英文:
Do I need JPanel always?
问题
我现在正在编写一个简单的GUI代码，用于启动游戏窗口。我只需要在窗口上添加“是否要开始游戏”消息和开始按钮。但是我对JFrame和JPanel有一些混淆的概念。实际上，我以为我需要将JPanel添加到JFrame以添加其他组件，比如JLabel、JButton等等。但我意识到我实际上不需要JPanel。我可以简单地使用add(button)、add(label)将组件添加到JFrame中。那么为什么我需要JPanel呢？我认为JFrame不需要JPanel，但JPanel需要JFrame。我理解得对吗？
英文:
I am now writing code simple GUI that's for start the game window. I only need Do you want to start game message and start button on the window. But I have a confusing concepts for the JFrame and JPanel. Actually, I thought I need to add JPanel to JFrame to add the other components such as JLabel, JButton,...etc. But I realized I don't actually need JPanel. I can just add the components simply use add(button), add(label) to JFrame. So why I need JPanel. And I think JFrame doesn't need JPanel but JPanel need JFrame. Am I understand correctly?
答案1
得分: 1
不，不总是这样。一个简单的图形用户界面可以通过将组件直接添加到JFrame来实现。但是为了获得更大的灵活性，您通常会使用JPanels。例如，要在GUI的不同部分使用不同的布局，将某些组件分组等等。
JFrame由JRootPane支持，其中的一部分是contentPane。
当您向JFrame添加组件时，实际上是将它们添加到内容面板，例如：frame.getContentPane().add(Component)。
JFrame是Swing GUI应用程序的常见起始场景，而JPanel旨在放置在另一个场景（容器）中。由于内容面板和JPanel都继承自相同的类（Container），因此在添加组件方面，您可以以类似的方式使用它们。
英文:
No, not always. A simple graphical user interface may be implemented by just adding components "directly" to a JFrame. But in order to get more flexibility, you would always use JPanels. For example, to employ different layouts in different parts of the GUI, to group certain components together, etc.
A JFrame is backed by a JRootPane, a part of which is a contentPane.
(image from Oracle Javadoc)
When you add components to a JFrame, you are really adding them to the content pane, e.g.: frame.getContentPane().add(Component).
A JFrame is a common starting scene of a Swing GUI application, while a JPanel is intended to be put in another scene (container). Since both content pane and a JPanel inherit from the same class (Container) you may use them in a similar manner, as far as adding components to them goes.
答案2
得分: 1
不需要。除非您需要一个Swing GUI，那么是的。
另一个答案回复类似这样的话：“不，您可以直接将组件添加到框架中”。他们忽略了的是添加到JFrame的组件会自动添加到内容窗格。内容窗格就是一个JPanel。
话虽如此：
- 我（以及许多其他人）建议设计一个基于主内容面板的应用程序，然后根据需要将该面板添加到顶级容器中。顶级容器可以是
JFrame、JWindow、JDialog、JOptionPane等。 - 是什么促使了这个问题？
JPanel是一个非常“轻量级”的容器（在多个方面都是如此）。一个GUI可以包含上千个组件而不会因此而负担沉重。当然，这是一个罕见的需求，但只是说...根据需要使用面板，不用担心它。
英文:
> Do I need JPanel always?
No. Well, unless you need a Swing GUI. Then yes.
Another answer replied words to the effect. "No, you can add components direct to a frame" What they missed was that components added to a JFrame are added to the content pane (automatically). The content pane is a JPanel.
Having said that:
- I (and many others) would recommend designing an app based around a main content panel, then adding that panel to a top-level container as needed. The top level container might be a
JFrame,JWindow,JDialog,JOptionPane.. - What prompted the question? A
JPanelis a very 'light weight' container (in more ways than one). A GUI can contain 1000s and not be burdened by doing so. Of course, that's a rare requirement, but just saying .. use panels as needed and don't worry about it.
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