the Internet or the company Intranet). >> >> I think that another (historical) reason was caused by the fact that >> displaying Swing controls used to be very slow on 32MB Windows 95 >> systems (or so). So it was a common practice to display some splash >> screen while constructing the content of the JPane then had quickly >> displayed the whole when the JPane was added to the Frame. >> >> The last but not the least reason is the ability to quickly change the >> content of the JFrame. Just have two contextual JPanes ready to be >> displayed and replace the ContentPane with the one that fits your >> context at that moment. Then change it again when the context changes. >> >> For other fancy effects one can produce by taking advantage of the >> JFrame layered structure, I found the O'Reilly's book "Swing Hacks - >> Tips and Tools for Building Killer GUIs", by Marinacci & Adamson. It >> implies some windows washing and meditation too so I cannot say I am an >> expert in killer GUIs based applications, but it worth to take a look at >> it. >> >> Hope it helps >> Mihai >> >> Mike M. Lin a �crit : >> >> >> >> > Thanks for the link, Mich�le. The interesting thing is that I didn't >> > need to the create a JPanel to do my layout. Immediately after >> > creating my JFrame, I just set the layout directly on it. >> >> > JFrame frame = new JFrame("It's time to play SHOW THAT FLAG"); >> > frame.setLayout(new BoxLayout( >> > frame.getContentPane(), BoxLayout.PAGE_AXIS)); >> >> > This >> > article,http://weblogs.java.net/blog/hansmuller/archive/2005/11/jframeadd_con..., >> > explains that this is actually an illusion -- a convenience feature >> > that actually sets the layout on the content pane of the frame. The >> > above is equivalent to this: >> >> > JFrame frame = new JFrame("It's time to play SHOW THAT FLAG"); >> > frame.getContentPane().setLayout(new BoxLayout( >> > frame.getContentPane(), BoxLayout.PAGE_AXIS)); >> >> > Even more interesting is that I never set the content pane of the >> > frame before setting the content pane's layout. How can I set the >> > layout on an object that doesn't exist? What I found out is that >> > every JFrame comes with a default content pane. What type of object >> > is it? Well let's find out... >> >> > public static void main(String[] args) { >> > JFrame frame = new JFrame(); >> > System.out.println("frame.getContentPane() is a " >> > + frame.getContentPane().getClass().getName()); >> > } >> >> > run: >> > frame.getContentPane() is a javax.swing.JPanel >> > BUILD SUCCESSFUL (total time: 2 seconds) >> >> > It's actually a JPanel. So if the JFrame already includes a default >> > content pane that's a JPanel, then why create another JPanel to slap >> > on top of it? In the LunarPhases example (http://137.166.68.100/java- >> > tut/uiswing/learn/example5.html), they could have done without the >> > mainPanel and instead added the selectPanel and displayPanel to the >> > lunarPhasesFrame's content pane. >> >> > One possible advantage that I could see is that the mainPanel is used >> > to throw a border around the edges of the frame so that the >> > selectPanel and displayPanel don't seem so cramped. If that's what >> > the purpose was, then it wasn't clear to me from reading the tutorial. >> >> > Thanks, >> > Mike >> >> > On Jul 21, 2:21 am, Mich�le Garoche <[email protected]> wrote: >> >> >> On 21 juil, 10:16, "Mike M. Lin" <[email protected]> wrote:> In the >> >> Swing homework, the example we key off of (lunar images) is set >> >> >>> up with a JFrame which holds a JPanel. that JPanel acts as a container >> >>> for two other JPanel's - one to house the combo box, the other to >> >>> house the image. >> >> >>> What is the purpose of the containing JPanel? I did my homework >> >>> assignment without that container and it seems to work just fine. I >> >>> just put my sub-panels directly on the JFrame. >> >> >>> It seems pretty useless to me in this program. What am I missing? >> >> >> You may have a look at this >> >> tutorial:http://download.oracle.com/docs/cd/E17409_01/javase/tutorial/uiswing/... >> >> Especially the section Tips on choosing a Layout Manager. > > -- > To post to this group, send email to > [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/javaprogrammingwithpassion?hl=en -- Sent from my mobile device -- To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/javaprogrammingwithpassion?hl=en
