选项卡上的 Java-Keylistener 不起作用

Question

我有一个带有几个元素的 GUI，我只是在这些元素上使用 Tab，在我指定的最后一个元素（即文本区域）上，如果我按下 Tab，我希望它产生一个事件。

它工作得非常好，因为我用输入按钮而不是标签按钮编写了我的代码，我不知道为什么。

我的 GUI 窗口：

这是我的代码：

textArea_beschreibung.addKeyListener(new KeyAdapter() {
    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_TAB){
            String dauervar = input_dauer.getText ();  //auslesen von benutzername
            String beschreibungvar = textArea_beschreibung.getText ();  //auslesen von benutzername
            String projektvar = (String)comboBox_projekt.getSelectedItem();
            String aktivitvar = (String)comboBox_aktivitaet.getSelectedItem();

            String datumvar = input_datum.getText ();  
            SimpleDateFormat df1 = new SimpleDateFormat("dd/MM/yyyy");
            Date date = null;
            try {
                date = df1.parse(datumvar);
            } catch (ParseException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            long epoch = date.getTime();
            String numberAsStringUnixTImestamp = String.valueOf(epoch / 1000);

            String [ ] datenarray = {"a","b","c","d","e","f"};  

            datenarray[0] = numberAsStringUnixTImestamp;
            datenarray[1] = dauervar;   
            datenarray[2] = beschreibungvar;    
            datenarray[3] = projektvar; 
            datenarray[4] = aktivitvar; 
            datenarray[5] = usernamevar;    

            String JsonArray = "{ \"" + "datum" + "\":\"" + datenarray[0] + "\", \"" + "dauer" + "\":\"" + datenarray[1] + "\", \"" + "beschreibung" + "\":\"" + datenarray[2] + "\", \"" + "projektname" + "\":\"" + datenarray[3] + "\", \"" + "kategorie" + "\":\"" + datenarray[4] + "\", \"" + "username" + "\":\"" + datenarray[5] + "\" }";

            input_datum.setText(reportDate);
            if(check_datum.isSelected()){
                CustomDateFinal[0] = datumvar;
                input_datum.setText(CustomDateFinal[0]);

            }                               
            input_dauer.setText(USERDefTimeJSON);
            textArea_beschreibung.setText("");
            comboBox_projekt.requestFocus();


            try {
                SimplePingPong.httpRequestVoid(JsonArray,"unused","werte");
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }

    }
});

Answer 1

在我指定的最后一个元素（即文本区域）上，如果我按下制表符，我希望它产生一个事件。

Tab 键由文本区域处理。默认的 Action 是在文本区域插入一个制表符。

要恢复默认选项卡逻辑，您可以使用以下任何一种：

/*
    This is my understanding of how tabbing works. The focus manager
    recognizes the following default KeyStrokes for tabbing:

    forwards:  TAB or Ctrl-TAB
    backwards: Shift-TAB or Ctrl-Shift-TAB

    In the case of JTextArea, TAB and Shift-TAB have been removed from
    the defaults which means the KeyStroke is passed to the text area.
    The TAB KeyStroke inserts a tab into the Document. Shift-TAB seems
    to be ignored.

    This example shows different approaches for tabbing out of a JTextArea
*/
import java.awt.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;

public class TextAreaTab extends JFrame
{
    public TextAreaTab()
    {
        Container contentPane = getContentPane();
        contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));

        contentPane.add( nullTraversalKeys() );
        contentPane.add( writeYourOwnAction() );
        contentPane.add( useKeyListener() );
        contentPane.add( addTraversalKeys() );
    }

    //  Reset the text area to use the default tab keys.
    //  This is probably the best solution.

    private JComponent nullTraversalKeys()
    {
        JTextArea textArea = new JTextArea(3, 30);

        textArea.setText("Null Traversal Keys\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );

        textArea.setFocusTraversalKeys(KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, null);
        textArea.setFocusTraversalKeys(KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, null);

        return scrollPane;
    }

    //  Replace the Tab Actions. A little more complicated but this shows
    //  how to create a custom Action so you have full control.

    private JComponent writeYourOwnAction()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Write Your Own Tab Actions\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );

        InputMap im = textArea.getInputMap();
        KeyStroke tab = KeyStroke.getKeyStroke("TAB");
        textArea.getActionMap().put(im.get(tab), new TabAction(true));
        KeyStroke shiftTab = KeyStroke.getKeyStroke("shift TAB");
        im.put(shiftTab, shiftTab);
        textArea.getActionMap().put(im.get(shiftTab), new TabAction(false));

        return scrollPane;
    }

    //  Use a KeyListener
    //  (not recommended, since Swing provides newer and better API's)

    private JComponent useKeyListener()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Use Key Listener\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );

        textArea.addKeyListener(new KeyAdapter()
        {
            public void keyPressed(KeyEvent e)
            {
                if (e.getKeyCode() == KeyEvent.VK_TAB)
                {
                    e.consume();
                    KeyboardFocusManager.
                        getCurrentKeyboardFocusManager().focusNextComponent();
                }

                if (e.getKeyCode() == KeyEvent.VK_TAB
                &&  e.isShiftDown())
                {
                    e.consume();
                    KeyboardFocusManager.
                        getCurrentKeyboardFocusManager().focusPreviousComponent();
                }
            }
        });

        return scrollPane;
    }

    //  Add Tab and Shift-Tab KeyStrokes back as focus traversal keys.
    //  Seems more complicated then just using null, but at least
    //  it shows how to add a KeyStroke as a focus traversal key.

    private JComponent addTraversalKeys()
    {
        JTextArea textArea = new JTextArea(3, 30);
        textArea.setText("Add Traversal Keys\n2\n3\n4\n5\n6\n7\n8\n9");
        JScrollPane scrollPane = new JScrollPane( textArea );

        Set set = new HashSet( textArea.getFocusTraversalKeys(
            KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS ) );
        set.add( KeyStroke.getKeyStroke( "TAB" ) );
        textArea.setFocusTraversalKeys(
            KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, set );

        set = new HashSet( textArea.getFocusTraversalKeys(
            KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS ) );
        set.add( KeyStroke.getKeyStroke( "shift TAB" ) );
        textArea.setFocusTraversalKeys(
            KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, set );

        return scrollPane;
    }

    class TabAction extends AbstractAction
    {
        private boolean forward;

        public TabAction(boolean forward)
        {
            this.forward = forward;
        }

        public void actionPerformed(ActionEvent e)
        {
            if (forward)
                tabForward();
            else
                tabBackward();
        }

        private void tabForward()
        {
            KeyboardFocusManager manager = KeyboardFocusManager.getCurrentKeyboardFocusManager();
            manager.focusNextComponent();
        }

        private void tabBackward()
        {
            KeyboardFocusManager manager = KeyboardFocusManager.getCurrentKeyboardFocusManager();
            manager.focusPreviousComponent();
        }
    }

    public static void main(String[] args)
    {
        try
        {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch (Exception e) { }
        TextAreaTab frame = new TextAreaTab();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

我质疑按下制表键时实际上是否进行了所有处理。 Tab 键的功能应该只是将焦点移动到下一个组件。

如果用户想要处理表单上的所有数据，那么您应该有某种用户可以单击的“处理数据”按钮。也许这个按钮就在文本区域之后。