Android Survival Guide - Two years of software development

Who I am
Born in the past millenium and still
an happy software developer

Mobile addicted
Android enthusiastic
Free software fan
Proud rider

… and Tiramisu' lover

rainbowbreeze

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

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 UIs
http://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 Devs
http://www.google.com/events/io/2011/sessions/android-protips-advanced-topics-for-expert-
android-app-developers.html

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


Useful online material - ListView

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

Lazy-loading of remote thumbnails
http://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

AsyncTask
Can 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/rainb
owbreeze/libs/logic/RainbowBaseBackgroundThread.java
http://code.google.com/p/rainbowlibs/source/browse/android/trunk/rainbowlibs/src/it/rainb
owbreeze/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 Pattern
Ensure 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;


Drawbacks
Singleton 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 Pattern
The 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.


public 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;
}


Drawbacks
Complex and less readable code
Chain of dependencies
More code to write

Solutions
Ioc/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;
}



Drawbacks
Cannot inject mock for testiong purposes

Solutions
Separate 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);
}

}



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;
}



…

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();



RoboGuice
Like Google Guice, but for Android
http://code.google.com/p/roboguice/
http://stackoverflow.com/questions/5067681/guice-performance-on-android

Other solutions
http://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 side
http://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

AndroidTestCase
access to a context
http://developer.android.com/reference/android/test/AndroidTestCase.html

ApplicationTestCase
test app lifecycle, inject mock context
http://developer.android.com/reference/android/test/ApplicationTestCase.html

Activity Testing API
test 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);



ProviderTestCase2
test contentProvicer with isolated context
http://developer.android.com/guide/topics/testing/contentprovider_testing.html

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

ViewAsserts, MoreAsserts
extended asserts


Test automation with monkey

adb shell monkey -p your.package.name -v 500
sends 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 them
http://developer.android.com/guide/developing/tools/monkeyrunner_concepts.html


Testing with external tools

Robotium
Automatic black-box test cases for Android applications, with
gesture and actions
http://code.google.com/p/robotium/

Robolectric
Fast 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, hw
Put some dirty if in code
http://code.google.com/p/iosched/



Resources

res/layout/main_activity.xml # For phones
res/layout-xlarge/main_activity.xml # Large screen
res/layout-sw600dp/main_activity.xml # For 7” tablets
res/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;
}

@Override
public 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 Package
Backport 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=17423
Bug: http://stackoverflow.com/questions/6250580/fragment-already-added-
illegalstateexception


Honeycomb Backward Compatibility

ActionBarSherlock
Library that uses native code for 3.x or its own code for 2.x
http://actionbarsherlock.com/

GreenDroid
Brand new actionbar implementation
http://android.cyrilmottier.com/?p=274


Useful libraries and resources
Android UI patterns blogs
http://www.androiduipatterns.com
http://www.androidpatterns.com

Android-ui-utils
Asset Studio, Pencil stencils, icon templates
http://code.google.com/p/android-ui-utils/

Additional Eclipse plugins for Android
sorce code, api level analysis
http://code.google.com/p/adt-addons/

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



Kernel source
to learn, to get inspired and to solve bugs!
http://grepcode.com/snapshot/repository.grepcode.com/java/ext/com.google.android/andro
id/2.3.4_r1/

Clean code in Android
IoC, Binding, Annotation etc
http://blog.springsource.com/2011/08/26/clean-code-with-android

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



Use Apache HTTP library instead of Java.Net
Https bugs, bufferization problems, etc
http://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 communities
mailing list, StackOveflow, ...
http://developer.android.com/resources/community-groups.html


Conclusion

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


Android Survival Guide - Two years of software development

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