引用的 https://www.jianshu.com/p/a436f5cec559
image.png
public class ItemGridDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private Drawable mDivider;
private int spanCount = -1;
//height width 单位为px
private int width = 5;
private Paint paint;
public ItemGridDecoration(Context context) {
init(context, width, android.R.color.black);
}
public ItemGridDecoration(Context context, int width) {
init(context, width, android.R.color.black);
}
public ItemGridDecoration(Context context, int width, int color) {
init(context, width, color);
}
private void init(Context context, int width, int color) {
this.width = width;
paint = new Paint();
paint.setColor(context.getResources().getColor(color));
final TypedArray a = context.obtainStyledAttributes(ATTRS);
mDivider = a.getDrawable(0);
a.recycle();
}
@Override
public void onDraw(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
drawHorizontal(c, parent);
drawVertical(c, parent);
}
@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
int position = parent.getChildAdapterPosition(view);
int childCount = parent.getAdapter().getItemCount();
int spanCount = getSpanCount(parent);
int drawRight = width;
int drawBottom = width;
int drawLeft = width;
int drawTop = width;
if (isLastRaw(parent, position, spanCount, childCount)) {
drawBottom = 0;
}
if (isFirstRaw(parent, position, spanCount, childCount)) {
drawTop = 0;
}
if (isLastColum(parent, position, spanCount, childCount)) {
drawRight = 0;
}
if (isFirstColum(parent, position, spanCount, childCount)) {
drawLeft = 0;
}
if (isLastItem(parent, position, childCount)) {
drawRight = 0;
}
outRect.set(drawLeft, drawTop, drawRight, drawBottom);
}
private void drawHorizontal(Canvas c, RecyclerView parent) {
spanCount = getSpanCount(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;
int right = child.getRight() + params.rightMargin;
final int top = child.getBottom() + params.bottomMargin;
// int bottom = top + mDivider.getIntrinsicHeight();
int bottom = top + width * 2;
if (isLastRaw(parent, i, spanCount, childCount)) {
// 如果是最后一行，则不需要绘制底部
bottom = top;
}
if (!isLastColum(parent, i, spanCount, childCount)) {
right = child.getRight() + params.rightMargin + width * 2;
}
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
c.drawRect(left, top, right, bottom, paint);
}
}
private void drawVertical(Canvas c, RecyclerView parent) {
spanCount = getSpanCount(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;
// int right = left + mDivider.getIntrinsicWidth();
int right = left + width * 2;
if (isLastColum(parent, i, spanCount, childCount)) {
// 如果是最后一列，则不需要绘制右边
right = left;
}
if (isLastItem(parent, i, childCount)) {
right = left;
}
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
c.drawRect(left, top, right, bottom, paint);
}
}
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;
}
private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if (childCount % spanCount == 0) {
childCount = childCount - spanCount;
} else {
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 {
// 如果是最后一行，则不需要绘制底部
if ((pos + 1) % spanCount == 0) {
return true;
}
}
}
return false;
}
private boolean isFirstRaw(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if (pos < spanCount) {
// 如果是第一行，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) {
if (pos < spanCount) {
// 如果是第一行，则不需要绘制底部
return true;
}
} else {
// 如果是第一行，则不需要绘制底部
if ((pos + 1) % spanCount == 1) {
return true;
}
}
}
return false;
}
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;
}
if ((pos + 1) % spanCount == 1 && childCount == 1) {// 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 isFirstColum(RecyclerView parent, int pos, int spanCount, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if ((pos + 1) % spanCount == 1) {
return true;
}
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();
if (orientation == StaggeredGridLayoutManager.VERTICAL) {
if ((pos + 1) % spanCount == 1) {
return true;
}
} else {
if (pos < spanCount) {
return true;
}
}
}
return false;
}
private boolean isLastItem(RecyclerView parent, int pos, int childCount) {
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
if ((pos + 1) == childCount) {
return true;
}
}
return false;
}
用法
recycleView.addItemDecoration(new ItemGridDecoration(this, dip2px(4), R.color.red));