Java “Container c=getContentPane();”的目的是什么？在摇摆？
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What is the purpose of "Container c=getContentPane();" in Swing?
提问by jaffar
import java.awt.*;
import javax.swing.*;
public class
import javax.swing.*;
import java.awt.*;
import javax.swing.tree.*;
import javax.swing.event.*;
/*<applet code="JT.class" width=200 height=300>
</applet>*/
public class JT extends JApplet {
JTree tree;
JTextField box;
Object nodeInfo;
String node1;
public void init() {
Container c=getContentPane();
c.setLayout(new BorderLayout());
DefaultMutableTreeNode topNode=new DefaultMutableTreeNode("qiscet");
DefaultMutableTreeNode cou=new DefaultMutableTreeNode("Courses");
DefaultMutableTreeNode mca=new DefaultMutableTreeNode("MCA");
DefaultMutableTreeNode mba=new DefaultMutableTreeNode("MBA");
DefaultMutableTreeNode tech=new DefaultMutableTreeNode("B.tech");
topNode.add(cou);
cou.add(mca);
cou.add(mba);
cou.add(tech);
DefaultMutableTreeNode manage=new DefaultMutableTreeNode("Management");
DefaultMutableTreeNode ac=new DefaultMutableTreeNode("Accounts");
DefaultMutableTreeNode sp=new DefaultMutableTreeNode("Sports");
DefaultMutableTreeNode lib=new DefaultMutableTreeNode("Library");
topNode.add(manage);
manage.add(ac);
manage.add(sp);
manage.add(lib);
tree=new JTree(topNode);
c.add(tree,BorderLayout.NORTH);
box=new JTextField("",80);
c.add(box,BorderLayout.SOUTH);
}
}
My question is without using "Container c=getContentPane();" i am getting correct output .How it is possible?What is the reason for this?
我的问题是不使用“Container c=getContentPane();” 我得到了正确的输出。怎么可能？这是什么原因？
回答by TofuBeer
To begin with Swing made you use getContentPane() for things like add() and setLayout() to make you realize that there were different layers. After a while I guess they conceded that it was a pain so they had the getContentPane() called internally so you didn't have to anymore.
Swing 开始让您使用 getContentPane() 来处理诸如 add() 和 setLayout() 之类的事情，让您意识到存在不同的层。过了一会儿，我猜他们承认这很痛苦，因此他们在内部调用了 getContentPane()，因此您不必再这样做了。
Lastly, after seven years, we've made jFrame.add equivalent to jFrame.getContentPane().add()
最后，七年后，我们使 jFrame.add 等同于 jFrame.getContentPane().add()
And here is a link to the rationale behind the original reason.
