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The BlackBerry and iPhone, which have appealing and high-volume mobile platforms, are addressing opposite ends of a spectrum. The BlackBerry is rock-solid for the enterprise business user. For a consumer device, it's hard to compete with the iPhone for ease of use and the "cool factor." Android, a young and yet-unproven platform, has the potential to play at both ends of the mobile-phone spectrum and perhaps even bridge the gulf between work and play.
Today, many network-based or network-capable appliances run a flavor of the Linux kernel. It's a solid platform: cost-effective to deploy and support and readily accepted as a good design approach for deployment. The UI for such devices is often HTML-based and viewable with a PC or Mac browser. But not every appliance needs to be controlled by a general computing device. Consider a conventional appliance, such as a stove, microwave or bread maker. What if your household appliances were controlled by Android and boasted a color touch screen? With an Android UI on the stove-top, the author might even be able to cook something.
In this article, learn about the Android platform and how it can be used for mobile and nonmobile applications. Install the Android SDK and build a simple application. Download the source code for the example application in this article.
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A brief history of Android
The Android platform is the product of the Open Handset Alliance, a group of organizations collaborating to build a better mobile phone. The group, led by Google, includes mobile operators, device handset manufacturers, component manufacturers, software solution and platform providers, and marketing companies. From a software development standpoint, Android sits smack in the middle of the open source world.
The first Android-capable handset on the market was the G1 device manufactured by HTC and provisioned on T-Mobile. The device became available after almost a year of speculation, where the only software development tools available were some incrementally improving SDK releases. As the G1 release date neared, the Android team released SDK V1.0 and applications began surfacing for the new platform.
To spur innovation, Google sponsored two rounds of "Android Developer Challenges," where millions of dollars were given to top contest submissions. A few months after the G1, the Android Market was released, allowing users to browse and download applications directly to their phones. Over about 18 months, a new mobile platform entered the public arena.
Back to top
The Android platform
With Android's breadth of capabilities, it would be easy to confuse it with a desktop operating system. Android is a layered environment built upon a foundation of the Linux kernel, and it includes rich functions. The UI subsystem includes:
Windows
Views
Widgets for displaying common elements such as edit boxes, lists, and drop-down lists
Android includes an embeddable browser built upon WebKit, the same open source browser engine powering the iPhone's Mobile Safari browser
Android boasts a healthy array of connectivity options, including WiFi, Bluetooth, and wireless data over a cellular connection (for example, GPRS, EDGE, and 3G). A popular technique in Android applications is to link to Google Maps to display an address directly within an application. Support for location-based services (such as GPS) and accelerometers is also available in the Android software stack, though not all Android devices are equipped with the required hardware. There is also camera support.
Historically, two areas where mobile applications have struggled to keep pace with their desktop counterparts are graphics/media, and data storage methods. Android addresses the graphics challenge with built-in support for 2-D and 3-D graphics, including the OpenGL library. The data-storage burden is eased because the Android platform includes the popular open source SQLite database. Figure 1 shows a simplified view of the Android software layers.As mentioned, Android runs atop a Linux kernel. Android applications are written in the Java programming language, and they run within a virtual machine (VM). It's important to note that the VM is not a JVM as you might expect, but is the Dalvik Virtual Machine, an open source technology. Each Android application runs within an instance of the Dalvik VM, which in turn resides within a Linux-kernel managed process, An Android application consists of one or more of the following classifications:
Activities
An application that has a visible UI is implemented with an activity. When a user selects an application from the home screen or application launcher, an activity is started.
Services
A service should be used for any application that needs to persist for a long time, such as a network monitor or update-checking application.
Content providers
You can think of content providers as a database server. A content provider's job is to manage access to persisted data, such as a SQLite database. If your application is very simple, you might not necessarily create a content provider. If you're building a larger application, or one that makes data available to multiple activities or applications, a content provider is the means of accessing your data.
Broadcast receivers
An Android application may be launched to process a element of data or respond to an event, such as the receipt of a text message.
An Android application, along with a file called AndroidManifest.xml, is deployed to a device. AndroidManifest.xml contains the necessary configuration information to properly install it to the device. It includes the required class names and types of events the application is able to process, and the required permissions the application needs to run. For example, if an application requires access to the network — to download a file, for example — this permission must be explicitly stated in the manifest file. Many applications may have this specific permission enabled. Such declarative security helps reduce the likelihood that a rogue application can cause damage on your device.
Today, many network-based or network-capable appliances run a flavor of the Linux kernel. It's a solid platform: cost-effective to deploy and support and readily accepted as a good design approach for deployment. The UI for such devices is often HTML-based and viewable with a PC or Mac browser. But not every appliance needs to be controlled by a general computing device. Consider a conventional appliance, such as a stove, microwave or bread maker. What if your household appliances were controlled by Android and boasted a color touch screen? With an Android UI on the stove-top, the author might even be able to cook something.
In this article, learn about the Android platform and how it can be used for mobile and nonmobile applications. Install the Android SDK and build a simple application. Download the source code for the example application in this article.
Back to top
A brief history of Android
The Android platform is the product of the Open Handset Alliance, a group of organizations collaborating to build a better mobile phone. The group, led by Google, includes mobile operators, device handset manufacturers, component manufacturers, software solution and platform providers, and marketing companies. From a software development standpoint, Android sits smack in the middle of the open source world.
The first Android-capable handset on the market was the G1 device manufactured by HTC and provisioned on T-Mobile. The device became available after almost a year of speculation, where the only software development tools available were some incrementally improving SDK releases. As the G1 release date neared, the Android team released SDK V1.0 and applications began surfacing for the new platform.
To spur innovation, Google sponsored two rounds of "Android Developer Challenges," where millions of dollars were given to top contest submissions. A few months after the G1, the Android Market was released, allowing users to browse and download applications directly to their phones. Over about 18 months, a new mobile platform entered the public arena.
Back to top
The Android platform
With Android's breadth of capabilities, it would be easy to confuse it with a desktop operating system. Android is a layered environment built upon a foundation of the Linux kernel, and it includes rich functions. The UI subsystem includes:
Windows
Views
Widgets for displaying common elements such as edit boxes, lists, and drop-down lists
Android includes an embeddable browser built upon WebKit, the same open source browser engine powering the iPhone's Mobile Safari browser
Android boasts a healthy array of connectivity options, including WiFi, Bluetooth, and wireless data over a cellular connection (for example, GPRS, EDGE, and 3G). A popular technique in Android applications is to link to Google Maps to display an address directly within an application. Support for location-based services (such as GPS) and accelerometers is also available in the Android software stack, though not all Android devices are equipped with the required hardware. There is also camera support.
Historically, two areas where mobile applications have struggled to keep pace with their desktop counterparts are graphics/media, and data storage methods. Android addresses the graphics challenge with built-in support for 2-D and 3-D graphics, including the OpenGL library. The data-storage burden is eased because the Android platform includes the popular open source SQLite database. Figure 1 shows a simplified view of the Android software layers.As mentioned, Android runs atop a Linux kernel. Android applications are written in the Java programming language, and they run within a virtual machine (VM). It's important to note that the VM is not a JVM as you might expect, but is the Dalvik Virtual Machine, an open source technology. Each Android application runs within an instance of the Dalvik VM, which in turn resides within a Linux-kernel managed process, An Android application consists of one or more of the following classifications:
Activities
An application that has a visible UI is implemented with an activity. When a user selects an application from the home screen or application launcher, an activity is started.
Services
A service should be used for any application that needs to persist for a long time, such as a network monitor or update-checking application.
Content providers
You can think of content providers as a database server. A content provider's job is to manage access to persisted data, such as a SQLite database. If your application is very simple, you might not necessarily create a content provider. If you're building a larger application, or one that makes data available to multiple activities or applications, a content provider is the means of accessing your data.
Broadcast receivers
An Android application may be launched to process a element of data or respond to an event, such as the receipt of a text message.
An Android application, along with a file called AndroidManifest.xml, is deployed to a device. AndroidManifest.xml contains the necessary configuration information to properly install it to the device. It includes the required class names and types of events the application is able to process, and the required permissions the application needs to run. For example, if an application requires access to the network — to download a file, for example — this permission must be explicitly stated in the manifest file. Many applications may have this specific permission enabled. Such declarative security helps reduce the likelihood that a rogue application can cause damage on your device.
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