我打印简单值以使用简单的for循环附加JTextArea，当我运行它时，如果我在控制台输出中打印值，它就会正常运行...
但是如果我在文本区域附加JTextArea并打印值，则在整个程序运行后将它们全部附加。
public class SwingThread {
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SwingThread window = new SwingThread();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public SwingThread() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane scrollPane = new JScrollPane();
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
JTextArea textArea = new JTextArea();
scrollPane.setViewportView(textArea);
JButton btnNewButton = new JButton("New button");
scrollPane.setColumnHeaderView(btnNewButton);
btnNewButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent arg0)
{
try
{
for(int i = 0 ; i <= 5 ; i++)
{
textArea.append("Value "+i+"\n");
System.out.println("Value is" + i);
Thread.sleep(1000);
}
}
catch(Exception e)
{
System.out.println("Error : "+e);
}
}
});
}
}
我想逐个追加，但是在整个程序运行后附加了它。
答案 0 :(得分：6)
您的问题在于使用Thread.sleep，因为当您在Swing事件线程（或事件调度线程的EDT）上调用它时，它将使整个Swing事件线程进入休眠状态。当发生这种情况时，无法执行此线程的操作，包括绘制GUI（更新它）以及与用户交互，这将完全冻结您的GUI - 不好。当前情况下的解决方案是使用Swing Timer作为伪循环。 Timer在后台线程中创建一个循环，并保证其ActionPerformed方法中的所有代码都将在Swing事件线程上调用，这是必需的，因为我们不希望从该线程附加到JTextArea。
正如其他人已经注意到的那样，如果你想要做的就是在Swing中执行延迟重复动作，那么是的，使用这个Swing Timer。另一方面，如果您希望在Swing中运行长时间运行的代码，则此代码将再次阻止EDT并冻结您的程序。对于这种情况，请使用后台线程，例如SwingWorker提供的后台线程。有关详细信息，请查看Lesson: Concurrency in Swing。
如，
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
// delay between timer ticks: 1000
int timerDelay = 1000;
new Timer(timerDelay, new ActionListener() {
private int counter = 0;
@Override
public void actionPerformed(ActionEvent e) {
// timer's stopping condition
if (counter >= MAX_VALUE) { // MAX_VALUE is a constant int = 5
((Timer) e.getSource()).stop();
} else {
textArea.append("Value " + counter + "\n");
}
counter++; // increment timer's counter variable
}
}).start();
}
});
整件事：
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.*;
import javax.swing.*;
public class SwingThread2 {
protected static final int MAX_VALUE = 5; // our constant
private JFrame frame;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SwingThread2 window = new SwingThread2();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public SwingThread2() {
initialize();
}
private void initialize() {
frame = new JFrame();
// frame.setBounds(100, 100, 450, 300); // avoid this
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane scrollPane = new JScrollPane();
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
JTextArea textArea = new JTextArea(15, 40);
scrollPane.setViewportView(textArea);
JButton btnNewButton = new JButton("New button");
scrollPane.setColumnHeaderView(btnNewButton);
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
// delay between timer ticks: 1000
int timerDelay = 1000;
new Timer(timerDelay, new ActionListener() {
private int counter = 0;
@Override
public void actionPerformed(ActionEvent e) {
// timer's stopping condition
if (counter >= MAX_VALUE) { // MAX_VALUE is a constant int = 5
((Timer) e.getSource()).stop();
} else {
textArea.append("Value " + counter + "\n");
}
counter++; // increment timer's counter variable
}
}).start();
}
});
// better to avoid setting sizes but instead to
// let the components size themselves vis pack
frame.pack();
frame.setLocationRelativeTo(null);
}
}
仅供参考，以下是上述相同程序的示例，该程序使用SwingWorker执行长时间运行操作，然后使用此操作更新JProgressBar。工作者非常简单，只需使用while循环就可以通过有限的随机数推进计数器变量。然后它传输使用这个值来更新它自己的progress属性（一个只能从0到100的值，因此在其他情况下，需要对该值进行规范化以符合这一点）。我将一个PropertyChangeListener附加到worker，每当工作程序的进度值发生更改时，以及SwingWorker更改状态时（例如操作完成时），都会在Swing事件线程上通知。在后一种情况下，worker的StateValue变为StateValue.DONE。然后，侦听器相应地更新GUI。如果有任何问题，请询问。
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Random;
import java.util.concurrent.ExecutionException;
import javax.swing.*;
public class SwingThread2 {
protected static final int MAX_VALUE = 5; // our constant
private JFrame frame;
private JProgressBar progressBar = new JProgressBar();
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
SwingThread2 window = new SwingThread2();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public SwingThread2() {
initialize();
}
private void initialize() {
frame = new JFrame();
// frame.setBounds(100, 100, 450, 300); // avoid this
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane scrollPane = new JScrollPane();
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
JTextArea textArea = new JTextArea(15, 40);
scrollPane.setViewportView(textArea);
JButton btnNewButton = new JButton("New button");
scrollPane.setColumnHeaderView(btnNewButton);
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
// delay between timer ticks: 1000
int timerDelay = 1000;
new Timer(timerDelay, new ActionListener() {
private int counter = 0;
@Override
public void actionPerformed(ActionEvent e) {
// timer's stopping condition
if (counter >= MAX_VALUE) { // MAX_VALUE is a constant
// int = 5
((Timer) e.getSource()).stop();
} else {
textArea.append("Value " + counter + "\n");
}
counter++; // increment timer's counter variable
}
}).start();
}
});
progressBar.setStringPainted(true);
JPanel bottomPanel = new JPanel();
bottomPanel.setLayout(new BoxLayout(bottomPanel, BoxLayout.LINE_AXIS));
bottomPanel.add(new JButton(new MyAction("Press Me")));
bottomPanel.add(progressBar);
frame.getContentPane().add(bottomPanel, BorderLayout.PAGE_END);
// better to avoid setting sizes but instead to
// let the components size themselves vis pack
frame.pack();
frame.setLocationRelativeTo(null);
}
private class MyAction extends AbstractAction {
public MyAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
public void actionPerformed(ActionEvent e) {
progressBar.setValue(0);
setEnabled(false);
MyWorker myWorker = new MyWorker();
myWorker.addPropertyChangeListener(new WorkerListener(this));
myWorker.execute();
}
}
private class WorkerListener implements PropertyChangeListener {
private Action action;
public WorkerListener(Action myAction) {
this.action = myAction;
}
@Override
public void propertyChange(PropertyChangeEvent evt) {
if ("progress".equals(evt.getPropertyName())) {
int progress = (int) evt.getNewValue();
progressBar.setValue(progress);
} else if ("state".equals(evt.getPropertyName())) {
if (evt.getNewValue() == SwingWorker.StateValue.DONE) {
action.setEnabled(true);
@SuppressWarnings("rawtypes")
SwingWorker worker = (SwingWorker) evt.getSource();
try {
// always want to call get to trap and act on
// any exceptions that the worker might cause
// do this even though get returns nothing
worker.get();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
}
}
}
private class MyWorker extends SwingWorker<Void, Void> {
private static final int MULTIPLIER = 80;
private int counter = 0;
private Random random = new Random();
@Override
protected Void doInBackground() throws Exception {
while (counter < 100) {
int increment = random.nextInt(10);
Thread.sleep(increment * MULTIPLIER);
counter += increment;
counter = Math.min(counter, 100);
setProgress(counter);
}
return null;
}
}
}