Android Survival Guide - Two years of software development

Android Survival GuideAlfredo Morresi (http://www.rainbowbreeze.it) Slide 1

Who I am

Born in the past millenium and still an happy software developer

Mobile addictedAndroid enthusiastic

Free software fanProud rider

… and Tiramisu' lover

rainbowbreeze


Overview

Online learnig resources

Paintless rotation with threads

Easy IoC/DI framework

Testing, from unit to automation

Honeycomb and backward compatibility

Libraries and frameworks

Q&A session


Chocolate Interaction model

Don't be scare: interact, collaborate, share your fun!


Useful online material – Patterns

Designing and Implementing Android UIshttp://www.google.com/events/io/2011/sessions/designing-and-implementing-android-uis-

for-phones-and-tablets.html http://code.google.com/p/iosched/

Advanced Topics for Expert Android App Devshttp://www.google.com/events/io/2011/sessions/android-protips-advanced-topics-for-expert-

android-app-developers.html

Developing Android REST client applicationshttp://www.google.com/events/io/2010/sessions/developing-RESTful-android-apps.html


Useful online material - ListView

The world of ListViewhttp://www.google.com/events/io/2010/sessions/world-of-listview-android.html

Lazy-loading of remote thumbnailshttp://android-developers.blogspot.com/2010/07/multithreading-for-performance.html

Drag and Drop capable ListView https://github.com/commonsguy/cwac-touchlist


Background thread, progress bar and rotation

Your application have to be smooth, don't use UI thread for long operation (> 200ms)

Yuo cannot update UI Thread from external threads

Use Activity.runOnUiThread(Runnable), View.post(Runnable), View.postDelayed(Runnable,

long), Handler to bypass the problem



public void onClick(View v) { //background thread new Thread(new Runnable() { public void run() { final Bitmap b = loadImageFromNetwork(); //update ui thread mImageView.post(new Runnable() { public void run() { mImageView.setImageBitmap(b); } }); } }).start();}



The simplest way

AsyncTaskCan access to UI Thread from separate thread

http://android-developers.blogspot.com/2009/05/painless-threading.html



protected void onCreate(Bundle savedInstanceState) { ... mLblResult = (TextView) findViewById(R.id.lblResult); LongTask longTask = new LongTask(); longTask.execute(); …}

private class LongTask extends AsyncTask<Void, Void, String> ... protected void onPostExecute(String result) { mLblResult.setText(result); }



But if the screen is rotated while the backgroud thread is still in execution?

UI not updated, dialogs disappear, NullPointerException, memory leaks...

OMG!



The clean way

- Define an Handler inside the Activity that process thread tasks (update/result)

- Create background thread passing the handler- Call the handler from the thread when a progress must be

published or the thread finish- Update activity reference inside thread using OnPause()

and OnResume()- Pay attention to OnStart and other Activity lifecycle events

http://code.google.com/p/rainbowlibs/source/browse/android/trunk/rainbowlibs/src/it/rainbowbreeze/libs/logic/RainbowBaseBackgroundThread.java

http://code.google.com/p/rainbowlibs/source/browse/android/trunk/rainbowlibs/src/it/rainbowbreeze/libs/ui/RainbowSplashScreenActivity.java



public class WebcamActivity extends Activity() {

private Handler mActivityHandler = new Handler() {

public void handleMessage(Message msg) { Log.debug("Message from external thread" + msg.what); switch (msg.what) { case RotationThread.OPERATION_STARTS: //create progress dialog + other UI operations break; case RotationThread.OPERATION_COMPLETED:

//remove the dialog + additional logic break; case RotationThread.OPERATION_ERROR: //remove the dialog + additional error logic




private RotatingThread mRotatingThread;

private void showWebcam() { //show a progress dialog showDialog(DIALOG_PREPARE_FOR_FULLSCREEN);

mRotatingThread = new RotatingThread( mActivityHandler,

webcamToShowId); mRotatingThread.start(); }



public class RotatingThread() extends Thread { private WeakReference<Handler> mCallerHandler;

public RotatingThread(Handler handler, int webcamId) { registerCallerHandler(handler); … }

public void registerCallerHandler(Handler newHandler { mCallerHandler = new WeakReference<Handler>(newHandler); }

public void unregisterCallerHandler() { mCallerHandler = null; }



public class RotatingThread() extends Thread { ...

public void run() { callHandlerAndRetry(OPERATION_STARTS);

//your long operation here

callHandlerAndRetry(OPERATION_COMPLETED); }



protected void callHandlerAndRetry(int messageCode) { for (int retries = 0; retries < TOTAL_RETRIES; retries++) {

if (null != mCallerHandler && null != mCallerHandler.get()) { Message message = mCallerHandler.get().obtainMessage(messageCode); message.arg1 = arg1; mCallerHandler.get().sendMessage(message); break; }

try { //what some times, maybe next time activity is ready Thread.sleep(INTERVAL_BETWEEN_RETRIES); } catch (InterruptedException ignoreExcepition) {} }}




@Override protected void onPause() { mRotatingThread.unregisterCallerHandler(); super.onPause(); }

@Override protected void onResume() { mRotatingThread.registerCallerHandler(mActivityHandler); super.onResume(); }




@Override public Object onRetainNonConfigurationInstance() { return mRotatingThread; }

@Override protected void onStart() { super.onStart(); mRotatingThread = (RotatinThread)getLastNonConfigurationInstance(); //nothing saved, first run of the activity if (null == mRotatingThread) showWebcam(); }



The short (but no totally complete) way

Use a Fragment and setRetainInstance(true)http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/

app/FragmentRetainInstance.html


Lazy loading singleton

Singleton PatternEnsure that only one instance of a class is created and provide a

global point of access to the object.

Create your own singleton or extend android.app.Application and modify its onCreate()

method.Base class for those who need to maintain global application state. You can provide your own implementation by specifying its name in

your AndroidManifest.xml’s <application> tag, which will cause that class to be instantiated for you when the process for your

application/package is created.



public class App extends Application { public static int myGlobalStaticValue; public int myGlobalValue;

@Override public void onCreate() { super.onCreate(); myGlobalStaticValue = 10; myGlobalValue = 20; }

<application android:name="it.rainbowbreeze.singleton.App">

int value = App.myGlobalStaticValue;int value = ((App)context.getApplication()).myGlobalValue;



DrawbacksSingleton is a pattern or an anti-pattern?

http://stackoverflow.com/questions/3826905/singletons-vs-application-context-in-android

OS may kill your application process, including the Application subclass instance. As a result the state is lost. When you later return to the application, then the OS will restore its activity

stack and Application subclass instance, but its fields will be null.

If you really need singleton, at least use lazy-loading singleton and avoid static fields to store

application lifecycle data



public class MySingleton() { private MySingleton mInstance;

public synchronized MySingleton getInstance(Context c) { if (null == mInstance) { mInstance = new MySingleton(context); } return mInstance; }

private MySingleton(Context appContext) { //initializes the object //reload SharedPreferences data }


Inversion of Control / Dependency Injection

Dependency Injection PatternThe object does not need to know in advance about how the

other part of the system works. Instead, the programmer provides (injects) the relevant system component in advance

along with a contract that it will behave in a certain way.http://en.wikipedia.org/wiki/Dependency_injection

Reduce the coupling among software components: better code testability, useful in libraries, clean

code.


Inversion of Control / Dependency Injectionpublic class ItemDao implements ItemDao {

public ItemDao(Context appContext) { //performs initialization }}

public DataManager implements IDataManager { INetManager mNetManager; IItemDao mItemDao;

public DataManager(INetManager netMngr, IItemDao itemDao) { mNetManager = netMngr; mItemDao = itemDao; }



DrawbacksComplex and less readable code

Chain of dependenciesMore code to write

SolutionsIoc/DI frameworks manage all the boring things!



public class AppEnv() { public static AppEnv i(Context appContext) { … mInstance = new AppEnv(appContext); return mInstance; }

private AppEnv(Context appContext) { mItemDao = new ItemDao(appContext); mDataManager = new DataManager(mNetMngr, mItemDao); }

ItemsDao mItemDao; public ItemsDao getItemDao(){ return mItemDao; }



DrawbacksCannot inject mock for testiong purposes

SolutionsSeparate the object factory from the singleton



public class ObjFactory {

public ItemDao createDao(Context appContext) { return new ItemDao(appContext); }

public DataManager createDataManager( INetManager netMngr, ItemDao itemDao) { return new DataManager(netManager, itemDao); }

}



public class AppEnv() { private static ObjFactory mObjFactory = new ObjFactory();

public static AppEnv i(Context c) { … mInstance = new AppEnv(c, mObjFactory); return mInstance; }

public static AppEnv i(Context c, ObjFactory customFactory) { … mInstance = new AppEnv(c, customFactory); return mInstance; }



public class AppEnv() { …

private AppEnv(Context appContext, ObjFactory objFactory) { mDao = objFactory.createDao(appContext); //... other initialization mDataManager = objFactory.createDataManager( mNetMngr, mDao); }

private ItemsDao mDao; public ItemsDao getItemDao(){ return mDao; }



--- inside your activity / component ---AppEnv appEnv = AppEnv.i(getContext());ItemDao dao = appEnv.getItemDao();

--- inside your test class ---MockObjFactory mockFactory = new MockObjFactory() { @Overrides public ItemDao createDao(Context appContext) { return new MockItemDao(appContext); }};AppEnv appEnv = AppEnv.i(getContext(), mockFactory);ItemDao dao = appEnv.getItemDao();



RoboGuiceLike Google Guice, but for Android

http://code.google.com/p/roboguice/http://stackoverflow.com/questions/5067681/guice-performance-on-android

Other solutionshttp://stackoverflow.com/questions/1029696/the-hunt-for-the-j2me-friendly-ioc-container-is-on


Testing - basic

Software testing = reduce risks of software implementation

Lot of support Android sidehttp://developer.android.com/guide/topics/testing/testing_android.html


Testing - first steps

Create new “Android Test Project”Create a class that extends TestCase

Code first test

Red, Green, Refactor!

http://developer.android.com/resources/tutorials/testing/helloandroid_test.html


Testing - first steps

public class MyFirstTest extends TextCase() { Private MyStringConverter mConverter;

public void setUp() { mConverter = new MyStringConverter(); }

public testUpperCaseConversion() { String result = mConverter.toUppercase(“ota2011”); assertEquals(“Wrong value”, “OTA2011”, result); }}


Testing with special Android Mock

AndroidTestCaseaccess to a context

http://developer.android.com/reference/android/test/AndroidTestCase.html

ApplicationTestCasetest app lifecycle, inject mock context

http://developer.android.com/reference/android/test/ApplicationTestCase.html

Activity Testing APItest activity lifecycle, inject mocks, send key or touch events, etc

http://developer.android.com/resources/tutorials/testing/activity_test.html

http://developer.android.com/guide/topics/testing/activity_testing.html



public class SpinnerActivityTest extends ActivityInstrumentationTestCase2<SpinnerActivity> {

protected void setUp() throws Exception { … mActivity = getActivity(); mSpinner = (Spinner) mActivity.findViewById(R.id.Spinner01); … } public void testSpinnerUI() { this.sendKeys(KeyEvent.KEYCODE_DPAD_CENTER); mPos = mSpinner.getSelectedItemPosition(); mSelection = (String)mSpinner.getItemAtPosition(mPos); assertEquals(resultText, mSelection);



ProviderTestCase2test contentProvicer with isolated context

http://developer.android.com/guide/topics/testing/contentprovider_testing.html

ServiceTestCasetest the service lifecycle, not the logic (detached)http://developer.android.com/guide/topics/testing/service_testing.html

ViewAsserts, MoreAssertsextended assertsextended asserts


Test automation with monkey

adb shell monkey -p your.package.name -v 500sends sequences of random events

http://developer.android.com/guide/developing/tools/monkey.html

monkeyrunner A Python program that runs an application, sends keystrokes to it,

takes screenshots of its user interface, and stores themhttp://developer.android.com/guide/developing/tools/monkeyrunner_concepts.html


Testing with external tools

RobotiumAutomatic black-box test cases for Android applications, with

gesture and actionshttp://code.google.com/p/robotium/

RobolectricFast and easy TDD, runs tests in normal JavaVM with mock

Android classes, no need to deploy on devicehttp://pivotal.github.com/robolectric/


Honeycomb and Backward Compatibility

Nowadays Android has two separate branches, but Ice Cream Sandwich will merge them

Avoid different versions of same app and prefer one adaptive Use alternative resources

AndroidManifest.xml filters for sdk, screen, hwPut some dirty if in code

http://code.google.com/p/iosched/



Resources

res/layout/main_activity.xml # For phonesres/layout-xlarge/main_activity.xml # Large screenres/layout-sw600dp/main_activity.xml # For 7” tabletsres/layout-sw720dp/main_activity.xml # For 10” tablets… and much more!

http://android-developers.blogspot.com/2011/07/new-tools-for-managing-screen-sizes.html



<manifest ... > <supports-screens android:smallScreens="false" android:normalScreens="false" android:largeScreens="false" android:xlargeScreens="true" android:requiresSmallestWidthDp="600" /> <application ... > ... </application></manifest>

http://android-developers.blogspot.com/2011/09/preparing-for-handsets.html http://android-developers.blogspot.com/2011/07/new-mode-for-apps-on-large-

screens.html



Dirty if

private static boolean fragmentsSupported = false;

private static void checkFragmentsSupported()throws NoClassDefFoundError { fragmentsSupported = android.app.Fragment.class != null;}

static { try { checkFragmentsSupported(); } catch (NoClassDefFoundError e) { fragmentsSupported = false; }


Testing with special Android Mock@Overridepublic void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

Intent intent = null; if (!fragmentsSupported) intent = new Intent(this, MainNonFragmentActivity.class); else intent = new Intent(this, MainFragmentActivity.class);

startActivity(intent); finish(); }}

http://blog.radioactiveyak.com/2011/02/strategies-for-honeycomb-and-backwards.html



Android Compatibility PackageBackport some 3.x APIs to 1.6 and 2.x

http://developer.android.com/sdk/compatibility-library.html

Support for Fragment, Loader, ViewPager

Native code on 3.x, library code on 2.x



Fragment

http://android-developers.blogspot.com/2011/03/fragments-for-all.html



setRetainInstance(true)activity is rotated but fragment is not destroyed and

recreated, lifecycle events are called.Finally!

Bug: http://code.google.com/p/android/issues/detail?id=17423Bug: http://stackoverflow.com/questions/6250580/fragment-already-added-

illegalstateexception


Honeycomb Backward Compatibility

ActionBarSherlockLibrary that uses native code for 3.x or its own code for 2.x

http://actionbarsherlock.com/

GreenDroidBrand new actionbar implementation

http://android.cyrilmottier.com/?p=274


Useful libraries and resources

Android UI patterns blogshttp://www.androiduipatterns.com http://www.androidpatterns.com

Android-ui-utilsAsset Studio, Pencil stencils, icon templates

http://code.google.com/p/android-ui-utils/

Additional Eclipse plugins for Androidsorce code, api level analysishttp://code.google.com/p/adt-addons/

Maven Android pluginhttp://code.google.com/p/maven-android-plugin/



Kernel sourceto learn, to get inspired and to solve bugs!

http://grepcode.com/snapshot/repository.grepcode.com/java/ext/com.google.android/android/2.3.4_r1/

Clean code in AndroidIoC, Binding, Annotation etc

http://blog.springsource.com/2011/08/26/clean-code-with-android

Crash reporthttp://androidblogger.blogspot.com/2010/03/crash-reporter-for-android-slight.html



Use Apache HTTP library instead of Java.NetHttps bugs, bufferization problems, etchttp://code.google.com/p/android/issues/detail?id=3164

http://groups.google.com/group/android-developers/msg/4ddd2e502f195e3a http://stackoverflow.com/questions/2105364/

Be part of communitiesmailing list, StackOveflow, ...

http://developer.android.com/resources/community-groups.html


Conclusion

Q & A(example: “Isn't it lunch time yet?”)

Technology

Android Survival Guide - Two years of software development