Simple Android Application

This is very first and simple Android Application in which i explain about Android File Directory Structure and with help of button i generate an Event.

Step For Creation An Android Application:

                          Opent Eclipse IDE -> File -> New -> Others

Here you can define following things:-

Enter Application Name 

Project Name

Project Package

Minimum Android SDK Version

Targeted Android SDK Version

Here you can Customize your Application Launcher Icon 

Enter The Name of Activity Class  and Layout .xml  File Name.

Android File Directory Architecture

src :- 

                 Contain  All .java source Code File .

gen-

          contain Automatic generated .java file. like R.java.

Note: R.java - It is an very important java file that contain all Resource File in Integer format.

bin:

     It Contain all Executable file like .apk

   Note : .apk file is finally executable file that install on Android Operating System.

libs: 

             It contain all important library.

assets:

While the res directory contains structured values which are known to the Android platform, the assets directory can be used to store any kind of data.

While you could also store uses data in the /res/raw folder. If you need access to original file names and file hierarchy, you can save these resources in the assets directory.

You access this data via the AssetsManager which you can access the getAssets() method.

res : It contains several resources.

Resource files

Android supports that resources, like images and certain XML configuration files, can be keep separate from the source code.

Resource files must be placed in the /res directory in a predefined sub-folder dependent on their type. You can also append additional qualifiers to the folder name to indicate that the related resources should be used for special configurations. For example you can specify that layout file is only valid for a certain screen size.

The following table give an overview of the supported resources and their standard folder prefix.

Resources

Resource	Folder	Description
Drawables	/res/drawables	Images (e.g. png or jpeg files) or XML files which describe a drawable.
Simple Values	/res/values	Used to define strings, colors, dimensions, styles and static arrays of strings or integers via XML files. By convention each type is stored in a separate file, e.g. strings are defined in theres/values/strings.xml file.
Layouts	/res/layout	XML file with layout description files used to define the user interface for activities andFragments.
Styles and Themes	/res/values	Files which define the appearance of your Android application.
Animations	/res/animator	Define animations in XML for the property animation API which allows to animate arbitrary properties of objects over time.
Raw data	/res/raw	Arbitrary files to save in their raw form. You access them via an InputStream.
Menus	/res/menu	Define the properties of entries for a menu.

AndroidManifest.xml

The components and settings of an Android application are described in the AndroidManifest.xml file. This file is known as the Android manifest file.

All activities, services and content providers components of the application must be statically declared in this file.Broadcast receiver can be defined statically in the manifest file or dynamically at runtime in the application.

The Android manifest file must also contain the required permissions for the application. For example if the application requires network access it must be specified here.

Now Code for activity xml file that is use to create View.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/LinearLayout1"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".FirstActivity" >

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_gravity="center_vertical|center"

        android:text="Click Me" />

</LinearLayout>

output Screen:

Now Code For Event:

package in.androidshivendra.firstapp;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;

public class FirstActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

//  Set ui xml for activity by calling setContentView(layout_Id);

setContentView(R.layout.activity_first);

//  Assing Id of Button

Button btn = (Button) findViewById(R.id.button1);

// Implementing event on Button.

btn.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

Toast.makeText(FirstActivity.this, "Hello Android Lover", Toast.LENGTH_LONG).show();

}

});

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.first, menu);

return true;

}

}

OutPut: