android
Madhukar Kunam 
Week2.pptxCOIT20270 Application Development for Mobile Platforms Week 2: Activities, Fragments and Intents
Dr. R. Balsys, CQU, 2018.
Source: Beginning Android Programming with Android Studio, J.F. DiMarzio, 2016
Week 2 – Activities, Fragments and Intents
Objectives to:
Understand Android activities and fragments
Use progress dialogs
Linking activities using intents
Resolving intent filter collisions
Returning results from an intent
Passing data using intent objects
CQU - COIT20270 Application Development for Mobile Platforms
Understanding Activities
Activities extend the Activity base class
The Activity base class life cycle includes onCreate(), onStart(), onResume(), onPause(), onStop(), onDestroy() and onRestart() events
Figure 3-1 in DiMarzio text shows the life-cycle of an activity and the stages it goes through
An activity usually occupies the whole screen but can behave as a dialog by modifying the <Activity> element by adding android:theme=“@android:style/Theme.Dialog” in the AndroidManifest.xml file
CQU - COIT20270 Application Development for Mobile Platforms
Demonstrate Explain script functions
3
Adding Themes to an Activity
In Android 6 a new theme, Material, has been used for the default look and feel
Use android:Theme=“@android:style/Theme.Material” in the application tag of the android.manifest file to set this as the default theme for the app
CQU - COIT20270 Application Development for Mobile Platforms
Hiding the Activity Title and Displaying a Dialog Window
The activity title can be hidden by importing android.view.Window and using requestWindowFeature(Window,FEATURE_NO_TITLE) in the onCreate() method
To display a dialog you implement the onCreateDialog() method
onCreateDialog() calls showDialog()that uses on integer to select the actual dialog to display
The Hiding the Activity Title Try It Out shows you how to display a dialog window when you need to get the user to confirm an action
CQU - COIT20270 Application Development for Mobile Platforms
Displaying a Progress Dialog
When an action will take more than 10 seconds a progress dialog should be displayed
To create a progress dialog you create an instance of the ProgressDialog class and call its show() method
An example is in the Displaying a Dialog section of the DiMarzio text
You can also set properties such as a progress icon, title and style. You also can add Cancel and OK buttons to the dialog
A more sophisticated version is given example is in the Displaying a Progress Dialog section of the DiMarzio text
CQU - COIT20270 Application Development for Mobile Platforms
Point out the (1,0) and (0,1) pixels to get the point home
6
Linking Activities Using Intents
Android applications can have more than 1 activity
Navigation between activities is achieved using intents
You add the name of the new class in the AndroidManifest.xml file and give it a unique label
You supply an intent filter and set the category for the intent filter as android.intent.category.DEFAULT
The DiMarzio text examples is in the Linking Activities with Intents try it out.
CQU - COIT20270 Application Development for Mobile Platforms
7
Resolving Intent Filter Collision
If more than two <intent-filter> elements have the same name then when the application is run Android will present the user with a list of choices to pick from
The chosen item becomes the default choice
To clear the default choice you have to go to the Application Settings to clear the default choice
CQU - COIT20270 Application Development for Mobile Platforms
Returning Results from an Intent
The startActivity() does not return data
If you need to return data from an Activity use the startActivityForResult() method instead
The startActivityForResult() method has a second parameter that returns a resultCode that identifies the activity being called
To return the value you need send the data back via the setData() method
The setData() method calls a setResult() method to set the resultCode
In the calling activity you implement the onActivityResult() method to deal with the result
CQU - COIT20270 Application Development for Mobile Platforms
Passing Data Using an Intent Object
Data is passed to an activity using an Intent object
The putExtra() method puts name:value pairs into an Intent object
A Bundle object can also attach data to Intent objects using the putExtra() method
To obtain the data in the Intent object use the getIntent() method and call its getStringExtra() method to get the string values using the putExtra() method
CQU - COIT20270 Application Development for Mobile Platforms
Explain script functions
10
…Passing Data Using an Intent Object
To retrieve the Bundle object use the getExtras() method
Individual name:value pairs are retrieved using the appropriate method, eg getString()
The data can also be retrieved using the setData() method
CQU - COIT20270 Application Development for Mobile Platforms
Explain script functions
11
Week 2 – Mobilising Your Apps
Objectives, to:
Understand fragments
Adding fragments dynamically
Fragment lifestyle
Fragment interactions
Calling built-in applications using intents
Understand the intent object
Use intent filters
Adding categories
Displaying notifications
CQU - COIT20270 Application Development for Mobile Platforms
Fragment
Fragments are contained within an Activity
Many Fragments can be contained within a single Activity
Fragments contain views that differ from one another
Fragments are a versatile way of of creating user interfaces for Android applications
Fragments can be dynamically added or removed from Activities
CQU - COIT20270 Application Development for Mobile Platforms
…Fragments
The Java class for a Fragment extends Fragment
To draw the UI for a Fragment you over-ride the onCreateView() method that returns a View object
In onCreateView() a LayoutInflater object inflates the UI from an XML file
You add a fragment to an Activity with the <fragment> element
The <fragment> element uses unique id’s for the element using the android:id or android:tag attributes
CQU - COIT20270 Application Development for Mobile Platforms
Adding Fragments Dynamically
It is more useful to be able to add Fragments at run-time than by configuring an XML file during design
You use the FragmentManager class to add fragments
Use the FragmentTransactions class to add, remove or replace fragments
To ensure changes take place you call the commit() method on your FragmentTransaction object
CQU - COIT20270 Application Development for Mobile Platforms
Life Cycle of a Fragment
When a Fragment is being created it goes through onAttach(), onCreate(), onCreateView() and onActivityCreated() states
When visible it goes through onStart() and onResume() states
When it goes into the background it goes through onPause() and onStop() states
When the Fragment is destroyed it goes through onPause(), onStop(), onDestroyView(), onDestroy() and onDetatch() states
CQU - COIT20270 Application Development for Mobile Platforms
…Life Cycle of a Fragment
When an Activity goes into the background it is placed into the back stack allowing it to resume if the Back button is pressed
Fragments must be manually placed in the back stack by calling the addToBackStack() method
CQU - COIT20270 Application Development for Mobile Platforms
Interactions Between Fragments
Fragments need to communicate with one-another to be effective
The activity to which a fragment belongs can be determined using the getActivity() method
Fragment Views can be found using the findViewById() method
The example in the Interaction Between Fragments try it out of the DiMarzio text demonstrates fragment interaction
CQU - COIT20270 Application Development for Mobile Platforms
Calling Built-in Applications Using Fragments
Intents can be used to call other Android applications from within a fragment
Intents are paired with action and data intents
The action and data pairs describe the operation to be performed
You create an Intent object and then pass action and data arguments to the Intent
CQU - COIT20270 Application Development for Mobile Platforms
The Intent Object
You can call another activity by passing its action to the constructor of an Intent object
You can also create an Intent object by passing in an action constant and data
For some Intents the data type is not needed, the MIME type is set using setType()
Intent objects can also be set using a category which groups activities into logical units for filtering
CQU - COIT20270 Application Development for Mobile Platforms
Using Intent Filters
In order for an activity to invoke another activity requires the use of an <intent-filter> in the AndroidManifest.xml file
If multiple actions match the intent-filter then a dialog appears for the user to choose the correct one
A createChooser() method can be used to customise this dialog and prevent a crash when no match is found
CQU - COIT20270 Application Development for Mobile Platforms
Adding Categories
To add a category you must first define an <intent-filter> for the category,
Eg. <category android:name=“abc.net.au/justin” />
You must also add the category using the addCategory() method on an Intent instance
eg. Intent I = new (….);
i.addCategory(“abc.net.au/justin”);
CQU - COIT20270 Application Development for Mobile Platforms
Displaying Notifications
The NotificationManager class is used to display persistent messages in the navigation bar at the top of the device
To use notifications you first declare a new Intent that uses the NotificationView.class
You also create a PendingIntent instance initialised using the getActivity() method to set the PendingIntent’s context, request code, intent and flags
You then obtain an instance of the NotificationManager class and create an instance of the Notification class
CQU - COIT20270 Application Development for Mobile Platforms
…Displaying Notifications
You then use the setLatestEventInfo() method on the Notification instance to setup the notification and its response
You then call the notify() method on your NotificationManager instance to display the notification
CQU - COIT20270 Application Development for Mobile Platforms
