androidx.recyclerview.widget.RecyclerView#getChildViewHolder ( )源码实例Demo

@Override
public boolean onInterceptTouchEvent(RecyclerView view, MotionEvent e) {
    View childView = view.findChildViewUnder(e.getX(), e.getY());
    if (childView != null && mListener != null) {
        if(mGestureDetector.onTouchEvent(e)) {
            mListener.onItemClick(view.getChildViewHolder(childView), view.getChildAdapterPosition(childView));
        }
        else if(e.getAction() == MotionEvent.ACTION_DOWN) {
            startDragX = (int) e.getRawX();
            startDragY = (int) e.getRawY();
            startDragItem = view.getChildViewHolder(childView);
        } else if (e.getAction() == MotionEvent.ACTION_UP) {
            int xCoord = (int) e.getRawX();
            int yCoord = (int) e.getRawY();
            RecyclerView.ViewHolder selectedView = view.getChildViewHolder(childView);
            if(Math.abs(startDragY-yCoord) > Math.abs(startDragX - xCoord)) {
                return false;
            }
            if(xCoord - startDragX > 10) {
                Log.d("**Russ", "flipright");
                mListener.onDragRight(startDragItem, view.getChildAdapterPosition(childView));
            } else if(startDragX - xCoord > 10) {
                Log.d("**Russ", "flipleft");
                mListener.onDragLeft(startDragItem, view.getChildAdapterPosition(childView));
            }
            return true;
        }
    }
    return false;
}
 

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
  final RecyclerView.ViewHolder holder = parent.getChildViewHolder(view);
  final int viewType = holder.getItemViewType();
  final FeatureItemDecoration decoration = viewTypeDecorationMap.get(viewType);
  if (decoration != null) {
    decoration.getItemOffsetsImpl(outRect, view, holder, parent, state);
  }
}
 

@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
  if (parent.getLayoutManager() == null) {
    return;
  }
  for (int i = 0; i < parent.getChildCount(); i++) {
    final View view = parent.getChildAt(i);
    final RecyclerView.ViewHolder holder = parent.getChildViewHolder(view);
    final int viewType = holder.getItemViewType();
    final FeatureItemDecoration decoration = viewTypeDecorationMap.get(viewType);
    if (decoration != null) {
      decoration.onDrawViewImpl(canvas, view, holder, parent, state);
    }
  }
}
 

@Override
public boolean hasDivider(RecyclerView parent, View view) {
    RecyclerView.ViewHolder holder = parent.getChildViewHolder(view);
    int viewType = holder.getItemViewType();
    return viewType != TYPE_HEADER && viewType != TYPE_TIP && !(viewType == TYPE_USER_RULE
            && ((RuleHolder) holder).mIsDragged);
}
 

public void updateActiveProgress(RecyclerView recyclerView) {
    int cnt = recyclerView.getChildCount();
    for (int i = 0; i < cnt; i++) {
        View view = recyclerView.getChildAt(i);
        RecyclerView.ViewHolder holder = recyclerView.getChildViewHolder(view);
        if (holder instanceof ActiveTransferHolder)
            ((ActiveTransferHolder) holder).updateProgress();
    }
}
 

/**
 * Don't call this method directly, it is called from
 * {@link EpoxyVisibilityTracker#processVisibilityEvents}
 *
 * @param child               the view to process for visibility event
 * @param detachEvent         true if the child was just detached
 * @param eventOriginForDebug a debug strings used for logs
 */
private void processChild(@NonNull View child, boolean detachEvent, String eventOriginForDebug) {
  final RecyclerView recyclerView = attachedRecyclerView;
  if (recyclerView != null) {
    // Preemptive check for child's parent validity to prevent `IllegalArgumentException` in
    // `getChildViewHolder`.
    final boolean isParentValid = child.getParent() == null || child.getParent() == recyclerView;
    final ViewHolder holder = isParentValid ? recyclerView.getChildViewHolder(child) : null;
    if (holder instanceof EpoxyViewHolder) {
      boolean changed = processVisibilityEvents(
          recyclerView,
          (EpoxyViewHolder) holder,
          detachEvent,
          eventOriginForDebug
      );
      if (changed) {
        if (child instanceof RecyclerView) {
          EpoxyVisibilityTracker tracker = nestedTrackers.get(child);
          if (tracker != null) {
            // If view visibility changed and there was a tracker on it then notify it.
            tracker.processChangeEvent("parent");
          }
        }
      }
    }
  }
}
 

/**
 * 遍历所有 {@link BaseHolder}, 释放他们需要释放的资源
 *
 * @param recyclerView {@link RecyclerView}
 */
public static void releaseAllHolder(RecyclerView recyclerView) {
    if (recyclerView == null) {
        return;
    }
    for (int i = recyclerView.getChildCount() - 1; i >= 0; i--) {
        final View view = recyclerView.getChildAt(i);
        RecyclerView.ViewHolder viewHolder = recyclerView.getChildViewHolder(view);
        if (viewHolder instanceof BaseHolder) {
            ((BaseHolder) viewHolder).onRelease();
        }
    }
}
 

/**
 * Returns, whether a divider should be drawn above a view, or not.
 *
 * @param view
 *         The view, which should be checked, as an instance of the class {@link View}. The
 *         view may not be null
 * @param recyclerView
 *         The recycler view, the given view belongs to, as an instance of the class {@link
 *         RecyclerView}. The recycler view may not be null
 * @return True, if a divider should be drawn above the given view, false otherwise
 */
private boolean shouldDrawDividerAbove(@NonNull final View view,
                                       @NonNull final RecyclerView recyclerView) {
    RecyclerView.ViewHolder viewHolder = recyclerView.getChildViewHolder(view);
    int position = viewHolder.getAdapterPosition();

    if (position > 0) {
        @SuppressLint("RestrictedApi") Preference preference = adapter.getItem(position);
        return preference instanceof PreferenceGroup;
    }

    return false;
}
 

@SuppressLint("NewApi")
protected void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int left;
    final int right;
    if (parent.getClipToPadding()) {
        left = parent.getPaddingLeft();
        right = parent.getWidth() - parent.getPaddingRight();
        canvas.clipRect(left, parent.getPaddingTop(), right,
                parent.getHeight() - parent.getPaddingBottom());
    } else {
        left = 0;
        right = parent.getWidth();
    }

    final int itemCount = parent.getChildCount();
    for (int i = 0; i < itemCount - mDividerOnLastItem; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.ViewHolder viewHolder = parent.getChildViewHolder(child);
        if (shouldDrawDivider(viewHolder)) {
            parent.getDecoratedBoundsWithMargins(child, mBounds);
            final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
            final int top = bottom - mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
    }
    canvas.restore();
}
 

@SuppressLint("NewApi")
protected void drawHorizontal(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int top;
    final int bottom;
    if (parent.getClipToPadding()) {
        top = parent.getPaddingTop();
        bottom = parent.getHeight() - parent.getPaddingBottom();
        canvas.clipRect(parent.getPaddingLeft(), top,
                parent.getWidth() - parent.getPaddingRight(), bottom);
    } else {
        top = 0;
        bottom = parent.getHeight();
    }

    final int itemCount = parent.getChildCount();
    for (int i = 0; i < itemCount - mDividerOnLastItem; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.ViewHolder viewHolder = parent.getChildViewHolder(child);
        if (shouldDrawDivider(viewHolder)) {
            parent.getLayoutManager().getDecoratedBoundsWithMargins(child, mBounds);
            final int right = mBounds.right + Math.round(child.getTranslationX());
            final int left = right - mDivider.getIntrinsicWidth();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
    }
    canvas.restore();
}
 

@Override
public boolean hasDivider(RecyclerView parent, View view) {
    RecyclerView.ViewHolder holder = parent.getChildViewHolder(view);
    int viewType = holder.getItemViewType();
    return viewType != TYPE_HEADER && viewType != TYPE_TEXT;
}