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Fragment的解析(二)
在 Fragment的解析(一)中讲到了BackStackRecord的run方法, 我们以OP_REPLACE 操作为例看看具体的执行过程:
//BackStackRecord.java run() .. case OP_REPLACE: { Fragment f = op.fragment; if (mManager.mAdded != null) { for (int i=0; i<mManager.mAdded.size(); i++) { Fragment old = mManager.mAdded.get(i); if (FragmentManagerImpl.DEBUG) Log.v(TAG, "OP_REPLACE: adding=" + f + " old=" + old); if (f == null || old.mContainerId == f.mContainerId) { if (old == f) { op.fragment = f = null; } else { if (op.removed == null) { op.removed = new ArrayList<Fragment>(); } op.removed.add(old); old.mNextAnim = op.exitAnim; if (mAddToBackStack) { old.mBackStackNesting += 1; if (FragmentManagerImpl.DEBUG) Log.v(TAG, "Bump nesting of " + old + " to " + old.mBackStackNesting); } mManager.removeFragment(old, mTransition, mTransitionStyle); } } } } if (f != null) { f.mNextAnim = op.enterAnim; mManager.addFragment(f, false); } } break;
可以看到,和当前事务的目标fragment有相同containerId的fragment都会被remove掉, 并记录在当前事务的操作对象的removed列表中(因为如果加入回退栈,回退的时候还会用来恢复),然后执行 FragmentManager的 removeFragment(Fragment f, .. ) 方法, 等到旧的fragment全部移除完, 就对当前事务的目标fragment 执行 addFragment操作。
这里说一下 attachFragment 和 addFragment的区别,相应的,detachFragment和removeFragment的区别也就显而易见了:
在FragmentManager中, mAdded 保存了执行 attach操作或add的fragment, 而 mActive 保存了执行过 add 操作的fragment,
mActive中的fragment是准备好可见或已经可见的fragment。这也是attach 和 add 的区别。BackStackRecord中的attach和detach方法都不需要 containerId, 而add 和remove都需要, 从这里也可以看出mAdded和mActive的区别。
attachFragment只把已经被detach的fragment 加入mAdded列表。detachFragment 则把fragment从mAdded列表移除。
在removeFragment方法中,如果fragment不在回退栈中或已经被 detach , 则该fragment会从fragmentManager的 mAdded列表移除。
public void removeFragment(Fragment fragment, int transition, int transitionStyle) { if (DEBUG) Log.v(TAG, "remove: " + fragment + " nesting=" + fragment.mBackStackNesting); final boolean inactive = !fragment.isInBackStack(); if (!fragment.mDetached || inactive) { if (mAdded != null) { mAdded.remove(fragment); } if (fragment.mHasMenu && fragment.mMenuVisible) { mNeedMenuInvalidate = true; } fragment.mAdded = false; fragment.mRemoving = true; moveToState(fragment, inactive ? Fragment.INITIALIZING : Fragment.CREATED, transition, transitionStyle, false); } }
addFragment 方法调用makeActive把fragment加入mActive列表并分配一个index, 注意这里是fragment的index, 回忆一下,对于加入到回退栈的 backStackRecord 事务也有一个index。
public void addFragment(Fragment fragment, boolean moveToStateNow) { if (mAdded == null) { mAdded = new ArrayList<Fragment>(); } if (DEBUG) Log.v(TAG, "add: " + fragment); makeActive(fragment); if (!fragment.mDetached) { if (mAdded.contains(fragment)) { throw new IllegalStateException("Fragment already added: " + fragment); } mAdded.add(fragment); fragment.mAdded = true; fragment.mRemoving = false; if (fragment.mHasMenu && fragment.mMenuVisible) { mNeedMenuInvalidate = true; } if (moveToStateNow) { moveToState(fragment); } } } ... void makeActive(Fragment f) { if (f.mIndex >= 0) { return; } if (mAvailIndices == null || mAvailIndices.size() <= 0) { if (mActive == null) { mActive = new ArrayList<Fragment>(); } f.setIndex(mActive.size(), mParent); mActive.add(f); } else { f.setIndex(mAvailIndices.remove(mAvailIndices.size()-1), mParent); mActive.set(f.mIndex, f); } if (DEBUG) Log.v(TAG, "Allocated fragment index " + f); }
无论是addFragment 、 removeFragment hi还是hide 、show、 attach、detach等, 最终都会调用moveToState(..),
可以假设FragmentManager的mCurState是RESUMED, 因为activity会对FragmentManager的状态进行更新:
//Activity.java final void performCreate(Bundle icicle) { onCreate(icicle); mVisibleFromClient = !mWindow.getWindowStyle().getBoolean( com.android.internal.R.styleable.Window_windowNoDisplay, false); mFragments.dispatchActivityCreated(); } final void performStart() { ... mFragments.dispatchStart(); ... } //这里执行了两边execPendingActions(), 是为了让在pendingActions列表中的fragment执行相应的生命周期方法 final void performResume() { performRestart(); mFragments.execPendingActions(); ..... mFragments.dispatchResume(); mFragments.execPendingActions(); ... } final void performPause() { mDoReportFullyDrawn = false; mFragments.dispatchPause(); ... } final void performStop() { .... mFragments.dispatchStop(); } final void performDestroy() { mDestroyed = true; mWindow.destroy(); mFragments.dispatchDestroy(); onDestroy(); if (mLoaderManager != null) { mLoaderManager.doDestroy(); } }
假设当前的mCurState是Resumed, f.mState 是INITIALIZING , 那么f的生命周期方法会从onAttach 执行到 onResume (被performResume 调用)。
注意这里的switch-case 语句没有break, 是一种特殊的用法。
Fragment的状态只有Initializing, Created, Stopped, Started几种, 那么当fragment处于Started状态是应该执行哪一个生命方法呢? onStop 还是 onResume (也就是说是正在进入视野还是在退出视野)), moveToState(..)方法通过Fragment的状态与目标状态newState的大小决定调用哪一个生命周期函数的:
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.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.mActivity = mActivity; f.mParentFragment = mParent; f.mFragmentManager = mParent != null ? mParent.mChildFragmentManager : mActivity.mFragments; f.mCalled = false; f.onAttach(mActivity); if (!f.mCalled) { throw new SuperNotCalledException("Fragment " + f + " did not call through to super.onAttach()"); } if (f.mParentFragment == null) { mActivity.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; 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.findViewById(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; f.mView = f.performCreateView(f.getLayoutInflater( f.mSavedFragmentState), container, f.mSavedFragmentState); if (f.mView != null) { f.mInnerView = f.mView; f.mView = NoSaveStateFrameLayout.wrap(f.mView); if (container != null) { Animation anim = loadAnimation(f, transit, true, transitionStyle); if (anim != null) { f.mView.startAnimation(anim); } 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.mResumed = true; 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(); f.mResumed = false; } 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 (!mActivity.isFinishing() && f.mSavedViewState == null) { saveFragmentViewState(f); } } 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; anim.setAnimationListener(new AnimationListener() { @Override public void onAnimationEnd(Animation animation) { if (fragment.mAnimatingAway != null) { fragment.mAnimatingAway = null; moveToState(fragment, fragment.mStateAfterAnimating, 0, 0, false); } } @Override public void onAnimationRepeat(Animation animation) { } @Override public void onAnimationStart(Animation animation) { } }); f.mView.startAnimation(anim); } 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(); } 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.mActivity = null; f.mParentFragment = null; f.mFragmentManager = null; f.mChildFragmentManager = null; } } } } } } f.mState = newState; }
执行完moveToState(..) 一系列方法, fragment就有了相应的状态(可见,不可见,暂停,活跃等)。
Fragment的解析(二)