原文地址:http://dwtedx.com/itshare_311.html
本Demo实现了Android类似于淘宝商品页展示的滑动效果(继续拖动,查看图文详情)、如果拖动了一半就会自动滑动到顶部、并带有动画效果、原理是通过两个ScrollView来实现的、上面的ScrollView放产品简介、下面的ScrollView放详细介绍、下面是应用简单的截图、具体效果大家可以下载源代码导入Eclipse查看
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;
}
} else if (state == AUTO_DOWN) {
mMoveLen += SPEED;
if (mMoveLen >= 0) {
mMoveLen = 0;
state = DONE;
mCurrentViewIndex = 0;
}
} else {
mTimer.cancel();
}
}
requestLayout();
}
};
重写dispatchTouchEvent方法
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
switch (ev.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
if (vt == null)
vt = VelocityTracker.obtain();
else
vt.clear();
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);
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 (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();
break;
case MotionEvent.ACTION_UP:
mLastY = ev.getY();
vt.addMovement(ev);
vt.computeCurrentVelocity(700);
// 获取Y方向的速度
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();
} catch (Exception e) {
e.printStackTrace();
}
break;
}
super.dispatchTouchEvent(ev);
return true;
}
ScrollViewContainer类有时会报错,在199行后面加上vt=null好像就没错误了!
Demo地址:http://download.youkuaiyun.com/detail/dodod2012/9451981