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

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);
        }

    }
}
 

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);
        }

    }
}
 

/**
 * 绘制分组Group
 *
 * @param c      Canvas
 * @param parent RecyclerView
 */
protected void onDrawGroup(Canvas c, RecyclerView parent) {
    int paddingLeft = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();
    int top, bottom;
    int count = parent.getChildCount();
    for (int i = 0; i < parent.getChildCount(); i++) {
        View child = parent.getChildAt(i);
        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        int key = params.getViewLayoutPosition();
        if (mGroup.containsKey(key)) {
            top = child.getTop() - params.topMargin - mGroupHeight;
            bottom = top + mGroupHeight;
            c.drawRect(paddingLeft, top, right, bottom, mBackgroundPaint);
            String group = mGroup.get(params.getViewLayoutPosition()).toString();
            float x;
            float y = top + mTextBaseLine;
            if (isCenter) {
                x = parent.getMeasuredWidth() / 2 - getTextX(group);
            } else {
                x = mPaddingLeft;
            }
            c.drawText(group, x, y, mTextPaint);
        }
    }
}
 

@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
    super.getItemOffsets(outRect, view, parent, state);

    measureItemView(view, parent);

    int viewWidth = view.getMeasuredWidth();
    if (spanCount * viewWidth < parent.getMeasuredWidth()) {
        int emptySpacePx = parent.getMeasuredWidth() - spanCount * viewWidth;
        outRect.left = outRect.right = emptySpacePx / (2 * spanCount);
    }
}
 

@Override
public void getItemOffsets(@NonNull final Rect outRect, @NonNull final View view, @NonNull final RecyclerView parent, @NonNull final RecyclerView.State state) {
  super.getItemOffsets(outRect, view, parent, state);

  outRect.right = this.width > 0 ? this.spacing / 2 : this.spacing;
  outRect.left = this.width > 0 ? this.spacing / 2 : 0;

  if ((state.getItemCount() - 1 == parent.getChildLayoutPosition(view))) {
    outRect.right = this.width > 0 ? ((parent.getMeasuredWidth() / 2) - (this.width / 2)) : 0;
  }
  if (parent.getChildLayoutPosition(view) == 0) {
    outRect.left = this.width > 0 ? ((parent.getMeasuredWidth() / 2) - (this.width / 2)) : 0;
  }
}
 

private void drawHorizontal(Canvas canvas, RecyclerView parent) {
  final int left = parent.getPaddingLeft();
  final int right = parent.getMeasuredWidth() - parent.getPaddingRight();
  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 top = child.getBottom() + layoutParams.bottomMargin;
    final int bottom = top + mDividerHeight;
    if (mPaint != null) {
      canvas.drawRect(left + mMarginLeft, top, right, bottom, mPaint);
    }
  }
}
 

@Override
public boolean isItemsFitOnScreen(RecyclerView recyclerView, int itemsSize) {
    calcItemWidth(recyclerView);
    int itemsWidth = itemWidth * (itemsSize);
    int containerWidth = recyclerView.getMeasuredWidth();
    return containerWidth >= itemsWidth;
}
 

/**
 * 绘制悬浮组
 *
 * @param c      Canvas
 * @param parent RecyclerView
 */
protected void onDrawOverGroup(Canvas c, RecyclerView parent) {
    int firstVisiblePosition = ((LinearLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
    if (firstVisiblePosition == RecyclerView.NO_POSITION) {
        return;
    }
    Group group = getCroup(firstVisiblePosition);
    if (group == null)
        return;
    String groupTitle = group.toString();
    if (TextUtils.isEmpty(groupTitle)) {
        return;
    }
    boolean isRestore = false;
    Group nextGroup = getCroup(firstVisiblePosition + 1);
    if (nextGroup != null && !group.equals(nextGroup)) {
        //说明是当前组最后一个元素，但不一定碰撞了
        View child = parent.findViewHolderForAdapterPosition(firstVisiblePosition).itemView;
        if (child.getTop() + child.getMeasuredHeight() < mGroupHeight) {
            //进一步检测碰撞
            c.save();//保存画布当前的状态
            isRestore = true;
            c.translate(0, child.getTop() + child.getMeasuredHeight() - mGroupHeight);
        }
    }
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();
    int top = parent.getPaddingTop();
    int bottom = top + mGroupHeight;
    c.drawRect(left, top, right, bottom, mBackgroundPaint);
    float x;
    float y = top + mTextBaseLine;
    if (isCenter) {
        x = parent.getMeasuredWidth() / 2 - getTextX(groupTitle);
    } else {
        x = mPaddingLeft;
    }
    c.drawText(groupTitle, x, y, mTextPaint);
    if (isRestore) {
        //还原画布为初始状态
        c.restore();
    }
}