Android Best Practices

ANDROID

Does not Suck anymore!

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

Android Design Patterns

http://developer.android.com/design/index.html

IOS Design

It was cool 2 years ago

Shut up and Show me Code Bitch!

Android Support Jar
● V4 ● V13
● Fragment ● FragmentCompat

● FragmentManager ● FragmentPagerAdapter

● FragmentTransaction ● FragmentStatePagerAdapter

● ListFragment

● DialogFragment

● LoaderManager

● Loader

● AsyncTaskLoader

● CursorLoader

Support Jar

Just change the import and use latest api's

It rocks!!!

Fragment
● Tablet and phone code comes together

● One ring to rule them all!!!

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 {

Create Fragment
DetailsFragment f = new DetailsFragment();

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

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();

Get the parameters
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

Bundle args = getArguments();
if (args != null) {
mLabel = args.getCharSequence("label", mLabel);
}
}

Inflate Views
● Design using XML

● And @java
View v = inflater.inflate(R.layout.hello_world, container, false);
View tv = v.findViewById(R.id.text);

DialogFragment
Better Back button support

public static class MyDialogFragment extends DialogFragment {

Other Fragments
● ListFragment
● PreferenceFragment

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

Great Man

● Jack Wharton
https://github.com/JakeWharton

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

ActionBarSherlock

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

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();

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

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);

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();
}

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");

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();
}

};

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

Do not use px
● Use dp and sp
<Button android:layout_width="wrap_content"

android:text="@string/clickme"
android:layout_marginTop="20dp" />

<TextView android:layout_width="match_parent"

android:textSize="20sp" />

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

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

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);

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);
}

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);

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/

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>

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

Dependency Injection
● Roboguice
http://code.google.com/p/roboguice/

● Guava
http://code.google.com/p/guava-libraries/

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
savedInstanceState) {
setContentView(R.layout.main);
setContentView(R.layout.main);
name = (TextView) findViewById(R.id.name); name.setText( "Hello, " + myName );
} }
} }

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

Open Source apps
● Google I/O 2012
http://code.google.com/p/iosched/

● Github app
https://github.com/github/android

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

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