我有一个Runnable，它从外部调用的exe读取Console输出（见下文），并将其写入日志文件和JTextArea。
但是我的Runnable在exe完全完成之前不会在JTextArea中显示控制台输出。如何在打印控制台输出时将其打印出来？
简短简洁代码示例如下：
//主
import java.awt.*;
import java.io.IOException;
import javax.swing.*;
public class Example extends JFrame {
private static final long serialVersionUID = 1L;
public static int maxX, maxY;
public static JTextArea ta = new JTextArea(20, 60);//For LOG display window
public static void main(String args[] ) throws IOException
{
new Example();
}
public Example() {
this.setTitle("Example");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//MAIN Panel
final JPanel main = new JPanel();
JButton RunButton = button.run(main);
main.add(RunButton);
Container container = getContentPane();
container.add(main);
this.pack();
this.setVisible(true);
}
}
//按钮动作侦听器
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;
public class button {
public static JButton run( final JPanel parent ) {
JButton RunButton = new JButton();
RunButton.setText("Start!");
RunButton.addActionListener(
new ActionListener()
{
public void actionPerformed( ActionEvent event)
{
try
{
//Set up LOG Display
JDialog dialog = new JDialog((JFrame)null, "Working...");
JPanel temp_panel = new JPanel();
temp_panel.add(new JScrollPane(Example.ta));
dialog.getContentPane().add(temp_panel);
dialog.pack();
dialog.setVisible(true);
//Build the Command
ArrayList<String> command = new ArrayList<String>();
command.add("ping");
command.add("127.0.0.1");
//Start the process
Process p = new ProcessBuilder(command).start();
//Starts LOG display capture in separate thread
SwingUtilities.invokeLater(new execute(p));
//Wait for call to complete
p.waitFor();
}
catch(Exception err)
{
JOptionPane.showMessageDialog( parent, "Error Executing Run!", "Warning", JOptionPane.ERROR_MESSAGE );
}
}//end ActionPerformed
});
return RunButton;
}
}
//可运行
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class execute implements Runnable {
String line;
Process p;
public execute ( Process process ) {
p = process;
}
public void run() {
try {
//Read Process Stream Output and write to LOG file
BufferedReader is = new BufferedReader( new InputStreamReader(p.getInputStream()));
while ( (line = is.readLine()) != null ) {
Example.ta.append(line + "\n");
}
System.out.flush();
} catch(Exception ex) { ex.printStackTrace(); }
}
}
答案 0 :(得分：3)
也许是因为你不尊重Swing's threading policy。所有对swing组件的访问都必须在事件派发线程中完成。因此，您的runnable应该使用SwingUtilities.invokeLater来更新EDT中的文本区域，而不是在单独的线程中。
编辑：正如他在评论中提到的那样：JTextArea.append是线程安全的，所以这里并不是绝对需要的。不过，我仍然会这样做，因为如果文本区域的附加被任何其他Swing交互替换或补充，那么它将不再是线程安全的。
也可能是外部进程没有发送任何换行符，这使得readLine阻塞直到找到一个或者到达通信结束。
答案 1 :(得分：3)
只是为了帮助矿工 - 下面是一个完整的简约（省略了一切并非绝对必要）的例子，确实在我的上下文中有效：每行在textArea中显示为read。它基本上使用了Justin建议的SwingWorker，并为了清晰起见重新安排了一些东西。
public class ProcessExample {
public static class ProcessWorker extends SwingWorker<Void, String> {
private JTextArea ta;
private List<String> process;
public ProcessWorker(List<String> command, JTextArea ta) {
this.process = command;
this.ta = ta;
}
@Override
protected Void doInBackground() throws Exception {
Process p = new ProcessBuilder(process).start();
// Read Process Stream Output and write to LOG file
BufferedReader is = new BufferedReader(new InputStreamReader(
p.getInputStream()));
String line;
while ((line = is.readLine()) != null) {
publish(line);
}
is.close();
return null;
}
@Override
protected void process(List<String> chunks) {
for (String string : chunks) {
ta.append(string + "\n");
}
}
}
private void startProcess(JTextArea ta) {
ArrayList<String> command = new ArrayList<String>();
command.add("ping");
command.add("127.0.0.1");
new ProcessWorker(command, ta).execute();
}
private JComponent getContent() {
JPanel main = new JPanel(new BorderLayout());
final JTextArea ta = new JTextArea(20, 60);
main.add(new JScrollPane(ta));
Action action = new AbstractAction("Start!") {
@Override
public void actionPerformed(ActionEvent e) {
startProcess(ta);
}
};
main.add(new JButton(action), BorderLayout.SOUTH);
return main;
}
public static void main(String args[]) throws IOException {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frame = new JFrame("Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new ProcessExample().getContent());
frame.pack();
frame.setVisible(true);
}
});
}
}
答案 2 :(得分：1)
您可以使用SwingWorker尝试相同的逻辑。您可以扩展此类，而不是实现runnable。它可以将你的文本区域作为参数，你可以发布数据，而不必处理SwingUtils.invokeLater，这很容易...
尝试：
public class execute extends javax.swing.SwingWorker {
String line;
Process p;
JTextArea jta;
File f = new File( properties.prop.getProperty( "LOG_FILE_DIR" ) + "\\PartGen.log");
public execute ( Process process , JTextArea jta ) {
p = process;
this.jta = jta;
}
//implements a method in the swingworker
public void doInBackground() throws Exception {
//Read Process Stream Output and write to LOG file
BufferedReader is = new BufferedReader( new InputStreamReader(p.getInputStream()));
while ( (line = is.readLine()) != null ) {
osfile.writeline(line, f);
publish(new String(line + "\n"));
}
System.out.flush();
return null;
}
//This will happen on the UI Thread.
public void process(List lines){
for(Object o : lines){
jta.append((String)o);
}
}
public void done(){
try{
get();
//You will get here if everything was OK. So show a popup or something to signal done.
}catch(Exception ex){
//this is where your IO Exception will surface, should you have one.
}
}
}
另外，在你的调用代码中，我假设它位于你的ui某处：
Process p = new ProcessBuilder(command).start();
execute ex = new execute( p , yourTextArea);
ex.execute();
我没有尝试编译这个，所以你可能需要检查API，但希望它会给你一个如何做的要点。
答案 3 :(得分：0)
问题不在于线程没有捕获数据，而是JTextArea只是没有刷新。 repaint()，revalidate()和updateUI()未刷新JTextArea，但以下内容确实如此：
Example.ta.update(Example.ta.getGraphics());
答案 4 :(得分：0)
这种情况下的问题是waitFor：
p.waitFor();
这会导致Button Action Listener等待该点，直到该过程完成。