==> Values
style.xml  --> same as style of css file in web technology
string.xml --> declare string as global
dimens.xml --> dimension and layout


==> Manifest
--> configuration about application (project)
--> each and every activity you have to register in manifest file

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.helloworld"
    android:versionCode="1"
    android:versionName="1.0" >		// package name 

    <uses-sdk
        android:minSdkVersion="8"	//minimum version code 
        android:targetSdkVersion="17" />	//target version code 

    <application
        android:allowBackup="true" 	//by default true
        android:icon="@drawable/ic_launcher"		//icon for your application visible in menu
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.helloworld.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>						// load start page of your application 
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>




===> android activity life cycle
suppose two activity a1,a2
1. create window for a1	actiity 		--> onCreate()
2. a1 activity visible to user			--> onStart()
3. Interaction of user with activity a1	--> onResume()
4. pause a1 activity					--> onPause()
5. create window for a2	activity 		--> onCreate()
6. a2 activity visible to user			--> onStart()
7. Invisible to user a1 activity		--> onStop()
8. Interaction of user with a2 activity	--> onResume()
9. destroy activity						--> onDestroy()