仿ViewPager效果二

1、采用ViewGroup实现

/**
 * 可以左右滑动切换屏幕的类
 * @author libin
 *
 */
public class ScrollLayout extends ViewGroup {
	private static final String TAG = "ScrollLayout";
	private Scroller mScroller;
	private VelocityTracker mVelocityTracker;
	private int mCurScreen;
	private int mDefaultScreen = 0;
	private static final int TOUCH_STATE_REST = 0;
	private static final int TOUCH_STATE_SCROLLING = 1;

	private static final int SNAP_VELOCITY = 600;
	private int mTouchState = TOUCH_STATE_REST;
	private int mTouchSlop;
	private float mLastMotionX;

	public ScrollLayout(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

	public ScrollLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		// TODO Auto-generated constructor stub
		mScroller = new Scroller(context);
		mCurScreen = mDefaultScreen;
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		if (changed) {
			int childLeft = 0;
			final int childCount = getChildCount();
			for (int i = 0; i < childCount; i++) {
				final View childView = getChildAt(i);
				if (childView.getVisibility() != View.GONE) {
					final int childWidth = childView.getMeasuredWidth();
					childView.layout(childLeft, 0, childLeft + childWidth,
							childView.getMeasuredHeight());
					childLeft += childWidth;
				}
			}
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		Log.e(TAG, "onMeasure");
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		final int width = MeasureSpec.getSize(widthMeasureSpec);

		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		if (widthMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only canmCurScreen run at EXACTLY mode!");
		}
		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		if (heightMode != MeasureSpec.EXACTLY) {
			throw new IllegalStateException(
					"ScrollLayout only can run at EXACTLY mode!");
		}
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}
		scrollTo(mCurScreen * width, 0);
	}

	/**
	 * * According to the position of current layout * scroll to the destination
	 * page.
	 */

	private void snapToDestination() {
		final int screenWidth = getWidth();
		final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
		snapToScreen(destScreen);
	}

	private void snapToScreen(int whichScreen) { // get the valid layout page
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		if (getScrollX() != (whichScreen * getWidth())) {
			final int delta = whichScreen * getWidth() - getScrollX();
			mScroller.startScroll(getScrollX(), 0, delta, 0,
					Math.abs(delta) * 2);
			mCurScreen = whichScreen;
			invalidate();
		}
	}

	public void setToScreen(int whichScreen) {
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		mCurScreen = whichScreen;
		scrollTo(whichScreen * getWidth(), 0);
	}

	public int getCurScreen() {
		return mCurScreen;
	}

	//在执行了invalidate()方法之后，程序便会执行computeScroll()方法
	@Override
	public void computeScroll() { 
		// 判断动画是否完成,返回true表示动画没有完成
		if (mScroller.computeScrollOffset()) {
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			postInvalidate();
		}
		Log.i(TAG, "computeScroll -- "+mScroller.getCurrX());
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(event);
		final int action = event.getAction();
		final float x = event.getX();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			Log.e(TAG, "event down!");
			//是否完成
			if (!mScroller.isFinished()) {
				mScroller.abortAnimation();
			}
			mLastMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			int deltaX = (int) (mLastMotionX - x);
			mLastMotionX = x;
			scrollBy(deltaX, 0);
			break;
		case MotionEvent.ACTION_UP:
			Log.e(TAG, "event : up");
			// if (mTouchState == TOUCH_STATE_SCROLLING) {
			final VelocityTracker velocityTracker = mVelocityTracker;
			velocityTracker.computeCurrentVelocity(1000);
			int velocityX = (int) velocityTracker.getXVelocity();//得到对应的速度值，大于0往做滑动，小于0往右
			Log.e(TAG, "velocityX:" + velocityX);

			if (velocityX > SNAP_VELOCITY && mCurScreen > 0) { //向左边
				Log.e(TAG, "snap left");
				snapToScreen(mCurScreen - 1);
			} else if (velocityX < -SNAP_VELOCITY
					&& mCurScreen < getChildCount() - 1) {
				// Fling enough to move right
				Log.e(TAG, "snap right");
				snapToScreen(mCurScreen + 1);
			} else {
				snapToDestination();
			}
			//回收
			if (mVelocityTracker != null) {
				mVelocityTracker.recycle();
				mVelocityTracker = null;
			}

			mTouchState = TOUCH_STATE_REST;
			break;
		case MotionEvent.ACTION_CANCEL:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return true;
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop);
		final int action = ev.getAction();
		if ((action == MotionEvent.ACTION_MOVE)
				&& (mTouchState != TOUCH_STATE_REST)) {
			return true;
		}
		final float x = ev.getX();
		switch (action) {
		case MotionEvent.ACTION_MOVE:
			final int xDiff = (int) Math.abs(mLastMotionX - x);
			if (xDiff > mTouchSlop) {
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;
		case MotionEvent.ACTION_DOWN:
			mLastMotionX = x;
			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
					: TOUCH_STATE_SCROLLING;
			break;
		case MotionEvent.ACTION_CANCEL:
		case MotionEvent.ACTION_UP:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return mTouchState != TOUCH_STATE_REST;
	}

}
           

2、继承HorizontalScrollView

public class MyScrollView extends HorizontalScrollView {
	private int subChildCount = 0;
	private ViewGroup firstChild = null;
	private int downX = 0;
	private int currentPage = 0;
	private ArrayList<Integer> pointList = new ArrayList<Integer>();

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

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

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

	private void init() {
		setHorizontalScrollBarEnabled(false);
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		receiveChildInfo();
	}

	public void receiveChildInfo() {

		firstChild = (ViewGroup) getChildAt(0);
		if (firstChild != null) {
			subChildCount = firstChild.getChildCount();
			for (int i = 0; i < subChildCount; i++) {
				if (((View) firstChild.getChildAt(i)).getWidth() > 0) {
					pointList.add(((View) firstChild.getChildAt(i)).getLeft());
				}
			}
		}

	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			downX = (int) ev.getX();
			break;
		case MotionEvent.ACTION_MOVE: {

		}
			break;
		case MotionEvent.ACTION_UP:
		case MotionEvent.ACTION_CANCEL: {
			if (Math.abs((ev.getX() - downX)) > getWidth() / 4) {
				if (ev.getX() - downX > 0) {
					smoothScrollToPrePage();
				} else {
					smoothScrollToNextPage();
				}
			} else {
				smoothScrollToCurrent();
			}
			return true;
		}
		}
		return super.onTouchEvent(ev);
	}

	private void smoothScrollToCurrent() {
		smoothScrollTo(pointList.get(currentPage), 0);
	}

	private void smoothScrollToNextPage() {
		if (currentPage < subChildCount - 1) {
			currentPage++;
			smoothScrollTo(pointList.get(currentPage), 0);
		}
	}

	private void smoothScrollToPrePage() {
		if (currentPage > 0) {
			currentPage--;
			smoothScrollTo(pointList.get(currentPage), 0);
		}
	}

	/**
	 * 下一页
	 */
	public void nextPage() {
		smoothScrollToNextPage();
	}

	/**
	 * 上一页
	 */
	public void prePage() {
		smoothScrollToPrePage();
	}

	/**
	 * 跳转到指定的页面
	 * 
	 * @param page
	 * @return
	 */
	public boolean gotoPage(int page) {
		if (page > 0 && page < subChildCount - 1) {
			smoothScrollTo(pointList.get(page), 0);
			currentPage = page;
			return true;
		}
		return false;
	}
}