【Android进阶】Android仿淘宝商品浏览滑（拖）动查看详情界面

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