RecycleView源码解析 - 1835434698/1835434698.github.io GitHub Wiki
mRunPredictiveAnimations
1、构造方法
三个构造方法最终都是调用的三参的构造方法。
public RecyclerView(@NonNull Context context) {
this(context, null);
}
public RecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public RecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
if (attrs != null) {
TypedArray a = context.obtainStyledAttributes(attrs, CLIP_TO_PADDING_ATTR, defStyle, 0);//加载资源文件中的样式
mClipToPadding = a.getBoolean(0, true);
a.recycle();
} else {
mClipToPadding = true;
}
setScrollContainer(true);//设置可滚动
setFocusableInTouchMode(true);//设置可以获取焦点
final ViewConfiguration vc = ViewConfiguration.get(context);//获取vie的配置
mTouchSlop = vc.getScaledTouchSlop();
mScaledHorizontalScrollFactor =
ViewConfigurationCompat.getScaledHorizontalScrollFactor(vc, context);
mScaledVerticalScrollFactor =
ViewConfigurationCompat.getScaledVerticalScrollFactor(vc, context);
mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();
mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
setWillNotDraw(getOverScrollMode() == View.OVER_SCROLL_NEVER);
mItemAnimator.setListener(mItemAnimatorListener);//设置动画效果
initAdapterManager();//初始化adapterManager 调用01
initChildrenHelper();//初始化子view的高 调用02
initAutofill();//初始化自动填充 调用03
// If not explicitly specified this view is important for accessibility.
if (ViewCompat.getImportantForAccessibility(this)
== ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
ViewCompat.setImportantForAccessibility(this,
ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
mAccessibilityManager = (AccessibilityManager) getContext()
.getSystemService(Context.ACCESSIBILITY_SERVICE);
setAccessibilityDelegateCompat(new RecyclerViewAccessibilityDelegate(this));
// Create the layoutManager if specified.
boolean nestedScrollingEnabled = true;
if (attrs != null) {
int defStyleRes = 0;
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RecyclerView,
defStyle, defStyleRes);
String layoutManagerName = a.getString(R.styleable.RecyclerView_layoutManager);
int descendantFocusability = a.getInt(
R.styleable.RecyclerView_android_descendantFocusability, -1);
if (descendantFocusability == -1) {
setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
}
mEnableFastScroller = a.getBoolean(R.styleable.RecyclerView_fastScrollEnabled, false);
if (mEnableFastScroller) {
StateListDrawable verticalThumbDrawable = (StateListDrawable) a
.getDrawable(R.styleable.RecyclerView_fastScrollVerticalThumbDrawable);
Drawable verticalTrackDrawable = a
.getDrawable(R.styleable.RecyclerView_fastScrollVerticalTrackDrawable);
StateListDrawable horizontalThumbDrawable = (StateListDrawable) a
.getDrawable(R.styleable.RecyclerView_fastScrollHorizontalThumbDrawable);
Drawable horizontalTrackDrawable = a
.getDrawable(R.styleable.RecyclerView_fastScrollHorizontalTrackDrawable);
initFastScroller(verticalThumbDrawable, verticalTrackDrawable,
horizontalThumbDrawable, horizontalTrackDrawable);
}
a.recycle();
createLayoutManager(context, layoutManagerName, attrs, defStyle, defStyleRes);
if (Build.VERSION.SDK_INT >= 21) {
a = context.obtainStyledAttributes(attrs, NESTED_SCROLLING_ATTRS,
defStyle, defStyleRes);
nestedScrollingEnabled = a.getBoolean(0, true);
a.recycle();
}
} else {
setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
}
// Re-set whether nested scrolling is enabled so that it is set on all API levels
setNestedScrollingEnabled(nestedScrollingEnabled);
}
//01
void initAdapterManager() {
//adapterHelper 维护adapter的状态等。后面再细讲
mAdapterHelper = new AdapterHelper(new AdapterHelper.Callback() {
@Override
public ViewHolder findViewHolder(int position) {
//根据position获取到viewHolder
final ViewHolder vh = findViewHolderForPosition(position, true);
if (vh == null) {
return null;
}
// ensure it is not hidden because for adapter helper, the only thing matter is that
// LM thinks view is a child.
if (mChildHelper.isHidden(vh.itemView)) {//判断该View是否显示在屏幕 调用 01-01
if (DEBUG) {
Log.d(TAG, "assuming view holder cannot be find because it is hidden");
}
return null;
}
return vh;
}
@Override
public void offsetPositionsForRemovingInvisible(int start, int count) {
offsetPositionRecordsForRemove(start, count, true);
mItemsAddedOrRemoved = true;
mState.mDeletedInvisibleItemCountSincePreviousLayout += count;
}
@Override
public void offsetPositionsForRemovingLaidOutOrNewView(
int positionStart, int itemCount) {
offsetPositionRecordsForRemove(positionStart, itemCount, false);
mItemsAddedOrRemoved = true;
}
@Override
public void markViewHoldersUpdated(int positionStart, int itemCount, Object payload) {
viewRangeUpdate(positionStart, itemCount, payload);
mItemsChanged = true;
}
@Override
public void onDispatchFirstPass(AdapterHelper.UpdateOp op) {
dispatchUpdate(op);
}
void dispatchUpdate(AdapterHelper.UpdateOp op) {
switch (op.cmd) {
case AdapterHelper.UpdateOp.ADD:
mLayout.onItemsAdded(RecyclerView.this, op.positionStart, op.itemCount);
break;
case AdapterHelper.UpdateOp.REMOVE:
mLayout.onItemsRemoved(RecyclerView.this, op.positionStart, op.itemCount);
break;
case AdapterHelper.UpdateOp.UPDATE:
mLayout.onItemsUpdated(RecyclerView.this, op.positionStart, op.itemCount,
op.payload);
break;
case AdapterHelper.UpdateOp.MOVE:
mLayout.onItemsMoved(RecyclerView.this, op.positionStart, op.itemCount, 1);
break;
}
}
@Override
public void onDispatchSecondPass(AdapterHelper.UpdateOp op) {
dispatchUpdate(op);
}
@Override
public void offsetPositionsForAdd(int positionStart, int itemCount) {
offsetPositionRecordsForInsert(positionStart, itemCount);
mItemsAddedOrRemoved = true;
}
@Override
public void offsetPositionsForMove(int from, int to) {
offsetPositionRecordsForMove(from, to);
// should we create mItemsMoved ?
mItemsAddedOrRemoved = true;
}
});
}
class ChildHelper{
final List<View> mHiddenViews;//缓存的屏幕之外的view视图
//01-01 ChildHelper的方法
boolean isHidden(View view) {
return mHiddenViews.contains(view);
}
}//02
private void initChildrenHelper() {
//子View帮助类
mChildHelper = new ChildHelper(new ChildHelper.Callback() {
@Override
public int getChildCount() {
return RecyclerView.this.getChildCount();//获取子View的数量
}
@Override
public void addView(View child, int index) {
if (VERBOSE_TRACING) {
TraceCompat.beginSection("RV addView");
}
RecyclerView.this.addView(child, index);//添加子view
if (VERBOSE_TRACING) {
TraceCompat.endSection();
}
dispatchChildAttached(child);
}
@Override
public int indexOfChild(View view) {
return RecyclerView.this.indexOfChild(view);//得到子view的位置
}
@Override
public void removeViewAt(int index) {//移除指定位置View
final View child = RecyclerView.this.getChildAt(index);
if (child != null) {
dispatchChildDetached(child);
// Clear any android.view.animation.Animation that may prevent the item from
// detaching when being removed. If a child is re-added before the
// lazy detach occurs, it will receive invalid attach/detach sequencing.
child.clearAnimation();
}
if (VERBOSE_TRACING) {
TraceCompat.beginSection("RV removeViewAt");
}
RecyclerView.this.removeViewAt(index);
if (VERBOSE_TRACING) {
TraceCompat.endSection();
}
}
@Override
public View getChildAt(int offset) {
return RecyclerView.this.getChildAt(offset);//得到指定位置的子view
}
@Override
public void removeAllViews() {//移除所有View
final int count = getChildCount();
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
dispatchChildDetached(child);
// Clear any android.view.animation.Animation that may prevent the item from
// detaching when being removed. If a child is re-added before the
// lazy detach occurs, it will receive invalid attach/detach sequencing.
child.clearAnimation();
}
RecyclerView.this.removeAllViews();
}
@Override
public ViewHolder getChildViewHolder(View view) {
return getChildViewHolderInt(view);//根据View的到ViewHolder
}
@Override
public void attachViewToParent(View child, int index,
ViewGroup.LayoutParams layoutParams) {
final ViewHolder vh = getChildViewHolderInt(child);
if (vh != null) {
if (!vh.isTmpDetached() && !vh.shouldIgnore()) {
throw new IllegalArgumentException("Called attach on a child which is not"
+ " detached: " + vh + exceptionLabel());
}
if (DEBUG) {
Log.d(TAG, "reAttach " + vh);
}
vh.clearTmpDetachFlag();
}
RecyclerView.this.attachViewToParent(child, index, layoutParams);//添加到父View
}
@Override
public void detachViewFromParent(int offset) {
final View view = getChildAt(offset);
if (view != null) {
final ViewHolder vh = getChildViewHolderInt(view);
if (vh != null) {
if (vh.isTmpDetached() && !vh.shouldIgnore()) {
throw new IllegalArgumentException("called detach on an already"
+ " detached child " + vh + exceptionLabel());
}
if (DEBUG) {
Log.d(TAG, "tmpDetach " + vh);
}
vh.addFlags(ViewHolder.FLAG_TMP_DETACHED);
}
}
RecyclerView.this.detachViewFromParent(offset);//分离从父View
}
@Override
public void onEnteredHiddenState(View child) {
final ViewHolder vh = getChildViewHolderInt(child);
if (vh != null) {
vh.onEnteredHiddenState(RecyclerView.this);//隐藏子View
}
}
@Override
public void onLeftHiddenState(View child) {
final ViewHolder vh = getChildViewHolderInt(child);
if (vh != null) {
vh.onLeftHiddenState(RecyclerView.this);
}
}
});
}//03
private void initAutofill() {
if (ViewCompat.getImportantForAutofill(this) == View.IMPORTANT_FOR_AUTOFILL_AUTO) {
ViewCompat.setImportantForAutofill(this,
View.IMPORTANT_FOR_AUTOFILL_NO_EXCLUDE_DESCENDANTS);
}
}//04
protected void onMeasure(int widthSpec, int heightSpec) {
if (mLayout == null) {
defaultOnMeasure(widthSpec, heightSpec);//测量宽高， 调用 04-01
return;
}
if (mLayout.isAutoMeasureEnabled()) {
final int widthMode = MeasureSpec.getMode(widthSpec);
final int heightMode = MeasureSpec.getMode(heightSpec);
/**
* This specific call should be considered deprecated and replaced with
* {@link #defaultOnMeasure(int, int)}. It can't actually be replaced as it could
* break existing third party code but all documentation directs developers to not
* override {@link LayoutManager#onMeasure(int, int)} when
* {@link LayoutManager#isAutoMeasureEnabled()} returns true.
*/
mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
final boolean measureSpecModeIsExactly =
widthMode == MeasureSpec.EXACTLY && heightMode == MeasureSpec.EXACTLY;
if (measureSpecModeIsExactly || mAdapter == null) {
return;
}
if (mState.mLayoutStep == State.STEP_START) {
dispatchLayoutStep1();
}
// set dimensions in 2nd step. Pre-layout should happen with old dimensions for
// consistency
mLayout.setMeasureSpecs(widthSpec, heightSpec);
mState.mIsMeasuring = true;
dispatchLayoutStep2();
// now we can get the width and height from the children.
mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
// if RecyclerView has non-exact width and height and if there is at least one child
// which also has non-exact width & height, we have to re-measure.
if (mLayout.shouldMeasureTwice()) {
mLayout.setMeasureSpecs(
MeasureSpec.makeMeasureSpec(getMeasuredWidth(), MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(getMeasuredHeight(), MeasureSpec.EXACTLY));
mState.mIsMeasuring = true;
dispatchLayoutStep2();
// now we can get the width and height from the children.
mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
}
} else {
if (mHasFixedSize) {
mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
return;
}
// custom onMeasure
if (mAdapterUpdateDuringMeasure) {
startInterceptRequestLayout();
onEnterLayoutOrScroll();
processAdapterUpdatesAndSetAnimationFlags();
onExitLayoutOrScroll();
if (mState.mRunPredictiveAnimations) {
mState.mInPreLayout = true;
} else {
// consume remaining updates to provide a consistent state with the layout pass.
mAdapterHelper.consumeUpdatesInOnePass();
mState.mInPreLayout = false;
}
mAdapterUpdateDuringMeasure = false;
stopInterceptRequestLayout(false);
} else if (mState.mRunPredictiveAnimations) {
// If mAdapterUpdateDuringMeasure is false and mRunPredictiveAnimations is true:
// this means there is already an onMeasure() call performed to handle the pending
// adapter change, two onMeasure() calls can happen if RV is a child of LinearLayout
// with layout_width=MATCH_PARENT. RV cannot call LM.onMeasure() second time
// because getViewForPosition() will crash when LM uses a child to measure.
setMeasuredDimension(getMeasuredWidth(), getMeasuredHeight());
return;
}
if (mAdapter != null) {
mState.mItemCount = mAdapter.getItemCount();//调用RecyclerView.Adapter的getItemCount
} else {
mState.mItemCount = 0;
}
startInterceptRequestLayout();
mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
stopInterceptRequestLayout(false);
mState.mInPreLayout = false; // clear
}
}
//04-01
void defaultOnMeasure(int widthSpec, int heightSpec) {
// calling LayoutManager here is not pretty but that API is already public and it is better
// than creating another method since this is internal.
final int width = LayoutManager.chooseSize(widthSpec,
getPaddingLeft() + getPaddingRight(),
ViewCompat.getMinimumWidth(this));
final int height = LayoutManager.chooseSize(heightSpec,
getPaddingTop() + getPaddingBottom(),
ViewCompat.getMinimumHeight(this));
setMeasuredDimension(width, height);
}//05
protected void onLayout(boolean changed, int l, int t, int r, int b) {
TraceCompat.beginSection(TRACE_ON_LAYOUT_TAG);
dispatchLayout();//分发布局， 调用 05-01
TraceCompat.endSection();
mFirstLayoutComplete = true;
}
void dispatchLayout() {
if (mAdapter == null) {
Log.e(TAG, "No adapter attached; skipping layout");
// leave the state in START
return;
}
if (mLayout == null) {
Log.e(TAG, "No layout manager attached; skipping layout");
// leave the state in START
return;
}
mState.mIsMeasuring = false;
if (mState.mLayoutStep == State.STEP_START) {
dispatchLayoutStep1();//内部通过调用LayoutManager然后又调用到 onCreateViewHolder与onBindViewHolder
mLayout.setExactMeasureSpecsFrom(this);
dispatchLayoutStep2();
} else if (mAdapterHelper.hasUpdates() || mLayout.getWidth() != getWidth()
|| mLayout.getHeight() != getHeight()) {
// First 2 steps are done in onMeasure but looks like we have to run again due to
// changed size.
mLayout.setExactMeasureSpecsFrom(this);
dispatchLayoutStep2();
} else {
// always make sure we sync them (to ensure mode is exact)
mLayout.setExactMeasureSpecsFrom(this);
}
dispatchLayoutStep3();
}//06
public void onDraw(Canvas c) {
super.onDraw(c);
final int count = mItemDecorations.size();
for (int i = 0; i < count; i++) {
mItemDecorations.get(i).onDraw(c, this, mState);//绘制动画
}
}//07
public void draw(Canvas c) {
super.draw(c);
final int count = mItemDecorations.size();
for (int i = 0; i < count; i++) {
mItemDecorations.get(i).onDrawOver(c, this, mState);//动画绘制结束。
}
// TODO If padding is not 0 and clipChildrenToPadding is false, to draw glows properly, we
// need find children closest to edges. Not sure if it is worth the effort.
boolean needsInvalidate = false;
if (mLeftGlow != null && !mLeftGlow.isFinished()) {
final int restore = c.save();
final int padding = mClipToPadding ? getPaddingBottom() : 0;
c.rotate(270);
c.translate(-getHeight() + padding, 0);
needsInvalidate = mLeftGlow != null && mLeftGlow.draw(c);
c.restoreToCount(restore);
}
if (mTopGlow != null && !mTopGlow.isFinished()) {
final int restore = c.save();
if (mClipToPadding) {
c.translate(getPaddingLeft(), getPaddingTop());
}
needsInvalidate |= mTopGlow != null && mTopGlow.draw(c);
c.restoreToCount(restore);
}
if (mRightGlow != null && !mRightGlow.isFinished()) {
final int restore = c.save();
final int width = getWidth();
final int padding = mClipToPadding ? getPaddingTop() : 0;
c.rotate(90);
c.translate(-padding, -width);
needsInvalidate |= mRightGlow != null && mRightGlow.draw(c);
c.restoreToCount(restore);
}
if (mBottomGlow != null && !mBottomGlow.isFinished()) {
final int restore = c.save();
c.rotate(180);
if (mClipToPadding) {
c.translate(-getWidth() + getPaddingRight(), -getHeight() + getPaddingBottom());
} else {
c.translate(-getWidth(), -getHeight());
}
needsInvalidate |= mBottomGlow != null && mBottomGlow.draw(c);
c.restoreToCount(restore);
}
// If some views are animating, ItemDecorators are likely to move/change with them.
// Invalidate RecyclerView to re-draw decorators. This is still efficient because children's
// display lists are not invalidated.
if (!needsInvalidate && mItemAnimator != null && mItemDecorations.size() > 0
&& mItemAnimator.isRunning()) {
needsInvalidate = true;
}
if (needsInvalidate) {
ViewCompat.postInvalidateOnAnimation(this);
}
}public final class Recycler {
//4级缓存
final ArrayList<ViewHolder> mAttachedScrap = new ArrayList<>();//存放全部的对象
ArrayList<ViewHolder> mChangedScrap = null;//发生改变的对象 1级
final ArrayList<ViewHolder> mCachedViews = new ArrayList<ViewHolder>();//存放remove调的视图的VIewHolder对象(保存的信息、绑定的数据未删除)，容量有限制默认是2。 2级
RecycledViewPool mRecyclerPool;//存放remove调的视图的VIewHolder对象（完全删除信息、数据等）。 3级
private final List<ViewHolder>
mUnmodifiableAttachedScrap = Collections.unmodifiableList(mAttachedScrap);//当前在报废列表中的不可修改的列表
private int mRequestedCacheMax = DEFAULT_CACHE_SIZE;//最大请求缓存个数，默认2.
int mViewCacheMax = DEFAULT_CACHE_SIZE;//最大View缓存个数，默认2.
private ViewCacheExtension mViewCacheExtension; //缓存扩展类，支持用户自定义 4级
static final int DEFAULT_CACHE_SIZE = 2;
}