Training Session 2 - Day 2
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The document provides an overview of Android system architecture, explaining its foundation on the Linux kernel and the use of libraries for functionality. It discusses key components like the Dalvik Virtual Machine, application framework, views, layouts, and the Android manifest, which contains essential information about the app. Additionally, it highlights the activity life cycle and the use of intents for communication between applications.
Training Session 2 - Day 2
- 1. HELLO WE MEET AGAIN
- 4. Android is built on top of Linux kernel.
- 5. Android is built on top of Linux kernel. Android uses a number of libraries to perform various functionalities.
- 6. Android is built on top of Linux kernel. Android uses a number of libraries to perform various functionalities. Just like the Java Virtual Machine in our computers, Android has its own Dalvik Virtual Machine optimized for itself.
- 7. Android is built on top of Linux kernel. Android uses a number of libraries to perform various functionalities. Just like the Java Virtual Machine in our computers, Android has its own Dalvik Virtual Machine optimized for itself. Higher-level services to applications in the form of Java classes: Application Framework.
- 8. Android is built on top of Linux kernel. Android uses a number of libraries to perform various functionalities. Just like the Java Virtual Machine in our computers, Android has its own Dalvik Virtual Machine optimized for itself. Higher-level services to applications in the form of Java classes: Application Framework. We will write applications to be installed on the Application layer only.
- 10. Android’s defined tags Introduction to xml Used to define some of the resources - Layouts - Strings Used in Android Manifest Preferred way for defining UI elements - Separation of code
- 11. Simple UI
- 12. LO AU YT Eclipse has a great UI creator - Generates all the xml for you Composed of View objects Can be specified for portrait or landscape - Different designs for different orientation.
- 13. VIEWS A layout/activity is composed of Views and ViewGroups. View is something that is visible. Examples: - - - - TextViews, Buttons, TimePicker, DatePicker
- 14. VIEWS 3 ways to declare width and height a. b. c. fill_parent wrap_content match_parent <Button android:id = “@+id/button” android:layout_width = “fill_parent” android:layout_height = “wrap_content” android:text = “Button”/> { DO NOT FORGET TO DEFINE US
- 15. VIEWS { <EditText android:id = “@+id/number” android:layout_width = “fill_parent” android:layout_height = “wrap_content” android:text = “number”/> You can change the type of inputs as necessary
- 16. VIEWS <TextView android:id = “@+id/result” android:layout_height = “wrap_parent” android:layout_weight = “fill_content” android:text = “invisible”/> 3 ways to declare visibility a. b. c. visible invisible gone
- 17. FrameLayout 4 One or more View can be grouped into a ViewGroup RelativeLayout 3 This is the <body> to your view. LinearLayout 2 ViewGroups 1 TableLayout 5 ScrollView, etc.
- 18. Each layout has something unique to it. Each layout has a purpose!
- 19. LinearLayout Declaring the XML namespace (done in the 1st ViewGroup) <LinearLayout xmlns:android=“http://schemas.android.com/apk/res/ android” android:layout_width= “match_parent” android:layout_height= “match_parent” android:orientation= “vertical”> … (TextViews, Buttons etc.) </LinearLayout> Unique for this ViewGroup a. Vertical b. Horizontal
- 20. RelativeLayout Does not have any android:orientation. Affects the layouts inside it Views are arranged according to references.
- 21. RelativeLayout <RelativeLayout ..> <Button android:id= “@+id/btn” android:layout_alignParentTop= "true" … /> <TextView android:layout_below = “@id/btn” … /> <TextView android:layout_toRightOf = “@id/btn” …/> <TextView android:layout_toLeftOf = “@id/btn” …/> <TextView android:layout_alignParentBottom = “true” .../> </RelativeLayout> Various other positioning techniques also there: alignLeft alignBaseLine above, etc.
- 23. LETS UNITE! <LinearLayout … > <RelativeLayout … > … </RelativeLayout> </LinearLayout>
- 24. You can use ViewGroup within ViewGroup LAYOUTCEPTION!
- 25. INTENTS
- 26. ENTS <a href= “target”>page 2</a> Intent ~ Redirecting ! Intent is used to call into android's drivers, other applications as well. Powerful inter/intra application messagepassing framework. While working with intents we also have to work with the Android Manifest
- 27. Android Manifest Presents essential information about the application to the Android system Information the system must have before it can run any of the application's code.
- 28. Remember this?
- 29. Manifest Name of the Java package for the application. It describes the components of the application the activities, services, broadcast receivers, and content providers.
- 30. Manifest It declares which permissions the application must have in order to access protected parts of the API and interact with other applications. It declares the minimum level of the Android API that the application requires … and much more.
- 31. MODIFICATION IN ANDROID MANIFEST Declares an activity (an Activity subclass) that implements part of the application’s visual user interface. <activity android:name=".OtherClass"> <intent-filter> <action android:name="android.intent.action.NAME"/> <category android:name="android.intent.category.DEFAULT"/> </intent-filter> </activity> The types of intents that an app can respond to Adds an action to an intent filter Adds a category name to an intent filter
- 32. In MainActivity Intent i = new Intent(MainActivity.this, OtherClass.class); // Instantiating the intent class i.putExtra(“name”, value); // values to be sent startActivity(i); // Starting the intent In OtherClass Intent i = getIntent(); //getting the intent object String name = i.getStringExtra(“name”); // getting value from passed intent Intents
- 33. HAVE YOU EVER WONDERED WHAT HAPPENS WHEN YOU PRESS THE BACK BUTTON/ HOME BUTTON ON ANDROID?
- 35. Activity Life Cycle onCreate() : instantiate views, setup references, implement listeners. onPause() : save data/state in the application. onResume() : can be used to load the saved state, is always called when the application comes into view.
- 36. THAT’S ALL FOLKS! WE’LL SEE YOU TOMORROW