java-使用ScrollPane自动滚动JTextArea？
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内容图文
我正在尝试建立一个动态日志窗口(基本上是一个自动滚动的jtext区域).
我遇到的问题是,尽管我在文本区域中打印了500行,但显示如下：
下面有我的代码：
import java.awt.Dimension;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.text.DefaultCaret;
public class Main {
private static JFrame mainFrame;
public static void main(String args[]) {
mainFrame = new JFrame();
mainFrame.setSize(500, 500);
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ControlPanel cp = new ControlPanel();
mainFrame.add(cp);
mainFrame.setVisible(true);
}
}
class ControlPanel extends JPanel {
private JButton resetButton = new JButton("Reset");
private JPanel logPanel = new JPanel();
private JLabel actionLogsLabel = new JLabel("Action Log");
private JLabel pointsLogsLabel = new JLabel("Points Log");
private JTextArea actionLog = new JTextArea();
private JTextArea pointsLog = new JTextArea();
private JScrollPane actionScroll;
private JScrollPane pointsScroll;
public ControlPanel() {
init();
this.add(resetButton);
this.add(logPanel);
}
private void init() {
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
this.setAlignmentX(LEFT_ALIGNMENT);
this.logPanel.setLayout(new BoxLayout(logPanel, BoxLayout.Y_AXIS));
this.logPanel.setAlignmentX(LEFT_ALIGNMENT);
actionLog.setPreferredSize(new Dimension(500, 300));
actionLog.setMaximumSize(actionLog.getPreferredSize());
actionLog.setEditable(false);
actionLog.setWrapStyleWord(true);
DefaultCaret caret = (DefaultCaret) actionLog.getCaret();
caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
pointsLog.setPreferredSize(new Dimension(500, 300));
pointsLog.setMaximumSize(pointsLog.getPreferredSize());
pointsLog.setEditable(false);
pointsLog.setWrapStyleWord(true);
pointsScroll = new JScrollPane(pointsLog, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
actionScroll = new JScrollPane(actionLog, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
logPanel.add(actionLogsLabel);
logPanel.add(actionScroll);
for(int i = 0; i < 500; i++) {
actionLog.setText(actionLog.getText() + "Line: " + i + "\n");
}
logPanel.add(pointsLogsLabel);
logPanel.add(pointsScroll);
}
}
希望有更多Swing经验的人可以花时间为我指出正确的方法.
解决方法:
永远不要这样做：
actionLog.setPreferredSize(new Dimension(500, 300));
由于这样做会人为地限制JTextArea的大小,从而导致当前使您烦恼的效果.另请注意,通常最好避免在任何内容上设置首选大小.
而是设置JTextARea的列数和行数.这可以通过setter方法或通过简单的构造函数调用来完成：JTextArea myTextArea = new JTextArea(rows,columns);
顺便说一句：我想知道JList是否对您更好.
MCVE示例：
import javax.swing.*;
import javax.swing.text.DefaultCaret;
public class Main2 {
private static void createAndShowGUI() {
JPanel mainPanel = new ControlPanel();
JFrame frame = new JFrame("Main2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
class ControlPanel extends JPanel {
private static final int LOG_ROWS = 15;
private static final int LOG_COLS = 40;
private JButton resetButton = new JButton("Reset");
private JPanel logPanel = new JPanel();
private JLabel actionLogsLabel = new JLabel("Action Log");
private JLabel pointsLogsLabel = new JLabel("Points Log");
private JTextArea actionLog = new JTextArea();
private JTextArea pointsLog = new JTextArea();
private JScrollPane actionScroll;
private JScrollPane pointsScroll;
public ControlPanel() {
init();
this.add(resetButton);
this.add(logPanel);
}
private void init() {
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
this.setAlignmentX(LEFT_ALIGNMENT);
this.logPanel.setLayout(new BoxLayout(logPanel, BoxLayout.Y_AXIS));
this.logPanel.setAlignmentX(LEFT_ALIGNMENT);
// !! actionLog.setPreferredSize(new Dimension(500, 300));
// !! actionLog.setMaximumSize(actionLog.getPreferredSize());
actionLog.setRows(LOG_ROWS); // !!
actionLog.setColumns(LOG_COLS); // !!
actionLog.setEditable(false);
actionLog.setWrapStyleWord(true);
DefaultCaret caret = (DefaultCaret) actionLog.getCaret();
caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
// !! pointsLog.setPreferredSize(new Dimension(500, 300));
// !! pointsLog.setMaximumSize(pointsLog.getPreferredSize());
pointsLog.setRows(LOG_ROWS); // !!
pointsLog.setColumns(LOG_COLS); // !!
pointsLog.setEditable(false);
pointsLog.setWrapStyleWord(true);
pointsScroll = new JScrollPane(pointsLog,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
actionScroll = new JScrollPane(actionLog,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
logPanel.add(actionLogsLabel);
logPanel.add(actionScroll);
for (int i = 0; i < 500; i++) {
actionLog.setText(actionLog.getText() + "Line: " + i + "\n");
}
logPanel.add(pointsLogsLabel);
logPanel.add(pointsScroll);
}
}
编辑
嵌套布局和JLists的示例：
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.*;
public class Main2B {
private static void createAndShowGUI() {
ControlPanel2B controlPanel = new ControlPanel2B();
controlPanel.setBorder(BorderFactory.createEtchedBorder());
JPanel mainPanel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
mainPanel.add(controlPanel, gbc);
JFrame frame = new JFrame("Main2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
@SuppressWarnings("serial")
class ControlPanel2B extends JPanel {
private static final int LOG_ROWS = 15;
private static final int LIST_WIDTH = 500;
private JButton resetButton = new JButton("Reset");
private JPanel logPanel = new JPanel();
private JLabel actionLogsLabel = new JLabel("Action Log");
private JLabel pointsLogsLabel = new JLabel("Points Log");
private DefaultListModel<String> actionLogListModel = new DefaultListModel<>();
private JList<String> actionLogList = new JList<String>(actionLogListModel);
private DefaultListModel<String> pointsLogListModel = new DefaultListModel<>();
private JList<String> pointsLogList = new JList<String>(pointsLogListModel);
private JScrollPane actionScroll;
private JScrollPane pointsScroll;
public ControlPanel2B() {
init();
this.add(resetButton);
this.add(logPanel);
}
private void init() {
actionLogList.setVisibleRowCount(LOG_ROWS);
pointsLogList.setVisibleRowCount(LOG_ROWS);
actionLogList.setFixedCellWidth(LIST_WIDTH);
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
this.setAlignmentX(LEFT_ALIGNMENT);
this.logPanel.setLayout(new BoxLayout(logPanel, BoxLayout.Y_AXIS));
this.logPanel.setAlignmentX(LEFT_ALIGNMENT);
pointsScroll = new JScrollPane(pointsLogList,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
actionScroll = new JScrollPane(actionLogList,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
logPanel.add(actionLogsLabel);
logPanel.add(actionScroll);
for (int i = 0; i < 500; i++) {
actionLogListModel.addElement("Line: " + i);
}
logPanel.add(pointsLogsLabel);
logPanel.add(pointsScroll);
}
}
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