Activities, Fragments, and Events

42 %
58 %
Information about Activities, Fragments, and Events

Published on January 16, 2014

Author: sicarii_13



An overview of the role activities, fragments and intents play in Android app development.

Activities, Fragments, and Events CPTR322: Mobile Application Development Henry Osborne

Topics Covered • • • • • • • The life cycle of an activity Customizing the UI using fragments Applying styles and themes to activities Displaying activities as dialog windows Understanding the concept of intents Linking activities using intent objects Displaying alerts using notifications

Understanding Activities

What are activities? • A window that contains the UI of an application • An application can have zero or more activities • Main purpose is to interact with the user • Life Cycle: the stages an activitiy goes through from the moment it appears on the screen to the moment it’s hidden.

Creating Activities • To create an activity, a Java class that extends the Activity base class is created. import; … public class Activity101Activity extends Activity { … } • The activity class loads it UI component using the XML file defined in the res/layout folder.

Declaring Activities • Each activity in the application, must be declared in the AndroidManifest.xml file. <activity android:label=“@string/app_name” android:name=“.Activity101Activity”> <intent-filter></intent-filter> </activity>

Activity Base Class onCreate() – Called when the activity is first created onStart() – Called when the activity becomes visible to the user onResume() – Called when the activity starts interacting with the user onPause() – Called when the current activity is being paused and the previous activity is being resumed • onStop() – Called when the activity is no longer visible • onDestroy() – Called before the activity is destroyed by the system • onRestart() – Called when the activity has been stopped and is restarting • • • •

Figure 1: Activity Life cycle

Applying Styles and Themes

Applying Dialog Theme <application android:icon=“@drawable/ic_launcher” android:theme=“@android:style/Theme.Dialog”> <activity android:label=“@string/app_name” android:name=“.Activity101Activity”> <intent-filter></intent-filter> </activity> </application>

Hiding Activity Title import android.view.Window; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.main); }

Linking Activities Using Intents


What is a Fragment? A Fragment is a piece of an application's user interface or behavior that can be placed in an Activity. Interaction with fragments is done through FragmentManager, which can be obtained via Activity.getFragmentManager() and Fragment.getFragmentManager().

Figure 2: An example of how two UI modules defined by fragments can be combined into one activity for a tablet design, but separated for a handset design.

Adding Fragments Dynamically • It is more useful if fragments are created and added to activites during runtime. • Allows for a customizable UI • E.g. If the application is running on a smartphone, you might fill the activity with a single fragment; if the activity is running on a tablet, you might then fill the activity with two or more fragments.

Fragment Life Cycle A fragment must always be embedded in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle. For example, when the activity is paused, so are all fragments in it, and when the activity is destroyed, so are all fragments.

Figure 3. The lifecycle of a fragment (while its activity is running).

Displaying Notifications

For important messages the NotificationManager is used to display a persistent message at the top of the device (commonly known as the status bar, sometimes referred to as the notification bar)

Activities, Fragments, and Events

Add a comment

Related presentations

Related pages

Fragments | Android Developers

You can combine multiple fragments ... share events with the activity and other fragments ... An activity is placed into a back stack of activities ...
Read more

android - Call fragment events from activity - Stack Overflow

Call fragment events from activity. ... now how do I get the activity to call events in fragment B? ... when to use Fragments vs Activities: 1.
Read more

Activities, Fragments, and Events - Education

1. Activities, Fragments, and Events CPTR322: Mobile Application Development Henry Osborne. 2. Topics Covered • • • • • • •The life cycle of ...
Read more

events - Android with only one activity and multiple ...

Android with only one activity and multiple fragments. ... receives its own input events, ... How many Activities vs Fragments? 368.
Read more

Activity | Android Developers

Fragments; Activity Lifecycle ... Finish this activity as well as all activities immediately below it in ... media key and volume events while this ...
Read more

Clean Android Code: Activities and Fragments – Android ...

Activities and Fragments are the most critical parts of Android application. Both represent an application screen that user will see. The difference would ...
Read more

GitHub - greenrobot/EventBus: Android optimized event bus ...

EventBus - Android optimized event bus that simplifies communication between Activities, Fragments, Threads, Services, etc. Less code, better quality.
Read more

Ease Communication Between Activities, Fragments, and Services

Ease communication between Activities, Fragments, Dialogs, Services, AsyncTaks, and Life Cycles of Anything by using event bus in Android. Event bus is an ...
Read more

GitHub - hehonghui/AndroidEventBus: A lightweight eventbus ...

AndroidEventBus - A lightweight eventbus library for android, simplifies communication between Activities, Fragments, Threads, Services, etc.
Read more