Android components
- 2. ANDROID CORE BUILDING BLOCKS An Android Component Is Simply A Piece Of Code That Has A Well Defined Life Cycle E.G. Activity, Receiver, Service Etc. The Core Building Blocks Or Fundamental Components Of Android Are Activities, Views, Intents, Services, Content Providers, Fragments And Androidmanifest.Xml.
- 4. ACTIVITY An activity is a class that represents a single screen. It is like a Frame in AWT. VIEW A view is the UI element such as button, label, text field etc. Anything that you see is a view.
- 5. INTENT Intent is used to invoke components. It is mainly used to: • Start the service • Launch an activity • Display a web page • Display a list of contacts • Broadcast a message • Dial a phone call etc.
- 6. SERVICE Service is a background process that can run for a long time. There are two types of services local and remote. Local service is accessed from within the application whereas remote service is accessed remotely from other applications running on the same device. CONTENT PROVIDER Content Providers are used to share data between the applications.
- 7. BROADCAST RECEIVER • A broadcast receiver (receiver) is an Android component which allows you to register for system or application events. All registered receivers for an event are notified by the Android runtime once this event happens.
- 8. FRAGMENT Fragments Are Like Parts Of Activity. An Activity Can Display One Or More Fragments On The Screen At The Same Time. ANDROIDMANIFEST.XML It contains informations about activities, content providers, permissions etc. It is like the web.xml file in Java EE.
- 9. • The AndroidManifest.xml file contains information of your package, including components of the application such as activities, services, broadcast receivers, content providers etc. • It performs some other tasks also: • It is responsible to protect the application to access any protected parts by providing the permissions.
- 10. • It also declares the android api that the application is going to use. • It lists the instrumentation classes. The instrumentation classes provides profiling and other informations. These informations are removed just before the application is published etc. • This is the required xml file for all the android application and located inside the root directory.
- 11. ELEMENTS OF THE ANDROIDMANIFEST.XML FILE <manifest> manifest is the root element of the AndroidManifest.xml file. It has package attribute that describes the package name of the activity class. <application> application is the subelement of the manifest. It includes the namespace declaration. The commonly used attributes are of this element are icon, label, theme etc.
- 12. <activity> activity is the subelement of application and represents an activity that must be defined in the AndroidManifest.xml file. It has many attributes such as label, name, theme, launchMode etc. <intent-filter> intent-filter is the sub-element of activity that describes the type of intent to which activity, service or broadcast receiver can respond to.
- 13. <action> It adds an action for the intent-filter. The intent-filter must have at least one action element. <category> It adds a category name to an intent-filter.
- 15. <MANIFEST XMLNS:ANDROID="HTTP://SCHEMAS.ANDROID.COM/APK/RES/ANDROID" PACKAGE="COM.JAVATPOINT.HELLO" ANDROID:VERSIONCODE="1" ANDROID:VERSIONNAME="1.0" > <USES-SDK ANDROID:MINSDKVERSION="8" ANDROID:TARGETSDKVERSION="15" /> <USES-PERMISSION ANDROID:NAME="ANDROID.PERMISSION.SEND_SMS"/> <APPLICATION ANDROID:ICON="@DRAWABLE/IC_LAUNCHER" ANDROID:LABEL="@STRING/APP_NAME" ANDROID:THEME="@STYLE/APPTHEME" >
- 16. <ACTIVITY ANDROID:NAME=".MAINACTIVITY" ANDROID:LABEL="@STRING/TITLE_ACTIVITY_MAIN" > <INTENT-FILTER> <ACTION ANDROID:NAME="ANDROID.INTENT.ACTION.MAIN" /> <CATEGORY ANDROID:NAME="ANDROID.INTENT.CATEGORY.LAUNCHE R" /> </INTENT-FILTER> </ACTIVITY> </APPLICATION> </MANIFEST>
- 17. ASSETS assets directory is more like a filesystem and provides more freedom to put any file you would like in there. You then can access each of the files in that system as you would when accessing any file in any file system through Java. This directory is good for things such as game details, dictionaries,...etc. Hope that helps.
- 18. LAYOUT Layout are used to define the actual UI(User interface) of our application. It holds all the elements (i.e. views) or the tools that we want to use in our application. For example, TextView, Button and other UI elements. TYPES OF LAYOUT • LINEAR LAYOUT • RELATIVE LAYOUT • TABLE LAYOUT • FRAMELAYOUT • ABSOLUTE LAYOUT
- 19. ANDROID R.JAVA FILE Android R.Java Is An Auto-generated File By aapt (Android Asset Packaging Tool) That Contains Resource Ids For All The Resources Of Res/ Directory. If You Create Any Component In The Activitymain.Xml File, Id For The Corresponding Component Is Automatically Created In This File. This Id Can Be Used In The Activity Source File To Perform Any Action On The Component.
- 20. USER COMPONENTS In android user interface is mainly built using View and ViewGroup objects. View objects are the basic units of user interface and also View object is a data structure whose properties store the layout parameters and content for a specific rectangular area of the screen.
- 21. Requests a permission that the application must be granted in order for it to operate correctly. Permissions are granted by the user when the application is installed (on devices running Android 5.1 and lower) or while the app is running (on devices running Android 6.0 and higher). USES-PERMISSION
- 22. USES-SDK This element is used to specify the API Level, not the version number of the SDK (software development kit) or Android platform. The API Level is always a single integer. You cannot derive the API Level from its associated Android version number android:minsdkversion android:targetsdkversion android:maxsdkversion
- 23. USES OF API LEVEL IN ANDROID • It lets the Android platform describe the maximum framework API revision that it supports • It lets applications describe the framework API revision that they require • It lets the system negotiate the installation of applications on the user's device, such that version-incompatible applications are not