What's the Enhancement of Appcompatactivity Over Actionbaractivity

What's the enhancement of AppCompatActivity over ActionBarActivity?

As Chris wrote, new deprecated version of ActionBarActivity (the one extending AppCompatActivity class) is a safe to use backward compatibility class. Its deprecation is just a hint for you asking to use new AppCompatActivity directly instead. AppCompatActivity is a new, more generic implementation which uses AppCompatDelegate class internally.

If you start a new development, then you should rather use new AppCompatActivity class right away. If you have a chance to update your app, then replace deprecated ActionBarActivity by the new activity as well. Otherwise you can stay with deprecated activity and there will be no difference in behavior at all.

Regarding AppCompatDelegate, it allows you to have new tinted widgets in an activity, which is neither AppCompatActivity nor ActionBarActivity.

For instance, you inherit an activity from an external library, which, in turn, does not inherit from AppCompatActivity but you want this activity to have tinted materials widgets (views). To make it happen you need to create an instance of AppCompatDelegate inside your activity, override methods of that activity like addContentView(), setContentView() etc. (see AppCompatDelegate javadoc for the full list of methods), and inside of those overridden methods forward the calls to the inner AppCompatDelegate instance. AppCompatDelegate will do the rest and your "old-fashion" activity will be "materialized".

The impact of changing ActionBarActivity to AppCompatActivity

Copied from sergej shafarenka's answer

ActionBarActivity (the one extending AppCompatActivity class) is a safe to use backward compatibility class. Its deprecation is just a hint for you asking to use new AppCompatActivity directly instead. AppCompatActivity is a new, more generic implementation which uses AppCompatDelegate class internally.

Regarding AppCompatDelegate, it allows you to have new tinted widgets in an activity, which is neither AppCompatActivity nor ActionBarActivity.

For instance, you inherit an activity from an external library, which, in turn, does not inherit from AppCompatActivity but you want this activity to have tinted materials widgets (views). To make it happen you need to create an instance of AppCompatDelegate inside your activity, override methods of that activity like addContentView(), setContentView() etc. (see AppCompatDelegate javadoc for the full list of methods), and inside those overridden methods forward the calls to inner AppCompatDelegate instance. AppCompatDelegate will do the rest and your "old-fashion" activity will be "materialized".

Should I replace ActionBarActivity with AppCompatActivity?

Yes. You should use AppCompatActivity.

The AppCompatActivity is a very new class and the training section on the android website is outdated.

Everything that you would do with ActionBarActivity will work mostly the same on AppCompatActivity.

For differences please read the post about it http://android-developers.blogspot.de/2015/04/android-support-library-221.html

Activity, AppCompatActivity, FragmentActivity, and ActionBarActivity: When to Use Which?

I thought Activity was deprecated

No.

So for API Level 22 (with a minimum support for API Level 15 or 16), what exactly should I use both to host the components, and for the components themselves? Are there uses for all of these, or should I be using one or two almost exclusively?

Activity is the baseline. Every activity inherits from Activity, directly or indirectly.

FragmentActivity is for use with the backport of fragments found in the support-v4 and support-v13 libraries. The native implementation of fragments was added in API Level 11, which is lower than your proposed minSdkVersion values. The only reason why you would need to consider FragmentActivity specifically is if you want to use nested fragments (a fragment holding another fragment), as that was not supported in native fragments until API Level 17.

AppCompatActivity is from the appcompat-v7 library. Principally, this offers a backport of the action bar. Since the native action bar was added in API Level 11, you do not need AppCompatActivity for that. However, current versions of appcompat-v7 also add a limited backport of the Material Design aesthetic, in terms of the action bar and various widgets. There are pros and cons of using appcompat-v7, well beyond the scope of this specific Stack Overflow answer.

ActionBarActivity is the old name of the base activity from appcompat-v7. For various reasons, they wanted to change the name. Unless some third-party library you are using insists upon an ActionBarActivity, you should prefer AppCompatActivity over ActionBarActivity.

So, given your minSdkVersion in the 15-16 range:

If you want the backported Material Design look, use AppCompatActivity
If not, but you want nested fragments, use FragmentActivity
If not, use Activity

Just adding from comment as note: AppCompatActivity extends FragmentActivity, so anyone who needs to use features of FragmentActivity can use AppCompatActivity.

diffrence between Appcompact activity and actionbar activity

ActionBarActivity is now deprecated. As of version 22.1 of the support library you should use AppCompatActivity.

Chris Banes (one of the authors of the AppCompat library) covered the refactor in detail here.

Why was ActionBarActivity deprecated

ActionBar is deprecated ever since Toolbar was introduced. Toolbar can be seen as a 'superset' of any action bar. So the 'old' ActionBar is now an example of a Toolbar. If you want similar functionality, but without deprecation warnings do the following:

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
if (toolbar != null) {
    toolbar.setTitle(R.string.app_name);
    setSupportActionBar(toolbar);
}

You need to define the Toolbar in your layout xml:

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toolbar"
    android:minHeight="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    android:popupTheme="@style/ThemeOverlay.AppCompat.Light">
</android.support.v7.widget.Toolbar>

With this new functionality you can create your own custom ActionBar and let Android do the heavy lifting. Just create your own custom view that extends from Toolbar.

Also, you should use AppCompatActivity instead of ActionBarActivity, it was introduced in the latest version of the appcompat library. So dont forget to update gradle

compile 'com.android.support:appcompat-v7:22.1.1'

What's the Enhancement of Appcompatactivity Over Actionbaractivity