Fragment与FragmentActivity的关系

前阵用viewpaper+fragment作滑动引导，查阅了下网上的资料，发如今有两种作法，一个是自建类直接继承Activity另外一种是继承FragmentActivity，非常迷惑，在查了些google的官方文档和StackOverflow以后有了些理解，在此坐下记录。下面的英文说明取自Stackoverflow，我的感受解释的很清楚。

A Fragment is a section of an Activity, which has:

• its own lifecycle
• receives its own input events
• can be added or removed while the Activity is running.

A Fragment must always be embedded in an Activity.

Fragments are not part of the API prior to HoneyComb (3.0). If you want to use Fragments in an app targeting a platform version prior to HoneyComb, you need to add the Support Package to your project and use the FragmentActivity to hold your Fragments. The FragmentActivity class has an API for dealing with Fragments, whereas the Activity class, prior to HoneyComb, doesn't.

If your project is targeting HoneyComb or newer only, you should use Activity and notFragmentActivity to hold your Fragments.

Some details:

Use android.app.Fragment with Activity. Use android.support.v4.app.Fragment withFragmentActivity. Don't add the support package Fragment to an Activity as it will cause an Exception to be thrown.

A thing to be careful with: FragmentManager and LoaderManager have separate support versions for FragmentActivity:

If you are using a Fragment in an Activity (HoneyComb and up), call

• getFragmentManager() to get android.app.FragmentManager
• getLoaderManager() to get android.app.LoaderManager

if you are using a Fragment in a FragmentActivity (pre-HoneyComb), call:

• getSupportFragmentManager() to get android.support.v4.app.FragmentManager.
• getSupportLoaderManager() to get android.support.v4.app.LoaderManager

so, dont do

myFragmentActivity.getLoaderManager()//don't do this, do myFragmentActivity.getSupportLoaderManager()

or

android.app.FragmentManager fm = myFragmentActivity.getSupportFragmentManager()//don't do this, do android.support.v4.app.FragmentManager fm = myFragmentActivity.getSupportFragmentManager()

Also useful to know is that while a fragment has to be embedded in an Activity it doesn't have to be part of the Activity layout. It can be used as an invisible worker for the activity, with no UI of its own.

总结来讲就是标红记录的说明：

一、fragmentactivity 继承自activity，用来解决android3.0 以前没有fragment的api，因此在使用的时候须要导入support包，同时继承fragmentActivity，这样在activity中就能嵌入fragment来实现你想要的布局效果。

二、固然3.0以后你就能够直接继承自Activity，而且在其中嵌入使用fragment了。

三、得到Manager的方式也不一样

3.0如下：getSupportFragmentManager()

3.0以上：getFragmentManager()