This document provides an overview of key Android development concepts and techniques. It discusses fragments, the support library, dependency injection, image caching, threading and AsyncTask, notifications, supporting multiple screens, and optimizing ListView performance. The document also recommends several popular Android libraries and open source apps that demonstrate best practices.

1. ANDROID
Does not Suck anymore!

2. Andy Rubin
No plans to leave Google. Oh, and just for
meme completeness -- there are over 900,000
android devices activated each day :-)

3. Android evolves

4. Android Design Patterns
http://developer.android.com/design/index.html

5. No More Menu Button

6. New Buttons

7. Notifications

8. Navigation

9. ActionBar

10. Action Bar Selection

11. MultiPane

12. Dialogs

13. Android is not ios

14. IOS Design
It was cool 2 years ago

15. Android is not ios

16. Fragmentation

17. Fragmentation

18. Fragmentation

19. Shut up and Show me Code Bitch!

20. Android Support Jar
● V4 ● V13
● Fragment ● FragmentCompat
● FragmentManager ● FragmentPagerAdapter
● FragmentTransaction ● FragmentStatePagerAdapter
● ListFragment
● DialogFragment
● LoaderManager
● Loader
● AsyncTaskLoader
● CursorLoader

21. Support Jar
Just change the import and use latest api's
It rocks!!!

22. Fragment
● Tablet and phone code comes together
● One ring to rule them all!!!

23. Fragment
Define in XML
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">
<fragment class="com.example.android.apis.app.FragmentLayout$TitlesFragment"
android:id="@+id/titles"
android:layout_width="match_parent" android:layout_height="match_parent" />
</FrameLayout>
Set Content in code
setContentView(R.layout.fragment_layout);
It works just like activity
public static class TitlesFragment extends ListFragment {

24. Create Fragment
DetailsFragment f = new DetailsFragment();
// Supply index input as an argument.
Bundle args = new Bundle();
args.putInt("index", index);
f.setArguments(args);

25. Fire the fragment
// Instantiate a new fragment.
Fragment newFragment = CountingFragment.newInstance(mStackLevel);
// Add the fragment to the activity, pushing this transaction
// on to the back stack.
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.simple_fragment, newFragment);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();

26. Get the parameters
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle args = getArguments();
if (args != null) {
mLabel = args.getCharSequence("label", mLabel);
}
}

27. Use XML
As much as you can

28. Inflate Views
● Design using XML
● And @java
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);

29. DialogFragment
Better Back button support
public static class MyDialogFragment extends DialogFragment {

30. Other Fragments
● ListFragment
● PreferenceFragment

31. Loaders
● Loader Callback Methods
onCreateLoader()
OnLoadFinished()
onLoaderReset()

32. Great Man
● Jack Wharton
https://github.com/JakeWharton

33. Libraries
● ActionBarSherlock
● ActivityCompat2
● NotificationCompat2
● NineOldAndroids
● SwipeToDismissNOA
● Android-ViewPagerIndicator

34. ActionBarSherlock
● At last you can use great ActionBar
● Just use
getSupportActionBar()
● Instead of
getActionBar()

35. NineOldAndroids
● ObjectAnimator.ofFloat(myObject, "translationY", -myObject.getHeight()).start();
AnimatorSet set = new AnimatorSet();
set.playTogether(
ObjectAnimator.ofFloat(myView, "rotationX", 0, 360),
ObjectAnimator.ofFloat(myView, "rotationY", 0, 180),
ObjectAnimator.ofFloat(myView, "rotation", 0, -90),
ObjectAnimator.ofFloat(myView, "translationX", 0, 90),
ObjectAnimator.ofFloat(myView, "translationY", 0, 90),
ObjectAnimator.ofFloat(myView, "scaleX", 1, 1.5f),
ObjectAnimator.ofFloat(myView, "scaleY", 1, 0.5f),
ObjectAnimator.ofFloat(myView, "alpha", 1, 0.25f, 1)
);
set.setDuration(5 * 1000).start();

36. ViewPagerIndicator
XML
<com.viewpagerindicator.TitlePageIndicator
android:id="@+id/titles"
android:layout_height="wrap_content"
android:layout_width="fill_parent" />

37. ViewPagerIndicator
@Java
//Set the pager with an adapter
ViewPager pager = (ViewPager)findViewById(R.id.pager);
pager.setAdapter(new TestAdapter(getSupportFragmentManager()));
//Bind the title indicator to the adapter
TitlePageIndicator titleIndicator = (TitlePageIndicator)findViewById(R.id.titles);
titleIndicator.setViewPager(pager);
titleIndicator.setOnPageChangeListener(mPageChangeListener);

38. Activity LifeCycle

39. Activity LifeCycle
public class Activity extends ApplicationContext {
protected void onCreate(Bundle savedInstanceState);
protected void onStart();
protected void onRestart();
protected void onResume();
protected void onPause();
protected void onStop();
protected void onDestroy();
}

41. Send Parameter
● Bundle
Send
Intent data = new Intent("my.action");
data.putExtra("point", point);
data.putExtra("noqs", noqs);
Get
Bundle b = getIntent().getExtras();
noqs = b.getInt("noqs");
point = b.getInt("point");

42. Send Parameter
Parcelable
protected static class Foo implements Parcelable {
public static final Parcelable.Creator<Foo> CREATOR = new Parcelable.Creator<Foo>() {
public Foo createFromParcel(Parcel source) {
final Foo f = new Foo();
f.str = (String) source.readValue(Foo.class.getClassLoader());
return f;
}
public Foo[] newArray(int size) {
throw new UnsupportedOperationException();
}
};

43. Support multiple Screens
res/layout/main.xml: single-pane layout
res/layout-large: multi-pane layout
res/layout-sw600dp: multi-pane layout
res/values/layouts.xml
res/values-sw600dp-land/layouts.xml
res/values-sw600dp-port/layouts.xml
res/values-large-land/layouts.xml
res/values-large-port/layouts.xml

44. Do not use px
● Use dp and sp
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/clickme"
android:layout_marginTop="20dp" />
<TextView android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="20sp" />

45. Bitmap Sizes
● xhdpi: 2.0
● hdpi: 1.5
● mdpi: 1.0 (baseline)
● ldpi: 0.75

46. Bitmap Resources
MyProject/
res/
drawable-xhdpi/
awesomeimage.png
drawable-hdpi/
awesomeimage.png
drawable-mdpi/
awesomeimage.png
drawable-ldpi/
awesomeimage.png

47. UI Thread
● WTF is ANR
Won't Work
handler=new Handler();
Runnable r=new Runnable()
{
public void run()
{
tv.append("Hello World");
}
};
handler.postDelayed(r, 1000);

48. Android Threads
@Override
publicvoid onClick(View v){
my_button.setBackgroundResource(R.drawable.icon);
// SLEEP 2 SECONDS HERE ...
Handler handler =newHandler();
handler.postDelayed(newRunnable(){
publicvoid run(){
my_button.setBackgroundResource(R.drawable.defaultcard);
}
},2000);
}

49. Android Threads
@Override
publicvoid onClick(View v){
my_button.setBackgroundResource(R.drawable.icon);
// SLEEP 2 SECONDS HERE ...
Handler handler =newHandler();
handler.postDelayed(newRunnable(){
publicvoid run(){
my_button.setBackgroundResource(R.drawable.defaultcard);
}
},2000);
}

50. AsyncTask
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
// Escape early if cancel() is called
if (isCancelled()) break;
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
}
new DownloadFilesTask().execute(url1, url2, url3);
new DownloadFilesTask().execute(url1, url2, url3);

51. HTTP Libraries
You can use Apache commons
Or I found these libraries well
http://loopj.com/android-async-http/
AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.google.com", new AsyncHttpResponseHandler() {
@Override
public void onSuccess(String response) {
System.out.println(response);
}
});
This works as well
http://code.google.com/p/android-query/

52. Push Notifications
● Google Cloud Messaging
http://developer.android.com/guide/google/gcm/index.html
@manifest.xml
<permission android:name="my_app_package.permission.C2D_MESSAGE" android:protectionLevel="signature" />
<uses-permission android:name="my_app_package.permission.C2D_MESSAGE" />
<receiver android:name="com.google.android.gcm.GCMBroadcastReceiver"
android:permission="com.google.android.c2dm.permission.SEND" >
...
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
<action android:name="com.google.android.c2dm.intent.REGISTRATION" />
<category android:name="my_app_package" />
</intent-filter>
</receiver>

53. Push Notifications
@java
GCMRegistrar.checkDevice(this);
GCMRegistrar.checkManifest(this);
final String regId = GCMRegistrar.getRegistrationId(this);
Get regId and fire it from server
You should use this library, all other are deprecated

54. Dependency Injection
● Roboguice
http://code.google.com/p/roboguice/
● Guava
http://code.google.com/p/guava-libraries/

55. WTF is DI
● Before DI ● After DI
class AndroidWay extends Activity { class RoboWay extends RoboActivity {
@InjectView(R.id.name) TextView
TextView name;
name;
public void onCreate(Bundle savedInstanceState) { public void onCreate(Bundle
super.onCreate(savedInstanceState);
savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setContentView(R.layout.main);
name = (TextView) findViewById(R.id.name); name.setText( "Hello, " + myName );
} }
} }

56. Image Caching
● Google I/O 2012 app has a great image
caching library
http://code.google.com/p/iosched/

57. Open Source apps
● Google I/O 2012
http://code.google.com/p/iosched/
● Github app
https://github.com/github/android

58. ListView
Most important widget
Fast ListView Tips
● Inflate once
● ViewHolder
● Use Tag
● Don't write a heavy code like network operation in getView
method
http://yekmer.posterous.com/fast-listview-scrolling-in-android