Java开发网 - contentPane = (JPanel) this.getContentPane()

Topic: contentPane = (JPanel) this.getContentPane()

1.contentPane = (JPanel) this.getContentPane()	Copy to clipboard
Posted by: zsh220824 Posted on: 2008-01-23 08:01 contentPane = (JPanel) this.getContentPane() 这个句子什么意思?其中(JPanel)格式对吗?谢谢

2.Re:contentPane = (JPanel) this.getContentPane() [Re: zsh220824]

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Posted by: tzutolin
Posted on: 2008-01-24 09:09

Hi zsh220824,

"this.getContentPane" returns a type of Container which is a parent class of JComponent as well as JPanel.

However, I don't see anything wrong syntatically here with your statement since you can do a strong type cast in Java (Please correct me if I am wrong).

This statment is basically get the contentPane from your JFrame and cast it to a JPanel and then reassign to a local variable which is named as contentPane.

Best Regards,
David

3.Re:contentPane = (JPanel) this.getContentPane() [Re: zsh220824]	Copy to clipboard
Posted by: zsh220824 Posted on: 2008-01-24 17:24 Mr.David,thank you for the reply.now I Learn SOME from you . I think that (JPanel) means the statement returns a JPanel,not a JComponent. Is it right?

4.Re:contentPane = (JPanel) this.getContentPane() [Re: zsh220824]	Copy to clipboard
Posted by: tzutolin Posted on: 2008-01-24 17:45 Hi zsh220824, The syntax () can be used as a type casting operator. So you can say that once we get the returned content pane and then we use (JPanel) to cast it to a JPanel. Best Regards, David