Android App Development Using Activities Lifecycle

Android Application Development Being Active Through Activities Ahsanul Karim [email_address] Sentinel Solutions Ltd. http://www.sentinelbd.com

Today We’re Covering… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Project Structure… Created Project has the following structure Project Structure -Source ( src ) -Generated Class ( gen ) -Android 1.6 library -Assets ( assets ) -Resource( res ) - drawable-hdpi - drawable-ldpi - drawable-mdpi - layout - values - AndroidMenifest.xml - default.properties

Project Structure (Contd.) -Source ( src ) We have used only one class here which is an Activity named HalloActivity. We’ll describe about Activity in detail with lifecycle shortly. For now we can consider Activity as Android analogue for the window or dialog in a desktop application. It can load view from xml layout (here main.xml under res/layout folder) In the HelloActivity class the view of the Activity is set from main.xml given below

Project Structure (Contd.) -res/layout/main.xml ,[object Object],[object Object]

Project Structure (Contd.) -res/drawable ,[object Object],[object Object],-assets Holds other static files you wish packaged with the application for deployment onto the device. In this project, we have none -gen/R.java -values/strings.xml

Project Structure (Contd.) -AndroidMenifest.xml XML file describing the application being built and what components – activities, services, etc. – are being supplied by that application

Let’s Build Something Useful… Objective: To get hands-on experience of building something useful more than just “Hallo World”. Plan: We’ll create a project to show how the basic building block Activity and some UI elements work. Output: User will push a button and see current time. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Let’s Build Something Useful(Contd.) Creating the Project: Start Eclipse and go to New > Project > Android Projec t

Let’s Build Something Useful(Contd.) Designing Layout (1) Edit layout/main.xml using the visual tool given by ADT by adding a TextView and a Button in a LinearLayout (more on layouts will be covered later)

Let’s Build Something Useful(Contd.) Designing Layout (2) The output xml is like below. We can directly edit layout xml to design the UI. Properties were set from the visual tool.

Let’s Build Something Useful(Contd.) Let’s infuse life to UI Activity with UI elements declared Initializing UI elements Auto-generated R.java ,[object Object],[object Object],[object Object]

Let’s Build Something Useful(Contd.) Complete Activity

Let’s Build Something Useful(Contd.) Creating Run Configuration and Run So, you can now create your own application

Android Activities Activity Activity provides a user generally with an interactive screen to do something like: Dialing the phone, View a map List of something for user to select or Anything you want your user to do ,[object Object],[object Object],The <action> element specifies that this is the "main" entry point to the application. The <category> element specifies that this activity should be listed in the system's application launcher (to allow users to launch this activity).

Android Activities (Contd..) Creating Activity We have already created Activities. But how did we create it? Let’s revisit… ,[object Object],[object Object],[object Object],[object Object],Open Questions:

Android Activities (Contd..) Next Step: Implementing User Interface ,[object Object],[object Object],Next Step: Implementing User Interface <manifest ... > <application ... > <activity android:name=".ExampleActivity" /> ... </application ... > ... </manifest > Next Step: Starting Activity Intent intent = new Intent(this, ToActivity.class); startActivity(intent); We can start another activity by calling startActivity() , passing it an Intent that describes the activity you want to start.

Android Application Anatomy (Contd.) Application= Set of Android Components ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Android App Development Using Activities Lifecycle

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