Question

您好我是Java编程的新手。我试图从Java执行外部命令，然后在JTextArea in real time中显示命令提示输出。该外部程序将每秒产生1行输出，然后在10秒后退出。

以下是我的Java代码：

original codes have been deleted to save space after reading Kumra's answer

当我在命令提示符窗口中手动运行program.exe时，输出会实时更新，如下所示：

<some warning message of the .exe program
    which should not affect the output of the program> // shown at t=0
output line 1   //shown at t=1
output line 2   //shown at t=2
output line 3   //shown at t=3
output line 4   //shown at t=4
output line 5   //shown at t=5
output line 6   //shown at t=6
output line 7   //shown at t=7
output line 8   //shown at t=8
output line 9   //shown at t=9
output line 10  //shown at t=10

Done. //shown at t=10.

当我在上面运行我的Java程序时，我认为JTextArea将实时更新以显示命令提示输出。不幸的是，它没有用。实际输出是这样的：

<some warning message of the .exe program
    which should not affect the output of the program> // shown at t=0

从t = 0到t = 10，JTextArea卡在上面的输出上。在t = 11时，它突然显示完整的输出：

<some warning message of the .exe program
    which should not affect the output of the program> // shown at t=0
output line 1   //shown at t=11
output line 2   //shown at t=11
output line 3   //shown at t=11
output line 4   //shown at t=11
output line 5   //shown at t=11
output line 6   //shown at t=11
output line 7   //shown at t=11
output line 8   //shown at t=11
output line 9   //shown at t=11
output line 10  //shown at t=11

Done. //shown at t=11

我可以知道我的代码有什么问题吗？任何人都可以教我如何在JTextArea in real time中显示命令提示输出？感谢。

编辑1：
我根据Kumar的答案编辑了代码，但它仍然无效。以下是最新的代码。

MyUI.java

public class MyUI extends JFrame
implements ActionListener, KeyListener, ChangeListener, WindowListener
{
    ...
    private JTextArea output;

    public void showMessage(String message)
    {
        output.append(message + "\n");
        output.setCaretPosition(output.getDocument().getLength());
    }
    ...

    public void actionPerformed(final ActionEvent e)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                if (xxxxx)
                {
                    myThreadInstance = new MyThread(xx,xxx,xx,xx,xx);
                    myThreadInstance.start();
                }
            }
        }
    }

}

MyThread.java

public class MyThread extends Thread
{
    ...
    public MyUI myFrame;
    ...

    public void run
    {
        try
        {
            String command = "program.exe arg1 arg2 arg3 arg4";

            List<String> items = Arrays.asList(command.split("\\s+"));

            builder = new ProcessBuilder(items);
            builder.redirectErrorStream(true);

            process = builder.start();

            input = new BufferedReader(new InputStreamReader(process.getInputStream()));

            String inputline = null;
            while ((inputline = input.readLine()) != null)
            {
                myFrame.showMessage(inputline);
            }
        }
        catch(){}
        finally{}
    }
}

Answer 1

试试这个......

始终保持UI工作在UI线程上，非UI工作在非UI线程上。
Event Dispatcher Thread是UI线程，负责Gui。
您正在UI线程上执行从t = 0到t = 10计数的过程，这就是原因你在t = 11之前看不到任何输出。
创建单独的帖子以对cmd进行计数，或使用提供的SwingWorker Swing以同步UI和非UI线程。

为什么我的代码无法实时更新JTextArea？

1 个答案: