AppCompatActivity、ActionBarActivity、FragmentActivity和Activity的区别

package com.chy.myapplication;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
/*
* support v4 FragmentActivity  兼容2.x模式下使用Fragment
* support v7 AppCompatActivity 兼容2.x模式下使用Fragment和ActionBar，ActionBarActivity是AppCompatActivity过时产品
* 如果3.0以上直接继承Activity，便可使用Fragment和ActionBar
*/
public class MainActivity extends AppCompatActivity {
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

Activity 发展到3.0（大概）之后，可以使用fragment了，但是support v4 提供了1.6~3.0的fragment兼容，所以如果需要用兼容版的fragment，则需要继承support v4提供的FragmentActivity。
而后一点点时间之后，3.0（大概）出现的ActionBar也被向前支持了，这次是出现在support v7里，如果需要使用兼容版的actionbar，则继承support v7提供的ActionBarActivity（它是继承FragmentActivity的）。
再然后也就是去年年底到今年，5.0提供了很多很多新东西，于是support v7也更新了，出现了AppCompatActivity , 具体功能请自行查找。

================================================================================================================================================================
以下内容来自Googlehttp://stackoverflow.com/questions/31297246/activity-appcompatactivity-fragmentactivity-and-actionbaractivity-when-tous

 =======================================================================================================================================

Activity is the base class of all other activities, I don't think it will be deprecated. The relationship among them is:

Activity <<<FragmentActivity <<< AppCompatActivity <<< ActionBarActivity

'<<<' means inheritance here. The reference said ActionBarActivity is deprecated, use AppCompatActivity instead.

So basically, using AppCompatActivity is always the right choise. The differences between them:

• Activity is the basic one.
• Based on Activity, FragmentActivity provides the ability to use Fragment.
• Based on FragmentActivity, AppCompatActivity provides features to ActionBar