Android自定义滚动选择器实例代码

package com.linzihui.widget;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 java.util.ArrayList;import java.util.List;import java.util.Timer;import java.util.TimerTask;/** * 自定义滚动选择器 *  * @author cuiran * */@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, 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;  }  @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, 0, 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);  }}