e612. Moving the Focus to the Next or Previous Focusable Component

Posted 2021-01-04 borter

The methods to move the focus to the next or to the previous focusable component are Component.transferFocus() and Component.transferFocusBackward().

This example modifies a component so that pressing the space bar or pressing F2 moves the focus to the next focusable component. Pressing shift space or shift F2 moves the focus to the previous focusable component.

    // Bind space and shift space
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke("SPACE"), nextFocusAction.getValue(Action.NAME));
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke("shift SPACE"), prevFocusAction.getValue(Action.NAME));
    
    // This key binding is required for text components. It hides the
    // default typed space key binding in a text component. If you don‘t
    // hide this key binding, typing the space key will insert a space into
    // the text component (as well as move the focus).
    // See e1003 覆盖一些和JTextComponent绑定的键 for more details.
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke(new Character(‘ ‘), 0), "unbound");
    
    // Bind F2 and shift F2
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke("F2"), nextFocusAction.getValue(Action.NAME));
    component.getInputMap(JComponent.WHEN_FOCUSED).put(
        KeyStroke.getKeyStroke("shift F2"), prevFocusAction.getValue(Action.NAME));
    
    // Add actions
    component.getActionMap().put(nextFocusAction.getValue(Action.NAME), nextFocusAction);
    component.getActionMap().put(prevFocusAction.getValue(Action.NAME), prevFocusAction);
    
    // The actions
    public Action nextFocusAction = new AbstractAction("Move Focus Forwards") {
        public void actionPerformed(ActionEvent evt) {
            ((Component)evt.getSource()).transferFocus();
        }
    };
    public Action prevFocusAction = new AbstractAction("Move Focus Backwards") {
        public void actionPerformed(ActionEvent evt) {
            ((Component)evt.getSource()).transferFocusBackward();
        }
    };

 

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