有多个面板与滚动窗格

Question

我创建了两个面板和一个主面板。每个面板都包含一个非常大的图像，我希望它们都可以滚动以查看图像的其余部分。但是当我在主面板中添加两个面板并运行它时，第一个面板太大了，它覆盖了第二个面板。我如何为两个面板实现ScrollPane？

import java.awt.BorderLayout;
import javax.swing.*;

public class BoardFrame extends JFrame {

   JPanel mainPanel = new JPanel(new BorderLayout());

   JLabel jLabel = new JLabel();
   JPanel jPanelNorth = new JPanel();
   JScrollPane scrollPane = new JScrollPane();

   JLabel jLabel2 = new JLabel();
   JPanel jPanelSouth = new JPanel();
   JScrollPane scrollPane2 = new JScrollPane();

   public BoardFrame() {
      jLabel.setIcon(new ImageIcon("an image here"));
      jPanelNorth.add(jLabel);

      jLabel2.setIcon(new ImageIcon("an image here"));
      jPanelSouth.add(jLabel2);

      mainPanel.add(jPanelNorth, BorderLayout.NORTH);
      mainPanel.add(jPanelSouth, BorderLayout.SOUTH);

      add(mainPanel);


      //where would I use this?
      //scrollPane.setViewportView();

   }
}

Answer 1

  

每个面板包含非常大的图像＆gt;

//JPanel mainPanel = new JPanel(new BorderLayout());
JPanel mainPanel = new JPanel(new GridLayout(0, 1));

您可能希望使用GridLayout，以便每个滚动窗格占据一半帧，以便显示尽可能多的每个图像。

//JScrollPane scrollPane = new JScrollPane();
JScrollPane scrollPane2 = new JScrollPane(jPanelNorth);

使用滚动窗格的最简单方法是使用要显示的组件创建滚动窗格，滚动窗格会将组件添加到视口中。

  //mainPanel.add(jPanelNorth, BorderLayout.NORTH);
  mainPanel.add(scrollPane); // don't need the constraint when using GridLayout.

然后将scrollPane添加到主面板，因为滚动窗格包含带有图像的面板。

Answer 2

似乎使用网格布局比使用边框布局要好得多，在这种情况下：

import java.awt.BorderLayout;
import javax.swing.*;

public class BoardFrame extends JFrame {
//1. use GridLayout with 2 rows and 1 column .
JPanel mainPanel = new JPanel(new GridLayout(2,1));

JLabel jLabel = new JLabel();
JPanel jPanelNorth = new JPanel();
JScrollPane scrollPane = new JScrollPane();

JLabel jLabel2 = new JLabel();
JPanel jPanelSouth = new JPanel();
JScrollPane scrollPane2 = new JScrollPane();

public BoardFrame() {
  jLabel.setIcon(new ImageIcon("an image here"));
  jPanelNorth.add(jLabel);

  jLabel2.setIcon(new ImageIcon("an image here"));
  jPanelSouth.add(jLabel2);


  //2.you should place .setViewportView() here :
  scrollPane.setViewportView(jPanelNorth);
  scrollPane2.setViewportView(jPanelSouth);


  mainPanel.add(scrollPane);//is in the top ("North")
  mainPanel.add(scrollPane2);//next ("South")

  //3.use setContentPane instead of add() 
  setContentPane(mainPanel);




}
}