Question

我是Java Swing的新手，我不熟悉不同的布局管理器。

我想创建一个框架，其中有3个面板，顶部有一个菜单栏，如下所示：

我曾尝试过边框布局，但只有在没有菜单栏的情况下才有效。我应该使用什么布局管理器？

Answer 1

您应该使用GridLayout，您可以指定行数和列数并向其中添加元素，例如，如果您说要2行3列并开始向其添加元素，则首先将3行添加到第1行和第3行你将基本上创建一个表并从左到右填充单元格从上到下（默认情况下），所以在你的情况下，你需要3行和1列，这里有一个例子可以帮助你

public class GridLayoutTut {
private JFrame mainFrame;

public static void main(String[] args) {
    GridLayoutTut swingLayoutDemo = new GridLayoutTut();
    swingLayoutDemo.showStuff();
}

private void showStuff() {
    JMenuBar menuBar = new JMenuBar();
    JMenu menu;
    menu = new JMenu("My menu");
    menuBar.add(menu);

    mainFrame = new JFrame("Java SWING Examples");
    mainFrame.setSize(400, 400);
    JPanel comp = new JPanel();
    comp.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Pane 1"));
    JPanel comp2 = new JPanel();
    comp2.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Pane 2"));
    JPanel comp3 = new JPanel();
    comp3.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Pane 3"));

    mainFrame.setLayout(new GridLayout(3, 1)); // 3 rows 1 column
    mainFrame.add(comp);
    mainFrame.add(comp2);
    mainFrame.add(comp3);
    mainFrame.add(menuBar);
    mainFrame.setJMenuBar(menuBar);
    mainFrame.setVisible(true);
}

}

Answer 2

我建议创建一个自定义LayoutManager。

这是一个基本的，可以满足您的要求：

import java.awt.*;
import java.util.ArrayList;

public class MyLayoutManager implements LayoutManager {
    private final int TOOLBAR_HEIGHT = 30;
    private final int WINDOW_WIDTH = 800;
    private final int WINDOW_HEIGHT = 600;

    //  CONSTRAINTS  //
    public static final String TOOLBAR = "TOOLBAR";
    public static final String BODY = "BODY";

    private ArrayList<Component> toolbarComponents = new ArrayList<>();
    private ArrayList<Component> bodyComponents = new ArrayList<>();

    @Override   // Called when JFrame.add() is used  //
    public void addLayoutComponent(String constraints, Component component) {

        switch(constraints) {
            case "TOOLBAR": toolbarComponents.add(component);   break;
            case "BODY":    bodyComponents.add(component);      break;
        }
    }


    @Override   //  Sets the bounds for each component  //
    public void layoutContainer(Container parent) {
        //  Toolbar  //
        int currentWidth = 0;
        for(Component c : toolbarComponents) {
            int width = c.getPreferredSize().width;
            c.setBounds(currentWidth, 0, width, TOOLBAR_HEIGHT);
            currentWidth += width;
        }

        //  Body  //
        int currentHeight = TOOLBAR_HEIGHT;
        for(Component c : bodyComponents) {
            int height = (parent.getHeight()-TOOLBAR_HEIGHT)/bodyComponents.size();
            c.setBounds(0, currentHeight, parent.getWidth(), height);
            currentHeight += height;
        }
    }


    @Override
    public Dimension minimumLayoutSize(Container parent) {
        return preferredLayoutSize(parent);
    }


    @Override   //  Called when JFrame.pack() is called  //
    public Dimension preferredLayoutSize(Container parent) {
        return new Dimension(WINDOW_WIDTH,WINDOW_HEIGHT);
    }


    @Override
    public void removeLayoutComponent(Component comp) {}

}

然后像这样实现它：

    JFrame frame = new JFrame("Interface");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new MyLayoutManager());

    frame.add(new JButton("Menu"), MyLayoutManager.TOOLBAR);
    frame.add(new JButton("File"), MyLayoutManager.TOOLBAR);
    frame.add(new JButton("Settings"), MyLayoutManager.TOOLBAR);

    JTextArea area1 = new JTextArea();
    area1.setBorder(new TitledBorder("title 1"));

    JTextArea area2 = new JTextArea();
    area2.setBorder(new TitledBorder("title 2"));

    frame.add(area1, MyLayoutManager.BODY);
    frame.add(area2, MyLayoutManager.BODY);

    frame.pack();

    frame.setVisible(true);

Answer 3

JFrame类有一个setJMenuBar(JMenuBar)方法，以便JMenuBar自动显示在JFrame的顶部。

对于面板的布局，我建议使用GridBagLayout。通过添加3个不同GridBagConstraints的面板你可以调整JFrame中的尺寸/位置。有关这些内容的含义，您需要阅读GridBagConstraints的javadoc。

    JFrame frame = new JFrame("Test");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JMenuBar menuBar = new JMenuBar();
    JMenu menu1 = new JMenu("Menu1");
    JMenu menu2 = new JMenu("Menu2");
    JMenu menu3 = new JMenu("Menu3");
    menuBar.add(menu1);
    menuBar.add(menu2);
    menuBar.add(menu3);
    frame.add(menuBar);
    frame.setJMenuBar(menuBar);

    JPanel panel1 = new JPanel();
    panel1.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Panel 1"));
    JPanel panel2 = new JPanel();
    panel2.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Panel 2"));
    JPanel panel3 = new JPanel();
    panel3.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.BLACK), "Panel 3"));

    frame.setLayout(new GridBagLayout());
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.fill = GridBagConstraints.BOTH;
    gbc.weightx = 1;
    gbc.gridy = 0;
    gbc.weighty = 0.1;
    frame.add(panel1, gbc);
    gbc.gridy = 1;
    gbc.weighty = 0.3;
    frame.add(panel2, gbc);
    gbc.gridy = 2;
    gbc.weighty = 0.2;
    frame.add(panel3, gbc);

    frame.setSize(400, 400);
    frame.setVisible(true);

我应该使用3个面板和菜单栏的布局？

3 个答案: