Programming in Java Netbeans - A Step by Step Tutorial for Beginners: Lesson 42
Lesson 42: Working with GUI controls: Java Menus
Welcome to Lesson 42 of Programming in Java NetBeans and in this particular lesson, we shall look at how we can use Java menus as part of this serialization of working with Graphical User Interface (GUI) controls in Java. Most GUI programs are menu driven and Java NetBeans does provide this option.
A Menu is a navigation control that enables users to access application options in a hierarchical manner. Most menus will contain menus items such as File, Edit, View, Tools, Help etc. Each menu item may contain a menu list of items which subsequently may contain sub-items and so on.
Menus come in different types and functionality; they can be ribbon menus, suspended menus, dropdown menus, sidebar menus etc. Menus can contain names of the item only, names of the item and icons or names of the item, icons and shortcuts. For this lesson, we’ll use the form we had in the previous lesson to learn more about menus.
Open the form again in design view so that you can edit it. On the Palette window under the Swing menu, locate for the menu bar control. Drag the menu bar control and drop it on the top part of the form as a horizontal bar and Java NetBeans will create a horizontal menu bar with default File and Edit menu items.
You will notice that dragging the menu bar control into the form with default File and Edit menu items does not add menu dropdown items. To add menu items as a dropdown list, right-click on the File on the menu we have just added, select Add From Palette >>Menu Item.
Selecting Menu Item from the above procedure will add a menu Item on the File menu and its shortcut option.
We are going to add three more items on the File menu; Open, Save and Exit. Double click on the default jMenuItem1 name and type Open as the first item. Add two more items as we have done above so that the menu now has three items; Open, Save and Exit.
From the image above, you will notice that there is an option to add shortcuts but these shortcuts have not been defined. To define your own shortcuts, for instance, for the Open menu item, click to select the shortcut and then locate for the Accelerator property on the menu properties window.
Clicking the button to the right-end of Accelerator property will display a dialog box where you can define the shortcut.
To define CTRL+O as the shortcut for Open, type O in the box and then uncheck the Shift checkbox and check Ctrl checkbox instead. For the shortcut to be added on the menu, click OK.
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To test the menu and find out if it is working, we’ll add an event in its ActionPerformed event and attach it to a message box that will pop up when the menu item is clicked.
Right-click on the Open menu item and select: Events >> Action >> ActionPerformed.
From the code stub that will appear, enter the following code for a JOptionPane message box:
javax.swing.JOptionPane.showMessageDialog(this, "Open option selected" ); //Type as one line
Run the form and try the menu by clicking on File >> Open, the message box with "Open option selected" textshould popup. Click OK on the message box and this time try the CTRL+O shortcut, the message box should popup again.
Go ahead and add the shortcut for Save and Exit menu items as CTRL+S and CTRL+X respectively the same way we have done on Open menu item. Menu functionality can be extended so that when we click on the File >> Open, an Open File dialog box will appear so that we can select the file we want to open. Open File dialog box helps users to open files from different locations in the computer. We’ll handle this in the next lesson.
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