The Following Are Some basic Concept of android for developers.JAR Files:-
The Java™ Archive (JAR) file format enables you to bundle multiple files into a single archive file.
Android Operation System
Android is an operating system based on Linux with a Java programming interface. Created By Google Through JAVA Language.
Activity
Activity represents the presentation layer of an Android application. A simplified (and slightly incorrect) description is that an Activity is a screen. This is slightly incorrect as Activities can be displayed as Dialogs or can be transparent. An Android application can have several Activities. Views and ViewGroups
Views are user interface widgets, e.g. buttons or text fields. The base class for all Views is android.view.View. Views often have attributes which can be used to change their appearance and behavior. A
ViewGroup is responsible for arranging other Views e.g. a ViewGroup is a layout manager. The base class for a layout manager is android.view.ViewGroups. ViewGroup also extends View. ViewGroups can be nestled to create complex layouts. You should not nestle ViewGroups too deeply as this has a negative impact on the performance. Intents
Intents are asynchronous messages which allow the application to request functionality from other components of the Android system, e.g. from Services or Activities. An application can call a component directly (explicit Intent ) or ask the Android system to evaluate registered components for a certain Intent (implicit Intents ). For example the application could implement sharing of data via an Intent and all components which allow sharing of data would be available for the user to select. Applications register themselves to an Intent via an IntentFilter. Intents allow to combine loosely coupled components to perform certain tasks. Services
Services perform background tasks without providing a user interface. They can notify the user via the notification framework in Android. ContentProvider
ContentProvider provides a structured interface to application data. Via a ContentProvider your application can share data with other applications. Android contains an SQLite database which is frequently used in conjunction with a ContentProvider to persist the data of the ContentProvider. BroadcastReceiver
BroadcastReceiver can be registered to receive system messages and Intents. A BroadcastReceiver will get notified by the Android system, if the specified situation happens. For example a BroadcastReceiver could get called once the Android system completed the boot process or if a phone call is received. (HomeScreen) Widgets
Widgets are interactive components which are primarily used on the Android homescreen. They typically display some kind of data and allow the user to perform actions via them. For example a Widget could display a short summary of new emails and if the user selects an email, it could start the email application with the selected email. Other
Android provide many more components but the list above describes the most important ones. Other Android components are "Live Folders" and "Live Wallpapers". Live Folders display data on the homescreen without launching the corresponding application.AndroidManifest.xml
The components and settings of an Android application are described in the fileAndroidManifest.xml. For example all Activities and Services of the application must be declared in this file. It must also contain the required permissions for the application. For example if the application requires network access it must be specified here.
R.java and Resources
The "gen " directory in an Android project contains generated values. R.java is a generated class which contains references to certain resources of the project. These resources must be defined in the "res" directory and can be XML files, icons or pictures. You can for example define values, menus, layouts or animations via XML files.
Context
The classandroid.content.Context provides the connections to the Android system. It is the interface to global information about the application environment. Context also provides access to Android Services, e.g. the Location Service. Activities and Services extend the Context class and can therefore be used as Context. Implement KeyWord
In Java Programming Language the Keywprd implement Specifies that given Class implements an interface.
Extends Keyword
The extends is jave keyword , which in inheritance Process of java. It specifies the super class in a class declaration using extends keyword.
Eclipse ADT PLUGIN LINK
https://dl-ssl.google.com/android/eclipse/.
Emulator Shortcuts
The following shortcuts are useful for working with the emulator.Alt+Enter Maximizes the emulator. Nice for demos.
Ctrl+F11 changes the orientation of the emulator.
F8 Turns network on / off.
Warnings Messages for Strings
The Android development tools are show warnings if you use hard-coded strings, for example in layout files. While for real application its best practice to use string resource files we use use Strings directly to simplify the creation of the examples.HOW TO ADD RESOURCES in String.XML file
<resources>
<string name="hello">Hello World, Convert!</string>
<string name="app_name">Temperature Converter</string>
<color name="myColor">#3399CC</color>
<string name="myClickHandler">myClickHandler</string>
<string name="celsius">to Celsius</string>
<string name="fahrenheit">to Fahrenheit</string>
<string name="calc">Calculate</string>
</resources>
Make a Edith Text control to Password
android:inputType="textPassword" Videos PROMO2nd Video
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