Android Jumpstart Jfokus

Jumpstart to AndroidApp developmentLars Vogelhttp://www.vogella.deTwitter: @vogella

What is Android?FundamentalsConstructs of AndroidLive CodingQ&A

About me – Lars VogelIndependent Eclipse and Android consultant,trainer and book authorEclipse committerMaintains http://www.vogella.de Java, Eclipseand Android related Tutorials with more then amillion visitors per month.

More Android Sessions:Wednesday, 11.10 -12.00 - So whats so cool about Android 4.xThuersday – Friday – Full day Android training

Android Experience?

What isAndroid?

Android from 10 000 feet- Open Source- Full stack based on Linux- Java programming interface- Project is lead by Google- Tooling available for Eclipse (and other IDEs)

On Android you develop in Java(There is also the NDK which allows development in C / C++...)

Overview of the API Capabilities Rich UI components Threads and Background Processing Full network stack (Http, JSON) Database available Images Access to the hardware (GPS, Camera, Phone) and much more............

Its likeprogramming forhardware which is10 years old

… with insameperformancerequirements

On Android you develop in JavaReally?

Android Programming You use the Java programming language but Android does not run Java Bytecode

DalvikRun Dalvik Executable Code (.dex)Tool dx converts Java Bytecode into .dex• Register based VM vrs. stack based as the JVM• .dex Files contain more then one class• Approx. 50 % of the size of a class file• op codes are two bytes instead of one in the JVM• As of Android 2.2 Dalvik JIT compiler• Primary engineer: Dan Bornstein

DeveloperToolchain

Android Development Tools (ADT)for EclipseEclipse based tooling• Provide the emulator• Wizard for creating new project• Additional Tooling, e.g views

Emulator QEMU-based ARM emulator runs same image as a device Use same toolchain to work with device or emulator Inital startup is slooooowwwwww.....

AndroidManifest.xml• General configuration files for your application• Contains all component definitions of your appication

Resources from /res areautomatically „indexed“

ADT maintains areference to allresources in the R.java

Main Android programming constructs Activity Views Intents Broadcast Receiver Services ContentProvider

Context

ContextGlobal information about an application environment.Allows access to application-specific resources and classesSupport application-level operations such as launchingactivities, broadcasting and receiving intents, etc.Basically all Android classes need a contextActivity extends Context

DemoActivities project Your first

ActivityExtends ContextAn activity is a single, focusedthing that the user can do.Kind of a screen but not entirely...

View vrs ViewGroupandroid.viewView: UI Widget - Button - TextView - EditText

Layoutsandroid.view.ViewGroup - Layout - extends View• Layouts are typically defined via XML files (resources)• You can assign properties to the layout elements to influence their behavior.

Demo – Hello JFokus

Andoid isallowed to killyour app tosave memory.

Life Cyle of an Activityvoid onCreate(Bundle savedInstanceState)void onStart()void onRestart()void onResume()void onPause()void onStop()void onDestroy()

States of an Activity• Active/ Running – Visible and interacts with user• Paused – still visible but partically obscured (other transparant activity, dialog or the phone screen), instance is running but might be killed by the system• Stopped – completely obscured, e.g. User presses the home screen button, instance is running but might be killed by the system• Killed – if stopped or paused, system might calling finish or by killing it

To test flip your device

Def inin gA ctiv itie s

Calling ActivitiesCalling Activitiescreates a stack ->Back button goesback to theprevious activity-> Think of it as astack of cards

Defining Activities• Create a class which extends „Activitiy“• Create an entry in „AndroidManifest.xml“ for the activity.• <activity android:name=“MyNewActivity“></a ctivity>

I had only thebest intents....

IntentsMessage passing mechanism to startActivities, Services or to trigger(system) events.Allow modular architectureCan contain data (extra)

Intents • Explicit: Asking someone to do something • Implicit: Asking the system who can do something Intent

Demo Intents

Implicit Intents• new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.vogella.de"));• new Intent(Intent.ACTION_CALL, Uri.parse("tel: (+49)12345789"));• new Intent(Intent.ACTION_VIEW, Uri.parse("geo:50.123,7.1434?z=19"));• new Intent("android.media.action.IMAGE_CAPTURE");

Gettings resultsIntent intent = newIntent("android.media.action.IMAGE_CAPTURE");startActivityForResult(intent, 0);public void onActivityResult(int requestCode, intresultCode, Intent data) { if (resultCode == Activity.RESULT_OK && requestCode== 0) { String result = data.toURI(); Toast.makeText(this, result, Toast.LENGTH_LONG); }}

XMLDrawables

XML Drawables• XML Resources• Can be used to define transitions, shapes or state A drawable resource is something that can be drawn to the screen

Services and receiver

ServicesAllow real multitasking and background processingDe-coupled from the Activity life-cyle

ServicesService runs in the background without interacting with the user.Android provides a multitude of system services• NotificationService• VibratorService• LocationService• AlarmService• ....Access via context.getSystemService(Context.CONST);You can define your own service for things that should run in thebackground

Notification Manager Demo

ServicesService runs in the background without interacting with the user.Android provides a multitude of system services• NotificationService• VibratorService• LocationService• AlarmService• ....Access via context.getSystemService(Context.CONST);You can define your own service for things that should run in thebackground

Broadcast Receiver – Listen to events Example: BATTERY_LOW, ACTION_BOOT_COMPLETED android.intent.action.PHONE_STATE Defined statically in manifest or temporary via code Broadcast Receiver only works within the onReceive() method C2DM

Own Service• Extend Service or IntentService• start with startService(Intent) or bindService(Intent).• onStartCommand is called in the service• bindService gets a ServiceConnection as parameter which receives a Binder object which can be used to communicate with the service

How to start a service Broadcast Receiver – Event: BOOT_COMPLETED Or ACTION_EXTERNAL_APPLICATIONS_A VAILABLE startService in the onReceiveMethod() Timer Service Start BroadcastReceiver which starts the service

Demo alarmreceiver.phone

Security

Each apps gets into own Linux userand runs in its own process

Android Application requiresexplicit permissions, e.g. for• DB access• Phone access• Contacts• Internet• System messages

Background Processing

Be fast!Avoid ApplicationNotRespondingError

Use Threads (not the UI one)• Long running stuff should run in the background• Thread cannot modify the UI• Synch with the UI thread runOnUiThread(new Runnable)

Handler and AsyncTask• Handler runs in the UI thread• Allows to send Message object and or to send Runnable to it handler.sendMessage(msg) handler.post(runnable)• AsyncTask for more complex work

AsyncTask• To use it subclass itAsyncTask <TypeOfVarArgParams , ProgressValue ,ResultValue>doInBackground() – Do the workonPostExecute() – Update the UI

Saving the thread• If a thread runs in your Activity you want to save it.

Lifecycle - Thread• If Activity is destroyed the Threads should be preserved.• Close down Dialogs in the onDestroy() method• One object can be saved via onRetainConConfigurationInstance()• Access via getLastNonConfigurationInstance()• Only use static inner classes in your Threads otherwise you create a memory leakage.

Option Menus and Action Bar

Option Menu & Action Bar• Option Menu displays if „Menu“ button is pressed• You can decided if the entries are displayed in the Action Bar or in a menu• Use „ifRoom“ flag if possible.

Preferences

Read and Write Preferences• Key – Value pairs• PreferenceManager.getDefaultShared Preferences(this); – To read: getString(key), get... – To change use edit(), putType(key, value), commit()• To maintain use PreferenceActivity

PreferenceActivity• Create resource file (preference)• New Activity which extends PreferenceActivity• To add preferences: – addPreferencesFromResource(R.xml.prefer ences);• Saving and edits will be handled automatically by the PreferenceActivity

ListView

ListViewCan be used to display a list of itemsGets his data from an adapter

Adapter Data for ListView defined by AdapterView per row definedby Adapter

ListActivityListActivity has already a predefined ListView with the id @android:id/listwhich will be used automatically.Provides nice method hooks for typical operations on listsIf you define your own layout this layout must contain a ListView with theID:@+android:id/list

What if the layout should not be static?

Define your own Adapter

Reuse existing rowsIf convertView is not null -> reuse itSaves memory and CPU power (approx. 150 % faster according toGoogle IO)Holder Pattern saves 25%

Views and Touch

There is more....

I havefeelings Camera API Motion Detection Location API (GIS) Heat Sensor Accelerator

Example Camera API

I can talk and hearInternet (java.net, Apache HttpClient, JSON...)BluetoothEmailSMSVoIP (SIP (Session Initiation Protocol))

Other CapabilitiesPush to deviceInteractive Widgets on the homescreenLive Wallpapers (as background)Animations and StylingSimple List handling(Multi-) TouchNFCCanvas / OpenGL ES (Game programming....)Native Rendering

Android 4.0

Whats so cool about Android 4.0?• Come to my talk on Wednesday... ;-)

SummaryAndroid powerful and well- designed development platform Easy to get started Power to the developer

Android: Where to go from here:Android Introduction Tutorial http://www.vogella.de/articles/Android/article.htmlOr Google for „Android Development Tutorial“Android SQLite and ContentProvider Bookhttp://www.amazon.com/dp/B006YUWEFEMore on Androidhttp://www.vogella.de/android.html

Thank youFor further questions:Lars.Vogel@gmail.comhttp://www.vogella.deTwitter http://www.twitter.com/vogellaGoogle+ http://gplus.to/vogella

License & Acknowledgements• This work is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany License – See http://creativecommons.org/licenses/by-nc-nd/3.0/de/deed.en_US

Android Jumpstart Jfokus

by Lars Vogel on Feb 13, 2012

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Android Jumpstart Jfokus — Presentation Transcript