show()is deprecated in
java.awt.Componentbut not in
Window.show()not only makes the window visible but also brings it to the front if it's already visible. Thus its behavior is a little different than
Component.show(). Bill Pugh explains:
The semantics of show() for Window are slightly different. If the Window is already visible, the window is moved to front. While for components, show() simply made the component visible. I'm guessing that given these different semantics, they decided that show() was still useful for Windows, since it did more than setting visibility.What bothers me about this is that
Unfortunately, things are a little more complicated. As a result of this change and the forwarding of new methods throught depreciated methods, this means that setVisible() has now unexpected semantics for Window. If you call setVisible(true) on a window that is already visible, it moves the window to the front.
Windowalready has a
toFront()method and a
setVisible()method. There's no need to combine them in a less obvious
show()method. Furthermore, invoking
setVisible()on a window simply results in a call to Window's
show()method anyway. Bottom line: I think this is simply a poor design choice.
Bill Pugh gets a free copy of JavaBeans for his answer just as soon as he sends me his snail mail address. More responses are on the responses page.
From: email@example.com (Bill Pugh) Message-Id: <199807012030.QAA03885@aufait.cs.umd.edu> The semantics of show() for Window are slightly different. If the Window is already visible, the window is moved to front. While for components, show() simply made the component visible. I'm guessing that given these different semantics, they decided that show() was still useful for Windows, since it did more than setting visibility. Unfortunately, things are a little more complicated. As a result of this change and the forwarding of new methods throught depreciated methods, this means that setVisible() has now unexpected semantics for Window. If you call setVisible(true) on a window that is already visible, it moves the window to the front. Bill Pugh firstname.lastname@example.org From: Charles LeRose <email@example.com> Subject: Question of the day > Can anyone explain to me why show() is deprecated > in java.awt.Component but not in java.awt.Window? Due to scheduling pressures, the deprecation tag could not be added before the API was declared frozen. Another possibility is that the loss of the show() method in the Window class would have left less than 4000 methods in that class. The embarrassment of allowing such a simple class to exist in the AWT was simply too much to bear, so they kept show() to flesh it out a bit. Date: Thu, 02 Jul 1998 10:17:17 -0500 From: Craig Doremus <firstname.lastname@example.org> Subject: Question of the Day Greetings! Here's my best answer to your question: Can anyone explain to me why show() is deprecated in java.awt.Component but not in java.awt.Window? I believe that the reason that show() in the Window class is still around because the method both makes the Window instance visible and brings it to the front (foreground). For other Components, show() is replaced by setVisible(), which only makes the component visible (repaints it). BTW, I think that Cafe au Lait is FANTASTIC! and that your Java Network Programming book is the best written book on Java -- I recommend it to every one I know. -- Craig ----------------------- Craig Doremus Programmer MacImage of Maine email@example.com 207-767-8241 ----------------------- From: "Erwin Moedersheim" <firstname.lastname@example.org> Subject: Q of the day: show() First answer: The semantics of the two methods are different. The semantics of the "show()" method in Window are "If this window is not yet visible, make it visible. If this window is already visible, then bring it to the front" (JDK1.0.2, and similar in JDK 1.1.6). Thus, the method "show()" method in Window not only renders it visible, it also brings it to the front.� On the other hand, the semantics of the deprecated method in Component were "Shows this component; if this component had been made invisible by a call to the hide method, makes this component visible again." In other words, it only sets the Component to visible or not. Apparently, the powers at Sun decided to turn "visible" into a Java Beans property of Component in JDK 1.1, renaming "show()" and "show(boolean)" to "setVisible(boolean)". However, the "show()" method of Window stayed, since it also executes the "toFront()" action. � 2) Second answer: You should know better than to question the authority of the Java PAS in this matter. Let's have fourty! (Push-ups or GridBagLayouts, that's up to you). � Cheers, Erwin Date: Wed, 1 Jul 1998 10:33:33 -0400 (EDT) From: Richard Jefts Well first off, Sun wanted to make the API more consistent with the JavaBeans spec, thus creating the setVisible method. For a component, setVisible does exactly what the deprecated show did. For a window, however, setVisible and show have two different meanings. setVisible only makes the window visible, while show makes the window visible and brings it to the front. In this way, unlike the old show method, setVisible does the same thing for both components and windows, making the API easier to understand. richie Richard Jefts email@example.com From: David Soroko <firstname.lastname@example.org> Subject: why show() is deprecated Here is what I think Component.show() is deprecated because it does not conform to the set/get pattern. The only reason I can think of not making Window.show() deprecated is that it has some functionality for which there is no decent alternative access (such as setVisible() is for show() ). My guess is that this functionality is the generation of the WINDOW_OPENED event which is fired the first time Window.show() is invoked. BTW internally Window.show() invokes the (deprecated) Component.show() -- David Soroko email@example.com Manna Network Technologies From: "Marlon Jacobs" <firstname.lastname@example.org> To: email@example.com "show() is depreciated in java.awt.Component but not in java.awt.Window" because components have to be arranged first and sorted and then added to a layout as if they are not the components would be clump together, whereas in windows objects are generally placed into the centre of a window.