Custom Views

Problem: You want to add an unsupported view in an interface file such as javax.swing.JProgressBar.

Solution: Place a custom view object and connect it to an outlet in File’s Owner.

In an Interface Builder file, place a custom view object in the main window. You can find this object in the Containers palette. Figure 19-1 shows this palette and a custom view placed in the main window.

Figure 19-1 Custom view object in window

Next, you need to assign the custom view to an NSView subclass. Before you can do this, you need to create an NSView subclass. Switch to the Classes pane in the nib file window and enter NSView in the Search field as shown in Figure 19-2.

Figure 19-2 Find NSView in class hierarchy

Select NSView if it is not already selected and press Return to subclass it. In the Info window, select Java as the language for the subclass. Then, provide a fully qualified name for the subclass. If the view represents a Swing class such as JProgressBar, use javax.swing.JProgressBar as shown in Figure 19-3. If the view represents a custom Swing subclass, specify the fully qualified name of that subclass.

Figure 19-3 Name the custom view class

Next, you need to associate the custom view you placed in the window with the new NSView subclass. Select the custom view widget in the main window and bring up the Attributes pane of the Info window. Select javax.swing.JProgressBar, as shown in Figure 19-4.

Figure 19-4 Associate custom view with NSView subclass

The name in the custom view should then change to the name of the new class, as shown in Figure 19-5.

Figure 19-5 Custom view as NSView subclass

Now you need to add an outlet to the interface file’s File’s Owner object for the custom view. This gives you programmatic access to the widget in the nib file’s controller class, which allows you to query and change the widget’s attributes. In the Classes pane of the nib file window, view the class hierarchy vertically and disclose the list starting with java.lang.Object as far as you can, as shown in Figure 19-6.

Figure 19-6 File’s Owner class

Select the last class in the hierarchy and bring up the Info window. Add an outlet to the class called customViewOutlet, as shown in Figure 19-7.

Figure 19-7 Add outlet to interface file

Next, you need to connect the custom view to the outlet you just created. Switch to the Instances pane of the nib file window and Control-drag from File’s Owner to the custom view in the main window as shown in Figure 19-8.

Figure 19-8 Connect new outlet to custom view

Then in the Connections pane of the Info window, select customViewOutlet and click Connect. The Connections pane of the Info window for File’s Owner should now appear as shown in Figure 19-9.

Figure 19-9 File’s Owner attributes

Save the interface file and open its controller class (.java file) in Project Builder. Add an instance variable for the outlet you added:

public JProgressBar customViewOutlet;

You now have a JProgressBar widget in your interface file. You can set its value by invoking customViewOutlet.setValue(int value) in the controller class. However, don’t attempt to invoke methods on the widget in the interface controller’s constructors as it may not be initialized at that point. Rather, override controllerDidLoadArchive as described in “Loading the Image” or check to see if the component is initialized by invoking isComponentPrepared.