Enforcing Permissions in Android Manifestxml

High-level permissions restricting access to entire components of the system or application can be applied through your AndroidManifest.xml All that this requires is including an android permission attribute on the desired component, naming the permission that will be used to control access to it. Activity permissions (applied to the < activity> tag) restrict who can start the associated activity. The permission is checked during Context.startActivity() and Activity.startSubActivity() if...

Emulator Startup Options

The emulator supports a variety of options that you can specify when launching the emulator, to control its appearance or behavior. Here's the command-line usage for launching the emulator with options emulator -option value -qemu args The table below summarizes the available options. Print a list of all emulator commands. Use < file> as the working user-data disk image. If -data is not used, the emulator looks for a file named userdata.img in - .android (Linux Mac) or C Documents and...

The Android Manifestxml File

AndroidManifest.xml is a required file for every application. It sits in the root folder for an application, and describes global values for your package, including the application components (activities, services, etc) that the package exposes and the implementation classes for each component, what kind of data each can handle, and where they can be launched. An important aspect of this file are the intent filters that it includes. These filters describe where and when that activity can be...

Storing Retrieving and Exposing Data

A typical desktop operating system provides a common file system that any application can use to store and read files that can be read by other applications (perhaps with some access control settings). Android uses a different system on Android, all application data (including files) are private to that application. However, Android also provides a standard way for an application to expose its private data to other applications. This section describes the many ways that an application can store...

Compound Components or Compound Controls

If you don't want to create a completely customized component, but instead are looking to put together a reusable component that consists of a group of existing controls, then creating a Compound Component (or Compound Control) might fit the bill. In a nutshell, this brings together a number of more atomic controls (or views) into a logical group of items that can be treated as a single thing. For example, a Combo Box can be thought of as a combination of a single line EditText field and an...

Android Developer Toolbox

If you've read Getting Started and Developing Apps, then you know how to build an Android application. (If you haven't read those sections you should now.) Android is a large system though, and there's a lot to learn. The best apps always make the most of the system's features. The links below tell you how to write code that bends the system to your will, allowing you to create cool custom components and do amazing things with the many available APIs. A manifesto explaining a technical...

Declaring and Enforcing Permissions

To enforce your own permissions, you must first declare them in your AndroidManifest. xml using one or more For example, an application that wants to control who can start one of its activities could declare a permission for this operation as follows Note that both a label and description should be supplied for the permission. These are string resources that can be displayed to the user when they are viewing a list of permissions (android label) or details on a single permission ( android...

Writing Efficient Android Code

There's no way around it Android devices are embedded devices. Modern handsets may be more like small handheld computers than mere phones these days, but even the fastest, highest-end handset doesn't even come close to the capabilities of even a modest desktop system. That's why it's very important to consider performance when you write Android applications. These systems are not that fast to begin with and they are also constrained by their battery life. This means that there's not a lot of...

Developing Android Applications

You can develop Android applications wit h the same high-quality tools you use to develop Java applications. The Android core libraries provide the functionality needed to build some amazingly rich mobile applications, and the Android development tools make running, debugging, and testing your applications a snap. This section explains the ins and outs of developing Android applications. It outlines the philosophy behind the system and then describes each of the key subsystems in detail. After...

Tutorial A Notepad Application

The tutorial in this section gives you a hands-on introduction to the Android framework and the tools you use to build applications on it. Starting from a preconfigured project file, it guides you through the process of developing a simple notepad application and provides concrete examples of how to set up the project, develop the application logic and user interface, and then compile and run the application. The tutorial presents the notepad application development as a set of exercises (see...

Creating a Content Provider

Here is how to create your own content provider to act as a public source for reading and writing a new data type 2. Define a public static final ContentURI named CONTENT_URI. This is the string that represents the full content URI that your content provider handles. You must define a unique string for this value the best solution is to use the fully-qualified class name of your content provider (lowercase). So, for example public static final ContentURI CONTENT_URI ContentURI.create( 3. Create...

Development Tools

The Android SDK includes a variety of custom tools that help you develop mobile applications on the Android platform. The most important of these are the Android Emulator and the Android Development Tools plugin for Eclipse, but the SDK also includes a variety of other tools for debugging, packaging, and installing your applications on the emulator. A virtual mobile device that runs on your computer. You use the emulator to design, debug, and test your applications in an actual Android run-time...

Using a Content Provider to Store and Retrieve Data

This section describes how to store and retrieve data using a content provider implemented by you or anyone else. Android exposes a number of content providers for a wide range of data types, from music and image files to phone numbers. You can see a list of content providers exposed through the convenience classes in the android.provider package. Android's content providers are loosely linked to their clients. Each content provider exposes a unique string a URI identifying the type of data...

Android Architecture

The following diagram shows the major components of the Android operating system. Each section is described in more detail below. Android will ship with a set of core applications including an email client, SMS program, calendar, maps, browser, contacts, and others. All applications are written using the Java programming language.