Android仿淘宝商品拖动查看详情及标题栏渐变功能

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.widget.RelativeLayout;
import android.widget.ScrollView;

import java.util.Timer;
import java.util.TimerTask;

/**
 * 包含两个ScrollView的容器
 *
 */
public class ScrollViewContainer extends RelativeLayout {

 /**
  * 自动上滑
  */
 public static final int AUTO_UP = 0;
 /**
  * 自动下滑
  */
 public static final int AUTO_DOWN = 1;
 /**
  * 动画完成
  */
 public static final int DONE = 2;
 /**
  * 动画速度
  */
 public static final float SPEED = 8.5f;

 private boolean isMeasured = false;

 /**
  * 用于计算手滑动的速度
  */
 private VelocityTracker vt;

 private int mViewHeight;
 private int mViewWidth;

 private View topView;
 private View bottomView;

 private boolean canPullDown;
 private boolean canPullUp;
 private int state = DONE;

 /**
  * 记录当前展示的是哪个view，0是topView，1是bottomView
  */
 private int mCurrentViewIndex = 0;
 /**
  * 手滑动距离，这个是控制布局的主要变量
  */
 private float mMoveLen;
 private MyTimer mTimer;
 private float mLastY;
 /**
  * 用于控制是否变动布局的另一个条件，mEvents==0时布局可以拖拽了，mEvents==-1时可以舍弃将要到来的第一个move事件，
  * 这点是去除多点拖动剧变的关键
  */
 private int mEvents;
 boolean isTuninginterface=true;
 private Handler handler = new Handler() {

  @Override
  public void handleMessage(Message msg) {
   if (mMoveLen != 0) {
    if (state == AUTO_UP) {
     mMoveLen -= SPEED;
     if (mMoveLen <= -mViewHeight) {
      mMoveLen = -mViewHeight;
      state = DONE;
      mCurrentViewIndex = 1;
      if(isTuninginterface){
       isTuninginterface=false;
      }
     }
    } else if (state == AUTO_DOWN) {
     mMoveLen += SPEED;
     if (mMoveLen >= 0) {
      mMoveLen = 0;
      state = DONE;
      mCurrentViewIndex = 0;
     }
    } else {
     mTimer.cancel();
    }
   }
   requestLayout();
  }

 };

 public ScrollViewContainer(Context context) {
  super(context);
  init();
 }

 public ScrollViewContainer(Context context, AttributeSet attrs) {
  super(context, attrs);
  init();
 }

 public ScrollViewContainer(Context context, AttributeSet attrs, int defStyle) {
  super(context, attrs, defStyle);
  init();
 }

 private void init() {
  mTimer = new MyTimer(handler);
 }

 @Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
  switch (ev.getActionMasked()) {
   case MotionEvent.ACTION_DOWN:
    if (vt == null)
     vt = VelocityTracker.obtain();//获得VelocityTracker类实例
    else
     vt.clear();
    mLastY = ev.getY();
    System.out.println("---ACTION_DOWN-mLastY------"+ev.getY());
    vt.addMovement(ev);
    mEvents = 0;
    break;
   case MotionEvent.ACTION_POINTER_DOWN:
   case MotionEvent.ACTION_POINTER_UP:
    // 多一只手指按下或抬起时舍弃将要到来的第一个事件move，防止多点拖拽的bug
    mEvents = -1;
    break;
   case MotionEvent.ACTION_MOVE:
    vt.addMovement(ev);//将事件加入到VelocityTracker类实例中
    if (canPullUp && mCurrentViewIndex == 0 && mEvents == 0) {
     mMoveLen += (ev.getY() - mLastY);
     // 防止上下越界
     if (mMoveLen > 0) {
      mMoveLen = 0;
      mCurrentViewIndex = 0;
     } else if (mMoveLen < -mViewHeight) {
      mMoveLen = -mViewHeight;
      mCurrentViewIndex = 1;
      if(isTuninginterface){
       isTuninginterface=false;
      }
     }
     if (mMoveLen < -8) {
      // 防止事件冲突
      ev.setAction(MotionEvent.ACTION_CANCEL);
     }
    } else if (canPullDown && mCurrentViewIndex == 1 && mEvents == 0) {
     mMoveLen += (ev.getY() - mLastY);
     // 防止上下越界
     if (mMoveLen < -mViewHeight) {
      mMoveLen = -mViewHeight;
      mCurrentViewIndex = 1;
     } else if (mMoveLen > 0) {
      mMoveLen = 0;
      mCurrentViewIndex = 0;
     }
     if (mMoveLen > 8 - mViewHeight) {
      // 防止事件冲突
      ev.setAction(MotionEvent.ACTION_CANCEL);
     }
    } else
     mEvents++;
    mLastY = ev.getY();
    // requestLayout：当view确定自身已经不再适合现有的区域时，该view本身调用这个方法要求parent view重新调用他的onMeasure onLayout来对重新设置自己位置。
    requestLayout();
    break;
   case MotionEvent.ACTION_UP:
    mLastY = ev.getY();
    vt.addMovement(ev);
    //参数：units 你想要指定的得到的速度单位，如果值为1，代表1毫秒运动了多少像素。如果值为1000，代表 1秒内运动了多少像素
    vt.computeCurrentVelocity(700);
    // 获取Y方向的速度 可以通过getXVelocity()和getYVelocity()获得横向和竖向的速率
    float mYV = vt.getYVelocity();
    if (mMoveLen == 0 || mMoveLen == -mViewHeight)
     break;
    if (Math.abs(mYV) < 500) {
     // 速度小于一定值的时候当作静止释放，这时候两个View往哪移动取决于滑动的距离
     if (mMoveLen <= -mViewHeight / 2) {
      state = AUTO_UP;
     } else if (mMoveLen > -mViewHeight / 2) {
      state = AUTO_DOWN;
     }
    } else {
     // 抬起手指时速度方向决定两个View往哪移动
     if (mYV < 0)
      state = AUTO_UP;
     else
      state = AUTO_DOWN;
    }
    mTimer.schedule(2);
    try {
     vt.recycle();
     vt=null;
    } catch (Exception e) {
     e.printStackTrace();
    }
    break;

  }
  super.dispatchTouchEvent(ev);
  return true;
 }

 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
  topView.layout(0, (int) mMoveLen, mViewWidth,
    topView.getMeasuredHeight() + (int) mMoveLen);
  bottomView.layout(0, topView.getMeasuredHeight() + (int) mMoveLen,
    mViewWidth, topView.getMeasuredHeight() + (int) mMoveLen
      + bottomView.getMeasuredHeight());
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  if (!isMeasured) {
   isMeasured = true;
   mViewHeight = getMeasuredHeight();
   mViewWidth = getMeasuredWidth();
   System.out.println("======onMeasure====mViewHeight======"+mViewHeight);
   System.out.println("======onMeasure====mViewWidth======"+mViewWidth);
   topView = getChildAt(0);
   bottomView = getChildAt(1);
   bottomView.setOnTouchListener(bottomViewTouchListener);
   topView.setOnTouchListener(topViewTouchListener);
  }
 }

 private OnTouchListener topViewTouchListener = new OnTouchListener() {

  @Override
  public boolean onTouch(View v, MotionEvent event) {
   ScrollView sv = (ScrollView) v;
   Log.i("------getScrollY------", sv.getScrollY()+"");
   Log.i("------getMeasuredHeight---getChildAt---", sv.getChildAt(0).getMeasuredHeight()+"");
   Log.i("------getMeasuredHeight---sv---", sv.getMeasuredHeight()+"");
   if (sv.getScrollY() == (sv.getChildAt(0).getMeasuredHeight() - sv
     .getMeasuredHeight()) && mCurrentViewIndex == 0)
    canPullUp = true;
   else
    canPullUp = false;
   return false;
  }
 };
 private OnTouchListener bottomViewTouchListener = new OnTouchListener() {

  @Override
  public boolean onTouch(View v, MotionEvent event) {
   ScrollView sv = (ScrollView) v;
   if (sv.getScrollY() == 0 && mCurrentViewIndex == 1)
    canPullDown = true;
   else
    canPullDown = false;
   return false;
  }
 };

 class MyTimer {
  private Handler handler;
  private Timer timer;
  private MyTask mTask;

  public MyTimer(Handler handler) {
   this.handler = handler;
   timer = new Timer();
  }

  public void schedule(long period) {
   if (mTask != null) {
    mTask.cancel();
    mTask = null;
   }
   mTask = new MyTask(handler);
   timer.schedule(mTask, 0, period);
  }

  public void cancel() {
   if (mTask != null) {
    mTask.cancel();
    mTask = null;
   }
  }

  class MyTask extends TimerTask {
   private Handler handler;

   public MyTask(Handler handler) {
    this.handler = handler;
   }

   @Override
   public void run() {
    handler.obtainMessage().sendToTarget();
   }

  }
 }
}