解决RecycleView分割线不居中的三种方法

public class SpacesItemDecoration extends RecyclerView.ItemDecoration {  private int mSpace;  private int mSpanCount; // RecyclerView有多少列  private boolean mHasPadding; // RecyclerView是否有Padding  public SpacesItemDecoration(int mSpace) {    this.mSpace = mSpace;    this.mHasPadding = true;  }  public SpacesItemDecoration(int mSpace, boolean hasPadding) {    this.mSpace = mSpace;    this.mHasPadding = hasPadding;  }  @Override  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {    // 初始化列数    if (mSpanCount == 0) {      this.mSpanCount = ((GridLayoutManager) parent.getLayoutManager()).getSpanCount();    }    int position = parent.getChildAdapterPosition(view); // item position    int column = position % mSpanCount; // item column    if (mHasPadding) {      outRect.left = mSpace - column * mSpace / mSpanCount; // spacing - column * ((1f / spanCount) * spacing)      outRect.right = (column + 1) * mSpace / mSpanCount; // (column + 1) * ((1f / spanCount) * spacing)      if (position < mSpanCount) { // top edge        outRect.top = mSpace;      }      outRect.bottom = mSpace; // item bottom    } else {      outRect.left = column * mSpace / mSpanCount; // column * ((1f / spanCount) * spacing)      outRect.right = mSpace - (column + 1) * mSpace / mSpanCount; // spacing - (column + 1) * ((1f /  spanCount) * spacing)      if (position >= mSpanCount) {        outRect.top = mSpace; // item top      }    }  }  public void setHasPadding(boolean hasPadding) {    this.mHasPadding = hasPadding;  }}

public class MutiItemDecoration extends RecyclerView.ItemDecoration {  public enum Type {    VERTICAL, HORIZONTAL, ALL  }  private Type type;//分割线类型  private int dividerSize = 10;//分割线尺寸  public MutiItemDecoration(MutiItemDecoration.Type type, int dividerSize) {    this.type = type;    this.dividerSize = dividerSize;  }  @Override  public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {    int spanCount = getSpanCount(parent);    int childCount = parent.getAdapter().getItemCount();    switch (type) {      case ALL:        if (itemPosition % spanCount == 0) {//第一列          if (isLastRaw(parent, itemPosition, spanCount, childCount)) {            outRect.set(0, 0, dividerSize / 2, 0);          } else {            outRect.set(0, 0, dividerSize / 2, dividerSize);          }        } else if (itemPosition % spanCount == spanCount - 1) {//最后一列          if (isLastRaw(parent, itemPosition, spanCount, childCount)) {            outRect.set(dividerSize / 2, 0, 0, 0);          } else {            outRect.set(dividerSize / 2, 0, 0, dividerSize);          }        } else {//中间列          if (isLastRaw(parent, itemPosition, spanCount, childCount)) {            outRect.set(dividerSize / 2, 0, dividerSize / 2, 0);          } else {            outRect.set(dividerSize / 2, 0, dividerSize / 2, dividerSize);          }        }        break;      case VERTICAL:        if (isLastRaw(parent, itemPosition, spanCount, childCount)) {          outRect.set(0, 0, 0, 0);        } else {          outRect.set(0, 0, 0, dividerSize);        }        break;      case HORIZONTAL:        if (isLastColum(parent, itemPosition, spanCount, childCount)) {          outRect.set(0, 0, 0, 0);        } else {          outRect.set(0, 0, dividerSize, 0);        }        break;    }  }  // 是否是最后一列  private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) {    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      if ((pos + 1) % spanCount == 0)        return true;    } else {      if (pos == childCount - 1)        return true;    }    return false;  }  // 是否是最后一行  private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      childCount = childCount - childCount % spanCount;      if (pos >= childCount)        return true;    } else {      if (pos == childCount - 1)        return true;    }    return false;  }  //返回列数  private int getSpanCount(RecyclerView parent) {    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      return ((GridLayoutManager) layoutManager).getSpanCount();    }    return -1;  }}

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {  private static final int[] ATTRS = new int[]{android.R.attr.listDivider};  private Drawable mDivider;  public DividerGridItemDecoration(Context context) {    final TypedArray a = context.obtainStyledAttributes(ATTRS);    mDivider = ContextCompat.getDrawable(context, R.drawable.shape_divider);    a.recycle();  }  @Override  public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {    drawHorizontal(c, parent);    drawVertical(c, parent);  }  private int getSpanCount(RecyclerView parent) {    // 列数    int spanCount = -1;    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      spanCount = ((GridLayoutManager) layoutManager).getSpanCount();    } else if (layoutManager instanceof StaggeredGridLayoutManager) {      spanCount = ((StaggeredGridLayoutManager) layoutManager)          .getSpanCount();    }    return spanCount;  }  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          + mDivider.getIntrinsicWidth();      final int top = child.getBottom() + params.bottomMargin;      final int bottom = top + mDivider.getIntrinsicHeight();      mDivider.setBounds(left, top, right, bottom);      mDivider.draw(c);    }  }  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();      if (i % 2 == 1) {        final int top = child.getTop() - params.topMargin;        final int bottom = child.getBottom() + params.bottomMargin;        final int left = child.getLeft() - params.rightMargin;        final int right = left + mDivider.getIntrinsicWidth() / 2;        mDivider.setBounds(left, top, right, bottom);        mDivider.draw(c);      } else {        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() / 2;        mDivider.setBounds(left, top, right, bottom);        mDivider.draw(c);      }      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 boolean isLastColum(RecyclerView parent, int pos, int spanCount,                int childCount) {    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边      {        return true;      }    } else if (layoutManager instanceof StaggeredGridLayoutManager) {      int orientation = ((StaggeredGridLayoutManager) layoutManager)          .getOrientation();      if (orientation == StaggeredGridLayoutManager.VERTICAL) {        if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边        {          return true;        }      } else {        childCount = childCount - childCount % spanCount;        if (pos >= childCount)// 如果是最后一列，则不需要绘制右边          return true;      }    }    return false;  }  private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,               int childCount) {    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();    if (layoutManager instanceof GridLayoutManager) {      childCount = childCount - childCount % spanCount;      if (pos >= childCount)// 如果是最后一行，则不需要绘制底部        return true;    } else if (layoutManager instanceof StaggeredGridLayoutManager) {      int orientation = ((StaggeredGridLayoutManager) layoutManager)          .getOrientation();      // StaggeredGridLayoutManager 且纵向滚动      if (orientation == StaggeredGridLayoutManager.VERTICAL) {        childCount = childCount - childCount % spanCount;        // 如果是最后一行，则不需要绘制底部        if (pos >= childCount)          return true;      } else      // StaggeredGridLayoutManager 且横向滚动      {        // 如果是最后一行，则不需要绘制底部        if ((pos + 1) % spanCount == 0) {          return true;        }      }    }    return false;  }  @Override  public void getItemOffsets(Rect outRect, int itemPosition,                RecyclerView parent) {    int spanCount = getSpanCount(parent);    int childCount = parent.getAdapter().getItemCount();    if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部    {      outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);    } else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边    {      outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());    } else {      outRect.set(0, 0, mDivider.getIntrinsicWidth(),          mDivider.getIntrinsicHeight());    }  }}