Android First Example: Hello World

Android First Example: Hello World
G.Morreale

Introduction:

Android is a software stack for mobile devices that includes an operating system, middleware and key applications. 

More details link: http://code.google.com/intl/it/android/documentation.html

The Android SDK contains API necessary to begin developing applications on the Android platform using the Java programming language.

In this article I point out the steps for making the hello world example and running it in the emulator.

The Steps:

In order to write the example follow these steps

• The Android SDK

• Download the sdk (select your developing platform) http://code.google.com/intl/it/android/download_list.html
  

• Extract it into your hard drive directory
  

• Java Code

• Make a new java project
  
• set in the project class path android.jar (you can find it in sdk zip file)
  
• make a new java class into Hello.java
  
• copy this source code in Hello.java:
  

//package name must be composed of at least two java identifiers
package my.android;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

    public class Hello extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Make a new text view passing Activity object
        TextView tv = new TextView(this);
        //Set a text into view
        tv.setText("Hello World");
        //set the view into activity view container
        setContentView(tv);
    }
}

• compile Hello.java code

• Build and install The apps

• In tools sdk directory you can find activitycreator.bat, launch it by passing the complete package name and class name:

activitycreator -o c:\android my.android.Hello

• The script prepare the android application putting it into c:\android directory
  

• Now you need ant tools in order to build the android application
  

Download it from: http://ant.apache.org/bindownload.cgi

• Go in c:\android directory
  
• Launch: "ant -f build.xml" command
  

(note: if you go in "Unable to locate tools.jar" error you must set correctly jdk classpath.)

you'll be left with a file named Hello-debug.apk under the 'bin' directory

• Go again in tools sdk directory.
  

Now you can use adb command in order to install the apk file into android emulator

• First launch the emulator (if you don't adb command fails)

(note: in order to launch emulator you must execute the emulator.exe command in sdk tools directory.)

• Then launch the follow command: adb install c:\android\bin\hello-debug.apk
  

• Run The example

• Close the emulator
  
• Re-launch the emulator
  

• Click on the arrow in the bottom of the screen so you open the application list, now you can 
  

• find hello application.. click on it to see the hello word string..
  

Conclusion 

It is only a small example introducing android development.

The next step is to go deep into

http://code.google.com/intl/it/android/documentation.html 

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