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

@Override
public void onDraw(@NotNull Canvas canvas, @NotNull RecyclerView parent, @NotNull RecyclerView.State state) {
    int dividerLeft = parent.getPaddingLeft();
    int dividerRight = parent.getWidth() - parent.getPaddingRight();

    int childCount = parent.getChildCount();
    for (int i = 0; i <= childCount - 2; i++) {
        View child = parent.getChildAt(i);

        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int dividerTop = child.getBottom() + params.bottomMargin;
        int dividerBottom = dividerTop + mDivider.getIntrinsicHeight();

        mDivider.setBounds(dividerLeft, dividerTop, dividerRight, dividerBottom);
        mDivider.draw(canvas);
    }
}
 

@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();

    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);

        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int top = child.getBottom() + params.bottomMargin;
        int bottom = top + mDivider.getIntrinsicHeight();

        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}
 

@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
    int width = parent.getWidth();
    int top;
    int childCount = parent.getChildCount() - (single ? 0 : 1);
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);
        View nextChild = i < childCount - 1 ? parent.getChildAt(i + 1) : null;
        int position = parent.getChildAdapterPosition(child);
        if (position < skipRows || child instanceof GraySectionCell || nextChild instanceof GraySectionCell) {
            continue;
        }
        top = child.getBottom();
        canvas.drawLine(LocaleController.isRTL ? 0 : AndroidUtilities.dp(72), top, width - (LocaleController.isRTL ? AndroidUtilities.dp(72) : 0), top, Theme.dividerPaint);
    }
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
  canvas.save();
  // Drawable width defines left/right padding. Drawable height defines divider height.
  final int left = parent.getPaddingStart() + divider.getIntrinsicWidth();
  final int right = parent.getWidth() - parent.getPaddingEnd() - divider.getIntrinsicWidth();

  final int childCount = parent.getChildCount();
  for (int i = 0; i < childCount; i++) {
    final View child = parent.getChildAt(i);
    parent.getDecoratedBoundsWithMargins(child, bounds);
    final int bottom = bounds.bottom + Math.round(child.getTranslationY());
    final int top = bottom - divider.getIntrinsicHeight();
    divider.setBounds(left, top, right, bottom);
    divider.draw(canvas);
  }
  canvas.restore();
}
 

public void drawHorizontal(Canvas c, RecyclerView parent) {
    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                .getLayoutParams();
        final int left = child.getLeft() - params.leftMargin;
        final int right = child.getRight() + params.rightMargin
                + mWidthDivider.getIntrinsicWidth();
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mWidthDivider.getIntrinsicHeight();
        mWidthDivider.setBounds(left, top, right, bottom);
        mWidthDivider.draw(c);
    }


}
 

@Override
public void onDrawOver(final Canvas c, final RecyclerView parent,
                       final RecyclerView.State state) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();

    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; ++i) {
        final View child = parent.getChildAt(i);

        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams();

        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + divider.getIntrinsicHeight();

        divider.setBounds(left, top, right, bottom);
        divider.draw(c);
    }
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    final int top = parent.getPaddingTop();
    final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();
    final int childSize = parent.getChildCount();
    for (int i = 0; i < childSize; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int left = child.getRight() + layoutParams.rightMargin;
        final int right = left + space;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }
    }
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    final int top = parent.getPaddingTop();
    final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom();
    final int childSize = parent.getChildCount();
    for (int i = 0; i < childSize; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int left = child.getRight() + layoutParams.rightMargin;
        final int right = left + space;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }
    }
}
 

private void drawHorizontal(Canvas canvas, RecyclerView parent) {
    int left = parent.getPaddingLeft();
    int right = parent.getMeasuredWidth() - parent.getPaddingRight();
    final int childSize = parent.getChildCount();
    for (int i = 0; i < childSize; i++) {
        final View child = parent.getChildAt(i);
        RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
        int top = child.getBottom() + layoutParams.bottomMargin;
        int bottom = top + space;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }

    }
}
 

@Override
public void onBindDragView(View clickedView, View dragView) {
    LinearLayout clickedLayout = (LinearLayout) clickedView;
    View clickedHeader = clickedLayout.getChildAt(0);
    RecyclerView clickedRecyclerView = (RecyclerView) clickedLayout.getChildAt(1);

    View dragHeader = dragView.findViewById(R.id.drag_header);
    ScrollView dragScrollView = dragView.findViewById(R.id.drag_scroll_view);
    LinearLayout dragLayout = dragView.findViewById(R.id.drag_list);
    dragLayout.removeAllViews();

    ((TextView) dragHeader.findViewById(R.id.text)).setText(((TextView) clickedHeader.findViewById(R.id.text)).getText());
    ((TextView) dragHeader.findViewById(R.id.item_count)).setText(((TextView) clickedHeader.findViewById(R.id.item_count)).getText());
    for (int i = 0; i < clickedRecyclerView.getChildCount(); i++) {
        View mapItemView = View.inflate(dragView.getContext(), R.layout.column_item, null);

        ((TextView) mapItemView.findViewById(R.id.text)).setText(((TextView) clickedRecyclerView.getChildAt(i).findViewById(R.id.text)).getText());
        dragLayout.addView(mapItemView);

        if (i == 0) {
            dragScrollView.setScrollY(-clickedRecyclerView.getChildAt(i).getTop());
        }
    }

    dragView.setPivotY(0);
    dragView.setPivotX(clickedView.getMeasuredWidth() / 2);
}
 

@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();
    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);
        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)child.getLayoutParams();
        int top = child.getBottom() + params.bottomMargin + (int)child.getTranslationY();
        int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}
 

@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();
}
 

private int getSubHeaderTop(@NonNull RecyclerView parent, @NonNull View child,
        @NonNull View header, @NonNull View subHeader, int adapterPos, int layoutPos) {

    int top = getAnimatedTop(child) - getSubHeaderHeightForLayout(subHeader);
    if (isFirstValidChild(layoutPos, parent)) {
        final int count = parent.getChildCount();
        final long currentHeaderId = adapter.getHeaderId(adapterPos);
        final long currentSubHeaderId = adapter.getSubHeaderId(adapterPos);

        // find next view with sub-header and compute the offscreen push if needed
        for (int i = layoutPos + 1; i < count; i++) {
            final View next = parent.getChildAt(i);
            int adapterPosHere = parent.getChildAdapterPosition(next);
            if (adapterPosHere != RecyclerView.NO_POSITION) {
                final long nextHeaderId = adapter.getHeaderId(adapterPosHere);
                final long nextSubHeaderId = adapter.getSubHeaderId(adapterPosHere);

                if ((nextSubHeaderId != currentSubHeaderId)) {
                    int headersHeight = getSubHeaderHeightForLayout(subHeader) +
                            getSubHeader(parent, adapterPosHere).itemView.getHeight();
                    if (nextHeaderId != currentHeaderId) {
                        headersHeight += getHeader(parent, adapterPosHere).itemView.getHeight();
                    }

                    final int offset = getAnimatedTop(next) - headersHeight;
                    if (offset < header.getHeight()) {
                        return offset;
                    } else {
                        break;
                    }
                }
            }
        }
    }

    return Math.max(header.getHeight(), top);
}
 

/**
 * {@inheritDoc}
 */
@Override
public void onDrawOver(@NonNull Canvas canvas, @NonNull RecyclerView parent,
        @NonNull RecyclerView.State state) {

    final int count = parent.getChildCount();
    long previousHeaderId = -1;

    for (int layoutPos = 0; layoutPos < count; layoutPos++) {
        final View child = parent.getChildAt(layoutPos);
        final int adapterPos = parent.getChildAdapterPosition(child);

        if (adapterPos != RecyclerView.NO_POSITION && hasHeader(adapterPos)) {
            long headerId = adapter.getHeaderId(adapterPos);

            if (headerId != previousHeaderId) {
                previousHeaderId = headerId;
                View header = getHeader(parent, adapterPos).itemView;
                canvas.save();

                final int left = child.getLeft();
                final int top = getHeaderTop(parent, child, header, adapterPos, layoutPos);
                canvas.translate(left, top);

                header.setTranslationX(left);
                header.setTranslationY(top);
                header.draw(canvas);
                canvas.restore();
            }
        }
    }
}
 

public void drawVertical(Canvas c, RecyclerView parent) {
    final int left = parent.getPaddingLeft();
    final int right = parent.getWidth() - parent.getPaddingRight();
 
    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int top = child.getBottom() + params.bottomMargin;
        final int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}
 

@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    int childCount = parent.getChildCount();
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();

    for (int i = 0; i < childCount - 1; i++) {
        View view = parent.getChildAt(i);
        float top = view.getBottom();
        float bottom = view.getBottom() + dividerHeight;
        c.drawRect(left, top, right, bottom, dividerPaint);
    }
}
 

protected int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos,
                         int layoutPos)
{
  int headerHeight = getHeaderHeightForLayout(header);
  int top = getChildY(parent, child) - headerHeight;
  if (sticky && layoutPos == 0) {
    final int count = parent.getChildCount();
    final long currentId = adapter.getHeaderId(adapterPos);
    // find next view with header and compute the offscreen push if needed
    for (int i = 1; i < count; i++) {
      int adapterPosHere = parent.getChildAdapterPosition(parent.getChildAt(translatedChildPosition(parent, i)));
      if (adapterPosHere != RecyclerView.NO_POSITION) {
        long nextId = adapter.getHeaderId(adapterPosHere);
        if (nextId != currentId) {
          final View next = parent.getChildAt(translatedChildPosition(parent, i));
          final int offset = getChildY(parent, next) - (headerHeight + getHeader(parent, adapter, adapterPosHere).itemView.getHeight());
          if (offset < 0) {
            return offset;
          } else {
            break;
          }
        }
      }
    }

    if (sticky) top = Math.max(0, top);
  }

  return top;
}
 

public void drawVertical(Canvas c, RecyclerView parent) {
    final int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        final int top = child.getTop() - params.topMargin;
        final int bottom = child.getBottom() + params.bottomMargin;
        final int left = child.getRight() + params.rightMargin;
        final int right = left + mDivider.getIntrinsicWidth();

        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}
 

private void drawVertical(Canvas canvas, RecyclerView parent) {
    canvas.save();
    final int left;
    final int right;
    //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
    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 childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        parent.getDecoratedBoundsWithMargins(child, mBounds);
        final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
        final int top = bottom - mDividerSize;
        mDividerPaint.setColor(mDividerColor);
        mDividerPaint.setStyle(Paint.Style.FILL);
        canvas.drawRect(left + mMarginStart, top + mMarginTop, right - mMarginEnd, bottom - mMarginBottom, mDividerPaint);
    }
    canvas.restore();
}
 

/***/
private void drawGrideview1(Canvas canvas, RecyclerView parent) {
    GridLayoutManager linearLayoutManager = (GridLayoutManager) parent.getLayoutManager();
    int childSize = parent.getChildCount();
    int top, bottom, left, right, spancount;
    spancount = linearLayoutManager.getSpanCount();
    for (int i = 0; i < childSize; i++) {
        final View child = parent.getChildAt(i);
        //画横线
        RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
        top = child.getBottom() + layoutParams.bottomMargin;
        bottom = top + space;
        left = layoutParams.leftMargin + child.getPaddingLeft() + space;
        right = child.getMeasuredWidth() * (i + 1) + left + space * i;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }
        //画竖线
        top = (layoutParams.topMargin + space) * (i / linearLayoutManager.getSpanCount() + 1);
        bottom = (child.getMeasuredHeight() + space) * (i / linearLayoutManager.getSpanCount() + 1) + space;
        left = child.getRight() + layoutParams.rightMargin;
        right = left + space;
        if (mDivider != null) {
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        if (mPaint != null) {
            canvas.drawRect(left, top, right, bottom, mPaint);
        }

        //画上缺失的线框
        if (i < spancount) {
            top = child.getTop() + layoutParams.topMargin;
            bottom = top + space;
            left = (layoutParams.leftMargin + space) * (i + 1);
            right = child.getMeasuredWidth() * (i + 1) + left + space * i;
            if (mDivider != null) {
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(canvas);
            }
            if (mPaint != null) {
                canvas.drawRect(left, top, right, bottom, mPaint);
            }
        }
        if (i % spancount == 0) {
            top = (layoutParams.topMargin + space) * (i / linearLayoutManager.getSpanCount() + 1);
            bottom = (child.getMeasuredHeight() + space) * (i / linearLayoutManager.getSpanCount() + 1) + space;
            left = child.getLeft() + layoutParams.leftMargin;
            right = left + space;
            if (mDivider != null) {
                mDivider.setBounds(left, top, right, bottom);
                mDivider.draw(canvas);
            }
            if (mPaint != null) {
                canvas.drawRect(left, top, right, bottom, mPaint);
            }
        }
    }
}