ViewPager维护child代码流程：
注：PagerAdapter 使用的是FragmentPagerAdapter类或者它的子类。
viewPager.populate()：
void populate(int newCurrentItem) { ItemInfo oldCurInfo = null; if (mCurItem != newCurrentItem) { oldCurInfo = infoForPosition(mCurItem); mCurItem = newCurrentItem; } if (mAdapter == null) { sortChildDrawingOrder(); return; } // Bail now if we are waiting to populate. This is to hold off // on creating views from the time the user releases their finger to // fling to a new position until we have finished the scroll to // that position, avoiding glitches from happening at that point. if (mPopulatePending) { if (DEBUG) Log.i(TAG, "populate is pending, skipping for now..."); sortChildDrawingOrder(); return; } // Also, don't populate until we are attached to a window. This is to // avoid trying to populate before we have restored our view hierarchy // state and conflicting with what is restored. if (getWindowToken() == null) { return; } mAdapter.startUpdate(this); final int pageLimit = mOffscreenPageLimit; final int startPos = Math.max(0, mCurItem - pageLimit); final int N = mAdapter.getCount(); final int endPos = Math.min(N-1, mCurItem + pageLimit); if (N != mExpectedAdapterCount) { String resName; try { resName = getResources().getResourceName(getId()); } catch (Resources.NotFoundException e) { resName = Integer.toHexString(getId()); } throw new IllegalStateException("The application's PagerAdapter changed the adapter's" + " contents without calling PagerAdapter#notifyDataSetChanged!" + " Expected adapter item count: " + mExpectedAdapterCount + ", found: " + N + " Pager id: " + resName + " Pager class: " + getClass() + " Problematic adapter: " + mAdapter.getClass()); } // Locate the currently focused item or add it if needed. int curIndex = -1; ItemInfo curItem = null; for (curIndex = 0; curIndex < mItems.size(); curIndex++) { final ItemInfo ii = mItems.get(curIndex); if (ii.position >= mCurItem) { if (ii.position == mCurItem) curItem = ii; break; } } if (curItem == null && N > 0) {
// 第一次初始化数据的时候会进入此处执行 curItem = addNewItem(mCurItem, curIndex); } // Fill 3x the available width or up to the number of offscreen // pages requested to either side, whichever is larger. // If we have no current item we have no work to do. if (curItem != null) { float extraWidthLeft = 0.f; int itemIndex = curIndex - 1; ItemInfo ii = itemIndex >= 0 ? mItems.get(itemIndex) : null; final int clientWidth = getClientWidth();
// 这里不知道为什么要加上Padding部分？？这样，就可能导致ViewPager里存活的Item比没有Padding时要多。 final float leftWidthNeeded = clientWidth <= 0 ? 0 : 2.f - curItem.widthFactor + (float) getPaddingLeft() / (float) clientWidth; for (int pos = mCurItem - 1; pos >= 0; pos--) {
// 如果有Padding部分的存在，leftWidthNeeded比extraWidthLeft大一点，这样Item就没有被删除。 if (extraWidthLeft >= leftWidthNeeded && pos < startPos) { if (ii == null) { break; } if (pos == ii.position && !ii.scrolling) { mItems.remove(itemIndex); mAdapter.destroyItem(this, pos, ii.object); if (DEBUG) { Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object)); } itemIndex--; curIndex--; ii = itemIndex >= 0 ? mItems.get(itemIndex) : null; } } else if (ii != null && pos == ii.position) { extraWidthLeft += ii.widthFactor; itemIndex--; ii = itemIndex >= 0 ? mItems.get(itemIndex) : null; } else { ii = addNewItem(pos, itemIndex + 1); extraWidthLeft += ii.widthFactor; curIndex++; ii = itemIndex >= 0 ? mItems.get(itemIndex) : null; } } float extraWidthRight = curItem.widthFactor; itemIndex = curIndex + 1; if (extraWidthRight < 2.f) { ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null; final float rightWidthNeeded = clientWidth <= 0 ? 0 : (float) getPaddingRight() / (float) clientWidth + 2.f; for (int pos = mCurItem + 1; pos < N; pos++) { if (extraWidthRight >= rightWidthNeeded && pos > endPos) { if (ii == null) { break; } if (pos == ii.position && !ii.scrolling) { mItems.remove(itemIndex); mAdapter.destroyItem(this, pos, ii.object); if (DEBUG) { Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object)); } ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null; } } else if (ii != null && pos == ii.position) { extraWidthRight += ii.widthFactor; itemIndex++; ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null; } else { ii = addNewItem(pos, itemIndex); itemIndex++; extraWidthRight += ii.widthFactor; ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null; } } } calculatePageOffsets(curItem, curIndex, oldCurInfo); } if (DEBUG) { Log.i(TAG, "Current page list:"); for (int i=0; i<mItems.size(); i++) { Log.i(TAG, "#" + i + ": page " + mItems.get(i).position); } } mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null); // 此处是ViewPager增加或删除child的入口。 mAdapter.finishUpdate(this); // Check width measurement of current pages and drawing sort order. // Update LayoutParams as needed. final int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { final View child = getChildAt(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); lp.childIndex = i; if (!lp.isDecor && lp.widthFactor == 0.f) { // 0 means requery the adapter for this, it doesn't have a valid width. final ItemInfo ii = infoForChild(child); if (ii != null) { lp.widthFactor = ii.widthFactor; lp.position = ii.position; } } } sortChildDrawingOrder(); if (hasFocus()) { View currentFocused = findFocus(); ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused) : null; if (ii == null || ii.position != mCurItem) { for (int i=0; i<getChildCount(); i++) { View child = getChildAt(i); ii = infoForChild(child); if (ii != null && ii.position == mCurItem) { if (child.requestFocus(View.FOCUS_FORWARD)) { break; } } } } } }
viewPager.addNewItem():
ItemInfo addNewItem(int position, int index) { ItemInfo ii = new ItemInfo(); ii.position = position;
// instantiateItem()之后的一系列方法调用，最终将增加项目这个操作添加到一个双向链表中。 ii.object = mAdapter.instantiateItem(this, position);
// getPageWidth()默认返回1.f，可以通过overrid此方法控制一屏显示多个item。 ii.widthFactor = mAdapter.getPageWidth(position); if (index < 0 || index >= mItems.size()) { mItems.add(ii); } else { mItems.add(index, ii); } return ii; }
fragmentPagerAdapter.instantiateItem():
在实例化FragmentPagerAdapter对象时，传入的是FragmentActivit.getSupportFragmentManager()，通过查阅原代码，发现最终传入的FragmentManagerImpl实例。
FragmentManagerImpl是FragmentManager一个内部类并且继承了FragmentManager。
public FragmentPagerAdapter(FragmentManager fm) {
mFragmentManager = fm;
}
public Object instantiateItem(ViewGroup container, int position) { if (mCurTransaction == null) {
// 因此此处实际是调用FragmentManagerImpl的beginTransaction()方法；
// 而返回的是BackStackRecord的实例。 mCurTransaction = mFragmentManager.beginTransaction(); } final long itemId = getItemId(position); // Do we already have this fragment? String name = makeFragmentName(container.getId(), itemId); Fragment fragment = mFragmentManager.findFragmentByTag(name); if (fragment != null) { if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment); mCurTransaction.attach(fragment); } else { fragment = getItem(position); if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
// 所以此处调用的是BackStackRecord的add()方法。 mCurTransaction.add(container.getId(), fragment, makeFragmentName(container.getId(), itemId)); } if (fragment != mCurrentPrimaryItem) { fragment.setMenuVisibility(false); fragment.setUserVisibleHint(false); } return fragment; }
fragmentManagerImpl.beginTransaction():
public FragmentTransaction beginTransaction() { return new BackStackRecord(this); }
backStackRecord.add():
public FragmentTransaction add(int containerViewId, Fragment fragment, String tag) { doAddOp(containerViewId, fragment, tag, OP_ADD); return this; }
backStackRecord.doAddOp():
private void doAddOp(int containerViewId, Fragment fragment, String tag, int opcmd) { fragment.mFragmentManager = mManager; if (tag != null) { if (fragment.mTag != null && !tag.equals(fragment.mTag)) { throw new IllegalStateException("Can't change tag of fragment " + fragment + ": was " + fragment.mTag + " now " + tag); } fragment.mTag = tag; } if (containerViewId != 0) { if (fragment.mFragmentId != 0 && fragment.mFragmentId != containerViewId) { throw new IllegalStateException("Can't change container ID of fragment " + fragment + ": was " + fragment.mFragmentId + " now " + containerViewId); } fragment.mContainerId = fragment.mFragmentId = containerViewId; } Op op = new Op(); op.cmd = opcmd; op.fragment = fragment; addOp(op); }
backStackRecord.addOp():
void addOp(Op op) { if (mHead == null) { mHead = mTail = op; } else { op.prev = mTail; mTail.next = op; mTail = op; } op.enterAnim = mEnterAnim; op.exitAnim = mExitAnim; op.popEnterAnim = mPopEnterAnim; op.popExitAnim = mPopExitAnim; mNumOp++; }
以上流程就完成了添加child的准备工作。
删除child的流程：
在populate()方法的for循环中，当child过多时就会进行删除(通过宽度进行控制)，删除代码：mAdapter.destroyItem，实际调用的是fragmentPagerAdapter.destroyItem.
fragmentPagerAdapter.destroyItem():
public void destroyItem(ViewGroup container, int position, Object object) { if (mCurTransaction == null) { mCurTransaction = mFragmentManager.beginTransaction(); } if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object + " v=" + ((Fragment)object).getView());
// 实际调用的是BackStackRecord的detach()方法。
// 因为mCurTransaction实际是一个BackStackRecord实例对象，具体参见：fragmentPagerAdapter.instantiateItem(): mCurTransaction.detach((Fragment)object); }
backStackRecord.detach():
public FragmentTransaction detach(Fragment fragment) { Op op = new Op(); op.cmd = OP_DETACH; op.fragment = fragment; addOp(op); return this; }
至此完成了删除child的准备工作。
最终的添加或删除工作还得回到populate()方法：mAdapter.finishUpdate。
fragmentPagerAdapter.finishUpdate():
public void finishUpdate(ViewGroup container) { if (mCurTransaction != null) {
// 实际是BackStackRecord的commitAllowingStateLoss()方法。 mCurTransaction.commitAllowingStateLoss(); mCurTransaction = null;
// 实际是FragmentManagerImpl的execPendingActions()方法。 mFragmentManager.executePendingTransactions(); } }
backStackRecord.commitAllowingStateLoss():
public int commitAllowingStateLoss() { return commitInternal(true); }
int commitInternal(boolean allowStateLoss) { if (mCommitted) throw new IllegalStateException("commit already called"); if (FragmentManagerImpl.DEBUG) { Log.v(TAG, "Commit: " + this); LogWriter logw = new LogWriter(TAG); PrintWriter pw = new PrintWriter(logw); dump(" ", null, pw, null); } mCommitted = true; if (mAddToBackStack) { mIndex = mManager.allocBackStackIndex(this); } else { mIndex = -1; }
// BackStackRecord实现了Runnable接口。
// 实际是FragmentManagerImpl的enqueueAction()方法。 mManager.enqueueAction(this, allowStateLoss); return mIndex; }
fragmentManagerImpl.enqueueAction():
public void enqueueAction(Runnable action, boolean allowStateLoss) { if (!allowStateLoss) { checkStateLoss(); } synchronized (this) { if (mDestroyed || mHost == null) { throw new IllegalStateException("Activity has been destroyed"); } if (mPendingActions == null) { mPendingActions = new ArrayList<Runnable>(); }
// 最终把BackStackRecord实例添加到了mPendingActions(这是一个ArrayList<Runnable>变量)。 mPendingActions.add(action); if (mPendingActions.size() == 1) { mHost.getHandler().removeCallbacks(mExecCommit); mHost.getHandler().post(mExecCommit); } } }
fragmentManagerImpl.executePendingTransaction():
public boolean executePendingTransactions() { return execPendingActions(); }
fragmentManagerImpl.executePendingActions():
public boolean execPendingActions() { if (mExecutingActions) { throw new IllegalStateException("Recursive entry to executePendingTransactions"); } if (Looper.myLooper() != mHost.getHandler().getLooper()) { throw new IllegalStateException("Must be called from main thread of process"); } boolean didSomething = false; while (true) { int numActions; synchronized (this) { if (mPendingActions == null || mPendingActions.size() == 0) { break; } numActions = mPendingActions.size(); if (mTmpActions == null || mTmpActions.length < numActions) { mTmpActions = new Runnable[numActions]; } mPendingActions.toArray(mTmpActions); mPendingActions.clear(); mHost.getHandler().removeCallbacks(mExecCommit); } mExecutingActions = true; for (int i=0; i<numActions; i++) {
// 这里最终调用BackStackRecord的run()方法。 mTmpActions[i].run(); mTmpActions[i] = null; } mExecutingActions = false; didSomething = true; } if (mHavePendingDeferredStart) { boolean loadersRunning = false; for (int i=0; i<mActive.size(); i++) { Fragment f = mActive.get(i); if (f != null && f.mLoaderManager != null) { loadersRunning |= f.mLoaderManager.hasRunningLoaders(); } } if (!loadersRunning) { mHavePendingDeferredStart = false; startPendingDeferredFragments(); } } return didSomething; }
backStackRecord.run():
public void run() { if (FragmentManagerImpl.DEBUG) Log.v(TAG, "Run: " + this); if (mAddToBackStack) { if (mIndex < 0) { throw new IllegalStateException("addToBackStack() called after commit()"); } } bumpBackStackNesting(1); TransitionState state = null; SparseArray<Fragment> firstOutFragments = null; SparseArray<Fragment> lastInFragments = null; if (SUPPORTS_TRANSITIONS) { firstOutFragments = new SparseArray<Fragment>(); lastInFragments = new SparseArray<Fragment>(); // 这里。。。 calculateFragments(firstOutFragments, lastInFragments); state = beginTransition(firstOutFragments, lastInFragments, false); } int transitionStyle = state != null ? 0 : mTransitionStyle; int transition = state != null ? 0 : mTransition; Op op = mHead; while (op != null) { int enterAnim = state != null ? 0 : op.enterAnim; int exitAnim = state != null ? 0 : op.exitAnim; switch (op.cmd) { case OP_ADD: { Fragment f = op.fragment; f.mNextAnim = enterAnim; mManager.addFragment(f, false); } break; case OP_REPLACE: { Fragment f = op.fragment; int containerId = f.mContainerId; if (mManager.mAdded != null) { for (int i = mManager.mAdded.size() - 1; i >= 0; i--) { Fragment old = mManager.mAdded.get(i); if (FragmentManagerImpl.DEBUG) Log.v(TAG, "OP_REPLACE: adding=" + f + " old=" + old); if (old.mContainerId == containerId) { if (old == f) { op.fragment = f = null; } else { if (op.removed == null) { op.removed = new ArrayList<Fragment>(); } op.removed.add(old); old.mNextAnim = exitAnim; if (mAddToBackStack) { old.mBackStackNesting += 1; if (FragmentManagerImpl.DEBUG) Log.v(TAG, "Bump nesting of " + old + " to " + old.mBackStackNesting); } mManager.removeFragment(old, transition, transitionStyle); } } } } if (f != null) { f.mNextAnim = enterAnim; mManager.addFragment(f, false); } } break; case OP_REMOVE: { Fragment f = op.fragment; f.mNextAnim = exitAnim; mManager.removeFragment(f, transition, transitionStyle); } break; case OP_HIDE: { Fragment f = op.fragment; f.mNextAnim = exitAnim; mManager.hideFragment(f, transition, transitionStyle); } break; case OP_SHOW: { Fragment f = op.fragment; f.mNextAnim = enterAnim; mManager.showFragment(f, transition, transitionStyle); } break; case OP_DETACH: { Fragment f = op.fragment; f.mNextAnim = exitAnim; mManager.detachFragment(f, transition, transitionStyle); } break; case OP_ATTACH: { Fragment f = op.fragment; f.mNextAnim = enterAnim; mManager.attachFragment(f, transition, transitionStyle); } break; default: { throw new IllegalArgumentException("Unknown cmd: " + op.cmd); } } op = op.next; } // 这里添加child mManager.moveToState(mManager.mCurState, transition, transitionStyle, true); if (mAddToBackStack) { mManager.addBackStackState(this); } }
Fragment的状态最终都是通过moveToState(Fragment, int, int, int, boolean)进行的，而添加和删除child就在其中。
void moveToState(Fragment f, int newState, int transit, int transitionStyle, boolean keepActive) { // Fragments that are not currently added will sit in the onCreate() state. if ((!f.mAdded || f.mDetached) && newState > Fragment.CREATED) { newState = Fragment.CREATED; } if (f.mRemoving && newState > f.mState) { // While removing a fragment, we can't change it to a higher state. newState = f.mState; } // Defer start if requested; don't allow it to move to STARTED or higher // if it's not already started. if (f.mDeferStart && f.mState < Fragment.STARTED && newState > Fragment.STOPPED) { newState = Fragment.STOPPED; } if (f.mState < newState) { // For fragments that are created from a layout, when restoring from // state we don't want to allow them to be created until they are // being reloaded from the layout. if (f.mFromLayout && !f.mInLayout) { return; } if (f.mAnimatingAway != null) { // The fragment is currently being animated... but! Now we // want to move our state back up. Give up on waiting for the // animation, move to whatever the final state should be once // the animation is done, and then we can proceed from there. f.mAnimatingAway = null; moveToState(f, f.mStateAfterAnimating, 0, 0, true); } switch (f.mState) { case Fragment.INITIALIZING: if (DEBUG) Log.v(TAG, "moveto CREATED: " + f); if (f.mSavedFragmentState != null) { f.mSavedFragmentState.setClassLoader(mHost.getContext().getClassLoader()); f.mSavedViewState = f.mSavedFragmentState.getSparseParcelableArray( FragmentManagerImpl.VIEW_STATE_TAG); f.mTarget = getFragment(f.mSavedFragmentState, FragmentManagerImpl.TARGET_STATE_TAG); if (f.mTarget != null) { f.mTargetRequestCode = f.mSavedFragmentState.getInt( FragmentManagerImpl.TARGET_REQUEST_CODE_STATE_TAG, 0); } f.mUserVisibleHint = f.mSavedFragmentState.getBoolean( FragmentManagerImpl.USER_VISIBLE_HINT_TAG, true); if (!f.mUserVisibleHint) { f.mDeferStart = true; if (newState > Fragment.STOPPED) { newState = Fragment.STOPPED; } } } f.mHost = mHost; f.mParentFragment = mParent; f.mFragmentManager = mParent != null ? mParent.mChildFragmentManager : mHost.getFragmentManagerImpl(); f.mCalled = false; f.onAttach(mHost.getContext()); if (!f.mCalled) { throw new SuperNotCalledException("Fragment " + f + " did not call through to super.onAttach()"); } if (f.mParentFragment == null) { mHost.onAttachFragment(f); } if (!f.mRetaining) { f.performCreate(f.mSavedFragmentState); } f.mRetaining = false; if (f.mFromLayout) { // For fragments that are part of the content view // layout, we need to instantiate the view immediately // and the inflater will take care of adding it. f.mView = f.performCreateView(f.getLayoutInflater( f.mSavedFragmentState), null, f.mSavedFragmentState); if (f.mView != null) { f.mInnerView = f.mView; if (Build.VERSION.SDK_INT >= 11) { ViewCompat.setSaveFromParentEnabled(f.mView, false); } else { f.mView = NoSaveStateFrameLayout.wrap(f.mView); } if (f.mHidden) f.mView.setVisibility(View.GONE); f.onViewCreated(f.mView, f.mSavedFragmentState); } else { f.mInnerView = null; } } case Fragment.CREATED: if (newState > Fragment.CREATED) { if (DEBUG) Log.v(TAG, "moveto ACTIVITY_CREATED: " + f); if (!f.mFromLayout) { ViewGroup container = null; if (f.mContainerId != 0) { container = (ViewGroup)mContainer.onFindViewById(f.mContainerId); if (container == null && !f.mRestored) { throwException(new IllegalArgumentException( "No view found for id 0x" + Integer.toHexString(f.mContainerId) + " (" + f.getResources().getResourceName(f.mContainerId) + ") for fragment " + f)); } } f.mContainer = container;
// 这里面会调用onCreateView()。 f.mView = f.performCreateView(f.getLayoutInflater( f.mSavedFragmentState), container, f.mSavedFragmentState); if (f.mView != null) { f.mInnerView = f.mView; if (Build.VERSION.SDK_INT >= 11) { ViewCompat.setSaveFromParentEnabled(f.mView, false); } else { f.mView = NoSaveStateFrameLayout.wrap(f.mView); } if (container != null) { Animation anim = loadAnimation(f, transit, true, transitionStyle); if (anim != null) { setHWLayerAnimListenerIfAlpha(f.mView, anim); f.mView.startAnimation(anim); }
// 添加child在这里哦。。。 container.addView(f.mView); } if (f.mHidden) f.mView.setVisibility(View.GONE); f.onViewCreated(f.mView, f.mSavedFragmentState); } else { f.mInnerView = null; } } f.performActivityCreated(f.mSavedFragmentState); if (f.mView != null) { f.restoreViewState(f.mSavedFragmentState); } f.mSavedFragmentState = null; } case Fragment.ACTIVITY_CREATED: case Fragment.STOPPED: if (newState > Fragment.STOPPED) { if (DEBUG) Log.v(TAG, "moveto STARTED: " + f); f.performStart(); } case Fragment.STARTED: if (newState > Fragment.STARTED) { if (DEBUG) Log.v(TAG, "moveto RESUMED: " + f); f.performResume(); f.mSavedFragmentState = null; f.mSavedViewState = null; } } } else if (f.mState > newState) { switch (f.mState) { case Fragment.RESUMED: if (newState < Fragment.RESUMED) { if (DEBUG) Log.v(TAG, "movefrom RESUMED: " + f); f.performPause(); } case Fragment.STARTED: if (newState < Fragment.STARTED) { if (DEBUG) Log.v(TAG, "movefrom STARTED: " + f); f.performStop(); } case Fragment.STOPPED: if (newState < Fragment.STOPPED) { if (DEBUG) Log.v(TAG, "movefrom STOPPED: " + f); f.performReallyStop(); } case Fragment.ACTIVITY_CREATED: if (newState < Fragment.ACTIVITY_CREATED) { if (DEBUG) Log.v(TAG, "movefrom ACTIVITY_CREATED: " + f); if (f.mView != null) { // Need to save the current view state if not // done already. if (mHost.onShouldSaveFragmentState(f) && f.mSavedViewState == null) { saveFragmentViewState(f); } }
// 这里面会调用onDestroyView()。 f.performDestroyView(); if (f.mView != null && f.mContainer != null) { Animation anim = null; if (mCurState > Fragment.INITIALIZING && !mDestroyed) { anim = loadAnimation(f, transit, false, transitionStyle); } if (anim != null) { final Fragment fragment = f; f.mAnimatingAway = f.mView; f.mStateAfterAnimating = newState; final View viewToAnimate = f.mView; anim.setAnimationListener(new AnimateOnHWLayerIfNeededListener( viewToAnimate, anim) { @Override public void onAnimationEnd(Animation animation) { super.onAnimationEnd(animation); if (fragment.mAnimatingAway != null) { fragment.mAnimatingAway = null; moveToState(fragment, fragment.mStateAfterAnimating, 0, 0, false); } } }); f.mView.startAnimation(anim); }
// 删除child在这里哦。。。 f.mContainer.removeView(f.mView); } f.mContainer = null; f.mView = null; f.mInnerView = null; } case Fragment.CREATED: if (newState < Fragment.CREATED) { if (mDestroyed) { if (f.mAnimatingAway != null) { // The fragment's containing activity is // being destroyed, but this fragment is // currently animating away. Stop the // animation right now -- it is not needed, // and we can't wait any more on destroying // the fragment. View v = f.mAnimatingAway; f.mAnimatingAway = null; v.clearAnimation(); } } if (f.mAnimatingAway != null) { // We are waiting for the fragment's view to finish // animating away. Just make a note of the state // the fragment now should move to once the animation // is done. f.mStateAfterAnimating = newState; newState = Fragment.CREATED; } else { if (DEBUG) Log.v(TAG, "movefrom CREATED: " + f); if (!f.mRetaining) { f.performDestroy(); } else { f.mState = Fragment.INITIALIZING; } f.mCalled = false; f.onDetach(); if (!f.mCalled) { throw new SuperNotCalledException("Fragment " + f + " did not call through to super.onDetach()"); } if (!keepActive) { if (!f.mRetaining) { makeInactive(f); } else { f.mHost = null; f.mParentFragment = null; f.mFragmentManager = null; f.mChildFragmentManager = null; } } } } } } if (f.mState != newState) { Log.w(TAG, "moveToState: Fragment state for " + f + " not updated inline; " + "expected state " + newState + " found " + f.mState); f.mState = newState; } }
在onCreateView()之后，完成child添加；在onDestroyView()之后，完成child删除。
无论怎样，Fragment状态的变更都是在moveToState函数中完成的，因此Fragment对应的View添加到其他ViewGroup中或者从ViewGroup中移出，都是从moveToState开始的。