Difference between Activity and AppCompatActivity
A ctivity is the fundamental block of creating Android Application. Activity is the base Class of all other Activities. Activity - fragmentactivity - AppCompatActivity - ActionBarActivity means, AppCompatActivity inherits FragmentActivity and FragmentActivity inherent Activity. in the Android Developer Documentation : For more read from Android developer Documentation : Activity | Android Developer A ppCompatActivity If you want to add ActionBar in the Activity when Android Application running API Level 7 or Higher by extending the class of the Activity. AppCompatActivity hierarchy : To use the AppCompatActivity, make sure you have the Google Support Library downloaded (you can check this in your Tools -> Android -> SDK manager). Then just include the gradle dependency in your app's gradle.build file : compile 'com.android.support:appcompat-v7:26.0.0-alpha1' For More read from Android Developer Documentation : AppCompat...