java - 如何将带有组件的 JPanel 对象添加到 JFrame

Question

我想将 JPanel 类型的对象添加到 JFrame。

我正在尝试这个，但是没有添加 Jpanel。

想法是:向 P2 添加一个 P5，该 P5 具有类 P5 中定义的组件。

会发生什么？，我不想在类 First_view 中创建所有 JPanel，因为代码会很困惑。

代码:

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

public class First_view extends JFrame {

    Container Frame;

    public First_view() {
        super("title");
        Frame = this.getContentPane();
        Frame.setLayout(new BorderLayout());

        Frame.add((new P2()), BorderLayout.WEST);

        setSize(900, 500);
        setLocationRelativeTo(null);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
}

class P2 extends JPanel {

    public P2() {
        this.setLayout(new BorderLayout());

        add((new P5()), BorderLayout.NORTH);
    }
}

class P5 extends JPanel {

    JScrollPane informacion = new JScrollPane(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
    JTextArea T1 = new JTextArea();

    public P5() {
        setLayout(new FlowLayout());
        setBorder(BorderFactory.createEmptyBorder(20, 10, 0, 0));
        add(setInformacion());
    }

    private JScrollPane setInformacion() {
        T1.append("Information, bla bla bla");

        T1.setEditable(false);
        T1.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        T1.setLineWrap(true);
        informacion.add(T1);
        informacion.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        return informacion;
    }
}

图片:

Answer 1

要在 JScrollPane 中显示的组件应该不 添加，而是使用 setViewportView。

private JScrollPane setInformacion() {
    T1.append("Information, bla bla bla");
    ...

    informacion.setViewportView(T1);

    ...
    informacion.setBorder(BorderFactory.createLineBorder(Color.BLACK));
    return informacion;
}

观察:传递给 JScrollPane 构造函数的参数顺序错误，即 vertical police 在前:

JScrollPane informacion = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
                                          JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

编辑:正如安德鲁评论的那样，扩展一个类只是为了使用它(JFrame、JPanel)并不是一个好主意。例如，我尽量不对您的原始流程进行太多更改: 包 cfh.test;

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


public class FirstView {

    private JFrame frame;
    private JTextArea informacionText;  // not sure if that is needed as field

    public FirstView() {
        informacionText = new JTextArea();
        informacionText.setEditable(false);
        informacionText.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        informacionText.setLineWrap(true);
        informacionText.append("Information, bla bla bla");


        JScrollPane scrollPane = new JScrollPane(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
                                                 JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        scrollPane.setViewportView(informacionText);


        JPanel infoPanel = new JPanel();
        infoPanel.setLayout(new FlowLayout());
        infoPanel.add(scrollPane);


        JPanel leftPanel = new JPanel();
        leftPanel.setLayout(new BorderLayout());
        leftPanel.add(infoPanel, BorderLayout.NORTH);
        // TODO consider moving above code to an own method returning the left panel

        frame = new JFrame("title");

        frame.setLayout(new BorderLayout());
        frame.add(leftPanel, BorderLayout.WEST);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(900,500);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}