//
// another example of the Java AWT, showing use of Checkbox and
//      CheckboxGroup classes.
// see class definition and main method for details.
//
import java.awt.* ;
import java.awt.event.* ;

//
// a CheckboxExample object is a CloseableFrame containing a number
//      of checkboxes, a Button, and a Label.  depending on the 
//      arguments to the constructor, the checkboxes may or may not be
//      grouped into a CheckboxGroup.  when the user clicks on the
//      button, the text (labels) associated with the selected 
//      checkboxes displayed in the Label.
//
class CheckboxExample extends CloseableFrame {

        Label display = new Label("", Label.CENTER) ;
        Checkbox[] boxes ;
        CheckboxGroup cbg ;

        CheckboxExample(boolean group, String[] items) {

                super("CheckboxExample") ;
                setLayout(new BorderLayout()) ;

                if (group)
                        cbg = new CheckboxGroup() ;
                else
                        cbg = null ;

                add(display, "North") ;

                // make checkboxes (with checkbox group if needed)
                //      and lay out using panel.
                Panel p1 = new Panel() ;
                boxes = new Checkbox[items.length] ;
                for (int i = 0 ; i < items.length ; i ++) {
                        if (group) 
                                boxes[i] = new Checkbox(items[i],
                                        cbg, (i==0)) ;
                        else
                                boxes[i] = new Checkbox(items[i]) ;
                        boxes[i].addItemListener(new ItemListener() {
                                // action to be performed when user 
                                //      selects a checkbox.
                                public void 
                                  itemStateChanged(ItemEvent e) {
                                        clearDisplay() ;
                                }
                        } ) ;
                        p1.add(boxes[i]) ;
                }
                add(p1, "Center") ;

                Button showB = new Button("display selections") ;
                showB.addActionListener(new ActionListener() {
                        // action to be performed when user clicks on
                        //      button.
                        public void actionPerformed(ActionEvent e) {
                                resetDisplay() ;
                        }
                } ) ;
                add(showB, "South") ;

                pack() ;
                show() ;

        }

        // clears display.
        // should probably be declared private, but calling a
        //      private method from an anonymous inner class (as above)
        //      apparently triggers a compiler bug, causing the 
        //      compiler to hang!).
        void clearDisplay() {
                display.setText("") ;
        }

        // displays current selection(s).
        // should probably be declared private, but calling a
        //      private method from an anonymous inner class (as above)
        //      apparently triggers a compiler bug, causing the 
        //      compiler to hang!).
        void resetDisplay() {
                String selected ;
                if (cbg != null) {
                        // if boxes are grouped into a CheckboxGroup
                        //      (only one at a time can be selected),
                        //      show selected box's label.
                        selected =
                                cbg.getSelectedCheckbox().getLabel() ;
                }
                else {
                        // if boxes are not grouped (any number can be
                        //      selected), display labels of all
                        //      selected boxes.
                        StringBuffer sb = new StringBuffer() ;
                        for (int i = 0 ; i < boxes.length ; i++) {
                                if (boxes[i].getState()) {
                                        sb.append(boxes[i].getLabel()) ;
                                        sb.append(' ') ;
                                }
                        }
                        selected = sb.toString() ;
                }
                display.setText("selected:  " + selected) ;
        }

        //
        // ---- main ---------------------------------------------------
        //
        // command-line arguments are y/n (enclose in CheckboxGroup),
        //      labels for Checkboxes.
        //
        public static void main(String[] args) {

                if (args.length < 2) {
                        System.out.println("Arguments are y/n, items") ;
                        System.exit(-1) ;
                }

                boolean group = args[0].equals("y") ;

                String[] items = new String[args.length-1] ;
                for (int i = 0 ; i < items.length ; i++) 
                        items[i] = args[i+1] ;

                CheckboxExample c = new CheckboxExample(group, items) ;
        }
}