Differences between AppCompatActivity, ActionBarActivity, FragmentActivity, and Activity,

Differences between AppCompatActivity, ActionBarActivity, FragmentActivity, and Activity,
AppCompatActivity, ActionBarActivity, FragmentActivity, Activity

Android SDK introduces Fragment, ActionBar, and other features in API Level 11 (Android 3.0.x). Earlier sdks did not include these features. To enable devices of earlier versions to use these features, no error is reported, google provides the Android Support Library.
For example, to use Fragment on a device before Android 3.0, You need to import the android-support-v4.jar compatibility package and use FragmentActivity (inherited from Activity) to solve the problem of not using Fragment. For another example, to use ActionBar on a low-version device, you need to use the ActionBarActivity provided by the android-support-v7 compatibility package (inherited from FragmentActivity ).
Android SDK from API Level 21 (Android5.0) began to introduce Material Design style controls, in order to make earlier versions of devices can also use these features, Google updated the android-support-v7 compatibility package, appCompatActivity is used to replace ActionBarActivity. If a new android-support-v7 is used and an attempt is made to change ActionCompatActivity in the code to ActionBarActivity, it will prompt that it is out of date.