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() { 
 
    @Override 
    public 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); 
  } 
 
  @Override 
  protected 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); 
  } 
 
  @Override 
  protected void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 
    // 根据index绘制view 
    if (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text 
    float 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data 
    for (int i = 1; (mCurrentSelected - i) >= 0; i++) { 
      drawOtherText(canvas,i,-1); 
    } 
    // 绘制下方data 
    for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++) { 
      drawOtherText(canvas,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),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; 
  } 
 
  @Override 
  public 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,10); 
  } 
 
  class MyTimerTask extends TimerTask { 
    Handler handler; 
 
    public MyTimerTask(Handler handler) { 
      this.handler = handler; 
    } 
 
    @Override 
    public void run() { 
      handler.sendMessage(handler.obtainMessage()); 
    } 
 
  } 
 
  public interface onSelectListener { 
    void onSelect(Pickers pickers); 
  } 
} 

package com.pickerscrollview.bean; 
 
import java.io.Serializable; 
 
/** 
 * 
 * @author zengtao 2015年5月20日下午7:18:14 
 * 
 */ 
public class Pickers implements Serializable { 
 
  private static final long serialVersionUID = 1L; 
 
  private String showConetnt; 
  private String showId; 
 
  public String getShowConetnt() { 
    return showConetnt; 
  } 
 
  public String getShowId() { 
    return showId; 
  } 
 
  public Pickers(String showConetnt,String showId) { 
    super(); 
    this.showConetnt = showConetnt; 
    this.showId = showId; 
  } 
 
  public Pickers() { 
    super(); 
  } 
 
} 

package com.pickerscrollview.ui; 
 
import java.util.ArrayList; 
import java.util.List; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.RelativeLayout; 
 
import com.pickerscrollview.bean.Pickers; 
import com.pickerscrollview.views.PickerScrollView; 
import com.pickerscrollview.views.PickerScrollView.onSelectListener; 
 
/** 
 * 主界面 
 * 
 * @author zengtao 2015年5月20日 下午7:36:03 
 * 
 */ 
public class MainActivity extends Activity { 
 
  private Button bt_scrollchoose; // 滚动选择器按钮 
  private PickerScrollView pickerscrlllview; // 滚动选择器 
  private List<Pickers> list; // 滚动选择器数据 
  private String[] id; 
  private String[] name; 
 
  private Button bt_yes; // 确定按钮 
  private RelativeLayout picker_rel; // 选择器布局 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
 
    initView(); 
    initLinstener(); 
    initData(); 
  } 
 
  /** 
   * 初始化 
   */ 
  private void initView() { 
    bt_scrollchoose = (Button) findViewById(R.id.bt_scrollchoose); 
    picker_rel = (RelativeLayout) findViewById(R.id.picker_rel); 
    pickerscrlllview = (PickerScrollView) findViewById(R.id.pickerscrlllview); 
    bt_yes = (Button) findViewById(R.id.picker_yes); 
  } 
 
  /** 
   * 设置监听事件 
   */ 
  private void initLinstener() { 
    bt_scrollchoose.setonClickListener(onClickListener); 
    pickerscrlllview.setonSelectListener(pickerListener); 
    bt_yes.setonClickListener(onClickListener); 
  } 
 
  /** 
   * 初始化数据 
   */ 
  private void initData() { 
    list = new ArrayList<Pickers>(); 
    id = new String[] { "1","2","3","4","5","6" }; 
    name = new String[] { "中国银行","农业银行","招商银行","工商银行","建设银行","民生银行" }; 
    for (int i = 0; i < name.length; i++) { 
      list.add(new Pickers(name[i],id[i])); 
    } 
    // 设置数据，默认选择第一条 
    pickerscrlllview.setData(list); 
    pickerscrlllview.setSelected(0); 
  } 
 
  // 滚动选择器选中事件 
  onSelectListener pickerListener = new onSelectListener() { 
 
    @Override 
    public void onSelect(Pickers pickers) { 
      System.out.println("选择：" + pickers.getShowId() + "--银行：" 
          + pickers.getShowConetnt()); 
    } 
  }; 
 
  // 点击监听事件 
  OnClickListener onClickListener = new OnClickListener() { 
 
    @Override 
    public void onClick(View v) { 
      if (v == bt_scrollchoose) { 
        picker_rel.setVisibility(View.VISIBLE); 
      } else if (v == bt_yes) { 
        picker_rel.setVisibility(View.GONE); 
      } 
    } 
  }; 
} 

UIBarButtonItem *doneBarButtonItem=[[UIBarButtonItem alloc] init];
doneBarButtonItem.title=@"Done";
self.navigationItem.rightBarButtonItem = doneBarButtonItem;
[doneBarButtonItem release];

解决方法

UIBarButtonItem *buttonHello = [[UIBarButtonItem alloc] initWithTitle:@"Say Hello"     
    style:UIBarButtonItemStyleBordered target:self action:@selector(sayHello:)];

[buttonHello setTarget:self];
[buttonHello setAction:@selector(sayHello:)];

- (IBAction)sayHello:(id)sender
{
    // code here
}