Introduction to Android Programming

19.3.2013

ContentBasic 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 WorldBuild Target: 

Select Android 2.1Application Name: 

Hello WorldPackage Name:  com.android.testCreate Activity:  HelloWorldPress "Finish"

Project Componentssrc – 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 Worldmodify HelloWorld.java

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XML fileUsed 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 LayoutsLinear Layout– It organizes controls vertical or horizontal

fashionRelative 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 controlFrame 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 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

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.xmlPromotes good programming styleStrings 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