Use RadioMenuItem and CheckMenuItem - JavaFX

Use RadioMenuItem and CheckMenuItem

Although the type of menu items used by the preceding examples are, as a general rule, the most commonly used, JavaFX defines two others: check menu items and radio menu items. These elements can streamline a GUI by allowing a menu to provide functionality that would otherwise require additional, stand-alone components. Also, sometimes including check or radio menu items simply seems most natural for a specific set of features. Whatever your reason, it is easy to use check and/or radio menu items in menus, and both are examined here.

To add a check menu item to a menu, use CheckMenuItem. It defines three constructors, which parallel the ones defined by MenuItem. The one used in this chapter is shown here:

CheckMenuItem(String name)

Here, name specifies the name of the item. The initial state of the item is unchecked. If you want to check a check menu item under program control, call setSelected( ), shown here:

final void setSelected(boolean selected)

If selected is true, the menu item is checked. Otherwise, it is unchecked.

Like stand-alone check boxes, check menu items generate action events when their state is changed. Check menu items are especially appropriate in menus when you have options that can be selected and you want to display their selected/deselected status.

A radio menu item can be added to a menu by creating an object of type RadioMenuItem. RadioMenuItem defines a number of constructors. The one used in this chapter is shown here:

RadioMenuItem(String name)

It creates a radio menu item that has the name passed in name. The item is not selected. As with the case of check menu items, to select a radio menu item, call setSelected( ), passing true as an argument.

RadioMenuItem works like a stand-alone radio button, generating both change and action events. Like stand-alone radio buttons, menu radio items must be put into a toggle group in order for them to exhibit mutually exclusive selection behavior.

Because both CheckMenuItem and RadioMenuItem inherit MenuItem, each has all of the functionality provided by MenuItem. Aside from having the extra capabilities of check boxes and radio buttons, they act like and are used like other menu items.

To try check and radio menu items, first remove the code that creates the Options menu in the MenuDemo example program. Then substitute the following code sequence, which uses check menu items for the Colors submenu and radio menu items for the Priority submenu.

// Create the Options menu.

Menu optionsMenu = new Menu("Options");

// Create the Colors submenu.

Menu colorsMenu = new Menu("Colors");

     //Use check menu items for colors. This allows

     //the user to select more than one color.

     CheckMenuItem red = new CheckMenuItem("Red");

     CheckMenuItem green = new CheckMenuItem("Green");

     CheckMenuItem blue = new CheckMenuItem("Blue");

     colorsMenu.getItems().addAll(red, green, blue);

     optionsMenu.getItems().add(colorsMenu);

     //Select green for the default color selection.

     green.setSelected(true);

     //Create the Priority submenu.

Menu priorityMenu = new Menu("Priority");

     //Use radio menu items for the priority setting.

     ///This lets the menu show which priority is used

     //and also ensures that one and only one priority

     //can be selected at any one time.

     RadioMenuItem high = new RadioMenuItem("High");

     RadioMenuItem low = new RadioMenuItem("Low");

     //Create a toggle group and use it for the radio menu items.

      ToggleGroup tg = new ToggleGroup();

high.setToggleGroup(tg);

low.setToggleGroup(tg);

     //Select High priority for the default selection.

     high.setSelected(true);

     //Add the radio menu items to the Priority menu and

     //add the Priority menu to the Options menu.

     priorityMenu.getItems().addAll(high, low);

     optionsMenu.getItems().add(priorityMenu);

     //Add a separator.

optionsMenu.getItems().add(new SeparatorMenuItem());

     //Create the Reset menu item.

     MenuItem reset = new MenuItem("Reset");

     optionsMenu.getItems().add(reset);

//Add Options menu to the menu bar.

mb.getMenus().add(optionsMenu);

After making the substitution, the check menu items in the Colors submenu look like those shown here:

Here is how the radio menu items in the Priority submenu now look: