Android fragment源码全解析

1    blankFragment=new BlankFragment();
2         fm=getFragmentManager();
3         FragmentTransaction ft=fm.beginTransaction();
4         ft.replace(R.id.rootView,blankFragment);
5         ft.commit();

 1 //下面的代码 来自于activity里面！！！！！！！！！！！！！！！
 2     public FragmentManager getFragmentManager() {
 3         //到这里能发现是mFragments返回给我们的FragmentManager
 4         return mFragments.getFragmentManager();
 5     }
 6 
 7 //继续往下跟 就会发现mFragments是由FragmentController的createController函数 构造出来的一个对象，
 8 //并且这个函数 需要传进去一个HostCallBack的对象
 9     final FragmentController mFragments = FragmentController.createController(new HostCallbacks());
10 
11 
12 
13 //下面的代码就来自于FragmentController 这个类！！！！！
14    private final FragmentHostCallback<?> mHost;
15 
16     //从这个函数就能看出来HostCallbacks 这个类肯定是FragmentHostCallback的子类了
17     public static final FragmentController createController(FragmentHostCallback<?> callbacks) {
18         return new FragmentController(callbacks);
19     }
20 
21     private FragmentController(FragmentHostCallback<?> callbacks) {
22         mHost = callbacks;
23     }
24 
25    //所以这个getFragmentManager返回的就是FragmentManager这个对象，并且这个对象是mHost的getFragmentManagerImpl函数返回的。
26     //这里结合构造函数一看就明白了，这个mHost就是我们在activity代码里面，第12行那里传进去的HostCallbacks这个对象来帮助初始化的
27     public FragmentManager getFragmentManager() {
28         return mHost.getFragmentManagerImpl();
29     }
30 
31 
32  //下面的代码在activity里
33 //这个地方一目了然 果然我们这个HostCallbacks 这个类是继承自FragmentHostCallback的，并且能看出来，我们这里把activity的引用也传进去了。
34 //所以能马上得出一个结论就是一个activity对应着一个HostCallbacks对象 这个对象持有本身这个activity的引用。传进去以后就代表FragmentController
35 //这个类的成员mHost 也持有了activity的引用
36  class HostCallbacks extends FragmentHostCallback<Activity> {
37         public HostCallbacks() {
38             super(Activity.this /*activity*/);
39         }
40 
41         @Override
42         public void onDump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
43             Activity.this.dump(prefix, fd, writer, args);
44         }
45         .................略过余下代码
46  }
47 
48  //下面的代码来源自 FragmentHostCallback<E> 这个抽象类
49 
50   public FragmentHostCallback(Context context, Handler handler, int windowAnimations) {
51         this(null /*activity*/, context, handler, windowAnimations);
52     }
53 
54     FragmentHostCallback(Activity activity) {
55         this(activity, activity /*context*/, activity.mHandler, 0 /*windowAnimations*/);
56     }
57 
58     //到这里就能看到FragmentHostCallback 持有了acitivty的引用 并且连activity的handler都一并持有！
59     FragmentHostCallback(Activity activity, Context context, Handler handler,
60             int windowAnimations) {
61         mActivity = activity;
62         mContext = context;
63         mHandler = handler;
64         mWindowAnimations = windowAnimations;
65     }

1 //下面的代码来源自抽象类FragmentHostCallback
2  FragmentManagerImpl getFragmentManagerImpl() {
3         return mFragmentManager;
4     }
5  //所以就能看出来 我们在activity中调用的getFragmentManger这个方法最终返回的是FragmentManagerImpl 这个类的对象了
6  final FragmentManagerImpl mFragmentManager = new FragmentManagerImpl();

 1  //源码来自于抽象类 FragmentManager
 2     public FragmentTransaction beginTransaction() {
 3         //可以看出来 返回的是BackStackRecord 这个类的对象
 4         return new BackStackRecord(this);
 5     }
 6 //下面的代码来自于BackStackState这个类
 7 //可以看到这个类是一个final类 
 8 final class BackStackState implements Parcelable {
 9 }
10 
11 //注意BackStackRecord这个类 和BackStackState 是在同一个文件内的 
12 //可以看一下BackStackRecord 是FragmentTransaction的子类 并且实现了
13 //BackStackEntry, Runnable这两个接口
14 final class BackStackRecord extends FragmentTransaction implements
15         FragmentManager.BackStackEntry, Runnable {
16     static final String TAG = FragmentManagerImpl.TAG;
17 
18     final FragmentManagerImpl mManager;
19 }
20 
21 //下面的这个class就是在BackStackRecord这个类的源码里面的，这里Op
22 //实际上就是一个双向链表结构
23  static final class Op {
24         Op next;
25         Op prev;
26         int cmd;
27         Fragment fragment;
28         int enterAnim;
29         int exitAnim;
30         int popEnterAnim;
31         int popExitAnim;
32         ArrayList<Fragment> removed;
33     }
34     

  1 //以下代码来源自backstackrecord 源码
  2 public FragmentTransaction replace(int containerViewId, Fragment fragment) {
  3         return replace(containerViewId, fragment, null);
  4     }
  5 
  6 //你看这里replace操作 你如果没有传进去一个有效的id的话 异常就会在这里出现了
  7     public FragmentTransaction replace(int containerViewId, Fragment fragment, String tag) {
  8         if (containerViewId == 0) {
  9             throw new IllegalArgumentException("Must use non-zero containerViewId");
 10         }
 11 
 12         //最终都是调用的doaAdddop这个方法来完成操作的
 13         doAddOp(containerViewId, fragment, tag, OP_REPLACE);
 14         return this;
 15     }
 16 
 17 //这个方法说白了 就是拼装下这个双向链表
 18      private void doAddOp(int containerViewId, Fragment fragment, String tag, int opcmd) {
 19         fragment.mFragmentManager = mManager;
 20 
 21         if (tag != null) {
 22             if (fragment.mTag != null && !tag.equals(fragment.mTag)) {
 23                 throw new IllegalStateException("Can't change tag of fragment "
 24                         + fragment + ": was " + fragment.mTag
 25                         + " now " + tag);
 26             }
 27             fragment.mTag = tag;
 28         }
 29 
 30         if (containerViewId != 0) {
 31             if (fragment.mFragmentId != 0 && fragment.mFragmentId != containerViewId) {
 32                 throw new IllegalStateException("Can't change container ID of fragment "
 33                         + fragment + ": was " + fragment.mFragmentId
 34                         + " now " + containerViewId);
 35             }
 36             fragment.mContainerId = fragment.mFragmentId = containerViewId;
 37         }
 38 
 39         Op op = new Op();
 40         op.cmd = opcmd;
 41         op.fragment = fragment;
 42         addOp(op);
 43     }
 44 
 45 //所以我们看到 replace操作或者是add remove这种操作 就是操作双向链表的 除此之外没有任何有意义的举动，最终反应到用户能感知的层面上全都是要走
 46  //commit这个函数的
 47      public int commit() {
 48         return commitInternal(false);
 49     }
 50 //构造函数再看一遍
 51 
 52  public BackStackRecord(FragmentManagerImpl manager) {
 53         mManager = manager;
 54     }
 55 int commitInternal(boolean allowStateLoss) {
 56         if (mCommitted) {
 57             throw new IllegalStateException("commit already called");
 58         }
 59         if (FragmentManagerImpl.DEBUG) {
 60             Log.v(TAG, "Commit: " + this);
 61             LogWriter logw = new LogWriter(Log.VERBOSE, TAG);
 62             PrintWriter pw = new FastPrintWriter(logw, false, 1024);
 63             dump("  ", null, pw, null);
 64             pw.flush();
 65         }
 66         mCommitted = true;
 67         if (mAddToBackStack) {
 68             mIndex = mManager.allocBackStackIndex(this);
 69         } else {
 70             mIndex = -1;
 71         } 
 72         //这个对象就是     final FragmentManagerImpl mManager; 我们在调用begin函数的时候传进去一个this指针 就是用来初始化他的
 73         mManager.enqueueAction(this, allowStateLoss);
 74         return mIndex;
 75     }
 76 
 77  //所以下面就是FragmentManagerImpl 的源码了 final class FragmentManagerImpl extends FragmentManager implements LayoutInflater.Factory2
 78 
 79 //这个函数就很关键了，这个mHost 前文介绍过 持有了activity的引用，所以这里你看 就是用activity的handler 去执行了mExecCommit 
 80 //注意是在activity的主线程去执行的mExecCommit 这个线程
 81   public void enqueueAction(Runnable action, boolean allowStateLoss) {
 82         if (!allowStateLoss) {
 83             checkStateLoss();
 84         }
 85         synchronized (this) {
 86             if (mDestroyed || mHost == null) {
 87                 throw new IllegalStateException("Activity has been destroyed");
 88             }
 89             if (mPendingActions == null) {
 90                 mPendingActions = new ArrayList<Runnable>();
 91             }
 92             mPendingActions.add(action);
 93             if (mPendingActions.size() == 1) {
 94                 mHost.getHandler().removeCallbacks(mExecCommit);
 95                 mHost.getHandler().post(mExecCommit);
 96             }
 97         }
 98     }
 99 //这个线程执行的execPendingActions 就是这个方法 这个方法也是在FragmentManagerImpl 里的。并不在activity里。所以commit操作就是最终让activity的主线程去执行了FragmentManagerImpl
100 //execPendingActions方法
101 Runnable mExecCommit = new Runnable() {
102         @Override
103         public void run() {
104             execPendingActions();
105         }
106     };
107 
108   /**
109      * 所以这个方法是只能在主线程里面做的
110      */
111     public boolean execPendingActions() {
112         if (mExecutingActions) {
113             throw new IllegalStateException("Recursive entry to executePendingTransactions");
114         }
115         
116         if (Looper.myLooper() != mHost.getHandler().getLooper()) {
117             throw new IllegalStateException("Must be called from main thread of process");
118         }
119 
120         boolean didSomething = false;
121 
122         while (true) {
123             int numActions;
124             
125             synchronized (this) {
126                 if (mPendingActions == null || mPendingActions.size() == 0) {
127                     break;
128                 }
129                 
130                 numActions = mPendingActions.size();
131                 if (mTmpActions == null || mTmpActions.length < numActions) {
132                     mTmpActions = new Runnable[numActions];
133                 }
134                 mPendingActions.toArray(mTmpActions);
135                 mPendingActions.clear();
136                 mHost.getHandler().removeCallbacks(mExecCommit);
137             }
138             
139             mExecutingActions = true;
140             for (int i=0; i<numActions; i++) {
141                 //你看这里run方法 回过头去 我们应该还能想起来backstackrecord这个类是继承了runnable这个接口的，所以最终我们还是要看看backstackrecord 的run方法里面都做了什么
142                 mTmpActions[i].run();
143                 mTmpActions[i] = null;
144             }
145             mExecutingActions = false;
146             didSomething = true;
147         }
148 
149         if (mHavePendingDeferredStart) {
150             boolean loadersRunning = false;
151             for (int i=0; i<mActive.size(); i++) {
152                 Fragment f = mActive.get(i);
153                 if (f != null && f.mLoaderManager != null) {
154                     loadersRunning |= f.mLoaderManager.hasRunningLoaders();
155                 }
156             }
157             if (!loadersRunning) {
158                 mHavePendingDeferredStart = false;
159                 startPendingDeferredFragments();
160             }
161         }
162         return didSomething;
163     }

  1 //以下代码就是backstackrecord里面的代码了
  2 //这个run方法 其实就是取op这个双向链表然后分析op.cmd的值 然后根据
  3 //这些不同的值 去调用FragmentManager里各种转换fragment
  4  public void run() {
  5         if (FragmentManagerImpl.DEBUG) {
  6             Log.v(TAG, "Run: " + this);
  7         }
  8 
  9         if (mAddToBackStack) {
 10             if (mIndex < 0) {
 11                 throw new IllegalStateException("addToBackStack() called after commit()");
 12             }
 13         }
 14 
 15         bumpBackStackNesting(1);
 16 
 17         SparseArray<Fragment> firstOutFragments = new SparseArray<Fragment>();
 18         SparseArray<Fragment> lastInFragments = new SparseArray<Fragment>();
 19         calculateFragments(firstOutFragments, lastInFragments);
 20         beginTransition(firstOutFragments, lastInFragments, false);
 21 
 22         Op op = mHead;
 23         while (op != null) {
 24             switch (op.cmd) {
 25                 case OP_ADD: {
 26                     Fragment f = op.fragment;
 27                     f.mNextAnim = op.enterAnim;
 28                     mManager.addFragment(f, false);
 29                 }
 30                 break;
 31                 case OP_REPLACE: {
 32                     Fragment f = op.fragment;
 33                     int containerId = f.mContainerId;
 34                     if (mManager.mAdded != null) {
 35                         for (int i = 0; i < mManager.mAdded.size(); i++) {
 36                             Fragment old = mManager.mAdded.get(i);
 37                             if (FragmentManagerImpl.DEBUG) {
 38                                 Log.v(TAG,
 39                                         "OP_REPLACE: adding=" + f + " old=" + old);
 40                             }
 41                             if (old.mContainerId == containerId) {
 42                                 if (old == f) {
 43                                     op.fragment = f = null;
 44                                 } else {
 45                                     if (op.removed == null) {
 46                                         op.removed = new ArrayList<Fragment>();
 47                                     }
 48                                     op.removed.add(old);
 49                                     old.mNextAnim = op.exitAnim;
 50                                     if (mAddToBackStack) {
 51                                         old.mBackStackNesting += 1;
 52                                         if (FragmentManagerImpl.DEBUG) {
 53                                             Log.v(TAG, "Bump nesting of "
 54                                                     + old + " to " + old.mBackStackNesting);
 55                                         }
 56                                     }
 57                                     mManager.removeFragment(old, mTransition, mTransitionStyle);
 58                                 }
 59                             }
 60                         }
 61                     }
 62                     if (f != null) {
 63                         f.mNextAnim = op.enterAnim;
 64                         mManager.addFragment(f, false);
 65                     }
 66                 }
 67                 break;
 68                 case OP_REMOVE: {
 69                     Fragment f = op.fragment;
 70                     f.mNextAnim = op.exitAnim;
 71                     mManager.removeFragment(f, mTransition, mTransitionStyle);
 72                 }
 73                 break;
 74                 case OP_HIDE: {
 75                     Fragment f = op.fragment;
 76                     f.mNextAnim = op.exitAnim;
 77                     mManager.hideFragment(f, mTransition, mTransitionStyle);
 78                 }
 79                 break;
 80                 case OP_SHOW: {
 81                     Fragment f = op.fragment;
 82                     f.mNextAnim = op.enterAnim;
 83                     mManager.showFragment(f, mTransition, mTransitionStyle);
 84                 }
 85                 break;
 86                 case OP_DETACH: {
 87                     Fragment f = op.fragment;
 88                     f.mNextAnim = op.exitAnim;
 89                     mManager.detachFragment(f, mTransition, mTransitionStyle);
 90                 }
 91                 break;
 92                 case OP_ATTACH: {
 93                     Fragment f = op.fragment;
 94                     f.mNextAnim = op.enterAnim;
 95                     mManager.attachFragment(f, mTransition, mTransitionStyle);
 96                 }
 97                 break;
 98                 default: {
 99                     throw new IllegalArgumentException("Unknown cmd: " + op.cmd);
100                 }
101             }
102 
103             op = op.next;
104         }
105         //我们也很容易就能看出来 最终都是走的 mManager.moveToState 这个方法
106 //同时moveToState 也是fragment状态分发最重要的方法了
107 
108         mManager.moveToState(mManager.mCurState, mTransition,
109                 mTransitionStyle, true);
110 
111         if (mAddToBackStack) {
112             mManager.addBackStackState(this);
113         }
114     }

  1 //下面的代码来自于fragmentmanager
  2 //我们首先来看一下movetostate这个函数总共有一个
  3 void moveToState(Fragment f)
  4 void moveToState(int newState, boolean always)
  5 void moveToState(int newState, int transit, int transitStyle, boolean always)
  6 void moveToState(Fragment f, int newState, int transit, int transitionStyle,
  7             boolean keepActive)
  8 
  9 //可以看到movetoState总共4种。
 10 //在详细介绍movetostate函数之前，我们先去看看这个函数的参数之一new state是什么
 11 
 12 //下面代码来自于fragment
 13 //其实new state 就是代表新的状态，总共他的值有7种 就全在这里了 预先都是定义好的
 14     static final int INVALID_STATE = -1;   // Invalid state used as a null value.
 15     static final int INITIALIZING = 0;     // Not yet created.
 16     static final int CREATED = 1;          // Created.
 17     static final int ACTIVITY_CREATED = 2; // The activity has finished its creation. 这个状态其实很好理解，
 18     //就是fragement在oncreate函数结束的时候会调用dispatchActivityCreated 就是通知fragment 跟你绑定的宿主activity已经走完onCreate了
 19     static final int STOPPED = 3;          // Fully created, not started.
 20     static final int STARTED = 4;          // Created and started, not resumed.
 21     static final int RESUMED = 5;          // Created started and resumed.
 22 
 23 
 24 //下面我们可以模拟一个流程 帮助大家理解这个状态到底是干嘛的 有什么用。
 25 //比如 我们先看看 fragmentactivity的源码，
 26 //首先我们假设 我们想看看activity 发生onResumne事件的时候 对fragment有什么影响
 27 protected void onResume() {
 28         super.onResume();
 29         mHandler.sendEmptyMessage(MSG_RESUME_PENDING);
 30         mResumed = true;
 31         mFragments.execPendingActions();
 32     }
 33 //继续追踪代码 发现最后是调用的onResumeFragments 这个方法
 34   final Handler mHandler = new Handler() {
 35         @Override
 36         public void handleMessage(Message msg) {
 37             switch (msg.what) {
 38                 case MSG_REALLY_STOPPED:
 39                     if (mStopped) {
 40                         doReallyStop(false);
 41                     }
 42                     break;
 43                 case MSG_RESUME_PENDING:
 44                     onResumeFragments();
 45                     mFragments.execPendingActions();
 46                     break;
 47                 default:
 48                     super.handleMessage(msg);
 49             }
 50         }
 51 
 52     };
 53 //原来当activity走onresume流程的时候 最终都是走到这里
 54 
 55 protected void onResumeFragments() {
 56         mFragments.dispatchResume();
 57     }
 58 //前面已经分析过mFragements就是FragmentController的对象
 59 //所以下面的代码 来自于FragmentController
 60  public void dispatchResume() {
 61      //前面的源码也分析过了mHost.mFragmentManager 就是 final FragmentManagerImpl mFragmentManager = new FragmentManagerImpl();
 62         mHost.mFragmentManager.dispatchResume();
 63     }
 64 
 65 //下面的代码来自fragmentmanager
 66 //一直追踪到这里就能明白 activity的声明周期 与fragment声明周期关联的时候 就是通过moveToState 这个函数来完成的
 67 public void dispatchResume() {
 68         mStateSaved = false;
 69         moveToState(Fragment.RESUMED, false);
 70     }
 71 
 72 //movetostate这个函数前面已经说过总共有4种 不一样的声明 但是最终起效果的只有这一个
 73 //这个函数非常的长 我就简单挑几个注意的点进行注释  代码我就不全部复制粘贴进来了。太长了
 74 //有兴趣的同学可以自己跟进去看看 其实逻辑挺简单的
 75 void moveToState(Fragment f, int newState, int transit, int transitionStyle,
 76             boolean keepActive) {
 77       ......
 78         if (f.mState < newState) {
 79             // For fragments that are created from a layout, when restoring from
 80             // state we don't want to allow them to be created until they are
 81             // being reloaded from the layout.
 82             if (f.mFromLayout && !f.mInLayout) {
 83                 return;
 84             }  
 85             if (f.mAnimatingAway != null) {
 86                 // The fragment is currently being animated...  but!  Now we
 87                 // want to move our state back up.  Give up on waiting for the
 88                 // animation, move to whatever the final state should be once
 89                 // the animation is done, and then we can proceed from there.
 90                 f.mAnimatingAway = null;
 91                 moveToState(f, f.mStateAfterAnimating, 0, 0, true);
 92             }
 93             switch (f.mState) {
 94                 case Fragment.INITIALIZING:
 95                  .........................................
 96                         }
 97                     }
 98                     f.mHost = mHost;
 99                     f.mParentFragment = mParent;
100                     f.mFragmentManager = mParent != null
101                             ? mParent.mChildFragmentManager : mHost.getFragmentManagerImpl();
102                     f.mCalled = false;
103                     //这个地方相信很多人一看就明白了，这行代码就说明了在onAttach的时候 就能使用和fragment关联的activity了，这也是为什么
104                     //fragment与activity通信时，我们喜欢定义接口来完成，并且在onAttach的时候绑定接口 的原因
105                     f.onAttach(mHost.getContext());
106                     if (!f.mCalled) {
107                         throw new SuperNotCalledException("Fragment " + f
108                                 + " did not call through to super.onAttach()");
109                     }
110                     if (f.mParentFragment == null) {
111                         mHost.onAttachFragment(f);
112                     }
113 
114                     if (!f.mRetaining) {
115                         f.performCreate(f.mSavedFragmentState);
116                     }
117                     f.mRetaining = false;
118                     if (f.mFromLayout) {
119                         // For fragments that are part of the content view
120                         // layout, we need to instantiate the view immediately
121                         // and the inflater will take care of adding it.
122                         f.mView = f.performCreateView(f.getLayoutInflater(
123                                 f.mSavedFragmentState), null, f.mSavedFragmentState);
124                         if (f.mView != null) {
125                             f.mInnerView = f.mView;
126                             if (Build.VERSION.SDK_INT >= 11) {
127                                 ViewCompat.setSaveFromParentEnabled(f.mView, false);
128                             } else {
129                                 f.mView = NoSaveStateFrameLayout.wrap(f.mView);
130                             }
131                             if (f.mHidden) f.mView.setVisibility(View.GONE);
132                             f.onViewCreated(f.mView, f.mSavedFragmentState);
133                         } else {
134                             f.mInnerView = null;
135                         }
136                     }
137                 case Fragment.CREATED:
138                 ......................
139     }

 1 //保存fragment状态的 主要是靠FragmentState 这个类来完成的
 2 final class FragmentState implements Parcelable 
 3 //可以看一下这个类的构造函数
 4  public FragmentState(Fragment frag) {
 5         mClassName = frag.getClass().getName();
 6         mIndex = frag.mIndex;
 7         mFromLayout = frag.mFromLayout;
 8         mFragmentId = frag.mFragmentId;
 9         mContainerId = frag.mContainerId;
10         mTag = frag.mTag;
11         mRetainInstance = frag.mRetainInstance;
12         mDetached = frag.mDetached;
13         mArguments = frag.mArguments;
14     }
15 
16 //再看一下这个类： 这里保存了3个数组 并且这3个数组元素都实现了Parcelable 接口
17 //这意味着他们都可以被序列化
18 final class FragmentManagerState implements Parcelable {
19     FragmentState[] mActive;
20     int[] mAdded;
21     BackStackState[] mBackStack;
22     
23     public FragmentManagerState() {
24     }
25     
26     public FragmentManagerState(Parcel in) {
27         mActive = in.createTypedArray(FragmentState.CREATOR);
28         mAdded = in.createIntArray();
29         mBackStack = in.createTypedArray(BackStackState.CREATOR);
30     }
31     
32     public int describeContents() {
33         return 0;
34     }
35 
36     public void writeToParcel(Parcel dest, int flags) {
37         dest.writeTypedArray(mActive, flags);
38         dest.writeIntArray(mAdded);
39         dest.writeTypedArray(mBackStack, flags);
40     }
41     
42     public static final Parcelable.Creator<FragmentManagerState> CREATOR
43             = new Parcelable.Creator<FragmentManagerState>() {
44         public FragmentManagerState createFromParcel(Parcel in) {
45             return new FragmentManagerState(in);
46         }
47         
48         public FragmentManagerState[] newArray(int size) {
49             return new FragmentManagerState[size];
50         }
51     };
52 }
53 
54 //上面那个类的3个属性 实际上对应保存着是fragemntmanager里的 三个成员
55 ArrayList<Fragment> mActive;//他还保存了mBackStack所有相关的fragment 所以mAdder是mActive的子集
56 ArrayList<Fragment> mAdded;
57 ArrayList<BackStackRecord> mBackStack;//这个就是保存调用了addToBackStack方法的FragementTransaction，你看就是这个东西记录了
58 //你commit的操作 所以当你调用了addToBackStack 以后再按返回键 就可以回到上一个fragment了

 1  //下面代码来自于fragmentactivity
 2  @Override
 3     protected void onStop() {
 4         super.onStop();
 5 
 6         mStopped = true;
 7         mHandler.sendEmptyMessage(MSG_REALLY_STOPPED);
 8 
 9         mFragments.dispatchStop();
10     }
11 
12 //来自于fragmentcontroller
13  public void dispatchStop() {
14         mHost.mFragmentManager.dispatchStop();
15     }
16 
17 //来自于fragemntmanager
18  public void dispatchStop() {
19         // See saveAllState() for the explanation of this.  We do this for
20         // all platform versions, to keep our behavior more consistent between
21         // them.
22         mStateSaved = true;
23         //你看这里就是转换了一下状态
24         moveToState(Fragment.STOPPED, false);
25     }
26 
27 //所以对应的你也能猜到了 当activity onresume的时候 这里也无非就是把fragement的状态 从stopped 变成resumed了。 fragement是实例并没有销毁 还在
28  public void dispatchResume() {
29         mStateSaved = false;
30         moveToState(Fragment.RESUMED, false);
31     }

  1  //下面代码来自于fragmentmanager
  2 //如果Fragment设置了fragment.setRetainInstance(true) 最终ams 会一步步调用到这个函数的
  3 //所以你看 这里就是返回了mActive 数组的拷贝呀！
  4  ArrayList<Fragment> retainNonConfig() {
  5         ArrayList<Fragment> fragments = null;
  6         if (mActive != null) {
  7             for (int i=0; i<mActive.size(); i++) {
  8                 Fragment f = mActive.get(i);
  9                 if (f != null && f.mRetainInstance) {
 10                     if (fragments == null) {
 11                         fragments = new ArrayList<Fragment>();
 12                     }
 13                     fragments.add(f);
 14                     f.mRetaining = true;
 15                     f.mTargetIndex = f.mTarget != null ? f.mTarget.mIndex : -1;
 16                     if (DEBUG) Log.v(TAG, "retainNonConfig: keeping retained " + f);
 17                 }
 18             }
 19         }
 20         return fragments;
 21     }
 22 
 23 //上面说了保存fragment实例 下面肯定要说如何存储fragemnt的实例的
 24 //下面代码来自于activity
 25 
 26     NonConfigurationInstances retainNonConfigurationInstances() {
 27         Object activity = onRetainNonConfigurationInstance();
 28         HashMap<String, Object> children = onRetainNonConfigurationChildInstances();
 29         List<Fragment> fragments = mFragments.retainNonConfig();
 30         ArrayMap<String, LoaderManager> loaders = mFragments.retainLoaderNonConfig();
 31         if (activity == null && children == null && fragments == null && loaders == null
 32                 && mVoiceInteractor == null) {
 33             return null;
 34         }
 35         //这里nci你看就知道了 看下类的源码你看他保存的东西 并没有做什么序列化反序列化的操作，
 36         //所以他可以保存任何东西！当然了，这个nci 是最终保存在activitythread对象里的，
 37         //activitytheread对象里有个键值对叫mActivies。他有个数据结构叫activityclientrecord
 38         //有兴趣的人可以去看下activitytheread的源码 这里不深入展开了。
 39         NonConfigurationInstances nci = new NonConfigurationInstances();
 40         //注意 nci.activity这个地方 可不是activity，他是activity源码中onRetainNonConfigurationInstance方法返回的对象咯，看63行就知道了
 41         nci.activity = activity;
 42         nci.children = children;
 43         nci.fragments = fragments;
 44         nci.loaders = loaders;
 45         if (mVoiceInteractor != null) {
 46             mVoiceInteractor.retainInstance();
 47             nci.voiceInteractor = mVoiceInteractor;
 48         }
 49         return nci;
 50     }.
 51 
 52 //所以看到这里就应该明白，如果你的setRetainInstance设置了true的话，当activity重新recreate的时候，虽然activity生成了一个全新的，fragmentmanger也是一个全新的，
 53  //但是你的fragment实际上还是旧的，生命周期会有一些不同的，不会有oncreate和ondestroy了。他会走85行那里的restoreAllState方法了
 54      static final class NonConfigurationInstances {
 55         Object activity;
 56         HashMap<String, Object> children;
 57         List<Fragment> fragments;
 58         ArrayMap<String, LoaderManager> loaders;
 59         VoiceInteractor voiceInteractor;
 60     }
 61 
 62 
 63 //下面这个方法在fragemntactitivy源码里
 64      public final Object onRetainNonConfigurationInstance() {
 65         if (mStopped) {
 66             doReallyStop(true);
 67         }
 68 
 69         Object custom = onRetainCustomNonConfigurationInstance();
 70 
 71         List<Fragment> fragments = mFragments.retainNonConfig();
 72         SimpleArrayMap<String, LoaderManager> loaders = mFragments.retainLoaderNonConfig();
 73 
 74         if (fragments == null && loaders == null && custom == null) {
 75             return null;
 76         }
 77 
 78         NonConfigurationInstances nci = new NonConfigurationInstances();
 79         nci.custom = custom;
 80         nci.fragments = fragments;
 81         nci.loaders = loaders;
 82         return nci;
 83     }
 84 
 85  //以下代码来自于fragmentmanger restoreAllState这个方法就是恢复保存的fragment实例的
 86      void restoreAllState(Parcelable state, List<Fragment> nonConfig) {
 87         // If there is no saved state at all, then there can not be
 88         // any nonConfig fragments either, so that is that.
 89         if (state == null) return;
 90         FragmentManagerState fms = (FragmentManagerState)state;
 91         if (fms.mActive == null) return;
 92         
 93         // First re-attach any non-config instances we are retaining back
 94         // to their saved state, so we don't try to instantiate them again.
 95         if (nonConfig != null) {
 96             for (int i=0; i<nonConfig.size(); i++) {
 97                 Fragment f = nonConfig.get(i);
 98                 if (DEBUG) Log.v(TAG, "restoreAllState: re-attaching retained " + f);
 99                 FragmentState fs = fms.mActive[f.mIndex];
100                 fs.mInstance = f;
101                 f.mSavedViewState = null;
102                 f.mBackStackNesting = 0;
103                 f.mInLayout = false;
104                 f.mAdded = false;
105                 f.mTarget = null;
106                 if (fs.mSavedFragmentState != null) {
107                     fs.mSavedFragmentState.setClassLoader(mHost.getContext().getClassLoader());
108                     f.mSavedViewState = fs.mSavedFragmentState.getSparseParcelableArray(
109                             FragmentManagerImpl.VIEW_STATE_TAG);
110                     f.mSavedFragmentState = fs.mSavedFragmentState;
111                 }
112             }
113         }
114         
115      .................................
116     }