Architecting Android Apps

8/18/2019 Architecting Android Apps

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Architecting Android AppsMarko Gargenta @Marakana

chitecting Android Apps Overview

http://localhost/Users/marko/github/android/courseware/Talks/Architecting_Android_Apps_Talk.html#slide-2


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About Marko Gargenta

Marko Gargenta

Entrepreneur, Author, SpeakerDeveloper of Android Bootcamp for Marakana.

Instructor for 1,000s of developers on Android at Qualcomm, Cisco, Motorola, Intel, DoD and

other great orgs.

Author of Learning Android published by O’Reilly.

Speaker at OSCON (4x), ACM, IEEE(2x), SDC(2x), AnDevCon(2x), DroidCon.

Co-Founder of SFAndroid.org

Co-Chair of Android Open conference: Android Open

http://androidopen.com/http://amzn.to/learningandroidhttp://marakana.com/training/android/android_bootcamp.html


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Architecting Android Apps Overview


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Architecting Android Apps Overview

he goal of this module is to introduce you to main components used to create

Android apps. By the end of this module, you should have a good idea what

Android app building blocks are, and their key properties.even iterations of an app:

Part 1 - Activities and Android UI

Part 2 - Intents, Action Bar, and More

Part 3 - Services

Part 4 - Content Providers

Part 5 - Lists and Adapters

Part 6 - Broadcast Receivers

Part 7 - App Widgets


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Yamba

Yamba

bjectives of Yamba

he objective of this module is to explain how to go about designing a typical

Android app. You will have a chance to see an example app, Yamba, using most

he standard Android building blocks. By the end of this talk, you should have

igh-level understanding about designing an Android app.


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Yamba Approach

Yamba OverviewYamba: Yet Another Micro-Blogging App

Comprehensive Android example application.Works with services that support Twitter API.

Project PhilosophySmall increments - build it organically

App must always run - whole and complete

Refactor when needed - do simplest thing first


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Part 1 - Activities and Android UI

Yamba Part 1


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Activity Overview

Example of Activities

An activity is roughly a screen.

A typical application may have many activities.

Activities are typically expensive and so are managed by the system.


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Activity Lifecycle

Activity Lifecycle

Activities are highly managed by the system’s ActivityManager.

ActivityManager drives the activity through its states.

You as an app developer get to say what happens on transitions.


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Activity Callbacks

ifecycle

onCreate()onCreate()

Used to setup your activity. You will almost always have to have it. Good place tnflate the UI and setup listeners.

onResume()onResume() and onPause()onPause()Use them to turn on and off things that you’d like to have running only while th

ctivity is visible. This is important for things that consume a lot of battery, such

s GPS and sensors.

onStart()onStart() and onStop()onStop()Use to setup code that starts/stops the activity. Unlike onResume()onResume() andonPause()nPause(), it includes Paused state as well.

onRestart()onRestart()alled when the activity is restarted. It is followed by onStart()onStart() andonResume()nResume().

onDestroy()onDestroy()A good place to do any cleanup before the activity is cleaned up from memory.his is the counter-part to onCreate()onCreate().

ther

onCreateOptionsMenu()onCreateOptionsMenu() and

onOptionsItemSelected()onOptionsItemSelected()Use them to setup your menu. onOptionsItemSelected()onOptionsItemSelected() loads the menu,ypically from an XML resource. onOptionsItemSelected()onOptionsItemSelected() is called whenen option menu item is clicked on.

Various listeners and event handlers, such as onClick()onClick()Used to handle the UI events.


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Registering Activity

Main Activity

egister the activity in the Android Manifest file:

Android Manifest file

he intent filter specifies that this activity is to be the main entry point into the

pplication as well as that it should be shown in the app launcher on home scre

ny other activity Android Manifest file

...

...

...

...


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Building Android UI

here are two approaches to building Android UI:

eclaratively

Declare UI in XML

Eclipse provides nice drag-n-drop tools

Inflate the XML views in Java

rogrammatically

Instantiate all widgets programmatically

Set properties for each

he best is to use both:

1. Star with declaring the look and feel using XML

2. Inflate XML into Java

3. Finish by programming the actions using Java


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Layouts and Views

Layouts and Views


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Part 2 - Intents, Action Bar, and More

Yamba Part 2


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Intent Overview

Example of Intents

Intents are like events or messages.

You can use them so start activities, start/stop services, or send broadcasts.

Intents can be implicit or explicit.


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Using Intents

startActivity()startActivity()tarts an activity specified by the intent. If activity does not exist already, it call

onCreate()nCreate() to create it. Otherwise, it calls onStart()onStart() and onResum()onResum().

startService()startService()tarts a service. Even if the service is not created yet, it called onCreate()onCreate() onhe service first.

stopService()stopService()tops a service that is already running. If service is not running, it does nothing

bindService()bindService()inds to a service. Requires that the service returns a binder via onBind()onBind()

method.

sendBroadcast()sendBroadcast()ends a broadcast. If there’s a broadcast receiver registered to filter for the sam

ction as this intent is specifying, that receiver’s onReceive()onReceive() method will bealled.


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Explicit and Implicit Intents

xplicit Intent ActivityDemo.java

thishis is the context from which this intent is being sent, in our case an Activity.

mplicit Intent ActivityDemo.java

equires that there’s an intent filter filtering for this particular intent, for examp

AndroidManifest.xml

...

startActivity(new Intent(this, AnotherActivity.class));

...

startService(new Intent(this, ServiceDemo.class));

...

...

startService(new Intent("marakana.intent.action.IntentServiceDemo"));

...

sendBroadcast(new Intent("marakana.intent.action.ReceiverDemo"));

...

...

...

...


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Intent Filter

ntent filter is a way for us to assign certain action to an activity, service, receive

r similar.

Action is one of system defined actions, or something you come up with.

ntent filter typically goes into Android Manifest file, within ,

service>, or elements.

Android Manifest file

...

...


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Action Bar

he action bar , introduced in Honeycomb (API 11) is a title bar that includes:

The application icon

The activity title

A set of user-selectable actions (optional)

A set of user-selectable navigation modes (optional)


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Enabling the Action Bar

Android automatically displays an action bar on an API 11+ system if the element of your applications manifest:

Sets minSdkVersionminSdkVersion to 11 or later, or

Sets targetSdkVersiontargetSdkVersion to 11 or later

ither or these settings enable the "holographic look and feel" introduced in

Honeycomb, which includes action bar support.

If neither minSdkVersionminSdkVersion nor targetSdkVersiontargetSdkVersion are set to 11+, then an API 11+ systemrenders the app in a legacy theme, without action bar support.

With the action bar enabled, legacy option menu items appear automatically in

he action bar’s overflow menu. You reveal the overflow menu with:

The hardware Menu button (if present), or

An additional button in the action bar (for devices without a hardware Menu button)


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Adding Action Items

o display an option menu item as an action item, in the menu resource file add

android:showAsAction="ifRoom"ndroid:showAsAction="ifRoom" to the element.

The device will display the item if there is room available in the action bar, otherwise the item

appears in the overflow menu.

Devices running API 10 or earlier ignore the showAsActionshowAsAction attribute.

f your menu item supplies both a title and an icon, the action item shows only

con by default.

To display the text title, add withText withText to the android:showAsActionandroid:showAsAction attribute. Forexample:

The withText withText value is a hint to the action bar. The action bar will show the title if possible, bu

might not if an icon is available and the action bar is constrained for space.


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Part 3 - Services

Yamba Part 3


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Service Overview

Example of a Service

Services are code that runs in the background.

They can be started and stopped. Services doesn’t have UI.

Keep in mind that service runs on the main application thread, the UI thread.


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Service Lifecycle

Service Lifecycle

Service starts and "runs" until it gets a request to stop.

Service will run on the main UI thread.

To offload work from main thread, use intent service.

Intent service uses worker thread, stops when done with work.

Services can be bound or unbound.


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Service Callbacks

onBind()onBind()equired, but for unbound services, we just return nullnull.

onCreate()onCreate()alled when service is first created.

onStartCommand()onStartCommand()alled is called every time service is started.

onDestroy()onDestroy()alled when service is stopped. It is subsequently destroyed.


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IntentService Callbacks

Constructort needs to pass the name of this service to its supersuper.

onCreate()onCreate()alled when service is first created.

onHandleIntent()onHandleIntent()his is where the work of the service runs.

onDestroy()onDestroy()alled when service is stopped. It is subsequently destroyed.


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Registering ServiceRegistering a service that will be called explicitly by its class name

Registering a service that will be called via action

...

...

...

...


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Part 4 - Content Providers

Yamba Part 4


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Content Provider Overview

Example of Content Provider

Content Providers share content with applications across application boundaries.

Examples of built-in Content Providers are:

Contacts

MediaStore

Settings and more.


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Typical Usage of Content Providers

Typical Usage of Content Providers


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Content Provider Lifecycle

Content Provider Lifecycle

Content provider is initiated first time it is used via a call to onCreate()onCreate().

There is no callback for cleaning up after the provider.

When modifying the data (insert/update/delete), open/close database atomically.

When reading the data, leave database open or else the data will get garbage collected.


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Content Provider Callbacks

onCreate()onCreate()Used to initialize this content provider. This method runs on UI thread, so shou

e quick. Good place to instantiate database helper, if using database.

getType()getType()eturns the mime time for the given uri. Typically, this MIME type will either be

omething like

vnd.android.cursor.item/vnd.marakana.android.lifecycle.statvnd.android.cursor.item/vnd.marakana.android.lifecycle.stator a single item or

vnd.android.cursor.dir/vnd.marakana.android.lifecycle.statuvnd.android.cursor.dir/vnd.marakana.android.lifecycle.statu

or multiple items.

insert()insert()nserts the values into the provider returning uri that points to the newly insert

ecord.

update()update()Updates records(s) specified by either the uri or selectionselection / selectionArgsselectionArgs

ombo. Returns number of records affected.

delete()delete()Deletes records(s) specified by either the uri or selectionselection / selectionArgsselectionArgsombo. Returns number of records affected.

query()query()Queries the provider for the record(s) specified by either uri

r`selection`/ selectionArgsselectionArgs / groupinggrouping / havinghaving combo.


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Registering Content ProviderRegistering in Android Manifest file

he authority of this provider must match the uri authority that this provider is

esponding to.

...

...


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Part 5 - Lists and Adapters

Yamba Part 5


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Lists and Adapters Overview

Lists and Adapters Overview

Adapters connect potentially large data sets to small views


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Fragments

Fragments


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So, What’s a Fragment?

A fragment is a class implementing a portion of an activity.

A fragment represents a particular operation or interface running within a larger activity.

Fragments enable more modular activity design, making it easier to adapt an application to

different screen orientations and multiple screen sizes.

Fragments must be embedded in activities; they cannot run independent of activities.

Most fragments define their own layout of views that live within the activity’s view hierarchy.

However, a fragment can implement a behavior that has no user interface component.

A fragment has its own lifecycle, closely related to the lifecycle of its host activity.

A fragment can be a static part of an activity, instantiated automatically during the activity’s

creation.

Or, you can create, add, and remove fragments dynamically in an activity at run-time.


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Loaders

oaders make it easy to load data asynchronously in an activity or fragment.

oaders have these characteristics:

They are available to every Activity and Fragment.

They provide asynchronous loading of data.

They monitor the source of their data and deliver new results when the content changes.

They automatically reconnect to the last loader’s cursor when being recreated after a

configuration change. Thus, they don’t need to re-query their data.

oaders were introduced in Honeycomb (API 11).

The Android Support Package includes support for loaders. By including the support packageyour application, you can use loaders even if your application for a minSdkVersionminSdkVersion of 4 orlater.


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Using Loaders in an Application

An application that uses loaders typically includes the following:

An ActivityActivity or FragmentFragment.

An instance of the LoaderManagerLoaderManager.

A CursorLoaderCursorLoader to load data backed by a ContentProviderContentProvider. Alternatively, you can

implement your own subclass of LoaderLoader or AsyncTaskLoaderAsyncTaskLoader to load data from some othsource.

A data source, such as a ContentProviderContentProvider, when using a CursorLoaderCursorLoader.

An implementation for LoaderManager.LoaderCallbacksLoaderManager.LoaderCallbacks. This is where you create newloader instances and manage your references to existing loaders.

A way of displaying the loader’s data, such as a SimpleCursorAdapterSimpleCursorAdapter.


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Availability of Fragments and Loaders

ragments: Implemented in Honeycomb (3.0) or Later

ragments were added to the Android API in Honeycomb, API 11.

he primary classes related to fragments are:

android.app.Fragmentandroid.app.Fragmenthe base class for all fragment definitions

android.app.FragmentManagerandroid.app.FragmentManagerhe class for interacting with fragment objects inside an activity

android.app.FragmentTransactionandroid.app.FragmentTransactionhe class for performing an atomic set of fragment operations

ragments: Implemented in Donut (1.6) or Later

oogle provides the Compatibility Package, a Java library that you can include in

pplication, implementing support for fragments and other Honeycomb feature

oaders).


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Part 6 - Broadcast Receivers

Yamba Part 6


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Broadcast Receiver Overview

Broadcast Receiver Lifecycle

An Intent-based publish-subscribe mechanism.

Great for listening system events such as SMS messages.


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Broadcast Receiver Callbacks

onReceive()onReceive()his is the only method you typically care about for a broadcast receiver. It is

alled when this receiver is invoked.


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Registering Broadcast ReceiverRegistering in Android Manifest file

Registering programmatically

...

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

...

// Create the receiver

receiver = new TimelineReceiver();

filter = new IntentFilter( UpdaterService.NEW_STATUS_INTENT );

}

protected void onResume() {

super.onResume();

super.registerReceiver(receiver, filter,

"com.marakana.yamba.SEND_TIMELINE_NOTIFICATIONS", null);

}

@Override

protected void onPause() {

super.onPause();

unregisterReceiver(receiver);

}

...


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Part 7 - App Widgets

Yamba Part 7


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App Widgets Overview

App widgets are miniature views that can live in other apps, such as Home app.

They are a special implementation of Broadcast Receivers.

eclaring an App WidgetWidgets are essentially Broadcast Receivers

Yamba App Widget registration in AndroidManifest.xml

pecifying Meta Data

Meta data specifies the default size of the widget, plus the update period.

Yamba Widget meta data


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Yamba App Widget Output

Yamba App Widget Output


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Quiz

1. Name four main Android app building blocks.

2. What is an activity?

3. Name major callback methods of an activity.

4. What is a service?

5. Name major callback methods of a service.

6. What is a broadcast receiver?

7. Name major callback methods of a broadcast receiver.

8. What is a content provider?

9. Name major callback methods of a content provider.

0. What does an Android app consist of?


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Architecting Android Apps Summary

his module was an introduction to main components that make up an app. By

ow, you should know of activities, services, providers and receivers as well as

ntents and other major components of an app.


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Architecting Android Apps Summary

hank you!

Marko Gargenta & Marakana Team@MarkoGargenta

pecial thanks to Ken Jones as well as the rest of Marakana team for research

elated to Fragments, Loaders, and many other new features of ICS.

lides & video of this presentation is available at Marakana.com

amba source code is available at https://github.com/marakana/yamba

c) Marakana.com
https://github.com/marakana/yambahttp://marakana.com/http://twitter.com/MarkoGargenta

Architecting Android Apps

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