Android RecyclerView 局部刷新分析

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
dispatchLayout();
mFirstLayoutComplete = true;
}

//2.mInPreLayout 设置为 true 后面有用
mState.mInPreLayout = mState.mRunPredictiveAnimations;

//5.保存动画信息相关
mViewInfoStore.addToPreLayout(holder, animationInfo);


           //3.如果holder确定要更新，就把它添加到 oldChangeHolders 集合中
long key = getChangedHolderKey(holder);
           mViewInfoStore.addToOldChangeHolders(key, holder);

           @VisibleForTesting
final LongSparseArray<RecyclerView.ViewHolder> mOldChangedHolders = new LongSparseArray<>();

   public void onLayoutChildren(Recycler recycler, State state) {
Log.e(TAG, "You must override onLayoutChildren(Recycler recycler, State state) ");
}


       private void processAdapterUpdatesAndSetAnimationFlags() {

           // 通常情况就是 ture
mState.mRunSimpleAnimations = true

   // 通常情况就是 ture
mState.mRunPredictiveAnimations = true

   mAdapterHelper.preProcess();

   for (int i = 0; i < count; i++) {
UpdateOp op = mPendingUpdates.get(i);
           case UpdateOp.UPDATE:
applyUpdate(op);
break;

               UpdateOp newOp = obtainUpdateOp(UpdateOp.UPDATE, tmpStart, tmpCount,
op.payload);
postponeAndUpdateViewHolders(newOp);

case UpdateOp.UPDATE:
mCallback.markViewHoldersUpdated(op.positionStart, op.itemCount, op.payload);
break;


               void initAdapterManager() {
mAdapterHelper = new AdapterHelper(new AdapterHelper.Callback() {

@Override
public void markViewHoldersUpdated(int positionStart, int itemCount, Object payload) {
viewRangeUpdate(positionStart, itemCount, payload);
mItemsChanged = true;
}

void viewRangeUpdate(int positionStart, int itemCount, Object payload) {
final int childCount = mChildHelper.getUnfilteredChildCount();
final int positionEnd = positionStart + itemCount;

if (holder.mPosition >= positionStart && holder.mPosition < positionEnd) {
// We re-bind these view holders after pre-processing is complete so that
// ViewHolders have their final positions assigned.
holder.addFlags(ViewHolder.FLAG_UPDATE);
holder.addChangePayload(payload);
// lp cannot be null since we get ViewHolder from it.
((LayoutParams) child.getLayoutParams()).mInsetsDirty = true;
}

processAdapterUpdatesAndSetAnimationFlags();


       if (mState.mTrackOldChangeHolders && holder.isUpdated() && !holder.isRemoved()
&& !holder.shouldIgnore() && !holder.isInvalid()) {
long key = getChangedHolderKey(holder);
// This is NOT the only place where a ViewHolder is added to old change holders
// list. There is another case where:
// * A VH is currently hidden but not deleted
// * The hidden item is changed in the adapter
// * Layout manager decides to layout the item in the pre-Layout pass (step1)
// When this case is detected, RV will un-hide that view and add to the old
// change holders list.
mViewInfoStore.addToOldChangeHolders(key, holder);
}

       @VisibleForTesting
final LongSparseArray<RecyclerView.ViewHolder> mOldChangedHolders = new LongSparseArray<>();


   //4.很重要，LayoutManager 开始工作
mLayout.onLayoutChildren(mRecycler, mState);

   for (int i = childCount - 1; i >= 0; i--) {
final View v = getChildAt(i);
scrapOrRecycleView(recycler, i, v);
}


           return ((LayoutParams) child.getLayoutParams()).mViewHolder;

   recycler.scrapView(view);

   不更新
   mAttachedScrap.add(holder);

   public final class Recycler {
final ArrayList<ViewHolder> mAttachedScrap = new ArrayList<>();


       更新的话
       mChangedScrap.add(holder);
       ArrayList<ViewHolder> mChangedScrap = null;

               ViewHolder tryGetViewHolderForPositionByDeadline(int position,
boolean dryRun, long deadlineNs) {

               if (mState.isPreLayout()) {
holder = getChangedScrapViewForPosition(position);


       final ViewHolder holder = mChangedScrap.get(i);



       holder = getScrapOrHiddenOrCachedHolderForPosition(position, dryRun);


       final ViewHolder holder = mAttachedScrap.get(i);

               Recycler
               final ViewHolder holder = mCachedViews.get(i);

                   final ArrayList<ViewHolder> mCachedViews = new ArrayList<ViewHolder>();



       final int offsetPosition = mAdapterHelper.findPositionOffset(position);
...
final int type = mAdapter.getItemViewType(offsetPosition);



       final View view = mViewCacheExtension
.getViewForPositionAndType(this, position, type);

                   //4. 从 RecycledViewPool 中查找
holder = getRecycledViewPool().getRecycledView(type);
...

           //5. 老实创建
holder = mAdapter.createViewHolder(RecyclerView.this, type);
...


           dispatchLayoutStep2



// Step 2: Run layout
mState.mInPreLayout = false;
mLayout.onLayoutChildren(mRecycler, mState);

来源：oschina

链接：https://my.oschina.net/u/4392473/blog/4366066

标签

android

LayoutManager

bind