@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
dispatchLayout();
mFirstLayoutComplete = true;
}
//2.mInPreLayout 設定為 true 後面有用
mState.mInPreLayout = mState.mRunPredictiveAnimations;
//5.儲存動畫資訊相關
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 mOldChangedHolders = new LongSparseArray<>();
public void onLayoutChildren(Recycler recycler, State state) {
Log.e(TAG, "You must override onLayoutChildren(Recycler recycler, State state) ");
}
private void processAdapterUpdatesAndSetAnimationFlags() {
// 通常情況就是 ture
mState.mRunSimpleAnimations = true
// 通常情況就是 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 mOldChangedHolders = new LongSparseArray<>();
//4.很重要，LayoutManager 開始工作
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 mAttachedScrap = new ArrayList<>();
更新的話
mChangedScrap.add(holder);
ArrayList 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 mCachedViews = new ArrayList();
final int offsetPosition = mAdapterHelper.findPositionOffset(position);
...
final int type = mAdapter.getItemViewType(offsetPosition);
final View view = mViewCacheExtension
.getViewForPositionAndType(this, position, type);
//4. 從 RecycledViewPool 中查找
holder = getRecycledViewPool().getRecycledView(type);
...
//5. 老實建立
holder = mAdapter.createViewHolder(RecyclerView.this, type);
...
dispatchLayoutStep2
// Step 2: Run layout
mState.mInPreLayout = false;
mLayout.onLayoutChildren(mRecycler, mState);