Swing：如何将组件高度设置为容器的高度？

Question

我想让一个组件占据Container的maximumAvailableHeight。例如，在下面粘贴的代码中，我将根帧设置为 800,600。我只想设置该帧的高度/宽度（我不想尝试对其子项进行像素化）。如果我运行它，我会看到一个对齐错误的 UI。

首先，我想要一个面板（位于根框架内）占据框架的 100% 高度（在本例中为 800 像素减去绘制框架标题所需的小空间）。

其次，在面板内我有一个树和文本区域。我希望它们都占据 100% 的高度，让树占据 30%，textArea 占据 70% 的宽度（如果树扩展到 10 层，那么我可以使用 ScrollPane）。

了解这是在 HTML 中最容易实现的。只需说 height=100% 和 width 为 30% 等，我们就完成了。有人知道这是否可以在 Swing 中完成？ （我可以通过设置像素高度和布局管理器来实现这一点，但我正在寻找最简洁的解决方案来设置百分比高度和宽度。）

package com.ekanathk.logger.gui;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;

public class TestFrame extends JFrame {
    public TestFrame() {
        super("Top Frame");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        JPanel panel = new JPanel();
        JTree env = getEnvironmentTree();
        env.expandRow(0);
        panel.add(new JScrollPane(env));
        panel.add(new JTextArea("Some contents"));
        getContentPane().add(panel);
        setSize(800, 600);
        SwingUtil.centerComponentOnScreen(this);
        setVisible(true);
    }

    private JTree getEnvironmentTree() {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
        JTree tree = new JTree(root);
        DefaultMutableTreeNode one = new DefaultMutableTreeNode("One");
        root.add(one);
        one.add(new DefaultMutableTreeNode("under one.1"));
        one.add(new DefaultMutableTreeNode("under one.2"));
        root.add(new DefaultMutableTreeNode("two"));
        root.add(new DefaultMutableTreeNode("three"));
        return tree;
    }

    public static void main(String[] args) {
        new TestFrame();
    }
}

Answer 1

这使用 GridBagLayout 来做你想做的事。您可以使用组件的 setMinimumSize 和 setPreferedSize。

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;

public class TestFrame extends JFrame {
    private static final long serialVersionUID = 1L;

    public TestFrame()  {
        super("Top Frame");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        JPanel panel = new JPanel(new GridBagLayout());

        JTree env = getEnvironmentTree();
        env.expandRow(0);

        GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.BOTH;
        c.weightx=.7;
        c.weighty=1;

        c.gridx=0;
        c.gridy=0;
        c.gridheight=1;
        c.gridwidth=7;
        panel.add(new JScrollPane(env),c);

        c.weightx=.3;
        c.gridx=7;
        c.gridy=0;
        c.gridheight=1;
        c.gridwidth=GridBagConstraints.REMAINDER;
        panel.add(new JTextArea("Some contents"),c);

        add(panel);
        setSize(800, 600);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    private JTree getEnvironmentTree() {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
        JTree tree = new JTree(root);
        DefaultMutableTreeNode one = new DefaultMutableTreeNode("One");
        root.add(one);
        one.add(new DefaultMutableTreeNode("under one.1"));
        one.add(new DefaultMutableTreeNode("under one.2"));
        root.add(new DefaultMutableTreeNode("two"));
        root.add(new DefaultMutableTreeNode("three"));
        return tree;
    }

    public static void main(String[] args) {
        new TestFrame();
    }
}

Answer 2

有许多layout managers 可以实现这一点——GridLayout（1x1 网格）、GridBagLayout，也许还有 BorderLayout。

Answer 3

这是使用 SpringLayout 的另一种方法。我无法让 Spring.width 和 Spring.height 工作，所以我使用了更详细的方式

import java.awt.BorderLayout;
import java.awt.Color;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTree;
import javax.swing.Spring;
import javax.swing.SpringLayout;
import javax.swing.tree.DefaultMutableTreeNode;

public class TestFrame extends JFrame {
    private static final long serialVersionUID = 1L;

    public TestFrame()  {
        super("Top Frame");
        setDefaultCloseOperation(EXIT_ON_CLOSE);        
        SpringLayout layout = new SpringLayout();
        JTree env = getEnvironmentTree();
        env.expandRow(0);
        JPanel contentPane = new JPanel(layout);
        contentPane.setLayout(layout);
        JScrollPane treePane = new JScrollPane(env);
        JTextArea area = new JTextArea("Some contents");
        contentPane.add(treePane);
        contentPane.add(area);        
        setLayout(new BorderLayout());
        add(contentPane);
        setSize(800, 600);

        SpringLayout.Constraints  cons;
        cons = layout.getConstraints(treePane);
        cons.setX(Spring.constant(0));
        cons.setY(Spring.constant(0));
        cons.setWidth(Spring.scale(layout.getConstraint(SpringLayout.EAST, contentPane), .7f));
        cons.setHeight(layout.getConstraint(SpringLayout.SOUTH, contentPane));

        cons = layout.getConstraints(area);
        cons.setX(layout.getConstraint(SpringLayout.EAST, treePane));
        cons.setY(Spring.constant(0));
        cons.setWidth(Spring.scale(layout.getConstraint(SpringLayout.EAST, contentPane), .3f));
        cons.setHeight(layout.getConstraint(SpringLayout.SOUTH, contentPane));
        setPreferredSize(getSize());
        setLocationRelativeTo(null);
        pack();
        setVisible(true);
    }

    private JTree getEnvironmentTree() {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
        JTree tree = new JTree(root);
        DefaultMutableTreeNode one = new DefaultMutableTreeNode("One");
        root.add(one);
        one.add(new DefaultMutableTreeNode("under one.1"));
        one.add(new DefaultMutableTreeNode("under one.2"));
        root.add(new DefaultMutableTreeNode("two"));
        root.add(new DefaultMutableTreeNode("three"));
        return tree;
    }

    public static void main(String[] args) {
        new TestFrame();
    }
}