将System.in重定向到摆动组件

Question

大家好，我正在使用Swing和Apache
Commons开发一个终端应用程序。我能够重定向System.out和System.err一个JTextArea很容易，但我怎么做到这一点的System.in？我需要重写Inputstream方法吗？我需要将Stringfrom
转换JTextArea为byte数组，然后将其传递给InputStream吗？代码示例会很好。

Answer 1

我最近尝试了同样的事情，这是我的代码：

class TexfFieldStreamer extends InputStream implements ActionListener {

    private JTextField tf;
    private String str = null;
    private int pos = 0;

    public TexfFieldStreamer(JTextField jtf) {
        tf = jtf;
    }

    //gets triggered everytime that "Enter" is pressed on the textfield
    @Override
    public void actionPerformed(ActionEvent e) {
        str = tf.getText() + "\n";
        pos = 0;
        tf.setText("");
        synchronized (this) {
            //maybe this should only notify() as multiple threads may
            //be waiting for input and they would now race for input
            this.notifyAll();
        }
    }

    @Override
    public int read() {
        //test if the available input has reached its end
        //and the EOS should be returned 
        if(str != null && pos == str.length()){
            str =null;
            //this is supposed to return -1 on "end of stream"
            //but I'm having a hard time locating the constant
            return java.io.StreamTokenizer.TT_EOF;
        }
        //no input available, block until more is available because that's
        //the behavior specified in the Javadocs
        while (str == null || pos >= str.length()) {
            try {
                //according to the docs read() should block until new input is available
                synchronized (this) {
                    this.wait();
                }
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            }
        }
        //read an additional character, return it and increment the index
        return str.charAt(pos++);
    }
}

并像这样使用它：

    JTextField tf = new JTextField();
    TextFieldStreamer ts = new TextFieldStreamer(tf);
    //maybe this next line should be done in the TextFieldStreamer ctor
    //but that would cause a "leak a this from the ctor" warning
    tf.addActionListener(ts);

    System.setIn(ts);

自从我编写Java以来​​已经有一段时间了，所以我可能不了解最新的模式。您可能还应该重载，int available()但是我的示例仅包含使它与BufferedReaders readLine()函数一起工作的最低要求。

编辑： 为了使它起作用，JTextField您必须使用implements KeyListener而不是，implements ActionListener然后addKeyListener(...)在TextArea上使用。您需要代替的功能actionPerformed(...)是public void keyPressed(KeyEvent e)，然后您必须进行测试，if (e.getKeyCode() == e.VK_ENTER)而不是使用整个文本，而只需使用游标前最后一行的子字符串即可，

//ignores the special case of an empty line
//so a test for \n before the Caret or the Caret still being at 0 is necessary
int endpos = tf.getCaret().getMark();
int startpos = tf.getText().substring(0, endpos-1).lastIndexOf('\n')+1;

输入字符串。因为否则，您每次按Enter时都将读取整个TextArea。