Android墨迹3.0特性介绍效果实现——做一个滚动的Layout

墨迹天气新版的开机介绍很漂亮，上下滚动翻页，翻页结束后元素会有动画效果，分析一下动画元素都是基本的Animation，没有用到最新的属性动画；上下翻页滚动的控件android没有提供，只有横向的Viewpager，这里有一种实现->点击打开链接，用到了开源的控件ViewPager-Android，我们这里试着手动实现一个上下滚动的翻页控件。

前期准备

首先我们用apktool把墨迹天气的安装包解压出来，取出其中的图片资源和布局文件，一共4个布局

翻页控件实现

要实现自定义布局，需要继承ViewGroup，然后实现onMeasure、onLayout方法

@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		int count = getChildCount();
		int height = getMeasuredHeight();
		int top = 0;
		for (int i = 0; i < count; ++i) {
			View childView = getChildAt(i);
			if (childView.getVisibility() != View.GONE) {
				childView.layout(l, top, r, top + height);
				top += height;
			}
		}
		mTotalHeight = height * (count - 1);
		mTolerance = height / 2;
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		int count = getChildCount();
		for (int i = 0; i < count; ++i) {
			View childView = getChildAt(i);
			measureChild(childView, widthMeasureSpec, heightMeasureSpec);
		}
	}

这时候在如果在activity中将View inflate出来再通过addview添加到控件中就会看到第一页的内容，但此时还不能滑动。下面我们就来实现上下滑动翻页。

要响应控件上的手势操作需要实现onTouchEvent方法：

	@Override
	public boolean onTouchEvent(MotionEvent event) {

		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(event);

		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			if (!mScroller.isFinished()) {
				mScroller.abortAnimation();
			}
			mLastY = (int) event.getY();
			mStartYPosition = getScrollY();
			break;
		case MotionEvent.ACTION_MOVE:
			int y = (int) event.getY();
			int distance = mLastY - y;
			int scrollY = getScrollY();
			// 边界检查
			if (distance < 0 && scrollY + distance < 0) {
				distance = 0 - scrollY;
			} else if (distance > 0 && scrollY + distance > mTotalHeight) {
				distance = mTotalHeight - scrollY;
			}
			scrollBy(0, distance);
			mLastY = y;
			break;
		case MotionEvent.ACTION_UP:

			mEndYPosition = getScrollY();
			int posDiff = mEndYPosition - mStartYPosition;

			mVelocityTracker.computeCurrentVelocity(1000);
			int velocityY = (int) mVelocityTracker.getYVelocity();
			mVelocityTracker.recycle();
			mVelocityTracker = null;

			if (Math.abs(velocityY) >= 600 || Math.abs(posDiff) > mTolerance) {
				int dis = 0;
				if (posDiff > 0) {
					dis = getMeasuredHeight() - posDiff;
				} else if (posDiff < 0) {
					dis = -(getMeasuredHeight() + posDiff);
				}
				mScroller.startScroll(0, 0, 0, dis);
			} else {
				mScroller.startScroll(0, 0, 0, -posDiff);
			}

			postInvalidate();
			break;
		default:
			break;
		}

		return true;
	}

@Override
	public boolean onTouchEvent(MotionEvent event) {

		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			mLastY = (int) event.getY();
			break;
		case MotionEvent.ACTION_MOVE:
			int y = (int) event.getY();
			int distance = mLastY - y;
			scrollBy(0, distance);
			mLastY = y;
			break;
		case MotionEvent.ACTION_UP:
			break;
		default:
			break;
		}

		return true;
	}

		case MotionEvent.ACTION_MOVE:
			int y = (int) event.getY();
			int distance = mLastY - y;
			int scrollY = getScrollY();
			// 边界检查
			if (distance < 0 && scrollY + distance < 0) {
				distance = 0 - scrollY;
			} else if (distance > 0 && scrollY + distance > mTotalHeight) {
				distance = mTotalHeight - scrollY;
			}
			scrollBy(0, distance);
			mLastY = y;
			break;

	@Override
	public void computeScroll() {

		if (mScroller.computeScrollOffset()) {
			int scroll = mScroller.getCurrY();
			if (scroll > 0 && mEndYPosition + scroll > mTotalHeight) {
				scroll = mTotalHeight - mEndYPosition;
			} else if (scroll < 0 && mEndYPosition + scroll < 0) {
				scroll = -mEndYPosition;
			}
			scrollTo(0, mEndYPosition + scroll);
			mIsScrolling = true;
			postInvalidate();
		} else if (mIsScrolling) {
			if (mPageScrollListener != null) {
				int position = getScrollY() / getMeasuredHeight();
				if (position != mCurrentPage) {
					mCurrentPage = position;
					mPageScrollListener.onPageChanged(mCurrentPage);
				}
			}
			mIsScrolling = false;
		}
	}

滚动结束后要通知控件的使用者翻页已完成，所以定义一个翻页完成的接口

public void setOnPageScrollListener(OnPageScrollListener listener) {
		mPageScrollListener = listener;
	}

	public interface OnPageScrollListener {
		public void onPageChanged(int position);
	}

剩下的就是在activity中加载动画了，每当翻页结束就播放相应页面的动画并清除上一页的动画效果

class MyPageScrollListener implements OnPageScrollListener {

		@Override
		public void onPageChanged(int position) {
			switch (position) {
			case 0:
				layout1AnimStart();
				break;
			case 1:
				layout2AnimStart();
				break;
			case 2:
				layout3AnimStart();
				break;
			case 3:
				layout4AnimStart();
				break;
			}
		}

	}

代码在这里->http://download.csdn.net/detail/xu_fu/7185403

原文：http://blog.csdn.net/xu_fu/article/details/23208397