Lecture Series on Android Programming Chapter.2 First Android Application Lecturer: Prof.Luqun Li ([email protected])[email protected] Teaching Assistants:

Lecture Series on Android Programming

Chapter.2 First Android Application

Lecturer: Prof.Luqun Li ([email protected])Teaching Assistants: Fengyou Sun, Haijun Yang, Ting Sun

Shanghai Normal University2

Contents

11 Set up the environment

22 Learing the Fundamental Components

33 Hello world

44Exploring the Structure of an Android Application


Introducing Andorid computing platform

55Analyzing the Stucture of an Andorid Application

66Analyzing the Notepad Application

77 Examining the Applicationg Lifecycle

88 Debugging the App


Setting Up Your Environment

To build Android applications, we need to establish a development environment. In Prepare the software bundles

Java JDK & Java Doc (optional)

IDE Environment can be setup by:

Approach.1 Use:Android SDK + ADT+Eclipes

Approach.2 Use:Android SDK+MotoDEV studio

See videos for: android related software's download & IDE setup


Aproach.1 Eclipse+Android SDK+ADT

step1

Downloading JDK 7 and Eclipse 4.2


Click to edit headline

step2

Downloading the Android SDK



step3

Installing Android Development Tools (ADT)


Learning the Fundamental Components

Every application framework has some key components that developers need to understand before they can begin to write applications based on the framework


The Fundamental Components

Activity

Content Provider

AndroidManifest.xm

View

Intent

Service


A Hello World Demo

Hello World!Now we ready to build our first

Android application. We’ll start by building a simple

“Hello World!” program. Create the skeleton of the application by following these steps:



step 1

Launch Eclipse and select File New Project. ➤ ➤In the “New Project” dialog box, select “Android” and then click “Next.” You will then see the “New Android Project” dialog box



step 2

enter HelloAndroid as the project name, pro.android asthe package name, HelloActivity as the activity name, and HelloAndroidApp as the application name



step 3

Click the “Finish” button, which tells ADT to generate the project skeleton for you.For now, open the HelloActivity.java file under he src folder and modify the onCreate() method as follows


/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);/** create a TextView and write Hello World! */ TextView tv = new TextView(this); tv.setText("Hello World!");/** set the content view to the TextView */setContentView(tv);}


create an Eclipse launch configuration

Next page

Click “Apply” and then “Run.” You should see the emulator launched with the Hello Android projec.

Under “Launch Action,” select “Launch” and select “pro.android.HelloActivity” from the drop-down list

Click the “Browse…” button and select the HelloAndroid project


create an Eclipse launch configuration

Create the Eclipse launch configuration

Rename the configuration RunHelloWorld.

In the “Run Configurations” dialog box, double-click “Android Application" in the left pane. The wizard will insert

a new configuration named “New Configuration.”

Select Run Run Configurations➤


Exploring the Structure of an Android Application

Although the size and complexity of Android applications can vary greatly, their structures will be similar

An Android application is primarily made up of three pieces



an Android application

the application descriptor

a collection of various resources

the application’s source code.


Analyzing the Notepad Applicationanalyzing its components will give you some realistic insight

into Android development.

Follow these steps to load the Notepad sample into the Eclipse IDE:

1. Start Eclipse.

2. Go to File ➤ New ➤ Project.

3. In the “New Project” dialog, select Android ➤ Android Project.


4.In the “New Android Project” dialog, select “Create project from existing source” and set the “Location” field to the path of the Notepad application. Note that the Notepad application is located in c:\AndroidSDK\samples\, which you downloaded earlier. After you set the path, the dialog reads the AndroidManifest.xml file and prepopulates the remaining fields in the “New Android Project” dialog box.

5. Click the “Finish” button.


Next, we see the activity execute a managed query and get a cursor for the result. A managed query means that Android will manage the returned cursor. In other words, if the application has to be unloaded or reloaded, neither the application nor the activity has to worry about positioning the cursor, loading it, or unloading it. The parameters to managedQuery(), shown in Table , are interesting


Parameters to Activity.managedQuery

Parameter Data Type Description

URI Uri URI of the content provider

projection String[] The column to return (column names)

selection String Optional where clause

selectionArgs String[] The arguments to the selection, if the query contains

sortOrder String Sort order to be used on the result set


Examining the Application Lifecycle The lifecycle of Android applications differs

greatly from the lifecycle of web-based J2EE applications. J2EE apps are loosely managed by the container they run in. For example, a J2EE container can remove an application from memory if it sits idle for a predetermined time period. But the container generally won’t move applications in and out of memory based on load and/or available resources. In other words, it’s up to the application owners to ensure that resources are available.


The concept of application lifecycle is logical, but a fundamental aspect of Android applications complicates matters. Specifically, the Android application architecture is compo- nent- and integration-oriented. This allows a rich user experience, seamless reuse, and easy application integration, but creates a complex task for the application-lifecycle manager.


The following graph shows the list of lifecycle methods that Android calls during the life of an activity. It’s important to understand when each of the methods is called by the system to ensure that you implement a stable application. Note that you do not need to react to all of these methods. If you do, however, be sure to call the superclass versions as well.


onRestart

onCreateronStar

onStoponDestroy

onResume onPause

Activity Start

Activity Stop


Debugging Your AppAfter we write a few lines of code for our first application,

we’ll start wondering if it’s pos- sible to have a debug session while you interact with your application in the emulator. Shortly after that, you’ll instinctively run to System.out.println(), which will fail because the code is running on the emulator and the sys-out statement is not fed back to the IDE. But don’t worry; the Android SDK includes a host of applications that we can use for debugging purposes.

The SDK also includes a file-explorer tool that you can use to view files on the device. These tools

are integrated with the Eclipse IDE



You can view the tools by selecting the Debug perspective in Eclipse. You can also launch each tool by going to Window Show ➤View Other Android.➤ ➤One of the tools that you’ll use throughout your Android development is LogCat. This tool displays the log messages that you emit using android.util.Log, exceptions, and so on. We

will introduce the other tools throughout the book.t.


Summary This chapter showed:

1. how to set up IDE

2. discussed & introduced views, activities, intents, content providers, and services.

3. Talk about the Android application lifecycle.

4. Finally, mentioned the Android SDK’s debugging tools

Documents

Lecture Series on Android Programming Chapter.2 First Android Application Lecturer: Prof.Luqun Li ([email protected])[email protected] Teaching Assistants: