JScrollPane问题

Question

我用滚动窗格创建了一个程序，但它无效。请查看源代码：

JInfoView.java

package view;
import javax.swing.*;
import java.util.*;
import java.awt.*;
public class JInfoView extends JPanel {
    private JButton button = new JButton("ADD");
    private JButton buttonDelete = new JButton("DEL");
    private JTextField input = new JTextField("Text", 5);
    private JLabel label = new JLabel("Test");
    public JInfoView() {
        this.setLayout(new FlowLayout());
        this.add(button);
        this.add(buttonDelete);
        this.add(input);
        this.add(label);
    }
}

JMainView.java

package view;
import java.awt.*;
import javax.swing.*;
import java.util.*;
import view.JInfoView;

public class JMainView extends JFrame {
    private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
    private JScrollPane scrollPane = new JScrollPane(mypanel);
    public JMainView() {
        super("Simple Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = this.getContentPane();
        container.setLayout(new FlowLayout());
        container.add(scrollPane);

        scrollPane.setVisible(true);
        scrollPane.setAutoscrolls(true); 

        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());       
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView()); 
        mypanel.add(new JInfoView());
    }

    public static void main(String[] args) {
        JMainView app = new JMainView();
        app.setVisible(true);
    }
}

我读过一个教程说：

//In a container that uses a BorderLayout:
textArea = new JTextArea(5, 30);
...
JScrollPane scrollPane = new JScrollPane(textArea);
...
setPreferredSize(new Dimension(450, 110));
...
add(scrollPane, BorderLayout.CENTER);

我已经完成了相同的步骤，

private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
private JScrollPane scrollPane = new JScrollPane(mypanel);

然后添加了scrollpane：

container.add(scrollPane);

哪里出错？ 编辑： 问题是滚动窗格不起作用。我在mypanel中添加了许多JInfoView， 但滚动不起作用..

Answer 1

如果JScrollPane位于CENTER的{​​{1}}，似乎可行。 E.G。

BorderLayout

Answer 2

您忘记添加scrollPane.setPreferredSize这样的电话：

public class JMainView extends JFrame {
    private JPanel mypanel = new JPanel(new GridLayout(0, 1, 30, 50));
    private JScrollPane scrollPane = new JScrollPane(mypanel);
    public JMainView() {
        super("Simple Example");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container container = this.getContentPane();
        container.setLayout(new FlowLayout());
        container.add(scrollPane);

        scrollPane.setVisible(true);
        scrollPane.setAutoscrolls(true);
        scrollPane.setPreferredSize(new Dimension(300, 400)); //========== this was missed

        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        mypanel.add(new JInfoView());
        this.pack();
    }

    public static void main(String[] args) {
        JMainView app = new JMainView();
        app.setVisible(true);
    }
}