javaswingfocusmnemonics

JCheckBox mnemonic without transferring focus

As per title, is it possible to change a JCheckBox selection state using a mnemonic key without transferring the focus to the component?

Current behavior as per GIF.
The wanted behavior would be the focus remaining on the "Type" text field.

enter image description here

Solution

  • Given that the mnemonic is registered as a key binding, in the scope of

    JComponent.WHEN_IN_FOCUSED_WINDOW

    See BasicButtonListener#updateMnemonicBinding

    We can simply override the key binding actions with our own ones.

    private class MnemonicCheckBox : JCheckBox(...) {
  override fun setMnemonic(mnemonic: Int) {
    super.setMnemonic(mnemonic)

    if (mnemonic != 0) {
      overrideMnemonicActions()
    }
  }

  private fun overrideMnemonicActions() {
    val mnemonicMask = UIUtilities.getSystemMnemonicKeyMask()
    val altGraphDownMask = InputEvent.ALT_GRAPH_DOWN_MASK

    getInputMap(WHEN_IN_FOCUSED_WINDOW).apply {
      // Pressed
      put(KeyStroke.getKeyStroke(mnemonic, mnemonicMask), "mnemonicPressed")
      put(KeyStroke.getKeyStroke(mnemonic, mnemonicMask or altGraphDownMask), "mnemonicPressed")

      // Released
      put(KeyStroke.getKeyStroke(mnemonic, mnemonicMask, true), "mnemonicReleased")
      put(KeyStroke.getKeyStroke(mnemonic, mnemonicMask or altGraphDownMask, true), "mnemonicReleased")
    }

    actionMap.apply {
      put("mnemonicPressed", object : AbstractAction() {
        override fun actionPerformed(event: ActionEvent) {
          model.isArmed = true
          model.isPressed = true
        }
      })
      put("mnemonicReleased", object : AbstractAction() {
        override fun actionPerformed(event: ActionEvent) {
          model.isPressed = false
          model.isArmed = false
        }
      })
    }
  }
}

    To maintain the semantic expressed in BasicButtonListener.Actions, we have overridden both the pressed and released actions to change the ButtonModel state.

    Example:

    enter image description here