我正在制作一个运行几个cmd命令的程序（USMT和文件传输）
它工作正常，但我只在完成操作后才从文本框中的cmd获取最后一行。我想让它打印cmd实时输出的内容。
public void load() throws IOException {
ProcessBuilder builder = new ProcessBuilder(
"cmd.exe", "/c", "cd \"C:\\usmt\" && loadstate.bat");
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while (true) {
line = r.readLine();
if (line == null) { break; }
cOut.setText(line);
System.out.println(line);
}
}
答案 0 :(得分：3)
问题的根本原因是您阻止了事件调度线程，这阻止了UI在命令执行之后才更新。
Swing是一个单线程框架，这意味着您不应该在EDT的上下文中执行阻塞或长时间运行的代码。 Swing也不是线程安全的，这意味着你永远不应该从EDT的上下文之外修改UI的状态。
有关详细信息，请参阅Concurrency in Swing
要解决此问题，您有两个基本选项。您可以使用Thread，但是您有责任确保将UI的任何和所有更新同步到EDT的上下文，或者您可以使用SwingWorker，例如......
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.ExecutionException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Runner {
public static void main(String[] args) {
new Runner();
}
public Runner() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea ta;
public TestPane() {
setLayout(new BorderLayout());
ta = new JTextArea(25, 80);
add(new JScrollPane(ta));
JButton execute = new JButton("Make it so");
execute.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
execute.setEnabled(false);
CommandWorker worker = new CommandWorker(ta, "cmd.exe", "/c", "cd \"C:\\usmt\" && loadstate.bat");
worker.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
switch (evt.getPropertyName()) {
case "state":
SwingWorker work = (SwingWorker) evt.getSource();
switch (worker.getState()) {
case DONE: {
try {
worker.get();
} catch (InterruptedException | ExecutionException ex) {
ex.printStackTrace();;
JOptionPane.showMessageDialog(TestPane.this, "Execution of command failed: " + ex.getMessage());
} finally {
execute.setEnabled(true);
}
}
break;
}
break;
}
}
});
worker.execute();
}
});
add(execute, BorderLayout.SOUTH);
}
}
public static class CommandWorker extends SwingWorker<List<String>, String> {
private JTextArea ta;
private List<String> commands;
public CommandWorker(JTextArea ta, List<String> commands) {
this.ta = ta;
this.commands = commands;
}
public CommandWorker(JTextArea ta, String... commands) {
this(ta, Arrays.asList(commands));
}
@Override
protected List<String> doInBackground() throws Exception {
List<String> output = new ArrayList<>(25);
ProcessBuilder builder = new ProcessBuilder(commands);
builder.redirectErrorStream(true);
Process p = builder.start();
try (BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()))) {
String line = null;
while ((line = r.readLine()) != null) {
output.add(line);
publish(line);
}
}
return output;
}
@Override
protected void process(List<String> chunks) {
for (String text : chunks) {
ta.append(text);
ta.append("\n");
}
}
}
}
请参阅 Worker Threads and SwingWorker了解更多详情
答案 1 :(得分：2)
目前，您正在使用readLine()阅读命令输出，然后直接将其放入setText()。
为了使代码实时更新，我们定义了一个新的Thread并使用该线程通过套接字读取OutputStream：
public void load() throws IOException {
Thread t = new Thread(() -> {
try {
ProcessBuilder builder = new ProcessBuilder(
"cmd.exe", "/c", "cd \"C:\\usmt\" && loadstate.bat");
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while (true) {
line = r.readLine();
if (line == null) {
break;
}
String l = line;
SwingUtilities.invokeLater(new Runnable() {
public void run() {
cOut.setText(l);
}
});
System.out.println(line);
}
} catch (IOException ex) {
ex.printStackTrace(); //Add a better error handling in your app
}
});
t.start();
}
在上面，我们定义了一个用于读取行的新线程。
有时，您需要将命令在屏幕上打印的所有行都放在屏幕上，这很容易使用StringBuilder：
String line;
StringBuilder total = new StringBuilder();
while (true) {
line = r.readLine();
if (line == null) {
break;
}
total.append(line).append('\n');
cOut.setText(total.toString());
System.out.println(line);
}
上面使用StringBuilder临时存储完成的结果，然后再将其写入屏幕。