Click here to close now.




















Welcome!

Java IoT Authors: Kaazing Blog, Mark Carrizosa, Kevin Benedict, Elizabeth White, Liz McMillan

Related Topics: Java IoT

Java IoT: Article

ArrayListModel with Swing's JList and JComboBox

A convenient way to use a simple collection

This article presents a data model based on a Collection implementation that can be used with Swing components JList and JComboBox. It also discusses a method to use these same concepts in constructing the user interface of an application.

Overview
Java Collections are indispensable for building any application, whether GUI or non-GUI. And the ArrayList class is a heavyweight in the java.util package. In a GUI application, the user often must choose items from a list, which can be presented in a variety of forms (drop down combo, list box, etc.). For example, the Java Swing components JList and JComboBox each have list data models - ListModel and ComboBoxListModel, respectively. Both components will react to changes in these models in keeping with the Model-View-Controller paradigm. However, neither of these models are based on a Collection, and therefore lack many of the convenient methods that the Collection interface provides. In addition, lists shown in an application are often populated from external sources (like a database) that return a Collection. Unfortunately, none of the Collection classes in Java broadcast changes to their contents, which is necessary for a user interface component to react to a true MVC data model.

The solution presented in this article to this dichotomy is simple - a subclass of the ArrayList Collection class that implements the ListModel Swing interface, the ArrayListModel class. A subclass, ArrayListComboBoxModel, which extends ArrayListModel implementing the ComboBoxModel model (which is itself a subclass of ListModel), is also presented.

Details
The ArrayListModel class implementation is very straightforward. You can probably already imagine what the methods look like. All ArrayList methods that modify the underlying collection are augmented. The superclass ArrayList method is invoked, and then the ArrayListModel publishes the underlying collection changes to all ListDataListeners that have been added (as part of satisfying the ListModel interface contract). Listing 1 shows the implementation of the add(), remove() and set() ArrayListModel methods.

Each method calls a corresponding fire method, which notifies any ListDataListeners what exactly in the collection has changed (see Listing 2).

Other methods in ArrayListModel work very similarly. For example, the clear() method calls the superclass method, and then fires a ListDataEvent signaling that all items from the collection (model) were removed. The ListDataEvent that is sent to each ListDataListener completely describes the collection elements (actually the indices) that have been added, removed, or modified. Because ArrayListModel implements the ListModel interface, the collection can be directly assigned as the data model of a JList. The ArrayListComboBoxModel class extends ArrayListModel implementing the two additional methods in the ComboBoxModel interface: getSelectedItem() and setSelectedItem().

To see these two classes in action, download the provided code and run the ArrayListModelTest class (see Figure 1). This is a Swing application consisting of a JToolBar, a JComboBox, and a JList. There are two data models used. One is an ArrayListModel that holds all of the data items, and the other is an empty ArrayListComboBoxModel used by both the JComboBox and JList components as their data models.

Figure 1 shows the contents of the combo and list boxes after the red, blue, magenta, and orange toolbar toggle buttons, respectively, have been pressed. Pressing a toggle button on the toolbar adds an item to the data model, while un-pressing it removes the corresponding data item from the model. The data model items are each an instance of a ColorItem, an internally defined class that consists of a name and an icon property (see Listing 3).

Listing 4 shows the method in the test program that constructs the JToolBar. The method has two arguments - an Iterator of ColorItem objects and the list to manipulate on toggle button press/un-press. The list parameter is actually the ArrayListComboBoxModel, but this method simply knows it as a generic List. Note that the ActionListener that is added to each toggle button is very trivial: it simply adds or removes the data item from the list as appropriate. The visual components (JList and JComboBox) attached to the single ArrayListComboBoxModel are automatically updated. A ListCellRenderer is used to render the ColorItem icon in the JList.

You can probably think of other uses for a Collection that announces changes to itself, and not necessarily in a GUI scenario. In that case, you might object to the fact that ArrayListModel and ArrayListComboBoxModel are connected to Java Swing, both in the interfaces they implement and the ListDataEvent/ListDataListener classes they consume. One possible solution to this would be to extend ArrayList as I have done but define your own event model and listener interface that would be more generic and not Swing biased. You could then use this class in a GUI application as I've shown by writing the necessary adapters to implement the ListModel and ComboBoxModel interfaces.

ListModels in Your UI
Have you ever considered all of the list-like elements in a GUI application? Many of the user interface constructs in your application can be thought of as lists of user interface elements that potentially have to be manipulated (items are added, ordered, and removed). Examples are menus, toolbars (their buttons), tabbed panes, internal frames of an MDI application, and potentially other custom components. And quite often you need to associate an icon, a tool tip, and some other visual component with each element.

Listing 5 shows an interface, UIElement, which defines these properties. Run the UIElementTest application that is provided as part of the code for this article. The application looks similar to ArrayListModelTest and has many of the same concepts (see Figures 2 and 3). The data model consists of UIElement objects that are obtained from a UIElementFactory. (The factory returns instances of an inner class, our ColorItem object from before that now implements the UIElement interface.) The application knows nothing about the underlying visuals, just that they implement the UIElement interface. The JList knows it can show icons from the elements and a tool tip for each element. The JList is populated by selecting toggle buttons on the toolbar as above (see Figure 2).

The toolbar is constructed in a method that is nearly identical to the one shown in Listing 4, except the ColorItem parameterized type is replaced by UIElement. When an element in the list is selected, the associated visual component is obtained from the UIElement in the list and shown in the line-bordered JPanel on the right (see Figure 3).

Note the use of tool tips in both the list and panel, which are provided by the getDescription() method of the UIElement data items. The ListCellRenderer for the JList reacts to the state of the Use large icons check box, calling the appropriate UIElement get*Icon() method. A simple change to my UIElementFactory could be coded to return a completely different implementation, but the rest of the application code would not have to be touched.

As you can see, we've implemented a simple list selection method that populates another part of the application upon selection. I would bet that most Swing developers have done something very similar in one or more applications they've worked on. And we've implemented a fairly rich user interface, with icons and tool tips using a single data model, with minimal code.

In my next article, I will present more of this list-based/UIElement framework for constructing an application's user interface. We'll start with an AbstractUIElement that will serve as the base class for our user interface data model. I'll also introduce the UIElementListModel class and its view counterpart, the UIElementListView interface (with an AbstractListView base class implementation).

Conclusion
In this article I have described a convenient way to use a simple collection (List) as the data model for JList and JComboBox Swing components. These components react to changes in the underlying collection, remaining synchronized with the data in the model. I have also introduced the beginning of a small framework that can assist in constructing a Swing application.

More Stories By Phil Herold

Phil Herold is VP and CTO of PocketScience LLC in Research Triangle Park, NC. He has over 24 years of experience in software engineering, and has been working with Java client technologies since 1996.

Comments (4) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Knut Vidar Siem 05/04/06 02:47:52 AM EDT

I noticed that ArrayListComboBoxModel is not generic although ArrayListModel is. I tried changing setSelectedItem(Object item) in ArrayListComboBoxModel to setSelectedItem(E item) (after having made the rest of the class generic with type E), but got the following error: "Name clash: The method setSelectedItem(E) of type ArrayListComboBoxModel has the same erasure as setSelectedItem(Object) of type ComboBoxModel but does not override it". Is there any way around this besides cocky casting from Object to E?

JDJ News Desk 11/07/05 11:14:43 AM EST

Java Developer's Journal - ArrayListModel with Swing's JList and JComboBox. This article presents a data model based on a Collection implementation that can be used with Swing components JList and JComboBox. It also discusses a method to use these same concepts in constructing the user interface of an application.

Java Developer's Journal News Desk 11/07/05 10:53:58 AM EST

This article presents a data model based on a Collection implementation that can be used with Swing components JList and JComboBox. It also discusses a method to use these same concepts in constructing the user interface of an application.

JDJ News Desk 11/07/05 10:13:56 AM EST

ArrayListModel with Swing's JList and JComboBox
This article presents a data model based on a Collection implementation that can be used with Swing components JList and JComboBox. It also discusses a method to use these same concepts in constructing the user interface of an application.

@ThingsExpo Stories
With the Apple Watch making its way onto wrists all over the world, it’s only a matter of time before it becomes a staple in the workplace. In fact, Forrester reported that 68 percent of technology and business decision-makers characterize wearables as a top priority for 2015. Recognizing their business value early on, FinancialForce.com was the first to bring ERP to wearables, helping streamline communication across front and back office functions. In his session at @ThingsExpo, Kevin Roberts, GM of Platform at FinancialForce.com, will discuss the value of business applications on wearable ...
With the proliferation of connected devices underpinning new Internet of Things systems, Brandon Schulz, Director of Luxoft IoT – Retail, will be looking at the transformation of the retail customer experience in brick and mortar stores in his session at @ThingsExpo. Questions he will address include: Will beacons drop to the wayside like QR codes, or be a proximity-based profit driver? How will the customer experience change in stores of all types when everything can be instrumented and analyzed? As an area of investment, how might a retail company move towards an innovation methodolo...
The Internet of Things (IoT) is about the digitization of physical assets including sensors, devices, machines, gateways, and the network. It creates possibilities for significant value creation and new revenue generating business models via data democratization and ubiquitous analytics across IoT networks. The explosion of data in all forms in IoT requires a more robust and broader lens in order to enable smarter timely actions and better outcomes. Business operations become the key driver of IoT applications and projects. Business operations, IT, and data scientists need advanced analytics t...
While many app developers are comfortable building apps for the smartphone, there is a whole new world out there. In his session at @ThingsExpo, Narayan Sainaney, Co-founder and CTO of Mojio, will discuss how the business case for connected car apps is growing and, with open platform companies having already done the heavy lifting, there really is no barrier to entry.
Contrary to mainstream media attention, the multiple possibilities of how consumer IoT will transform our everyday lives aren’t the only angle of this headline-gaining trend. There’s a huge opportunity for “industrial IoT” and “Smart Cities” to impact the world in the same capacity – especially during critical situations. For example, a community water dam that needs to release water can leverage embedded critical communications logic to alert the appropriate individuals, on the right device, as soon as they are needed to take action.
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
SYS-CON Events announced today that Micron Technology, Inc., a global leader in advanced semiconductor systems, will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Micron’s broad portfolio of high-performance memory technologies – including DRAM, NAND and NOR Flash – is the basis for solid state drives, modules, multichip packages and other system solutions. Backed by more than 35 years of technology leadership, Micron's memory solutions enable the world's most innovative computing, consumer,...
As more intelligent IoT applications shift into gear, they’re merging into the ever-increasing traffic flow of the Internet. It won’t be long before we experience bottlenecks, as IoT traffic peaks during rush hours. Organizations that are unprepared will find themselves by the side of the road unable to cross back into the fast lane. As billions of new devices begin to communicate and exchange data – will your infrastructure be scalable enough to handle this new interconnected world?
Through WebRTC, audio and video communications are being embedded more easily than ever into applications, helping carriers, enterprises and independent software vendors deliver greater functionality to their end users. With today’s business world increasingly focused on outcomes, users’ growing calls for ease of use, and businesses craving smarter, tighter integration, what’s the next step in delivering a richer, more immersive experience? That richer, more fully integrated experience comes about through a Communications Platform as a Service which allows for messaging, screen sharing, video...
SYS-CON Events announced today that Pythian, a global IT services company specializing in helping companies leverage disruptive technologies to optimize revenue-generating systems, has been named “Bronze Sponsor” of SYS-CON's 17th Cloud Expo, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Founded in 1997, Pythian is a global IT services company that helps companies compete by adopting disruptive technologies such as cloud, Big Data, advanced analytics, and DevOps to advance innovation and increase agility. Specializing in designing, imple...
In his session at @ThingsExpo, Lee Williams, a producer of the first smartphones and tablets, will talk about how he is now applying his experience in mobile technology to the design and development of the next generation of Environmental and Sustainability Services at ETwater. He will explain how M2M controllers work through wirelessly connected remote controls; and specifically delve into a retrofit option that reverse-engineers control codes of existing conventional controller systems so they don't have to be replaced and are instantly converted to become smart, connected devices.
SYS-CON Events announced today that IceWarp will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. IceWarp, the leader of cloud and on-premise messaging, delivers secured email, chat, documents, conferencing and collaboration to today's mobile workforce, all in one unified interface
WebRTC has had a real tough three or four years, and so have those working with it. Only a few short years ago, the development world were excited about WebRTC and proclaiming how awesome it was. You might have played with the technology a couple of years ago, only to find the extra infrastructure requirements were painful to implement and poorly documented. This probably left a bitter taste in your mouth, especially when things went wrong.
Too often with compelling new technologies market participants become overly enamored with that attractiveness of the technology and neglect underlying business drivers. This tendency, what some call the “newest shiny object syndrome,” is understandable given that virtually all of us are heavily engaged in technology. But it is also mistaken. Without concrete business cases driving its deployment, IoT, like many other technologies before it, will fade into obscurity.
Consumer IoT applications provide data about the user that just doesn’t exist in traditional PC or mobile web applications. This rich data, or “context,” enables the highly personalized consumer experiences that characterize many consumer IoT apps. This same data is also providing brands with unprecedented insight into how their connected products are being used, while, at the same time, powering highly targeted engagement and marketing opportunities. In his session at @ThingsExpo, Nathan Treloar, President and COO of Bebaio, will explore examples of brands transforming their businesses by t...
As more and more data is generated from a variety of connected devices, the need to get insights from this data and predict future behavior and trends is increasingly essential for businesses. Real-time stream processing is needed in a variety of different industries such as Manufacturing, Oil and Gas, Automobile, Finance, Online Retail, Smart Grids, and Healthcare. Azure Stream Analytics is a fully managed distributed stream computation service that provides low latency, scalable processing of streaming data in the cloud with an enterprise grade SLA. It features built-in integration with Azur...
Akana has announced the availability of the new Akana Healthcare Solution. The API-driven solution helps healthcare organizations accelerate their transition to being secure, digitally interoperable businesses. It leverages the Health Level Seven International Fast Healthcare Interoperability Resources (HL7 FHIR) standard to enable broader business use of medical data. Akana developed the Healthcare Solution in response to healthcare businesses that want to increase electronic, multi-device access to health records while reducing operating costs and complying with government regulations.
For IoT to grow as quickly as analyst firms’ project, a lot is going to fall on developers to quickly bring applications to market. But the lack of a standard development platform threatens to slow growth and make application development more time consuming and costly, much like we’ve seen in the mobile space. In his session at @ThingsExpo, Mike Weiner, Product Manager of the Omega DevCloud with KORE Telematics Inc., discussed the evolving requirements for developers as IoT matures and conducted a live demonstration of how quickly application development can happen when the need to comply wit...
The Internet of Everything (IoE) brings together people, process, data and things to make networked connections more relevant and valuable than ever before – transforming information into knowledge and knowledge into wisdom. IoE creates new capabilities, richer experiences, and unprecedented opportunities to improve business and government operations, decision making and mission support capabilities.
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...