1. Activities, Fragments, and Intents

2. Activities
Activity – window that contains the user interface of your application
May have zero or more activities
Many purpose of activity is to interact with user
Activity Life Cycle

3. Fragments Android 4.0 introduced Fragments
Fragment is miniature activity that can be grouped to form an activity

4. Intent
Intent – glue that enables different activities from different applications to work together seamlessly
Used to call built-in applications such as:
the Browser
Phone
Maps
Etc.

5. Activity
Activity base class defines a series of events that govern the life cycle of an activity
onCreate() – called when the activity is first created
onStart() – called when activity becomes visible to user
onResume() – called when activity starts interacting with user
onPause() – called when current activity is being paused and previous activity is being resumed
onStop() – called when activity is no longer visible to user
onDestroy() – called before activity is destroyed by system
onRestart() – called when activity has been stopped and is restarting again

6. Activity
import android.os.Bundle; Import android.app.Activity public class MainActivity extends Activity { /** Called when activity is first created. protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); }

7. Activity
By default, the activity created for you contains the onCreate() event.
User Interface component is loaded using XML file defined in your res/layout folder – main.xml
Every activity you have in your application must be declared in your AndroidManifest.xml file

8. Activity Life Cycle

9. Activity An Activity is destroyed when you click the Back button
The state the Activity is in will be lost
Additional code is required to preserve its state when it is destroyed
Guidelines to follow:
Use onCreate() to create and instantiate objects you will be using in your application
Use onResume() to start any services or code that needs to run while your Activity is in the foreground
Use the onPause() to stop any services or code that does not need to run when your Activity is not in the foreground
Use the onDestroy() to free up resources before your Activity is destroyed

10. Link Activities using Intents
In Android, you navigate between activities through an Intent
An Activity is made up of:
a UI component (main.xml) and
a class component (.java file)
AndroidManifest.xml file, add the Activity with an Intent
<activity
android:name=".SecondActivity"
android:label="Second Activity" >
<intent-filter>
<action android:name="com.example.SecondActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>

11. Link Activities using Intents
public void onClick(View view) {
startActivity(new Intent("com.example.SecondActivity")); }
Activities can be invoked by any application running on the device.
Fundamental concept in Android
startActivity() method invokes another Activity
Does not return a result to the current Activity
To pass data back from an Activity, use the startActivityForResult() method

12. Fragments