What is a top-level window in java awt?
Question
I found this line on the java docs tutorial site- "A Frame is a top-level window with a title and a border". Here, what is the meaning of "top-level window"?
4 answers
solution1
1 2017-03-06 12:56:06
In GUI toolkits such as AWT, a top-level window is a window which is usually known to the OS (heavy-weight components).
Side note: AWT (and even Swing) is a pretty old technology. I recommend to use JavaFX where possible.
solution2
1 2017-03-06 20:20:37
A 'top-level window' or 'top level container' is something that can be shown on screen without having to add it to another component. We would start a GUI with a top level container, and then add panels and components to that TLC. EG of top level containers..
- AWT -
Frame,Window,Dialog.. - Swing -
JFrame,JWindow,JDialog,JOptionPane.. - Java-FX -
Stage(I have not used Java-FX much, so am unfamiliar with the other variants of TLCs, but see the Java-FX API docs for other examples).
See also this answer for many good reasons to abandon AWT components in favor of Swing. As to abandoning Swing for Java-FX, I'll be unwilling to do so until Java-FX is promoted to the Java API's Java docs, and makes it into the official Java Tutorial. Sun, then Oracle, has a bad habit of hyping many technologies only to later quietly drop support & development for them.
solution3
-1 2017-03-06 12:53:32
a window without a parent.
a window can have child windows alright and they have a parent then
solution4
-1 2017-03-06 13:04:44
Observe difference among these classes.
Frame is top level window because it has border and title. An instance of frame can have a menubar. Without those it is mere is an instance of java.awt.Window class.
Window class: It has neither border not title. Window class is not attached to nor embedded within another container.
Dialog: It has border and title. An instance of the Dialog class cannot exist without an associated instance of the Frame class.
Panel: just a generic container to hold components. Its instance provides a container to which to add components.
Note: Revert me back if further clarification is required.
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