实现原理使用LinearSnalphelper实现元素居中（如果对SnapHelper不了解的话建议百度下），使用ViewType实现偏移。
具体效果：
实现：
package com.david.mytest.test.wheeltest;
import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.support.annotation.Nullable; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.LinearSnapHelper; import android.support.v7.widget.RecyclerView; import android.util.AttributeSet; import android.util.TypedValue; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView;
import com.david.mytest.R; import com.david.mytest.ui.pulltorefresh.pulltorefreshorigin.progress.Utils;
import java.util.ArrayList; import java.util.List;
/** * Created by wb-cuiweixing on 2016/7/5. */ public class RecyclerWheelView extends RecyclerView { public interface OnSelectListener{ void onSelect(int position); }
private ArrayList<String> mData; private int mOffset = 2;//默认每页显示五条 private float mItemHeight; private int mWidth; private LinearLayoutManager mManager; private LinearSnapHelper mSnapHelper; private OnSelectListener mOnSelectListener; public RecyclerWheelView(Context context) { super(context); initData(); } public RecyclerWheelView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); initData(); } public RecyclerWheelView(Context context, @Nullable AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initData(); } private void initData() { mData = new ArrayList<>(); mItemHeight = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 45, getResources().getDisplayMetrics()); mManager = new LinearLayoutManager(getContext()); mManager.setOrientation(LinearLayoutManager.VERTICAL); if (null == paint) { paint = new Paint(); paint.setColor(Color.parseColor("#83cde6")); paint.setStrokeWidth(Utils.dp2px(getResources(), 1f)); } post(new Runnable() { @Override public void run() {//RecyclerView还未初始化完成不能直接调用其方法否则会报空指针，类构造方法中只能进行初始化成员变量 getLayoutParams().height = (int) (mItemHeight * (mOffset * 2 + 1)); setLayoutManager(mManager); setAdapter(new MySpaceAdapter()); getAdapter().notifyDataSetChanged(); mWidth = getWidth(); } }); mSnapHelper = new LinearSnapHelper(); mSnapHelper.attachToRecyclerView(this); } public ArrayList<String> getData() { if (mData.size() < 1) { return null; } ArrayList<String> data = new ArrayList<>(); for (int i = 1; i < mData.size() - 1; i++) { data.add(mData.get(i)); } return data; } public void setData(ArrayList<String> data) { this.mData.clear(); this.mData.addAll(data); mData.add(0, null); mData.add(null); if (getAdapter() != null) getAdapter().notifyDataSetChanged(); } private List<TextView> textViews; /** * RecyclerView实现WheelView */ class MySpaceAdapter extends RecyclerView.Adapter { MySpaceAdapter() { textViews = new ArrayList<>(); } @Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { if (viewType == 1) { return new SpaceViewHolder(new View(getContext())); } else { View view = LayoutInflater.from(getContext()).inflate(R.layout.item_recycler_wheel, parent, false); textViews.add((TextView) view); return new NormalViewHolder(view); } } @Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { if (holder instanceof NormalViewHolder) { TextView textView = ((NormalViewHolder) holder).mText; textView.setText(mData.get(position)); } } @Override public int getItemCount() { return mData.size(); } @Override public int getItemViewType(int position) { return (position == 0 || position == mData.size() - 1) ? 1 : 0; } } class NormalViewHolder extends RecyclerView.ViewHolder { TextView mText; NormalViewHolder(View itemView) { super(itemView); mText = (TextView) itemView; mText.getLayoutParams().height = (int) mItemHeight; } } class SpaceViewHolder extends RecyclerView.ViewHolder { SpaceViewHolder(View itemView) { super(itemView); //根据每一条高度及偏移量设置高度 float height = mOffset * mItemHeight; itemView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, (int) height)); } } @Override protected void onScrollChanged(int l, int t, int oldl, int oldt) { super.onScrollChanged(l, t, oldl, oldt); /** * 手动滑动或者惯性滑动时触发该方法，不过由于本身没有滑动所以l,t,oldl,oldt都是0 * 此处只是在滑动时设置相应状态 */ View viewContainer = mSnapHelper.findSnapView(mManager);//获取中间位置的view TextView textView = ((NormalViewHolder) getChildViewHolder(viewContainer)).mText; int centerPosition = mData.indexOf(textView.getText().toString()); if (mCenterPosition == centerPosition) { return; } mCenterPosition = centerPosition; for (TextView view : textViews) {//设置选中颜色 view.setTextColor(Color.parseColor("#dddddd")); if (view == textView) { view.setTextColor(Color.parseColor("#0288ce")); } } if (mOnSelectListener != null) { //第一条是占位条 mOnSelectListener.onSelect(mCenterPosition - 1); } } private int mCenterPosition;//获取选中位置时要减一（有占位条） private Paint paint; /** * 获取选中区域的边界 */ private int[] selectedAreaBorder; private int[] obtainSelectedAreaBorder() { if (null == selectedAreaBorder) { selectedAreaBorder = new int[2]; selectedAreaBorder[0] = (int) (mItemHeight * mOffset); selectedAreaBorder[1] = (int) (mItemHeight * (mOffset + 1)); } return selectedAreaBorder; } @Override public void onDraw(Canvas c) { super.onDraw(c); c.drawLine(mWidth * 1.0F / 6, obtainSelectedAreaBorder()[0], mWidth * 5 / 6, obtainSelectedAreaBorder()[0], paint); c.drawLine(mWidth * 1.0F / 6, obtainSelectedAreaBorder()[1], mWidth * 5 / 6, obtainSelectedAreaBorder()[1], paint); } public void setmOnSelectListener(OnSelectListener mOnSelectListener) { this.mOnSelectListener = mOnSelectListener; }}
一般是用点击确定后获取选中位置，OnSelectListener是在滑动选中时执行的。
