Android Tutorial

1

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Android Terminology

• Component Activities, content providers,
  broadcast receivers, and services that together
  make up an application
• Activity A single user-based task, usually, but
  not always, containing views
• Content Provider A component that serves data to
  other applications
• Broadcast receiver Component receiving
  notifications from other activities
• Service Background process responding local or
  remote application requests
• View Base class for most layout components
• UI Control textView, EditText, CheckBox,
  RadioButton, Spinner, etc.
• Layout Visual arrangement of containers and
  views
• Context Object containing the global state of an
  application environment
• Intent Asynchronous launching (or communication)
  message
• Intent Filter Criteria an Android device uses to
  find matching activities

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Android Terminology (cont.)

• Preference A key/value pair, which defines a
  user option
• Context Menu A menu executing after a long click
• Long Click Analogous to right clicks Hold click
  for approximately two seconds
• Modal Dialog requiring a response before
  continuing an activity
• Localize Separate data from an application, so
  changes don't require changing source. Refer to
  the data by an identifier name.
• Faded Edge An edge of a scrollable area that is
  faded to indicate that more information exists
• Fragment An independent module tightly bound to
  an application
• Bundle A set of key/value data pairs for
  persisting an application state

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Android Terminology (cont.)

• Gravity Determine alignment of text within a
  view of different size. Values can include top,
  bottom, left, center, fill
• Content Provider Wrapper for data, exposing data
  (SQL for example) to multiple applications, using
  a standard API.
• Cursor An object containing rows extracted from
  an SQL table
• Projection The columns of an SQL table of
  interest
• Live Folder Deprecated mechanism to display data
  on home page
• Developers now use Widgets
• Live updates display automatically
• Widgets Miniature icon-based application view
  (clock, battery charge percent) embedded on the
  home screen or application
• Live Wallpaper Dynamic interactive home screen
  backgrounds

5
Creating an Android Application

• Perform the following steps
• Create a new Android project in Eclipse with the
  wizard icon
• Register activities, specify Content Providers,
  Services, and security specifications in
  AndroidManifest.xml
• Create localized literals in the res/values
  directory
• Create other resources in various res directories
• Create UI layouts in the res/layouts directory
• Code the activity java class in the package folder

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Step 1 Eclipse Android Project Wizard

• First Screen
• Name the project
• Use workspace or browse to a new location
• Second Screen Pick an Android version
• The oldest version has the most compatibility
• Newer versions obviously have more features
• Some newer features are backwards compatible
• Third Screen Pick a package name
• Example com.acorns.lesson or com.cs415.name
• Click finish to complete the process

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Android Application Project Structure
8
Automatically Generated Files

• package com.paad.helloworldpublic final class
  BuildConfig
• public final static boolean DEBUG true

• package com.paad.helloworldpublic final class R
  
• public static final class attr
• public static final class drawable
• public static final int ic_launcher0x7f020000
  
• public static final class layout
• public static final int main0x7f030000
• public static final class string
• public static final int app_name0x7f040001
  
• public static final int hello0x7f040000

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Step 2 Create the Manifest

• The new project wizard
• Automatically Creates a default
  AndroidManifest.xml file
• Creates a default activity in the project
  directory
• Alter the manifest
• Register activities with intents, permissions,
  content providers, services, etc.
• There are two possibilities
• Edit the manifest directly
• Use the Manifest Editor that displays when
  clicking the AndroidManifest.xml file

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HelloWorld Manifest

• lt?xml version"1.0" encoding"utf-8"?gt
• ltmanifest xmlnsandroid"http//schemas.android.co
  m/apk/res/android" package"com.paad.helloworld"
  androidversionCode"1" androidversionName"1
  .0" gt
• ltuses-sdk androidminSdkVersion"1" // User
  cannot install if less (1default)
• androidtargetSdkVersion"15" /gt // Verify
  features between min target
• ltapplication androidicon"_at_drawable/ic_launc
  her"
• androidlabel"_at_string/app_name" gt
• ltactivity androidlabel"_at_string/app_name"
  
• androidname".MyActivity" gt
• ltintent-filter gt
• ltaction androidname"android.intent.action.MAI
  N" /gt
• ltcategory androidname"android.intent.category
  .LAUNCHER" /gt
• lt/intent-filtergt
• lt/activitygt
• lt/applicationgt
• lt/manifestgt

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Step 2 Register Activities
Definition A focused single task

• How? Alter the manifest!
• Create additional activities
• Create and/or fragments with intents,
  permissions, content providers, services, etc.
• There are two possibilities
• Edit the manifest directly
• Use the GUI that displays when clicking the
  AndroidManifest.xml file(Double click
  AndroidManifest.xml, click on application, scroll
  down and click on add, Choose activity from the
  dropdown, give it a name, and click finish to
  start coding)

12
Intent
Definition Messages that asynchronously launch
or communicate with other applications/activities

• Android Intent Resolver
• Applications sends intents to the Android system
• The Android intent resolver searches all
  application intent filters to find the most
  suitable matching activity
• Intents can target a single application or
  multiple applications broadcast for sequential
  handling
• Intent Filters
• Intent fields contain criteria fields defining
  whether an activity is appropriate
• Criteria fields include actions, a category, path
  to data, MIME type, a handling class, and
  security restrictions

More Details later
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Manifest Intent Filter Example
Note An intent launches an activity

• ltintent-filtergt
• ltaction androidname"android.inte
  nt.action.MAIN" /gt
• ltcategory androidname"android.in
  tent.category.LAUNCHER" /gt
• lt/intent-filtergtltintent-filtergt
• ltaction androidname"android.inte
  nt.action.VIEW" /gt
• ltaction androidname"android.inte
  nt.action.EDIT" /gt
• ltaction androidname"android.inte
  nt.action.PICK" /gt
• ltcategory androidname"android.in
  tent.category.DEFAULT" /gt
• ltdata androidmimeType"vnd.androi
  d.cursor.dir/vnd.google.note" /gt
• lt/intent-filtergtltintent-filtergt
• ltaction androidname"android.inte
  nt.action.GET_CONTENT" /gt
• ltcategory androidname"android.in
  tent.category.DEFAULT" /gt
• ltdata androidmimeType"vnd.androi
  d.cursor.item/vnd.google.note" /gt
• lt/intent-filtergt

The Main Entry when a user launches the
application
Launched by other applications for list access
Launched by other applications for single item
access
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Providing Access to NotePad Data

• ltintent-filtergt
• ltaction androidname"android.intent.action.VIEW"
  /gt
• ltaction androidname"android.intent.action.EDIT"
  /gt
• ltaction androidname"android.intent.action.PICK
  " /gt
• ltcategory androidname"android.intent.category.D
  EFAULT" /gt
• ltdata androidmimeType"vnd.android.cursor.dir/vn
  d.google.note" /gt
• lt/intent-filtergt

• Declares legal activity operations on a note
  directory.
• URI, vnd.android.cursor.dir/vnd.google.note ,
  retrieves a cursor of zero or more items
  (vnd.android.cursor.dir) with note pad data
  (vnd.google.note).
• Legal actions view or edit the directory of data
  (VIEW and EDIT ), or pick and return a particular
  note (PICK).
• Activities launched without a explicit package
  name require the DEFAULT category, or they will
  not be resolved

15
Another Android Manifest

• lt?xml version"1.0" encoding"utf-8"?gt
• ltmanifest xmlnsandroid"http//schemas.android.co
  m/apk/res/android"
• package"com.bikerolas"
  androidversionCode"30" androidversionName"1.2
  "gt
• ltuses-permission androidname"android.permiss
  ion.RECEIVE_BOOT_COMPLETED" /gt
• ltuses-permission androidname"android.permiss
  ion.ACCESS_LOCATION /gt
• ltuses-permission androidname"android.permiss
  ion.ACCESS_GPS" /gt
• ltuses-permission androidname"android.permiss
  ion. ACCESS_CELL_ID /gt
• ltapplication androidicon"_at_drawable/flingicn1"
• androidlabel"_at_string/app_name"
  androiddebuggable"false"gt
• ltactivity androidname".Fling"
  androidlabel"_at_string/app_name"gt
• ltintent-filtergtltaction
  androidname"android.intent.action.MAIN" /gt
• ltcategory androidname"android.intent.category.
  LAUNCHER" /gt lt/intent-filtergt
• lt/activitygt
• ltservice androidname".FlingService" /gt
• ltreceiver androidname".FlingServiceManager"
  androidpermission"android.permission.RECEIVE_B
  OOT_COMPLETED"gt
• ltintent-filtergtltaction androidname"android.int
  ent.action.BOOT_COMPLETED" /gt lt/intent-filtergt
• lt/receivergtlt/applicationgtltuses-sdk
  androidminSdkVersion"2"gtlt/uses-sdkgt
• lt/manifestgt

Note ACCESS_LOCATION and ACCESS_GPS were used by
earlier Android versions and are now deprecated
16
Localize Strings
How? Create XML files in the res/values
directory Why? Promotes Internationalize and
easier maintenance

• Example (Strings.xml)
• lt?xml version"1.0" encoding"utf-8"?gt
• ltresourcesgt
• ltstring name"hello"gtHello World,
  MyActivity!lt/stringgt
• ltstring name"app_name"gtPA4AD_Ch02_Hello_Worldlt/s
  tringgt
• lt/resourcesgt
• Build Android creates gen/ltpackageNamegt/R.java
  automatically from the information in
  res/Strings.xml
• Java Access setTitle(getText(R.string.hello))
• Manifest XML Access androidlabel"_at_string/app_na
  me"

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Layout Example (main.xml)
How? Store xml text files in the res/layouts
directory

• lt?xml version"1.0" encoding"utf-8"?gt
• ltLinearLayout xmlnsandroid"http//schemas.androi
  d.com/apk/res/android" androidorientation"verti
  cal" androidlayout_width"fill_parent"
  androidlayout_height"fill_parent"gt ltTextView
  androidlayout_width"fill_parent"
  androidlayout_height"wrap_content"
  androidtext"_at_string/hello" /gt
• lt/LinearLayoutgt
• Notes
• fill_parent (or match_parent Android 2.0 and
  later) fill the entire space of the parent layout
• Wrap_content uses as little space as needed
• LinearLayout is a vertical or horizontal list of
  items (like BoxLayout in Swing)

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The Java Code

• package com.paad.helloworld
• import android.app.Activity
• import android.os.Bundle
• public class MyActivity extends Activity
• / Called when the Activity is created or
  restarted. /
• _at_Override public void onCreate(Bundle
  savedState)
• super.onCreate(savedState)
  setContentView(R.layout.main)

A Bundle is a bunch of key/value pairs for
Applications to restore their state after an
Android termination
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Android Emulator

• Start the Emulator from Eclipse
• Right click on the application
• Select run as and then Android application
• To debug Select debug as and then Android
  Application
• After the first time, just click the run icon at
  the top of the Eclipse window
• Important notes
• The emulator takes quite a bit of time to launch
  be patient
• Dont shut down the emulator between application
  runs. Closing leads to long start up times, and
  sometimes confuses Eclipse
• Every Eclipse run reinstalls and re-launches the
  application

20
Debugging Applications

• Set debuggable"true" in the ltapplicationgt tag
• This is automatic when debugging in the emulator
• Manually explicitly set preference to debug on a
  real device
• Eclipse views
• DDMS Dalvik Debug Monitor Server
• Simulate Event Global Positioning Service (GPS),
  phone calls, Short Message System (SMS), etc.
• Debug Start with "Debug as"
• Execute emulator to get a terminal window and
  execute Linux commands to connect to SQL, execute
  queries, etc.
• ADB (Android Debug Bridge) Debug on actual
  devices (if debugging enabled) using Eclipse
  Note ADB is part of the SDK platform tools
• Techniques Logcat displays console output, Trace
  , Breakpoints, Strict mode

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Enable Device Debugging

• Eclipse windowgtopen perspective-gtothergtDDMS
• Enable debugging on device
• Older devices settingsgtapplicationsgtdevelopment
• Newer devices settingsgtabout phonegt tap build
  seven timesgt back

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Debugging Techniques

• Tracing the execution
• Start android.os.Debug.startmethodTracing("foo")
  
• Stop android.os.Debug.stopMethodTracing()
• Writes output to foo.trace on the emulator or
  device
• Log class
• Analogous to Java System.out.println or
  Javascript Console.log
• Example Log.v("category string", "message")
• Asynchronous Alert Dialogs AlertDialog.Builder
  build new AlertDialog(context)build.setTitle("
  Some Message")AlertDialog ad
  builder.create()ad.show()
• Breakpoints Set Eclipse breakpoint and use
  "Debug as" option

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Strict Mode (Android 2.3 and newer)

• Report violations and IO Operations Disk reads,
  disk writes, etc.
• Common options when detection occurs Write a Log
  message, display a dialog message, or crash the
  application
• ExampleStrictMode.setVMPolicy(new
  StrictMode.VMPolicy.builder() .detectDiskWrites()
  .detectLeakedSqlLiteObjects() .penaltyLog().penal
  tyDeath().build())
• Note The build retuns a ThreadPolicy object to
  the VM Policy builder
• Detect if in debug modeApplicationInfo info
  getContext().getApplicationInfo()if (info.flags
  ApplicationInfo.FLAG_DEBUGGABLE) ! 0) /
  code here /