Question

我有一个包含JTextArea的JScrollPane。当窗口最小化然后恢复时，JScrollPane将自行折叠。请注意，只有当JTextArea中的文本超出JTextArea的给定宽度和/或高度（即，出现水平或垂直滚动条）时，才会发生此挤压。

这里提出这个问题：JScrollpane loses size after minimize提出了同样的问题，但除了向JScrollPane添加weightx，weighty和fill约束之外，问题永远不会得到解决，我已经开始这样了。

以下是演示此问题的简化示例。在窗口最小化和恢复后，如何让JScrollPane维持其大小？

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.ExecutionException;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.border.EtchedBorder;

public class GUITest implements ActionListener {

    JButton button = new JButton("Button");
    JTextArea textArea = new JTextArea();
    SwingWorker<String, String> mySwingWorker = null;

    public static void main(String[] args) throws IOException {
        GUITest tracer = new GUITest();
    }

    public GUITest() throws IOException {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    createAndShowGUI();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public void createAndShowGUI() throws IOException {
        JFrame frame = new JFrame("GUI Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new GridBagLayout());
        GridBagConstraints mainPanelConstraints = new GridBagConstraints();
        mainPanelConstraints.gridx = 0;
        mainPanelConstraints.gridy = 0;
        mainPanelConstraints.fill = GridBagConstraints.BOTH;
        button.addActionListener(this);
        mainPanel.add(button, mainPanelConstraints);
        mainPanelConstraints.gridx = 0;
        mainPanelConstraints.gridy = 1;
        mainPanelConstraints.fill = GridBagConstraints.BOTH;
        mainPanel.add(buildTextAreaPanel(), mainPanelConstraints);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setVisible(true);
    }

    private JPanel buildTextAreaPanel() {
        JPanel textAreaPanel = new JPanel();
        textAreaPanel.setLayout(new GridBagLayout());
        GridBagConstraints textAreaPanelConstraints = new GridBagConstraints();
        textAreaPanel.setBorder(BorderFactory.createTitledBorder(new EtchedBorder(EtchedBorder.RAISED), "TextArea"));
        textArea.setColumns(30);
        textArea.setRows(15);
        textArea.setEditable(false);
        JScrollPane textAreaScrollPane = new JScrollPane(textArea);
        textAreaScrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        textAreaScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
        textAreaPanelConstraints.gridx = 0;
        textAreaPanelConstraints.gridy = 0;
        textAreaPanelConstraints.weightx = 1.0;
        textAreaPanelConstraints.weighty = 1.0;
        textAreaPanelConstraints.fill = GridBagConstraints.BOTH;
        textAreaPanel.add(textAreaScrollPane, textAreaPanelConstraints);
        return textAreaPanel;
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button) {
            mySwingWorker = new MySwingWorker();
            mySwingWorker.execute();
        }
    }

    private class MySwingWorker extends SwingWorker<String, String> {
        public String doInBackground() throws Exception {
            for (int i = 0; i < textArea.getRows(); i++) {
                publish("text\n");
            }
            publish("more text\n");

            return "Done.";
        }
        public void process(List<String> chunks) {
            for (String msg : chunks) {
                textArea.append(msg);
            }
        }   
        public void done() {
            try {
                String msg = get();
                textArea.append("\n" + msg);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }

    }

}

Answer 1

您需要在两种布局中设置weightx和weighty。在createAndShowGui中，在添加文本区域面板之前将mainPanelConstraints.weightx和mainPanelConstraints.weighty设置为1.

Answer 2

将父容器（内容窗格）的布局设置为FlowLayout

...
frame.getContentPane().setLayout(new FlowLayout());
frame.getContentPane().add(mainPanel);
...

Answer 3

我通过删除所有GridBagLayouts并将其替换为BorderLayouts来解决此特定代码示例中的收缩问题。我不知道为什么JScrollPane会像你在使用GridBagLayout时发现的那样做出反应。

从类构造函数启动Event Dispatch线程我感到非常不舒服。我将SwingUtilities invokeLater移动到main方法中。

无论如何，这是代码。

package com.ggl.testing;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.List;
import java.util.concurrent.ExecutionException;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
import javax.swing.border.EtchedBorder;

public class JScrollPaneTest implements ActionListener {

    JButton button = new JButton("Button");
    JTextArea textArea = new JTextArea();
    SwingWorker<String, String> mySwingWorker = null;

    public static void main(String[] args) throws IOException {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                try {
                    new JScrollPaneTest().createAndShowGUI();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });

    }

    public JScrollPaneTest() throws IOException {

    }

    public void createAndShowGUI() throws IOException {
        JFrame frame = new JFrame("JScrollPane Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(true);

        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        mainPanel.add(button, BorderLayout.NORTH);
        mainPanel.add(buildTextAreaPanel(), BorderLayout.CENTER);

        button.addActionListener(this);

        frame.add(mainPanel, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

    private JPanel buildTextAreaPanel() {
        JPanel textAreaPanel = new JPanel();
        textAreaPanel.setLayout(new BorderLayout());
        textAreaPanel.setBorder(BorderFactory.createTitledBorder(
                new EtchedBorder(EtchedBorder.RAISED), "TextArea"));

        textArea.setColumns(30);
        textArea.setRows(15);
        textArea.setEditable(false);

        JScrollPane textAreaScrollPane = new JScrollPane(textArea);

        textAreaPanel.add(textAreaScrollPane, BorderLayout.CENTER);
        return textAreaPanel;
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button) {
            mySwingWorker = new MySwingWorker();
            mySwingWorker.execute();
        }
    }

    private class MySwingWorker extends SwingWorker<String, String> {
        public String doInBackground() throws Exception {
            for (int i = 0; i < textArea.getRows(); i++) {
                publish("text\n");
            }
            publish("more text\n");

            return "Done.";
        }

        public void process(List<String> chunks) {
            for (String msg : chunks) {
                textArea.append(msg);
            }
        }

        public void done() {
            try {
                String msg = get();
                textArea.append("\n" + msg);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }

    }

}

JScrollPane窗口缩小/折叠最小化

3 个答案: