Android applications are written in Java — not the full-blown Java that J2EE developers are used to, but a subset of Java that is sometimes known as the Dalvik virtual machine. This smaller subset of Java excludes classes that don’t make sense for mobile devices. If you have any experience in Java, you should be right at home.
It may be a good idea to keep a Java reference book on hand, but in any case, you can always Google what you don’t understand. Because Java is nothing new, you can find plenty of examples on the Web that demonstrate how to do just about anything.
In Java source code, not all libraries are included. Verify that the package is available to you. If it’s not, an alternative is probably bundled with Android that can work for your needs.
It may be a good idea to keep a Java reference book on hand, but in any case, you can always Google what you don’t understand. Because Java is nothing new, you can find plenty of examples on the Web that demonstrate how to do just about anything.
In Java source code, not all libraries are included. Verify that the package is available to you. If it’s not, an alternative is probably bundled with Android that can work for your needs.
Activities :-
Android applications are made up of one or more activities. Your app must contain at least one activity, but an Android application can contain several. Think of an activity as being a container for your UI, holding your UI as well as the code that runs it. It’s kind of like a form, for you Windows programmers out there. I discuss activities in more detail in Chapters 3 and 5.
Intents Intents make up the core message system that runs Android. An intent is composed of an action that it needs to perform (View, Edit, Dial, and so on) and data. The action is the general action to be performed when the intent is received, and the data is the data to operate on. The data might be a contact item, for example.
Intents are used to start activities and to communicate among various parts of the Android system. Your application can either broadcast an intent or receive an intent.
Sending messages with intents When you broadcast an intent, you’re sending a message telling Android to make something happen. This intent could tell Android to start a new activity from within your application, or it could start a different application.
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