CHAPTER 4
Fragments
ActionBar
Menus
• Explore how to build applications that
use an ActionBar and Fragments
• Understand the Fragment lifecycle
• Learn to configure the ActionBar
• Implement Fragments with Responsive
Design Techniques
• Explore animation in Fragment
Transactions
• Experiment with Fragments, ListViews,
and ArrayAdapters
4.1 Fragmentation and Android
Fragments
• There are many shapes and screen sizes and
different performance characteristics
• Multiple versions of Android are being used
• This translates into a wider audience to build
applications for
• When designing and coding layouts, there are
several factors to consider, such as spacing,
positioning, size, and the grouping of user
interface controls
• Layouts must be compatible with many physical
screens
• A Fragment is modeled as a subdivision of
an Activity
• Fragment is integrated into an Activity,
and needs an Activity to run
• The advantage of building applications
that use Fragments is their ability to
easily present a consistently welldesigned user interface
• Fragments are particularly helpful in
adapting a user experience across a wide
range of devices.
4.2 The Fragment Lifecycle
• Fragments are associated with an activity and
can be created, added or removed while the
activity is running
• Similar to an Activity, a Fragment has its own
lifecycle, as well as its own user interface
• The Fragment’s lifecycle is connected to the
activity that owns it
• Each fragment has its own callback methods in
the standard Activity lifecycle.
Callbacks used in the lifecycle of a
Fragment.
• onCreateView() – bring a fragment to resumed state, interacting
with user
• onInflate() – called every time fragment is inflated
• onActivityCreated() – called when fragment’s activity has been
created and this fragment’s view hierarchy is instantianted
• onAttach() – called after the fragment has been attached to an
activity
• onDestroyView() – informs the fragment that its view is being
destroyed so that it can clean up any associated resources. Called
after onStop() and before onDestroy()
• onDetach() – called when fragment is no longer attached to its
activity, after on Destroy(). This is the final call before the fragment
object is released to garbage collector
4.3 Action Bar
• The action bar provides information and
displays control elements to the user.
• In a basic configuration, the action bar
displays the application icon and a title
• The title often identifies the running activity
• Users are given an indication of where they
are and a consistent identity from which to
recognize the application
Action bar features:
• Application Icon
• Action Items
• Action overflow
4.4 ActionBar Configurations
• Control elements that appear directly on the
action bar as an icon and/or text are known as
action buttons
• When an Activity starts, its associated layout is
inflated on the screen and the action bar is
populated with action buttons
• The activity's onCreateOptionsMenu()
method is responsible for inflating a menu
hierarchy from a specified XML resource file
4.4.1 Overflow on the Action Bar
• Narrow devices can often require the use of
the overflow button
• When creating layouts on devices with a
narrow screen, use ifRoom to request that an
item appear in the action bar
• Allow the system to move elements into the
overflow when there is not enough room
4.4.2 Adding an Action View
• An action view is simply a widget that appears in
the action bar as a substitute for an action button
• An action view provides quick access to heavily
used actions
• Consider a collapsible search view widget. A
search action view can be added as an embedded
search view widget in the action bar
• To declare an action view, the actionLayout or
actionViewClass attribute can be added to an
item to specify either a layout resource or a
widget class
4.5 Responsive Design with Fragments
• Responsive design works across different screens
sizes
• Responsive design techniques should also be
applied to Android applications for solving
interactive design and layout problems
• Responsive design is used for heavy data driven
content.
• Adaptive design is primarily used for the rearrangement of fixed user interface elements in
an application
• Responsive design revolves around a
master/detail flow interface design
pattern
• The user is provided with a list of items
• Upon selecting one of the items,
additional information relating to that
item is then presented to the user
• This design concept is called responsive in
the sense that list and detail panels of the
app can change based on the width of the
device
• On a large tablet-sized Android device, the
screen is large enough to display both
panels
• The master list can appear as a narrow
vertical panel along the left hand edge of
the screen while the remainder of the
screen can display the detail panel
• This arrangement is referred to as twopane mode.
• Responsive design makes use of Fragments
• A user interface can be divided into multiple
panes using Fragments and reused in more
than one screen of an application, as shown
in the following figure
• Fragments can be combined or separated on
a device
• When building an application that follows a
similar master/detail design pattern, the
application often needs a set of Java and
XML layout resource files
4.6 Animation in Fragment
Transactions
• Transition animations can be applied directly to
fragments that are entering and exiting a
transaction
• The FragmentManager provides the structure
that handles transactions between fragments
• A transaction refers to the sequence of steps that
add, replace, or remove fragments.
• Operations performed by the FragmentManager
will occur inside a transaction
4.7 ListViews and Dynamic Data
• A ListView is similar to a ScrollView
• A ScrollView is an extension of the
FrameLayout, and is suitable for holding a
single control element
• It provides the user with the scroll mechanism
to reveal more content than can be displayed
on the screen at once
• A LinearLayout, containing multiple View
items, can be placed within a ScrollView
• A ListView is a specialized control that is
optimized for displaying long lists of items
• When the data content for the layout is
dynamic or not pre-determined, it is
possible to use a layout that subclasses an
AdapterView to populate the layout with
views at runtime
4.8 Handling Click Events in a ListView
• A ListView might be populated with items that
need to respond to a click event
• You can respond to click events on an item in
an AdapterView by implementing the
AdapterView.OnItemClickListener interface
• The onItemClick () callback method will always
be invoked when an item in the AdapterView
has been clicked.