Android is stack of software .It behave as software as well as development tool. Android is Linux based. This platform written in java and its core library written C, C++ and Java. Android support lots of Screen sizes like pad, tablet and television. It’s also support lots third party API or SDK for development like Facebook, Google+, Twitter. Firstly we should know about the architecture of android, lets discuss about the android architecture:
Our android architecture mainly divided into 4 parts:
• Applications: In this section all android apps are installed and these are visible to user and user can interact with all these apps.
• Application Framework: This section contain all kind of manager like Activity manager, Wifi manager, Location manager etc. These manger are interfaces between system and applications.
• Libraries: this section contain all like Sqlite, Media framework, SSL, SGL & other core libraries.
• Linux Kernel: This section contain all driver like Display, Camera, Keyboard, WIFI and other drivers ,this provides abstraction between hardware and it’s all essential hardware drivers like camera, keypad, display etc.
Android has lots features and Components which android application efficient and effective like:
• Activities: It is one of main component of android application this contain Java code as well as all user interface, all view will display in this activity. We can make view in xml file and give declaration in this. Activity has own life cycle and it contain valuable method which are necessary for making android applications. All activities declare in manifest file.
Activity Life cycle:-
OnCreate(): This is the first method of activity life cycle all view declaration in this method & we also set view in this method. This method invoke when
Activity instance invoke.
OnStart() :- after oncreate() this method will call and this method also invoke when activity is no longer in background .
OnResume(): This follows
Onstart() method. This method is invoked again after
onPause() method. This method actually resumes the instance of activity.
OnPause(): whenever user click on home button or back button than this method is used for saving instance of activity ,this method always kept instance of activity .& when user click on same application activity instance will resume by
OnStop(): This method called when our activity is no longer in background. This method is called automatically.
OnDestroy(): This method is called when activity called
finish() method. Whenever activity instance destroy this method is auto called.
• Broadcast Receiver: this another component of android applications, these receiver are used for receiving broadcast messages generate from other application or by self-system. Broadcast Receiver working in two parts :- a. Creating broadcast receiver. b. Register broadcast receiver. After receding messages you can perform any action whatever you like perform just need to define that action in onReceive() method .
• Services: These are another component of android apps ,these are mainly working on main threads & most important thing about to know regarding services is there is no user interface with these services and these working and background .these is another type of services is Intent services . these may be or may not be dependent on instance of activity
• Content Provider: These set of structured data formats and user can use these are per requirements ,these are mainly used for sharing data between applications .for example Our contacts we can share those contact in any applications .we can also define our own type Content provider as well
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