Introduction to Android Programming

19.3.2013

Content

Basic environmental structureBuilding a simple appDebugging

Basic environmental structure

Create a very simple applicationExamine its structureRun it on a real deviceRun it on the emulator

Create a new Android project (File > New > Android Application)

Name that appears

on device

Directoryname

Class toautomatically

create

Javapackage

Androidversion

Set your project:

Project Name:  Hello World

Build Target:  Select Android

2.1

Application Name:  Hello World

Package Name:  com.android.test

Create Activity:  HelloWorld

Press "Finish"

Project Components

src – your source codegen – auto-generated code (usually

R.java)Included librariesResources– Drawables (like .png images)– Layouts– Values (like strings)

Manifest file

Sourcecode

Auto-generatedcode

UIlayout

Stringconstants

Configuration

Now you have your project created let's write some code!

Your code is located in a file called HelloWorld.java in the src folder.

Your screen layout file is main.xml in the layout directory.

Project files

1 public class HelloAndroid extends Activity {2  /** Called when the activity first created. */3    @Override4    public void onCreate(Bundle savedInstanceState) 5 {6      super.onCreate(savedInstanceState);7        setContentView(R.layout.main);8    }9 }

HelloWorld.javaSourcecode

Inherit from the Activity Class

Set the layout of the view as described in the main.xml layout

Hello World

modify HelloWorld.java

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XML file

Used to define some of the resources– Layouts (UI)– Strings–Manifest file

res/layout: contains layout declarations of the app, UIs are built according to the layout file

Elements and layouts

ImageButtonEditText

CheckBoxButton

RadioButtonToggleButton

RatingBar

DatePickerTimePicker

SpinnerAutoComplete

GalleryMapViewWebView

Elements and layouts

Types of Layouts

Linear Layout– It organizes controls vertical or horizontal

fashion

Relative Layout,– It organizes controls relative to one

another.

Table Layout– A grid of made up of rows and columns,

where a cell can display a view control

Frame Layout– Frame layouts are the normal layout of

choice when you want to overlap different views stacked on top the other.

Layout

Open main.xml in Layout mode

select main.xml to view/edit the xml markup

Drag a button on to layout

Linear LayoutLinear Layout

Layout

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main.xml<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android=http://schemas.android.com/apk/res/android android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /></LinearLayout>

TextView, display static text

TextView, display static text

A reference to String resource ‘hello’

A reference to String resource ‘hello’

1 <?xml version="1.0" encoding="utf-8"?>2 <resources>3 <string name="hello">Hello World, HelloAndroid!4 </string>5 <string name="app_name">Hello, Android</string>6 </resources>

strings.xml

In res/valuesstrings.xml

Promotes good programming style

Strings are just one kind of ‘Value’

Manifest File

Contains characteristics about your application

NEED to specify it in manifest file– Have more than one Activity in app,– Services and other components too– Important to define permissions and

external libraries, like Google Maps API

Manifest File – Adding an Activity

1 <?xml version="1.0" encoding="utf-8"?> 2 <manifest 3 xmlns:android="http://schemas.android.com/apk/res/android" 4 package="edu.upenn.cis542" 5 android:versionCode="1" 6 android:versionName="1.0"> 7 <application android:icon="@drawable/icon" 8 android:label="@string/app_name"> 9 <activity android:name=".HelloAndroid"10 android:label="@string/app_name">11 <intent-filter>12 <action 13 android:name="android.intent.action.MAIN" />14 <category 15 android:name="android.intent.category.LAUNCHER"/>16 </intent-filter>17 </activity>18 </application>19 </manifest>

AndroidManifest.xml

Run Hello WorldSelect HelloWorld Project, Run->Run as->Android Application

ADT will start a proper AVD and run HelloWorld app on it

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You may receive "Android AVD Error" if you have not setup an android emulator

device.

Select yes to setup a new Android Virtual Device

Select "New"

Create newAndroid Virtual Device

• Name: Android 2.1

• Target: Android 2.1 API Level

7• SD card Size:

4000 MiB• Rest as default settings

Press "Create AVD". Be patient it will take a minute to create your new AVD.

Select your new AVD and run your application.

To get it running…

Emulator

On Phone

Should be enabled on phone to use developer features

In the main apps screen select:→ Settings → Applications → Development → USB debugging (needs to be checked)

How to Debug

Log.v(tag, message); Window > Show View > Other > Android

> LogCat

To show a pop-up window:Toast.makeText( getApplicationContext(), message, Toast.LENGTH_LONG).show();

Logcat Information

Log.e("MyTag", "Error message with my own tag");Log.w("dalvikvm", "VM Warning message"); Log.d("MyTag", "Debug message");Log.i("MainActivity","Information message"); Log.v("MyTag", "Verbose message"); Log.f(“Fail", "What a Terrible Failure");

Useful sources

Android Official Site

• http://www.android.com

Android SDK, Tutorial, Concepts and API docs

• http://androidappdocs.appspot.com/index.html

Android Development Community

• http://www.anddev.org/

30 Days Android Apps Development

• http://bakhtiyor.com/category/30-days-of-android-apps/ 36