Android Development Workshop

Android Development Workshop - Presentation Transcript

“I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone.” Bjarne Stroustrup copyright © 2008 cod technologies ltd www.codtech.com

agenda ● introduction to android ● android architecture ● building blocks ● your first android application ● testing and performance ● best practices copyright © 2008 cod technologies ltd www.codtech.com

introduction to android after this section you will... ● identify unique features of android platform ● compare android against other platforms ● understand android building blocks copyright © 2008 cod technologies ltd www.codtech.com

what is android ? ● android is the first complete, open and free mobile platform ● developed by Open Handset Alliance ● software stack than includes – operating system – middleware – key applications – rich set of APIs Portions of this page are reproduced from work created and shared by Google and used according to terms described in the Creative Commons 2.5 Attribution License. copyright © 2008 cod technologies ltd www.codtech.com

is android linux ? NO, android is not linux ! android is based on a linux kernel but it's not GNU/Linux ● no native windowing system ● no glibc support ● no GNU/Linux utilities copyright © 2008 cod technologies ltd www.codtech.com

so is android java ? NO, android is not java ! android is not an implementation of any of the Java variants ● uses the java language ● implements part of the Java5 SE specification ● runs on a dalvik virtual machine instead of JVM copyright © 2008 cod technologies ltd www.codtech.com

android linux kernel android is based on a linux 2.6 kernel, providing rnel, p ● security ● memory management ● process management ● network stack ● driver model ● abstraction layer kernel source: source.android.com copyright © 2008 cod technologies ltd www.codtech.com

linux kernel enhancements android introduces some linux kernel patches ● alarm ● ashmem ● binder ● power management ● low memory killer (no swap space available) ● logger copyright © 2008 cod technologies ltd www.codtech.com

unique platform characteristics android characteristics not found on other platforms ● open source ● “all applications are equal” model ● dalvik virtual machine copyright © 2008 cod technologies ltd www.codtech.com

other characteristics interesting features as well, but they are more common across other mobile platforms ● application framework enabling reuse of components ● integrated browser based on WebKit OSS engine ● 3D graphics based on the OpenGL ES ● SQLite for structured data storage ● media support for common audio, video, and still images ● camera, GPS, compass, and accelerometer copyright © 2008 cod technologies ltd www.codtech.com

android building blocks after this section you will... ● recognize the fundamental building blocks ● use these building blocks to create applications ● understand applications lifecycle copyright © 2008 cod technologies ltd www.codtech.com

Activities states ● active – at the top of the stack ● paused – lost focus but still visible – can be killed by LMK ● stopped – not at the top of th stack ● dropped – killed to reclaim its memory copyright © 2008 cod technologies ltd www.codtech.com

Views ● Views are basic building blocks ● know how to draw themselves ● respond to events ● organized as trees to build up GUIs ● described in XML in layout resources copyright © 2008 cod technologies ltd www.codtech.com

pattern: load layout android compiles the XML layout code that is later loaded in code usually by public void onCreate(Bundle savedInstanceState) { ... setContentView(R.layout.filename); ... } copyright © 2008 cod technologies ltd www.codtech.com

pattern: ids using a unique id in a XML View definition permits locating it later in Java code private View name; public void onCreate(Bundle savedInstanceState) { ... name = (View) findViewById(R.id.name); ... } copyright © 2008 cod technologies ltd www.codtech.com

Intents ● Intents are used to move from Activity to Activity ● describes what the application wants ● provides late runtime binding primary attributes attribute description action the general action to be performed, such as VIEW, EDIT, MAIN, etc. data the data to operate on, such as a person record in the contacts database, as URI copyright © 2008 cod technologies ltd www.codtech.com

Services ● services run in the background ● don't interact with the user ● run on the main thread of the process ● is kept running as long as – is started – has connections copyright © 2008 cod technologies ltd www.codtech.com

ConentProviders ● ContentProviders are objects that can – retrieve data – store data ● data is available to all applications ● only way to share data across packages ● usually the backend is SQLite ● they are loosely linked to clients ● data exposed as a unique URI copyright © 2008 cod technologies ltd www.codtech.com

AndroidManifest.xml ● control file that tells the system what to do and how the toplevel components are related ● it's the “glue” that actually specifies which Intents your Activities receive ● specifies permissions copyright © 2008 cod technologies ltd www.codtech.com

your first android after this section you will... ● create your own android map project ● design the UI ● externalize resources ● react to events ● run the application copyright © 2008 cod technologies ltd www.codtech.com

default application ● autogenerated application template ● default resources – icon – layout – strings ● default AndroidManifest.xml ● default run configuration copyright © 2008 cod technologies ltd www.codtech.com

designing the UI this simple UI designs contains ● the window title ● a spinner (drop down box) containing the desired location over the map ● a map displaying the selected location copyright © 2008 cod technologies ltd www.codtech.com

create the layout ● remove old layout ● add a RelativeLayout ● add a View (MapView not supported by ADT) ● replace View by com.google.android.m apview ● change id to mapview ● add a Spinner filling parent width copyright © 2008 cod technologies ltd www.codtech.com

run the application ● com.google.android. maps it's an optional library not included by default ● add <uses-library android:name=\"com.go ogle.android.maps\" / > to manifest as application node copyright © 2008 cod technologies ltd www.codtech.com

Google Maps API key ● checking DDMS logcat we find java.lang.IllegalArgumentException: You need to specify an API Key for each MapView. ● to access Google Maps we need a key ● application must be signed with the same key ● key can be obtained from Google ● MapView should include android:apiKey=\"0GNIO0J9wdmcNm4gCV6S0nlaFE8bHa9W XXXXXX\" copyright © 2008 cod technologies ltd www.codtech.com

MapActivy ● checking DDMS logcat again java.lang.IllegalArgumentException: MapViews can only be created inside instances of MapActivity. ● change base class to MapActivity ● fix imports ● add unimplemented methods copyright © 2008 cod technologies ltd www.codtech.com

where is the map ? ● still no map displayed ● check DDMS logcat ● lots of IOExceptions ! ● some uses permissions are missing – ACCESS_COARSE_LOCATION – INTERNET copyright © 2008 cod technologies ltd www.codtech.com

finally our map still some problems ... ● spinner is covered android:layout_alignPa rentTop=\"true\" ● has no prompt prompt: @string/prompt ● externalize resource copyright © 2008 cod technologies ltd www.codtech.com

pattern: adapters an Adapter object acts as a bridge between an AdapterView and the underlying data for that view ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource( this, R.array.array, android.R.layout.layout); view.setAdapter(adapter); The Adapter is also responsible for making a View for each item in the data set. copyright © 2008 cod technologies ltd www.codtech.com

pattern: resources resources are external files (that is, noncode files) that are used by your code and compiled into your application at build time. <resources> <string-array name=”array”> <item>item</item> </string-array> </resources> res = getResources().getType(id); copyright © 2008 cod technologies ltd www.codtech.com

arrays.xml <?xml version=\"1.0\" encoding=\"UTF-8\"?> <resources>  <string-array name=\"location_names\"> <item>Mediamatic Duintjer</item> <item>NH Hotel</item> <item>Airport</item> </string-array> <string-array name=\"locations\"> <item>52.363125,4.892070,18</item> <item>37.244832,-115.811434,9</item> <item>-34.560047,-58.44924,16</item> </string-array> </resources> copyright © 2008 cod technologies ltd www.codtech.com

complete the class ● create the locations array locations = getResources().getStringArray(R.array.locations); ● get the views (ids pattern) spinner = (Spinner) findViewById(R.id.Spinner01); mapView = (MapView) findViewById(R.id.mapview); ● create the adapter ArrayAdapter<CharSequence> adapter = ArrayAdapter. createFromResource(this, R.array.location_names, android.R.layout.simple_spinner_item); spinner.setAdapter(adapter) copyright © 2008 cod technologies ltd www.codtech.com

almost there ● map is displayed ● spinner is displayed ● drop down is displayed ● but there's no selection button ... adapter. setDropDownViewResource( android.R.layout. simple_spinner_dropdown_item ); copyright © 2008 cod technologies ltd www.codtech.com

respond to events ● when an item is selected map should be centered at that location spinner. setOnItemSelectedListener( new OnItemSelectedListener() { }); ● invoke goToSelectedLocation(ar g2); copyright © 2008 cod technologies ltd www.codtech.com

goToSelectedLocation protected void goToSelectedLocation(int position) { String[] loc = locations[position].split(\",\"); double lat = Double.parseDouble(loc[0]); double lon = Double.parseDouble(loc[1]); int zoom = Integer.parseInt(loc[2]); GeoPoint p = new GeoPoint((int)(lat * 1E6), (int)(lon * 1E6)); Log.d(TAG, \"Should go to \" + p); mapController.animateTo(p); mapController.setZoom(zoom); } copyright © 2008 cod technologies ltd www.codtech.com

more events ● turn map clickable android:clickable=\"true” ● override onKeyDown switch (keyCode) { case KeyEvent.KEYCODE_I: mapController.zoomIn(); break; case KeyEvent.KEYCODE_O: mapController.zoomOut(); break; case KeyEvent.KEYCODE_S: mapView.setSatellite( !mapView.isSatellite()); break; } copyright © 2008 cod technologies ltd www.codtech.com

testing and performance after this section you will... ● understand the best practices to develop for android ● identify the alternatives to test units, services and applications ● performance copyright © 2008 cod technologies ltd www.codtech.com

best practices ● consider performance, android is not a desktop ● avoid creating objects ● use native methods ● prefer virtual over interface ● prefer static over virtual ● avoid internal getter/setters ● declares constants final ● avoid enums copyright © 2008 cod technologies ltd www.codtech.com

testing ● android sdk 1.0 introduces – ActivityUnitTestCase to run isolated unit tests – ServiceTestCase to test services – ActivityInstrumentationTestCase to run functional tests of activities ● ApiDemos includes some test samples ● monkey, generates pseudorandom of user events copyright © 2008 cod technologies ltd www.codtech.com

1000000 1500000 2000000 2500000 3000000 500000 0 Add a local variable Add a member variable Call String.length() Call empty static native method Call empty static method performance Call empty virtual method Call empty interface method Call Iterator:next() on a HashMap Call put() on a HashMap Inflate 1 View from XML Inflate 1 LinearLayout with 1 TextView copyright © 2008 cod technologies ltd www.codtech.com Inflate 1 LinearLayout with 6 View Inflate 1 LinearLayout with 6 TextView Launch an empty activity Time