Ac#vity is the basic building block of a mobile app interface. It represents a single screen with a user interface. An app uses Ac#vity classes to build a series of screens that the user can navigate between via intents. The Ac#vity lifecycle involves callback methods like onCreate, onStart, onResume etc that are important for initializing and releasing resources. Transi#ons between Ac#vi#es can be customized with anima#ons. Data can be passed between Ac#vi#es via intents and bundles. The manifest declares Ac#vi#es and their launch points and filters.

1. Ac#vity & Intent

2. [Recap] What is Ac#vity?
Ac$vity
Ac$vity class takes care of crea$ng a
window for you in which you can place
your UI

3. Introduc#on to Ac#vity
• Ac$vity is one of the core and key
system in Android
• Very important, you can’t just
know about it, you have to
MASTER at it
• Key message to fully understand:
• Lifecycle

4. Play around: Hide The Title Bar
1) Hide by Code
2) Hide by Style
Why do we hide it?
Live DemoCustom Title Bar No Title Bar at all

5. Play around: Styles & Theme

6. Naviga#on: The second Ac#vity
1) Create New Ac$vity
2) Try to startActivity
3) See what happened?
4) Play around with AndroidManifest.xml
5) Now try again
Live Demo

7. Intent
An Intent is a messaging object
you can use to request an ac$on
from another app component.
Live Demo
?

8. Lab: Intent & Bundle
Q: Why we need to send data through Intent?
A: Because Ac)vity is independent to each other
… Play Play Play …

9. Understand how Android OS works
• Secret: Actually Launcher
(Home Screen) is also an
Ac$vity !
• And launcher also launch
our applica$on through
Intent and startActivity
Live Demo

10. Intent Filter
<activity
android:name="com.example.helloworld.MainActivity"
android:theme="@style/AppTheme"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Take a look into AndroidManifest.xml

11. What happened when app launched?
Tasks and Back Stack
Live Demo

12. The Ac#vity Lifecycle
IMPORTANT ALERT

13. The Ac#vity Lifecycle #2

14. What do we do in each lifecycle event in prac#cal?
onCreate
Ini$alize UI Elements
onResume or onStart
Ini$alize System
Resources (GPS,
Camera, etc)
onDestroy
Mostly do nothing
onPause or onStop
Release System
Resources (GPS,
Camera, etc)
Stop CPU consuming
task like Anima$on,
Timer
Commit unsaved
changes
Pause Game
Why or?

15. Save & Restore Instance State
Live Demo

16. You will a liOle bit confuse now
But it will be be^er when you prac$ce more
(and more)
(and more)
(and more)

17. Best Prac#ces: Ac#vity Code Structure
• In The Android Cheese Sheet

18. How to return from Ac#vity
Live Demo
finish()
FirstAc)vity
startActivity(...)
SecondAc)vity

19. GeRng a Result from an Ac#vity
Live Demo
setResult(...);
finish()
FirstAc)vity
startActivityForResult(...)
SecondAc)vity

20. The Screen Orienta#on
android:screenOrientation=["unspecified" | "behind" |
"landscape" | "portrait" |
"reverseLandscape" | "reversePortrait" |
"sensorLandscape" | "sensorPortrait" |
"userLandscape" | "userPortrait" |
"sensor" | "fullSensor" | "nosensor" |
"user" | "fullUser" | "locked"]
Live Demo
You can fix the Ac$vity’s orienta$on in AndroidManifest.xml
Sugges$on: Fix Orienta$on to portrait at the beginning
(why?)

21. SoS Keyboard Mode
android:windowSoftInputMode=["stateUnspecified",
"stateUnchanged",
"stateHidden",
"stateAlwaysHidden",
"stateVisible",
"stateAlwaysVisible",
"adjustUnspecified",
"adjustResize",
"adjustPan"]
Live Demo
You can change behavior of sod keyboard in Ac$vity through
AndroidManifest.xml

22. Ac#vity Transi#on
• Basically transi$on will be done by default seengs
• But you can override it (but not so recommend unless it is by design)
• Example: <?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
android:interpolator="@android:anim/accelerate_interpolator"
android:fromAlpha="0.0" android:toAlpha="1.0" android:duration="2000" />
res/anim/fade_in.xml
<?xml version="1.0" encoding="utf-8"?>
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
android:interpolator="@android:anim/accelerate_interpolator"
android:fromAlpha=“1.0" android:toAlpha=“0.0" android:duration="2000" />
res/anim/fade_out.xml
overridePendingTransition(R.anim.fade_in, R.anim.fade_out);

23. Recap
• Every$me you create a new Ac$vity, declare in AndroidManifest.xml
immediately
• Ac)vity Lifecycle is very very very important
• In can effect your lifecycle as an Android App Developer as well
• Most of the Android Developer doesn’t know about Lifecycle clearly and
that lead to app’s quality problem
• Crash
• Malfunc$onal

24. Ac#vity Types
Ac$vity
ListAc$vity PreferenceAc$vity LauncherAc$vity FragmentAc$vity
Ac$onBarAc$vity
AppCompatAc$vity
…