背景：其实我们都知道，在我们做开发的过程中，会遇到Android 自身所带控件不够的情况，那么这个时候，就需要我们自定义控件，所以，也就造成了，在开发的过程中，我们一定要掌握好自定义控件，不然，当你去一家公司，产品萌妹子过来找你，这个效果很不错，问你能不能实现的时候，你难道能有理由说不行么，男人嘛，哪里能说不行了，直接用浑厚的声音告诉她，行，怎么不行，直接KO她。
一：多的不说，效果图，先走起
哎，请见谅，不会做那种动画的效果图
二：实例源码
（1）自定义控件
package com.pickerscrollview.views;import java.util.ArrayList;import java.util.List;import java.util.Timer;import java.util.TimerTask;import android.annotation.SuppressLint;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Paint.Align;import android.graphics.Paint.FontMetricsInt;import android.graphics.Paint.Style;import android.os.Handler;import android.os.Message;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import com.pickerscrollview.bean.Pickers;/** * 自定义滚动选择器 * * @author zengtao 2015年5月20日 下午7:36:03 * */@SuppressLint({ "HandlerLeak", "ClickableViewAccessibility" })public class PickerScrollView extends View {public static final String TAG = "PickerView";/** * text之间间距和minTextSize之比 */public static final float MARGIN_ALPHA = 2.8f;/** * 自动回滚到中间的速度 */public static final float SPEED = 2;private List<Pickers> mDataList;/** * 选中的位置，这个位置是mDataList的中心位置，一直不变 */private int mCurrentSelected;private Paint mPaint;private float mMaxTextSize = 20;private float mMinTextSize = 10;private float mMaxTextAlpha = 255;private float mMinTextAlpha = 120;private int mColorText = 0x333333;private int mViewHeight;private int mViewWidth;private float mLastDownY;/** * 滑动的距离 */private float mMoveLen = 0;private boolean isInit = false;private onSelectListener mSelectListener;private Timer timer;private MyTimerTask mTask;Handler updateHandler = new Handler() {@Overridepublic void handleMessage(Message msg) {if (Math.abs(mMoveLen) < SPEED) {mMoveLen = 0;if (mTask != null) {mTask.cancel();mTask = null;performSelect();}} else// 这里mMoveLen / Math.abs(mMoveLen)是为了保有mMoveLen的正负号，以实现上滚或下滚mMoveLen = mMoveLen – mMoveLen / Math.abs(mMoveLen) * SPEED;invalidate();}};public PickerScrollView(Context context) {super(context);init();}public PickerScrollView(Context context, AttributeSet attrs) {super(context, attrs);init();}public void setOnSelectListener(onSelectListener listener) {mSelectListener = listener;}private void performSelect() {if (mSelectListener != null)mSelectListener.onSelect(mDataList.get(mCurrentSelected));}public void setData(List<Pickers> datas) {mDataList = datas;mCurrentSelected = datas.size() / 2;invalidate();}/** * 选择选中的item的index * * @param selected */public void setSelected(int selected) {mCurrentSelected = selected;int distance = mDataList.size() / 2 – mCurrentSelected;if (distance < 0)for (int i = 0; i < -distance; i++) {moveHeadToTail();mCurrentSelected–;}else if (distance > 0)for (int i = 0; i < distance; i++) {moveTailToHead();mCurrentSelected++;}invalidate();}/** * 选择选中的内容 * * @param mSelectItem */public void setSelected(String mSelectItem) {for (int i = 0; i < mDataList.size(); i++)if (mDataList.get(i).equals(mSelectItem)) {setSelected(i);break;}}private void moveHeadToTail() {Pickers head = mDataList.get(0);mDataList.remove(0);mDataList.add(head);}private void moveTailToHead() {Pickers tail = mDataList.get(mDataList.size() – 1);mDataList.remove(mDataList.size() – 1);mDataList.add(0, tail);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);mViewHeight = getMeasuredHeight();mViewWidth = getMeasuredWidth();// 按照View的高度计算字体大小mMaxTextSize = mViewHeight / 8.0f;mMinTextSize = mMaxTextSize / 2f;isInit = true;invalidate();}private void init() {timer = new Timer();mDataList = new ArrayList<Pickers>();mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mPaint.setStyle(Style.FILL);mPaint.setTextAlign(Align.CENTER);mPaint.setColor(mColorText);}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);// 根据index绘制viewif (isInit)drawData(canvas);}private void drawData(Canvas canvas) {// 先绘制选中的text再往上往下绘制其余的textfloat scale = parabola(mViewHeight / 4.0f, mMoveLen);float size = (mMaxTextSize – mMinTextSize) * scale + mMinTextSize;mPaint.setTextSize(size);mPaint.setAlpha((int) ((mMaxTextAlpha – mMinTextAlpha) * scale + mMinTextAlpha));// text居中绘制，注意baseline的计算才能达到居中，y值是text中心坐标float x = (float) (mViewWidth / 2.0);float y = (float) (mViewHeight / 2.0 + mMoveLen);FontMetricsInt fmi = mPaint.getFontMetricsInt();float baseline = (float) (y – (fmi.bottom / 2.0 + fmi.top / 2.0));int indexs = mCurrentSelected;String textData = mDataList.get(indexs).getShowConetnt();canvas.drawText(textData, x, baseline, mPaint);// 绘制上方datafor (int i = 1; (mCurrentSelected – i) >= 0; i++) {drawOtherText(canvas, i, -1);}// 绘制下方datafor (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++) {drawOtherText(canvas, i, 1);}}/** * @param canvas * @param position *距离mCurrentSelected的差值 * @param type *1表示向下绘制，-1表示向上绘制 */private void drawOtherText(Canvas canvas, int position, int type) {float d = (float) (MARGIN_ALPHA * mMinTextSize * position + type* mMoveLen);float scale = parabola(mViewHeight / 4.0f, d);float size = (mMaxTextSize – mMinTextSize) * scale + mMinTextSize;mPaint.setTextSize(size);mPaint.setAlpha((int) ((mMaxTextAlpha – mMinTextAlpha) * scale + mMinTextAlpha));float y = (float) (mViewHeight / 2.0 + type * d);FontMetricsInt fmi = mPaint.getFontMetricsInt();float baseline = (float) (y – (fmi.bottom / 2.0 + fmi.top / 2.0));int indexs = mCurrentSelected + type * position;String textData = mDataList.get(indexs).getShowConetnt();canvas.drawText(textData, (float) (mViewWidth / 2.0), baseline, mPaint);}/** * 抛物线 * * @param zero *零点坐标 * @param x *偏移量 * @return scale */private float parabola(float zero, float x) {float f = (float) (1 – Math.pow(x / zero, 2));return f < 0 ? 0 : f;}@Overridepublic boolean onTouchEvent(MotionEvent event) {switch (event.getActionMasked()) {case MotionEvent.ACTION_DOWN:doDown(event);break;case MotionEvent.ACTION_MOVE:doMove(event);break;case MotionEvent.ACTION_UP:doUp(event);break;}return true;}private void doDown(MotionEvent event) {if (mTask != null) {mTask.cancel();mTask = null;}mLastDownY = event.getY();}private void doMove(MotionEvent event) {mMoveLen += (event.getY() – mLastDownY);if (mMoveLen > MARGIN_ALPHA * mMinTextSize / 2) {// 往下滑超过离开距离moveTailToHead();mMoveLen = mMoveLen – MARGIN_ALPHA * mMinTextSize;} else if (mMoveLen < -MARGIN_ALPHA * mMinTextSize / 2) {// 往上滑超过离开距离moveHeadToTail();mMoveLen = mMoveLen + MARGIN_ALPHA * mMinTextSize;}mLastDownY = event.getY();invalidate();}private void doUp(MotionEvent event) {// 抬起手后mCurrentSelected的位置由当前位置move到中间选中位置if (Math.abs(mMoveLen) < 0.0001) {mMoveLen = 0;return;}if (mTask != null) {mTask.cancel();mTask = null;}mTask = new MyTimerTask(updateHandler);timer.schedule(mTask, 0, 10);}class MyTimerTask extends TimerTask {Handler handler;public MyTimerTask(Handler handler) {this.handler = handler;}@Overridepublic void run() {handler.sendMessage(handler.obtainMessage());}}public interface onSelectListener {void onSelect(Pickers pickers);}}
（2）实体类风不懂云的漂泊，天不懂雨的落魄，眼不懂泪的懦弱，
