Training android

Editor
Nguyễn Đức Minh Khôi
nguyenducminhkhoi@gmail.com
nguyenducminhkhoi.blogspot.com

Training
Android
@HCMC University of Technology
Summer 2012

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Training Android June 2012

Introduction – What is Android?
The Android operating system was developed by
Android, Inc.,
Was acquired by Google in July 2005.
Developing Android apps is the openness of the
platform
The operating system is open source and free.

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Introduction (cont.)
Java:
was a logical choice for the Android platform
enables you to develop apps that will run on a variety of
devices without any platform-specific code.
is object oriented and has access to powerful class
libraries that help you develop apps quickly.

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XML:
enables you to better separate the presentation of your
application from the code that controls its behavior.
makes it easier to visualize the structure of your UI, so
it's easier to debug problems
Is similar to HTML

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Multitouch screen:

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Android versions:
Android 1.6 (Donut)
Android 2.0–2.1 (Eclair)
Android 2.2 (Froyo)
Android 2.3 (Gingerbread)
Android 3.0 (Honeycomb)
Android 4.0 (Ice Cream Sandwich)
Android 5.0 (Jelly Beans)
See more at:
http://developer.android.com/resources/dashboard/platform
-versions.html

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Types of android apps (go to
https://play.google.com/store) for more details
Other sites you can download apps:

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How to set up
Software and hardware system requirement:
To develop Android apps you need a Windows®,
Linux or Mac OS X system.
Java SE 5 or higher Software Development Kit
Eclipse 3.7 (Indigo) IDE for Java Developers
Android SDK versions 2.2, 2.3.3 and 3.x
ADT (Android Development Tools) Plugin for Eclipse

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How to set up (cont.)
Install JDK (Java Development Kit) 6:
Go to www.oracle.com/technetwork/java/javase/index-
137561.html
Install Eclipse IDE
Go to www.eclipse.org/downloads
Choose Eclipse IDE for Java Developers
Install the Android SDK
Go to www.developer.android.com/sdk/index.html
Click and choose your suitable platform
Install ADT plugin for Eclipse
Go to www.developer.android.com/sdk/eclipse-adt.html
carefully follow the instructions for downloading
and installing the ADT Plugin

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Install Android platform:

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Creating Android Virtual Device (AVD):
The Android emulator, included in the Android SDK,
allows you to run Android apps in a simulated environment
on your computer rather than on an actual Android device.

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Source for learning
Best resource for learning and referencing:
http://developer.android.com/index.html

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Source for learning (cont.)

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Source for learning (cont.)

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Welcome apps (cont.)

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Eclipse IDE

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Eclipse IDE (cont.)
Create new Project:

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Eclipse IDE (cont.)
Platform Codename API Level
Android 1.5 Cupcake 3
Android 1.6 Donut 4
Android 2.1 Eclair 7
Android 2.2 Froyo 8
Android 2.3 - Gingerbread 9
Android 2.3.2
Android 2.3.3 - 10
Android 2.3.7
Android 3.0 Honeycomb 11
Android 3.1 12

Android 3.2 13

Android 4.0 - Ice Cream 14
Android 4.0.2 Sandwich
Android 4.0.3 - 15
Android 4.0.4

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Developing GUI

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Developing GUI (cont.)

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Running the Welcome apps
To run the app in
an Android
Virtual Device
(AVD), right click
the app’s root
node in
the Package
Explorer window
and select Run
As > Android
Application.

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Building Features
Each app below will expand on one Class hour
By practicing these apps you will learn some
interesting features
Each app will contain:
Introductionsand objectives
New Features
Building GUI
Adding functions
Results

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Building Features
Each app below will expand on one Class hour
By practicing these apps you will learn some
interesting features
Each app will contain:
Introductionsand objectives
Technologies Overview
Building GUI
Adding functions
Results

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Building Features (cont.)
1.Tip Calculator App
2.Favorite Twitter Searches App
3.Flag Quiz Game App
4.Cannon Game App
5.Spot on Game App
6.Doodlz App
7.Address Book App
8.Slideshow App
9.Enhanced Slideshow App
10.Weather Viewer App

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Tips Calculator App
Objectives:
Building an Android App with
Java
Design a GUI using a
TableLayout
Directly edit the XML of a GUI
layout to customize properties
Use Android Activity’s subclass
interact with EditTexts, a
TextView and a SeekBar.

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Tips Calculator App (cont.)
Introduction:
“The Tip Calculator app calculates and displays tips
for a restaurant bill. As the user enters a bill total,
the app calculates and displays the tip amount and
total bill for three common tipping percentages—
10%, 15% and 20%. The user can also specify a
custom tip percentage by moving the thumb of a
Seekbar—this updates the percentage shown to the
right of the Seekbar. The suggested tips and bill
totals are updated in response to each user
interaction.”

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Technologies Overview:
TableLayout and TableRow introduction
See more at:
•www.developer.android.com/reference/android/widget/TableLayout.html
•www.developer.android.com/reference/android/widget/TableRow.html

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Building GUI:
Create GUI with the following information

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main.xml describe GUI like figure above
String.xml

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Adding Functions:
Remember when you want to import some library, use just
type the name of the class (don’t need to complete) and press
(Ctrl + Space), it will import immediately
Class Activity of package android.app provides the basic
lifecycle methods of an app—we’ll discuss these shortly.
Class Bundle of package android.os represents an app’s state
information. An app can save its state when it’s sent to the
background by the operating system—for example, when the
user launches another app or a phone call is received.

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Android apps doesn’t have main method
four types of components—activities, services, content providers and
broadcast receivers
A separate activity is typically associated with each screen of an app
Throughout its life an activity can be in one of several states—active (or
running), paused or stopped.
An active (or running) activity is visible on the screen and “has the focus”
A paused activity is visible on the screen but doesn’t have the focus. can be
killed when its memory is needed by the operating system
A stopped activity is not visible on the screen and is likely to be killed by the
system when its memory is needed.
See more at:
www.developer.android.com/reference/android/app/Activity.html

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Override method:
onCreate: called by the system when an Activity is
starting—that is, when its GUI is about to be
displayed so that the user can interact with the
Activity.
onSaveInstanceState: called by the system when the
configuration of the device changes during the app’s
execution
 Remember: Each activity lifecycle method you override
must call the superclass’s version of that method first;
otherwise, an exception will be thrown when that method is
called.

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R content class:
Class drawable—contains constants for any drawable
items, such as images, that you put in the various
drawable folders in your app’s res folder
Class id—contains constants for the GUI components
in your XML layout files
Class layout—contains constants that represent each
layout file in your project (such as, main.xml)
Class string—contains constants for each String in
the strings.xml file

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Results:

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Favorite Twitter Searches App
Objectives:
SharedPreferences, Buttons, Nested Layouts, Intents,
AlertDialogs, Inflating XML Layouts and the Manifest File
Use a ScrollView to display objects that do not fit on the
screen.
Programmatically open a website in a web browser by
using an Intent.
Programmatically hide the soft keyboard.

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Favorite Twitter Searches App (cont.)
Introduction:
“The Favorite Twitter Searches app allows users to save
their favorite (possibly lengthy) Twitter search strings
with easy-to-remember, user-chosen, short tag names.
Users can then conveniently follow the tweets on their
favorite topics. Twitter search queries can be finely tuned
using Twitter’s search operators
(dev.twitter.com/docs/using-search)—but more complex
queries are lengthy, time consuming and error prone to
type on a mobile device. The user’s favorite searches are
saved on the device, so they’re immediately available
each time the app launches.”

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Technologies Overview:
ScrollView: is a ViewGroup that can contain other Views (like a layout)
and that lets users scroll through content too large to display on the
screen.
To read the key/value pairs from this file we’ll use SharedPreferences
objects (package android.content). To modify the file’s contents, we’ll
use SharedPreferences.Editor objects (package android.content). The
keys in the file must be Strings, and the values can be Strings or
primitive-type values
Intents are typically used to launch activities—they indicate an action
to be performed and the data on which that action is to be performed.
We load the URL into a web browser by creating a new Intent for
viewing a URL, then passing that Intent to the startActivity method,
which our Activity inherits indirectly from class Context

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New Features:
LayoutInflater programmatically creates these GUI components
from a predefined XML layout. The LayoutInflater inflates an XML
layout file, thus creating the components specified in the XML.
You can display messages and confirmations like these with an
AlertDialog. We specify the settings for the dialog with an
AlertDialog.Builder object, then use it to create the AlertDialog.
The AndroidManifest.xml file is created for you when you
create an app using the ADT Plugin in Eclipse. This file specifies
settings such as the app’s name, the package name, the target
and minimum SDKs, the app’s Activity name(s) and more

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Building the GUI:

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Adding functions:
Package android.widget contains the widgets (i.e., GUI
components) and layouts that are used in Android GUIs. Class
Button of package android.widget represents a simple push
button that the user touches to get the app to perform a specific
action. You implement interface View.OnClickListener of package
android.view to specify the code that should execute when the
user touches a Button
Overridden Method OnCreate of Class Activity, called by system
when:
when the app loads
if the app’s process was killed by the operating system while the
app was in the background, and the app is then restored
each time the configuration changes, such as when the user
rotates the device or opens/closes a physical keyboard.

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Adding functions:
Method getSharedPreferences to get a SharedPreferences
object that can read tag/query pairs stored previously (if any) from
the "searches" file.
The first argument indicates the name of the file that contains
the data.
The second argument specifies the accessibility of the file and
can be set to one of the following options:
MODE_PRIVATE— The file is accessible only to this app. In most
cases, you’ll use this constant as the second argument to
getSharedPreferences.
MODE_WORLD_READABLE— Any app on the device can read from
the file.
MODE_WORLD_WRITABLE— Any app on the device can write to
the file.

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AndroidManifest.xml
For complete information, refer to this
page:
www.developer.android.com/guide/topics/manifest/manif
est-intro.html

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Flag Quiz Game App
Objectives:
Assets, AssetManager, Tweened Animations, Handler, Menus
and Logging Error Messages.
Use an AssetManager to get a list of all assets in an app.
Use random-number generation to vary flag choices.
Use a Drawable to display a flag image in an ImageView.
Use a Handler to schedule a future action.
Use an ArrayList to hold collections of items and a
HashMap to hold name–value pairs.
Override Activity’s onCreateOptionsMenu method to create a
Menu and MenuItems that enable the user to configure the
app’s options.
Use Android’s logging mechanism to log error messages.

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Flag Quiz Game App (cont.)
Introduction:
“The Flag Quiz Game app tests the user’s ability to correctly
identify country flags. Initially, the app presents the user with a
flag image and three possible answers—one matches the flag
and the others are randomly selected, nonduplicated incorrect
answers. The app displays the user’s progress throughout the
quiz, showing the question number (out of 10) in a TextView
above the current flag image.”

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Technologies Overview:
Using the App’s assets Folder: the assets folder may contain files of any
type that can be organized in subfolders—we maintain the flag images for
each region in a separate subfolder. Files in the assets folders are accessed
via an AssetManager (package android.content.res), which can provide a
list of all of the file names in a specified subfolder of assets and can be
used to access each asset.
Using a Menu to Provide App Options: override Activity’s
onCreateOptionsMenu method and add the options to the Menu that the
method receives as an argument. Activity method
onOptionsItemSelected is called to respond to the selection.
Using a Handler to Execute a Runnable in the Future: . Handler method
postDelayed receives as arguments a Runnable to execute and a delay in
milliseconds.

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Technologies Overview (cont.):
Animating the Flag When an Incorrect Choice Is Touched:
AnimationUtils static method loadAnimation to load the animation from
an XML file that specifies the animation’s options. We also specify the
number of times the animation should repeat with Animation method
setRepeatCount and perform the animation by calling View method
startAnimation (with the Animation as an argument) on the ImageView.
Logging Exception Messages with Log.e: When exceptions occur, you
can log them for debugging purposes with Android’s built-in logging
mechanism, which uses a circular buffer to store the messages for a short
time. Android provides class Log (package android.util) with several static
methods that represent messages of varying detail.
Java Data Structures: ArrayList<String>, Map<String, Boolean>,
Set<String>

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Building the App GUI:
Main.xml Linear Layout

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colors.xml & dimen.xml:

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string.xml:

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Study more:
View animations to create a shake effect that consists of three
animations in an animation set a collection of animations which make up
a larger animation. Animation sets may contain any combination of
tweened animations— alpha (transparency), scale (resize), translate
(move) and rotate.
android:fromXDelta attribute is the View’s offset when the animation
starts and the android:toXDelta attribute is the View’s offset when the
animation ends. These attributes can have
absolute values (in pixels)
a percentage of the animated View’s size
a percentage of the animated View’s parent’s size
The android:duration attribute specifies how long the animation lasts in
milliseconds.
android:startOffset attribute to specify the number of milliseconds into
the future at which an animation should begin.

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Building the App
AndroidManifest.xml:

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Cannon Game App
Objectives:
Create a simple game app that’s easy to code and fun to play.
Create a custom SurfaceView subclass and use it to display the
game’s graphics from a separate thread of execution.
Draw graphics using Paints and a Canvas.
Override Activity’s onTouchEvent to process touch events when
the user touches the screen or drags a finger on the screen.
Use a GestureDetector to recognize more sophisticated user
touch motions, such as double taps.
Perform simple collision detection.
Add sound to your app using a SoundPool and the
AudioManager.
Override three additional Activity lifecycle methods.

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Cannon Game App (cont.)
Introduction:
“The Cannon Game app challenges you to destroy a seven-
piece target before a ten-second time limit expires. The game
consists of four visual components—a cannon that you control,
a cannonball, the target and a blocker that defends the target.
You aim the cannon by touching the screen—the cannon then
aims at the touched point. The cannon fires a cannonball when
you double-tap the screen. At the end of the game, the app
displays an AlertDialog indicating whether you won or lost, and
showing the number of shots fired and the elapsed time”

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Technologies Overview
Defining String Formatting Resources in strings.xml
Attaching a Custom View to a Layout
Using the Resource Folder raw
Activity Lifecycle Methods onPause and onDestroy:
Method onPause is called for the current Activity when another activity
receives the focus, which sends the current activity to the background. We
use onPause to suspend game play so that the game does not continue
executing when the user cannot interact with it.
When an Activity is shut down, its onDestroy method is called. We use this
method to release the app’s sound resources.
Overriding Activity Method onTouchEvent

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Technologies Overview (cont.)
GestureDetector and SimpleOnGestureListener:
A GestureDetector allows an app to react to more sophisticated
user interactions such as flings, double-taps, long presses and scrolls.
Your apps can respond to such events by implementing the methods
of the GestureDetector.
GestureDetector.SimpleOnGestureListener is an adapter class that
implements all the methods of these two interfaces, so you can
extend this class and override just the method(s) you need from
these interfaces.
Adding Sound with SoundPool and AudioManager
Frame-by-Frame Animation with Threads, SurfaceView and
SurfaceHolder
Simple Collision Detection
Drawing Graphics Using Paint and Canvas

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Building App’s GUI and resource files:

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Building App’s GUI and resource files (cont.):

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Building App’s GUI and resource files (cont.):
The notation 1$ in %1$.1f (line 5) indicates that the first argument after
the format String should replace the format specifier %1$d. Similarly,
%2$.1f indicates that the second argument after the format String should
replace the format specifier %2$.1f.

Adding functions (regarding to instructors)

Training android

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