JPanel的内容存在混淆 [英] The JPanel contentpane confusion

问题描述

我正在学习Java Swing，并且我将一个menuBar附加到框架中。默认情况下，这应该调用 jframe.getContentPane（）。add（child）。当我运行脚本时，menuBar没有出现。但是按钮位于顶部y = 0，如果这是有意义的。

I am learning Java Swing and I appended a menuBar to the frame. By default this should call jframe.getContentPane().add(child). When I ran the script the menuBar didn't show up. But the button was at the very top "y=0" if that makes sense.

然后我意识到我的错误，我实际上必须放入菜单栏中的菜单。然后menuBar出现了。让我想到的是......menubarcontentpane实际上是2个面板？这让我感到困惑。因为这很像一个小组。但 getContentPane（）返回一个Container，而不是JPanel对象，所以我很困惑。

Then I realized my mistake I actually had to put in a menu in the menubar. Then the menuBar showed up. So that got me thinking...is the "menubar" "contentpane" actually 2 panels? It is confusing the hell out of me. Because that acted a lot like a panel. But getContentPane() returns a Container, not a JPanel object so I'm confused.

如果是这样，这是否意味着直接转储到框架中的唯一东西就是Jpanel对象？因此，JButtons，JLabel不直接在一个框架中...
这是否意味着，jpanels是嵌套的？
还有一件令我困惑的事情。如果jpanel可以控制事物的位置，那么LayoutManager是什么？ ：S
谢谢，请回答好像是2岁的老人问为什么天空是蓝色的，哈哈;）

If so, does that mean that the only thing that is dumped directly into a frame are just Jpanel objects? Hence JButtons, JLabels are not directly in a frame... Does that mean, jpanels are "nested"? One more thing that is confusing me. If a jpanel can control how things are positioned, what is a LayoutManager for? :S Thanks, and please answer as if to a 2yr old asking why the sky is blue,ha ;)

推荐答案

一些随意的想法：

• 是的，JPanels和其他组件通常是嵌套的。这是对Swing / AWT布局管理器的必要理解。


• 虽然JFrame的返回类型是 getContentPane（）在技​​术上是一个Container，它也是一个JPanel（最终从Container继承）。


• 我相信你可以制作任何派生自ContainerPane的东西，但你需要注意它是不透明的。

• Yes, JPanels and other components are often "nested". This is where a firm understanding of the Swing/AWT layout managers is essential.
• While the type returned by a JFrame's getContentPane() is technically a Container, it's also a JPanel (which inherits eventually from Container).
• I believe that you can make anything that derives from Container the contentPane, but you need to take care that it is opaque.

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