组件作用为类似ViewPager但直接插视图的横向滚动容器。
修改自：http://blog.csdn.net/yaoyeyzq/article/details/7571940
在该组件基础上修正了滚动速度，使其匹配ViewPager的滚动速度，以下为代码：
import android.content.Context; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.widget.Scroller; /** * @author */ public class ScrollLayout extends ViewGroup { private static final int MAX_SETTLE_DURATION = 600; // ms private Scroller mScroller; private VelocityTracker mVelocityTracker; /** * 当前的屏幕位置 */ private int mCurScreen; /** * 设置默认屏幕的属性，0表示第一个屏幕 */ private int mDefaultScreen = 0; /** * 标识滚动操作已结束 */ private static final int TOUCH_STATE_REST = 0; /** * 标识正在执行滑动操作 */ private static final int TOUCH_STATE_SCROLLING = 1; /** * 标识滑动速率 */ private static final int SNAP_VELOCITY = 600; /** * 当前滑动状态 */ private int mTouchState = TOUCH_STATE_REST; /** * 在用户触发ontouch事件之前,我们认为用户能够使view滑动的距离（像素） */ private int mTouchSlop; /** * 手指触碰屏幕的最后一次x坐标 */ private float mLastMotionX; /** * 手指触碰屏幕的最后一次y坐标 */ @SuppressWarnings("unused") private float mLastMotionY; public ScrollLayout(Context context) { super(context); mScroller = new Scroller(context); mCurScreen = mDefaultScreen; mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); } public ScrollLayout(Context context, AttributeSet attrs) { super(context, attrs); mScroller = new Scroller(context); mCurScreen = mDefaultScreen; mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); } public ScrollLayout(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); 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) { 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); } // 初始化视图的位置 scrollTo(mCurScreen * width, 0); } /** * 根据滑动的距离判断移动到第几个视图 */ public void snapToDestination(int velocity) { final int screenWidth = getWidth(); final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth; snapToScreen(destScreen, velocity); } /** * 滚动到制定的视图 * * @param whichScreen 视图下标 */ public void snapToScreen(int whichScreen, int velocity) { whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1)); if (getScrollX() != (whichScreen * getWidth())) { final int delta = whichScreen * getWidth() - getScrollX(); // 计算duration int width = getWidth(); int halfWidth = width / 2; float distanceRatio = Math.min(1f, 1.0f * Math.abs(delta) / width); float distance = halfWidth + halfWidth * distanceInfluenceForSnapDuration(distanceRatio); int duration = 4 * Math.round(1000 * Math.abs(distance / Math.abs(velocity))); duration = Math.min(duration, MAX_SETTLE_DURATION); // 开始滚动 mScroller.startScroll(getScrollX(), 0, delta, 0, duration); 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; } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { scrollTo(mScroller.getCurrX(), mScroller.getCurrY()); postInvalidate(); } } @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: 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: final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000); int velocityX = (int) velocityTracker.getXVelocity(); if (velocityX > SNAP_VELOCITY && mCurScreen > 0) { // 向左移动 snapToScreen(mCurScreen - 1, velocityX); } else if (velocityX < -SNAP_VELOCITY && mCurScreen < getChildCount() - 1) { // 向右移动 snapToScreen(mCurScreen + 1, velocityX); } else { snapToDestination(velocityX); } if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } mTouchState = TOUCH_STATE_REST; break; case MotionEvent.ACTION_CANCEL: mTouchState = TOUCH_STATE_REST; break; } return true; } float distanceInfluenceForSnapDuration(float f) { f -= 0.5f; // center the values about 0. f *= 0.3f * Math.PI / 2.0f; return (float) Math.sin(f); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { final int action = ev.getAction(); if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) { return true; } final float x = ev.getX(); final float y = ev.getY(); 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; mLastMotionY = y; 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; } }