Slides from developer.android.com and adopted from Janzen

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Android built on Linux 2.6 kernel
What is a kernel?
Provides security, memory management, process management, network stack, and driver model
Abstraction layer between hardware and the software stack
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A set of C/C++ libraries exposed to developers through the application framework
System C library - a BSD-derived implementation of the standard
C system library (libc), tuned for embedded Linux-based devices
Media Libraries - based on PacketVideo's OpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3,
AAC, AMR, JPG, and PNG
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A set of C/C++ libraries exposed to developers through the application framework
Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications
FreeType - bitmap and vector font rendering
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A set of C/C++ libraries exposed to developers through the application framework
LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view
SGL - the underlying 2D graphics engine
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A set of C/C++ libraries exposed to developers through the application framework
3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer
SQLite - a powerful and lightweight relational database engine available to all applications
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Runtime libraries provide most of the functionality in the core Java libraries
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Each app has a process and an instance of Dalvik VM
Uses Dalvik Executable (.dex) format – low memory footprint
VM is register based runs compiled Java classes
The linux kernel provides Dalvik with needed functionality
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Named for Dalvik in Iceland, a fishing village where ancestors of Dan Bornstein lived.
Dalvik is discontinued process virtual machine as of Android version 4.4 (KitKat)
The successor of Dalvik is Android Runtime (ART), which uses the same bytecode and .dex files, aiming at performance I improvements transparent to end users.
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The framework allows developers to build cool apps
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Set of services and systems
Views to build apps: lists, grids, text boxes, buttons, browser
Content providers enable apps to share data between each other
Resource manager for access to non-code resources such as localized strings, graphics, and layout files
A Notification manager that enables all applications to display custom alerts in the status bar
Activity manager manages lifecycle of apps and provides a common navigation backstack
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Basic block for a UI component, occupying a rectangle on the screen
It draws and handles events
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Widgets – interactive UI components
Buttons, text fields, spinners, date picker, map,etc.
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ViewGroup – ways to group other views
Layouts – invisible containers holding views and define properties
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Core applications ship with android.
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Value
Strings, colors, dimensions, arrays (strings, integers, typed), bool, ID,
Drawable – something drawn to the screen
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Bitmaps, NinePatch (stretchable) images
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PNG is preferred, JPG, and GIF supported
Layout
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Layouts define the look of your activity, can specify in XML or with code, XML often easier
Animations
Property – modify object’s property values over time
Tween – rotate, move, stretch, and fade a view
Frame – to display a sequence of images
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Color State List – change color based on state
Example: button is pressed, focused, or neither, define color for each
Menu – defines app menu (options, context, submenu, …) that can be inflated
Style – defines the format and look of a UI for view or activity
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Written in Java, using Android SDK to compile into an
Android Package
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Each app lives in its own security sandbox (principle of
least privilege: only access to what it needs)
Android OS is multi-user with each app a user
Each app gets a user ID
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Can be shared between apps (also share same process and VM)
Each process has own VM – runs in isolation
Each app has its own process – started for any component
Can request permission to access device data (SMS, camera…)
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Granted at install time
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Intents and Intent Filters
Activities
Services
Content Providers
Broadcast Receivers
App Widgets
Processes and Threads
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Intents and Intent Filters
An Intent is a messaging object you can use to request an action from another app component. Intents (an asynchronous message) are used to start components
(except content providers)
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Content providers are activated when targeted by a request from a
ContentResolver. Call query() on a ContentResolver to query a content
Provider
Start Activity - An Activity represents a single screen in an app. You can start a new instance of an Activity by passing an Intent to startActivity().
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Start Service - A Service is a component that performs operations in the background without a user interface. You can start a service to perform a onetime operation (such as download a file) by passing an Intent to startService().
Deliver Broadcast - A broadcast is a message that any app can receive. The system delivers various broadcasts for system events, such as when the system boots up or the device starts charging. You can deliver a broadcast to other apps by passing an Intent to sendBroadcast(), sendOrderedBroadcast(), or sendStickyBroadcast().
An Intent filter specifies the types of intents that an activity, service, or broadcast receiver can respond to. An intent filter declares the capabilities of its parent component.
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Activities
A single screen with a user interface
Example – text message screen, inbox, compose email, etc.
They are independent
An app may have more than one
Typically, one activity in an application is specified as the "main" activity, which is presented to the user when launching the application for the first time.
Can be started by other applications (if allowed)
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Activities
Fragments - A Fragment represents a behavior or a portion of user interface in an Activity. You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities.
Loaders – They make it easy to asynchronously load data in an activity or fragment. They are available to every Activity and
Fragment. Monitor the source of their data and deliver new results when the content changes
Tasks and Back Stack - A task is a collection of activities that users interact with when performing a certain job. The activities are arranged in a stack (the "back stack"), in the order in which each activity is opened. When the user presses the Back button, the current activity is popped from the top of the stack (the activity is destroyed) and the previous activity resumes (the previous state of its UI is restored). Activities in the stack are never rearranged, only pushed and popped from the stack
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Services
Runs in the background for long-running operations or remote processes
Has no user interface
Example – play music, fetch data
An activity can start a service, or bind to a service for interaction.
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Content Providers
Manages a shared set of application data
 Stored in the file system, an SQLite database, on the web, any other persistent location you have access to
Other apps can query or modify data (if allowed)
Example: contact information
Can also be used for private app data
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Broadcast Receivers
Responds to system-wide broadcasts
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Generally originate from system, i.e. low battery, screen off, picture taken.
Apps can also broadcast, i.e. data ready for use
No user interface but may create a status bar notification
Generally a gateway to other components and light weight
 i.e. start a service to perform work based on an event
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Any application can start another application’s component
Will start a process for the component’s app, not run in yours
Means no single entry point (i.e main())
You can’t start it, need to have system deliver a message with your intent to start a component
Makes it much easier to add functionality to your app
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App Widgets are miniature application views that can be embedded in other applications (such as the Home screen) and receive periodic updates. These views are referred to as Widgets in the user interface, and you can publish one with an App Widget provider.
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When an application component starts and the application does not have any other components running, the Android system starts a new Linux process for the application with a single thread of execution. By default, all components of the same application run in the same process and thread (called the "main" thread).
If an application component starts and there already exists a process for that application (because another component from the application exists), then the component is started within that process and uses the same thread of execution.
You can arrange for different components in your application to run in separate processes, and you can create additional threads for any process.
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Each app has an AndroidManifest.xml file
Declare all the components in this file
 In root of app project directory
Identify user permissions required by app (ie internet access, rw contacts,…)
Declare minimum API level required
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Declare hardware and software features used or required i.e camera, bluetooth services, camera, multitouch screen
API libraries needed by app for linking
And more
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Adapted from Janzen

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Generated by Android
External Activity
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AdventDevos displays the calendar of dates
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Devo displays a single devotion
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Intent myIntent = new Intent(AdventDevos.this, Devo.class); myIntent.putExtra("ButtonNum", "" + index); startActivity(myIntent);

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AdventDevos displays the calendar of dates
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Devo displays a single devotion
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Bundle extras = getIntent().getExtras();
String value = extras.getString("ButtonNum");
Integer buttonNum = Integer.valueOf(value);

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Devos has button to URL
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Browser launched
Intent i = new Intent(Intent.ACTION_VIEW,
Uri.parse("http://www.biblegateway.com/passage/?search="+ passage +"&version=NIV")); startActivity(i);
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“An activity is a single, focused thing that the user can do.
Almost all activities interact with the user, so the Activity class takes care of creating a window for you in which you can place your UI with setContentView(View).” http://developer.android.com/reference/android/app/
Activity.html#ActivityLifecycle
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http://developer.android.com/guide/topics/manifest/manifest-intro.html
<?xml version="1.0" encoding="utf-8"?> Each upload to PlayStore requires versionCode increment
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.simexusa.adventdevotions" android:versionCode="2" android:versionName="1.0">
Specifies icon for launching app
<application android:icon="@drawable/star" android:label="@string/app_name" android:debuggable="false">
<activity android:name=".AdventDevos" android:label="@string/app_name">
<intent-filter>
Specifies icon label for launching app
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Devo"/>
</application>
<uses-sdk android:minSdkVersion=“19" />
Specifies activity to be launched at startup
<uses-permission android:name="android.permission.INTERNET" />
</manifest>
SDK version required by app

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See main.xml and devo.xml
Activity associates with layout xml file using setContentView(R.layout.main); or setContentView(R.layout.devo); in onCreate()
Note TableLayout and TableRow similar to <table> and <tr> in html
Note use of dimen (see values/dimens.xml) and color (see values/colors.xml)
Also see strings.xml
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<?xml version= "1.0" encoding= "utf-8" ?>
<LinearLayout xmlns:android= "http://schemas.android.com/apk/res/android" android:orientation= "vertical" android:layout_width= "fill_parent" android:layout_height= "fill_parent" android:background= "@color/background" >
<TableLayout android:layout_width= "wrap_content" android:id= "@+id/TableLayout01" android:layout_height= "wrap_content" >
<TableRow android:paddingTop= "8px" >
<Button android:text= "Nov. 29" android:id= "@+id/Button01" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:textSize= "@dimen/button_width" ></Button>
<Button android:text= "Nov. 30" android:id= "@+id/Button02" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:textSize= "@dimen/button_width" ></Button>
<Button android:text= "Dec. 1" android:id= "@+id/Button03" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:textSize= "@dimen/button_width" ></Button>
<Button android:text= "Dec. 2" android:id= "@+id/Button04" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:textSize= "@dimen/button_width" ></Button>
</TableRow > …
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<?xml version= "1.0" encoding= "utf-8" ?>
<LinearLayout xmlns:android= "http://schemas.android.com/apk/res/android" android:orientation= "vertical" android:layout_width= "fill_parent" android:layout_height= "fill_parent" android:gravity= "center_horizontal" android:background= "@color/background" >
<TextView android:text= "Date" android:id= "@+id/Date" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:gravity= "center_horizontal" android:textStyle= "italic" android:textSize= "@dimen/reference_width" android:typeface= "serif" android:textColor= "@color/text" ></TextView>
<TextView android:text= "Title" android:id= "@+id/Title" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:gravity= "center_horizontal" android:textStyle= "bold" android:textSize= "@dimen/reference_width" android:typeface= "serif" android:textColor= "@color/text" ></TextView>
<Button android:text= "Read Scripture" android:id= "@+id/ButtonScripture" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:gravity= "center_horizontal" android:textSize= "@dimen/reference_width" ></Button>
<ScrollView android:id= "@+id/ScrollView01" android:layout_height= "fill_parent" android:layout_width= "fill_parent" >
<TextView android:text= "Body" android:id= "@+id/Body" android:layout_width= "wrap_content" android:layout_height= "wrap_content" android:gravity= "left" android:textSize= "@dimen/reference_width" android:typeface= "serif" android:textColor= "@color/text" ></TextView>
</ScrollView>
</LinearLayout>
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<?xml version= "1.0" encoding= "utf-8" ?>
<resources>
<dimen name= "button_width" >17sp</dimen>
<dimen name= "reference_width" >20sp</dimen>
</resources>
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<?xml version= "1.0" encoding= "utf-8" ?>
<resources>
<color name= "background" >#AAFFFF99</color>
<color name= "text" >#FF000000</color>
</resources>
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<?xml version= "1.0" encoding= "utf-8" ?>
<resources>
<string name= "hello" >Hello World,
AdventDevos!</string>
<string name= "app_name" >Advent
Devotions</string>
</resources>
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All Apps have resources (non-code)
Images, audio, animations, menus, styles, colors, layouts…
Can update app characteristics without modifying code
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Can have device dependent resources
Different hardware capabilities
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Can have user dependent resources
Languages, preferences, etc
Each resource has unique integer ID
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Use a qualifier to decide which set of resources to use
Portrait vs landscape
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Adapted from Janzen
Except as otherwise noted, the content of this presentation is licensed under the Creative Commons Attribution 2.5 License.

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http://developer.android.com/guide/topics/fundamentals.html
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has focus, accepting UI events onResume to onPause
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Visible, but does not have focus onStart to onStop
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onCreate to onDestroy
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Processes keep around for as long as possible, will kill less important processes
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Foreground activity at top of screen user interacting with - most important.
Only killed if out of memory
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Visible activity is visible to user but not in foreground, is extremely important
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Only killed if required to keep the foreground activity running.
Background activity is not visible (paused) so not critical,
System may kill to reclaim memory for foreground or visible processes.
If user navigates back to activity, onCreate(Bundle) called
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Empty process is hosting no components.
Killed very quickly as memory becomes low.
Background operations executed in BroadcastReceiver or Service to keep process around. http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle
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Campus Maps App
Shows user location on campus map image http://market.android.com/search?q=pname:com.simexusa.campusmaps_full
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Campus Maps
Turn on/off GPS to save battery when UI not in focus
}
@Override protected void onPause() { super .onPause();
//stop receiving GPS and Orientation data locationManager.removeUpdates(locationListener);
}
@Override protected void onResume() { super .onResume();
//restart receiving GPS and Orientation data locationManager.requestLocationUpdates(provider, 2000, 10, locationListener);
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Campus Maps
Save state as app could get killed after onStop()
@Override protected void onStop() { super .onStop(); savePreferences();
}
@Override
} protected void onStart() { super .onStart(); restoreUIState();
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Campus Maps
Save state as app could get killed after onStop()
} private void savePreferences() {
SharedPreferences cmSharedPreferences = getSharedPreferences( CMPREFS ,Activity.
MODE_PRIVATE );
SharedPreferences.Editor editor = cmSharedPreferences.edit(); editor.putBoolean( VIRTUAL_MODE , inVirtualMode); editor.putInt( MAP_INDEX , curMapIndex); editor.commit();
} private void restoreUIState() {
SharedPreferences cmSharedPreferences = getSharedPreferences( CMPREFS ,Activity.
MODE_PRIVATE ); inVirtualMode = cmSharedPreferences.getBoolean( VIRTUAL_MODE , true ); curMapIndex = cmSharedPreferences.getInt( MAP_INDEX , 0);
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View
Control
ViewGroup
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Layout
Widget (Compound Control)
Many expected Views
Button, CheckBox, RadioButton
TextView, EditText, ListView
Can be customized by extending and overriding onDraw()
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Layouts can specify UI elements (provided and custom) res/layout
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Icon Menu (up to 6 icons)
Expanded Menu (from More on Icon Menu)
Submenus
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Active or running
Top of stack
In foreground of screen
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Paused
Visible but lost focus
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Stopped
Obscured by another activity
No longer visible, but keeps state
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Dead
If paused or stopped can be killed or asked to finish
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Must be restarted
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Called when fist created
Static setup
Create views, bind data, …
Provides Bundle containing activity’s previously frozen state, if there was one
Always followed by onStart()
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Called after activity has been stopped, prior to it being restarted
Followed by onStart()
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Called when activity becomes visible to user
Followed by onResume() if activity comes to the foreground or onStop() if becomes hidden
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Called when activity will start interacting with user
Activity now on top of activity stack, with user input going to it.
Followed by onPause()
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Called when system about to start resuming a previous activity.
Use to commit unsaved changes to persistent data, stop animations, and anything else consuming CPU
Needs to be very quick since next activity will not resume until done
Followed by OnResume()
(activity returns back to front) or onStop()
(becomes invisible)
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Called when the activity is no longer visible
Another activity covering it
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New activity started
Existing activity moved to front
This one being destroyed
Followed by onRestart()
(activity coming back for interaction) or onDestroy() (going away)
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Final call before being destroyed
Activity finished (finish() called)
Destroyed by system to save space
Use isFinishing() to figure out which
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Ringer in Vibrate mode based on Calendar notifications
Roll Taker using the Camera
Sync events on multiple different Calendars
Developing useful widgets
Shopping app with nice features (camera, barcode support)
Deal Monitoring app
Weather reporter
International student app (TAMUCC or just CS)
Paint mixer
Islander game, lane based attack, islander theme (tiki)
Humans and Zombies
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