如何给RecyclerView 添加不同的分割线:
UI出的效果图:
RecyclerView添加不同分割线.png
关键点:
自定义
ItemDecoration关键的方法:
RecyclerView的getChildAdapterPosition(View child)方法:
返回这个itemView 对应的 adapter position
这个adapter position 是适配器里的数据position 拿到了这个position,就能知道viewType 了
/**
* Return the adapter position that the given child view corresponds to.
*
* @param child Child View to query
* @return Adapter position corresponding to the given view or {@link #NO_POSITION}
*/
public int getChildAdapterPosition(View child) {
final ViewHolder holder = getChildViewHolderInt(child);
return holder != null ? holder.getAdapterPosition() : NO_POSITION;
}
code
public class DifWidthDecoration extends RecyclerView.ItemDecoration {
private Context mContext;
private Drawable mDividerWidth;
private Drawable mDividerNarrow;
private int mOrientation;
public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
public DifWidthDecoration(Context context, int oritation) {
this.mContext = context;
this.mOrientation = oritation;
this.mDividerWidth = context.getResources().getDrawable(R.drawable.divider_wider);
this.mDividerNarrow = context.getResources().getDrawable(R.drawable.divider_narrow);
setOrientation(oritation);
}
//设置屏幕方向
public void setOrientation(int orientation) {
if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
throw new IllegalArgumentException("invalid orientation");
}
this.mOrientation = orientation;
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
if (mOrientation == HORIZONTAL_LIST) {
//横向 list 画竖线
drawVerticalLine(c, parent, state);
} else if (mOrientation == VERTICAL_LIST) {
//竖向list 画横线
drawHorizontalLine(c, parent, state);
}
}
private static final String TAG = "DifWidthDecoration";
private void drawHorizontalLine(Canvas c, RecyclerView parent, RecyclerView.State state) {
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
final int childCount = parent.getChildCount();
int blankWidth = DisplayUtil.getScreenWidth(mContext) / 10;
Log.d(TAG, String.format("childCount -> %d", childCount));
//由于RecyclerViwe 复用ItemView 这里的childCount 是用户可见的 count
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
//接上面:所以要拿到itemView 对应的adapter position,但是方法的参数里不像getItemOffsets()里回调了View view
//所以 自己取到child 通过RecyclerView 的 getChildAdapterPosition(child) 来取到adapterPosition
//旧的写法 parent.getAdapter().getItemType(i) -> 会造成 分割线的错乱
int adapterPosition = parent.getChildAdapterPosition(child);
int type = parent.getAdapter().getItemViewType(adapterPosition);
if (type == DifferentDividerAdapter.item_type_group) {
//拿到child 的布局信息
final RecyclerView.LayoutParams params =
(RecyclerView.LayoutParams) child.getLayoutParams();
final int top = child.getBottom() + params.bottomMargin;
final int bottom = top + mDividerWidth.getIntrinsicHeight();
mDividerWidth.setBounds(left, top, right, bottom);
mDividerWidth.draw(c);
} else if (type == DifferentDividerAdapter.item_type_child) {
//拿到child 的布局信息
final RecyclerView.LayoutParams params =
(RecyclerView.LayoutParams) child.getLayoutParams();
final int top = child.getBottom() + params.bottomMargin;
final int bottom = top + mDividerNarrow.getIntrinsicHeight();
mDividerNarrow.setBounds(left + blankWidth, top, right, bottom);
mDividerNarrow.draw(c);
}
}
}
private void drawVerticalLine(Canvas c, RecyclerView parent, RecyclerView.State state) {
int top = parent.getPaddingTop();
int bottom = parent.getHeight() - parent.getPaddingBottom();
final int childCount = parent.getChildCount();
int blankWidth = DisplayUtil.getScreenWidth(mContext) / 10;
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
int adapterPosition = parent.getChildAdapterPosition(child);
int type = parent.getAdapter().getItemViewType(adapterPosition);
if (type == DifferentDividerAdapter.item_type_group) {
//拿到child 的布局信息
final RecyclerView.LayoutParams params =
(RecyclerView.LayoutParams) child.getLayoutParams();
final int left = child.getRight() + params.rightMargin;
final int right = left + mDividerWidth.getIntrinsicWidth();
mDividerWidth.setBounds(left, top, right, bottom);
mDividerWidth.draw(c);
} else if (type == DifferentDividerAdapter.item_type_child) {
//拿到child 的布局信息
final RecyclerView.LayoutParams params =
(RecyclerView.LayoutParams) child.getLayoutParams();
final int left = child.getRight() + params.rightMargin;
final int right = left + mDividerNarrow.getIntrinsicWidth();
mDividerNarrow.setBounds(left, top + blankWidth, right, bottom);
mDividerNarrow.draw(c);
}
}
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
int adapterPosition = parent.getChildAdapterPosition(view);
int type = parent.getAdapter().getItemViewType(adapterPosition);
if (mOrientation == HORIZONTAL_LIST) {
if (type == DifferentDividerAdapter.item_type_group) {
//画竖线 向右偏移divider 的宽度
outRect.set(0, 0, mDividerWidth.getIntrinsicWidth(), 0);
} else if (type == DifferentDividerAdapter.item_type_child) {
outRect.set(0, 0, mDividerWidth.getIntrinsicWidth(), 0);
}
} else if (mOrientation == VERTICAL_LIST) {
if (type == DifferentDividerAdapter.item_type_group) {
//画横线 向下偏移divider 的高度
outRect.set(0, 0, 0, mDividerWidth.getIntrinsicHeight());
} else if (type == DifferentDividerAdapter.item_type_child) {
outRect.set(0, 0, 0, mDividerNarrow.getIntrinsicHeight());
}
}
}
}
效果:
最终效果.png
注意:
onDrawOver() -> drawHorizontalLine(Canvas c, RecyclerView parent, RecyclerView.State state)这里:
final int childCount = parent.getChildCount();
由于RecyclerViwe 复用ItemView 这里的childCount 是用户可见的 count
所以最开始我这样取得itemType :
int type = parent.getAdapter().getItemVieType(i);
直接用遍历时的 i 作为了view 对应的adapter position,
是错误的,随着RecyclerView 的滑动,会造成Divider的错乱(具体表现为:向下移动,好奇的可以自试一下)
因为这个 i 是关于 childCount 的,而childCount 最多就是 屏幕上能展示出的itemView的个数
