Fragment在android3.0(api11)開始才有的，剛開始是為了適配平板而推出（現(xiàn)在用處很多），現(xiàn)在在Android日常開發(fā)中被越來越多的使用谆吴，F(xiàn)ragment不能獨(dú)立存在它必須依附于四大組件之一Activity(將此activity稱為宿主activity)而存在,同時activity必須是FragmentActivity及其子類（所以我們直接繼承AppCompatActivity (extends FragmentActivity)同樣可以使用Fragment）

• Fragment是Object類的子類
  public class Fragment extends Object implements ComponentCallbacks2, View.OnCreateContextMenuListener

• Fragment的子類有：
  DialogFragment,ListFragment,PreferenceFragment,WebViewFragment

• 使用Fragment需要使用FragmentManager來進(jìn)行管理Activity.getFragmentManager,Fragment.getFragmentManager

• Lifecycle（生命周期）
  由于它的使用依賴于宿主activity踩晶，所以fragment的生命周期與宿主Activity的生命周期息息相關(guān)

• 當(dāng)宿主activity執(zhí)行到生命周期的onResume()時砰粹，F(xiàn)ragment的生命周期方法依次執(zhí)行以下方法來源于官網(wǎng)

  1. onAttach(Activity) called once the fragment is associated with its activity.
  2. onCreate(Bundle) called to do initial creation of the fragment.
  3. onCreateView(LayoutInflater, ViewGroup, Bundle) creates and returns the view hierarchy associated with the fragment.
  4. onActivityCreated(Bundle) tells the fragment that its activity has completed its own [Activity.onCreate()](https://developer.android.com/reference/android/app/Activity.html#onCreate(android.os.Bundle)).
  5. onViewStateRestored(Bundle) tells the fragment that all of the saved state of its view hierarchy has been restored.
  6. onStart() makes the fragment visible to the user (based on its containing activity being started).
  7. onResume() makes the fragment begin interacting with the user (based on its containing activity being resumed).

• 當(dāng)fragment不再被使用蛛淋，將執(zhí)行以下方法

  1. onPause()fragment is no longer interacting with the user either because its activity is being paused or a fragment operation is modifying it in the activity.
  2. onStop() fragment is no longer visible to the user either because its activity is being stopped or a fragment operation is modifying it in the activity.
  3. onDestroyView() allows the fragment to clean up resources associated with its View.
  4. onDestroy() called to do final cleanup of the fragment's state.
  5. onDetach() called immediately prior to the fragment no longer being associated with its activity.

• 啟動一個Activity時咙好，F(xiàn)ragment與Activity的生命周期分別執(zhí)行的方法如下

1、fragment的生命周期包含在整個宿主activity的方法中
2褐荷、fragment的創(chuàng)建在整個activity的創(chuàng)建完成之前勾效，fragment的銷毀在activity銷毀之前
3、相同生命周期方法叛甫，fragment先執(zhí)行與宿主activity
4葵第、無論宿主activity中有多少fragment，當(dāng)activity銷毀時合溺，所有的fragment均會銷毀

啟動/銷毀宿主Activity時Fragment的生命周期方法執(zhí)行順序(靜態(tài)加載方式)

• Fragment的使用方式

getFragmentManager().beginTransaction().add(containerId, fragment實(shí)例對象).commit();

• 靜態(tài)加載
  在activity的layout布局文件中使用卒密，fragment標(biāo)簽并設(shè)置name屬性，在啟動activity不需要添加額外代碼即可加載fragment

 <fragment
        android:name="FragmentTwo所在包.FragmentTwo"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

• 動態(tài)加載
  在Activity的layout中不使用fragment標(biāo)簽棠赛，使用一個容器(比如：FrameLayout哮奇、RelativeLayout等)替代

/** 
* activity容器
*/
 <LinearLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical" />

• 使用方法1:
  fragmentManager為Activity的方法，F(xiàn)ragmentOne 繼承自app包下Fragment

 fragmentManager.beginTransaction().replace(R.id.fragment_container, FragmentOne()).commit()

• 使用方法2:
  （supportFragmentManager為FragmentActivity中方法睛约，F(xiàn)ragmentTwo為v4包下的framgnet）

supportFragmentManager.beginTransaction().replace(R.id.fragment_container, FragmentTwo()).commit()

備注：動態(tài)添加多個fragment時鼎俘，每次都需要開啟一個新事務(wù)beginTransaction，因?yàn)槊看螆?zhí)行commit后均會置空辩涝，所以FragmentTransaction 不能定義為全局變量贸伐，否則程序crash

• Fragment的數(shù)據(jù)傳遞

//設(shè)置數(shù)據(jù)源
fragment.setArguments(Bundle bundle)
//獲取數(shù)據(jù)
Bundle bundle=getArguments();

• Fragment與Activity的通信方式
  fragment是依附于activity而存在的，所以能直接獲取彼此的實(shí)例對象（適用于activity中動態(tài)添加fragment的情況）

  • fragment中獲取activity的某個屬性或方法：在activity中將這個屬性或方法定義為public類型怔揩，在fragment中通過((宿主Activity)getActivity).屬性（方法）來獲取,注意進(jìn)行非空判斷捉邢，activity中獲取fragment的屬性或方法通過fragment的實(shí)例對象來獲取即可（只需要在framgnet中將 對應(yīng)的聲明為public類型即可）
  • 其他：通過廣播BroadcastReceiver,回調(diào)方法，EventBus等

• Fragment與Fragment的通信方式
  通過宿主activity來實(shí)現(xiàn)通信, BroadcastReceiver 全局變量等

• Back Stack

// on to the back stack.
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.replace(R.id.simple_fragment, newFragment);
    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
    ft.addToBackStack(null);//添加到回退棧
    ft.commit();

• Fragment設(shè)置動畫