如何在vaadin TextArea中检测输入键按下

Question

I am using a vaadin TextArea as a rough console. The user can enter commands which should be executed when he presses the enter key. Is there a way to specify this with a listener on the TextArea?

The closest thing I found is to use:

TextArea textArea = new TextArea();
textArea.addTextChangeListener(this);
textArea.setTextChangeEventMode(TextChangeEventMode.EAGER);

And handle the text change event:

@Override
public void textChange(TextChangeEvent event) {
   System.out.println(event.getText());
}

This is however triggered as soon as text has been entered in the TextArea. I would like to be notified only when the enter key has been pressed.

Answer 1

You cannot listen to shortcut keys on the textarea itself, but a simple solution would be to add a submit button and use enter as it's shortcut:

Button b = new Button("submit", new Button.ClickListener() {
    @Override
    public void buttonClick(ClickEvent event) {
        // handle your event
    }
});
layout.addComponent(b);
b.setClickShortcut(KeyCode.ENTER);

You can hide the button itself if you don't wish it:

b.setVisible(false);

Another solution would be to use ShortcutActions and Handlers as described in here: https://vaadin.com/book/-/page/advanced.shortcuts.html

But in either case you have to take into account that listening to enter key will cause a conflict when using a TextArea component because you also need to use the same key to get to the next line in the TextArea.

Answer 2

You can add a ShortcutListener to the TextArea, like this:

TextArea textArea = new TextArea();
textArea.addShortcutListener(enter);

Now you just have to initialize some ShortcutListener as follows:

ShortcutListener enter = new ShortcutListener("Enter", KeyCode.ENTER, null) {

    @Override
    public void handleAction(Object sender, Object target) {
        // Do nice stuff
        log.info("Enter pressed");
    }
};

Answer 3

For this, we use the following utility function

/**
 * Perform the specified action when the text field has focus and `ENTER` is pressed.
 * 
 * @param tf The {@link com.vaadin.ui.TextField text field} or 
 * {@link com.vaadin.ui.TextArea text area)
 * @param action The action to perform
 */
public static void onKeyEnter(AbstractTextField tf, Consumer<AbstractTextField> action) {
    tf.addFocusListener(event -> {
        final Registration r = tf.addShortcutListener(
            new ShortcutListener("Enter", KeyCode.ENTER, null) {

                @Override
                public void handleAction(Object sender, Object target) {
                    // sender: UI, target: TextField
                    assert target == tf;
                    action.accept(tf);
                }
            });
        tf.addBlurListener(e -> r.remove());
    });        
}

To use it:

final TextField searchField = new TextField(); // or TextArea
searchField.setPlaceholder("Search text (ENTER)...");
// ..
onKeyEnter(searchField, tf -> doSearch(tf.getValue()));

Answer 4

//Refactored for vaadin 7

 public static void onKeyEnter(AbstractTextField tf, Consumer<AbstractTextField> action) {
    tf.addFocusListener(event -> {
      ShortcutListener scl = new ShortcutListener("Enter", KeyCode.ENTER, null) {
        public void handleAction(Object sender, Object target) {
          assert target == tf;
          action.accept(tf);
        }
      };
      tf.addShortcutListener(scl);
      tf.addBlurListener(e -> tf.removeShortcutListener(scl));
    });
  }