Java ScrollPane/JPanel

Question

我有一个包含多个Object(自定义类扩展Jpanel)对象的JPanel。JPanel有一个7行1列的网格布局。我试图将一个包含7个对象的JPanel添加到另一个JScrollPane中，这样我就可以滚动查看所有的对象，但它做了一些奇怪的事情。无论JPanel中有多少对象，滚动条都不会显示。有什么想法吗？提前谢谢。

    import java.awt.BorderLayout;
    import java.awt.Color;
    import java.awt.Dimension;
    import java.awt.GridLayout;

    import javax.swing.BorderFactory;
    import javax.swing.JFrame;
    import javax.swing.JLabel;
    import javax.swing.JPanel;
    import javax.swing.JScrollBar;
    import javax.swing.JScrollPane;
    import javax.swing.ScrollPaneLayout;    

    public class Main {
    @SuppressWarnings("deprecation")
    public static void main(String[] args) {
          JFrame frame = new JFrame("Test");
          frame.setLayout(new BorderLayout());

          JLabel title = new JLabel("Game", JLabel.CENTER);
          title.setPreferredSize(new Dimension(60,60));
          title.setBorder(BorderFactory.createLineBorder(Color.black,5));
          frame.add(title,BorderLayout.NORTH);

          frame.setSize(850,480);
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

          Grid g = new Grid(); 

          JPanel jp = new JPanel();
          jp.setLayout(new GridLayout(1,3));
          jp.add(g);

          JPanel test = new JPanel();         


          test.setLayout(new GridLayout(7,1));

          test.add(p1);
          test.add(p2);
          test.add(p3);
          test.add(p4);
          test.add(p5);
          test.add(p6);
          test.add(p7);
          JScrollPane jsp = new JScrollPane(test);
          jsp.setViewportView(test);
          jsp.getVerticalScrollBar().setUnitIncrement(50);
          jsp.setCorn
          jsp.setVerticalScrollBarPolicy(22);               

          jp.add(jsp,BorderLayout.EAST);    

          frame.add(jp);
          frame.setLocationRelativeTo(null);
          frame.setVisible(true);
          }      
      }

Answer 1

jp JPanel使用JPanel的默认FlowLayout，这可能会阻止您调整JScrollPane的大小并查看它是否工作正常。为什么不将JScrollPane添加到JFrame的contentPane中，或者让jp使用BorderLayout？此外，您也不需要设置JScrollPane的测试，因为您已经通过将“viewportView”传递给它的构造函数来执行此操作。

Answer 2

你的代码不能编译。请看下面的代码。它可以垂直和水平滚动。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

class MyPanel extends JPanel {
    MyPanel(Color c) {
        setBackground(c);
    }
}

public class Test {
    public static void main(String[] args) {
        JPanel panel = new JPanel();
        // the size of this panel is larger than the frame
        panel.setPreferredSize(new Dimension(500, 2000));
        panel.setLayout(new GridLayout(7, 1));
        // add 7 sub panels
        panel.add(new MyPanel(Color.magenta));
        panel.add(new MyPanel(Color.cyan));
        panel.add(new MyPanel(Color.blue));
        panel.add(new MyPanel(Color.green));
        panel.add(new MyPanel(Color.yellow));
        panel.add(new MyPanel(Color.orange));
        panel.add(new MyPanel(Color.red));

        JScrollPane scroll = new JScrollPane(panel);
        scroll.setViewportView(panel);
        scroll.getVerticalScrollBar().setUnitIncrement(50);

        JFrame frame = new JFrame("Test");
        frame.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(scroll);
        frame.setVisible(true);
    }
}