import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

public class MultiViewGroup1 extends ViewGroup {
	private Context mContext;
	private static String TAG = "MultiViewGroup";
	public int curScreen = 0;

	public void PageChage(int index) {

	}

	/*
	 * 获取当前界面
	 */
	public int getCurScreen() {
		return curScreen;
	}

	/*
	 * 设置当前界面
	 */
	public void setCurScreen(int curScreen) {
		//this.curScreen = curScreen;
		snapToScreen(curScreen);
	}

	private Scroller mScroller = null;
	private static final int TOUCH_STATE_REST = 0;
	private static final int TOUCH_STATE_SCROLLING = 1;
	private int mTouchState = TOUCH_STATE_REST;

	public static int SNAP_VELOCITY = 600;
	private int mTouchSlop = 0;
	private float mLastionMotionX = 0;
	private float mLastMotionY = 0;

	private VelocityTracker mVelocityTracker = null;

	public MultiViewGroup1(Context context) {
		super(context);
		mContext = context;
		init();
	}

	public MultiViewGroup1(Context context, AttributeSet attrs) {
		super(context, attrs);
		mContext = context;
		init();
	}

	private void init() {
		mScroller = new Scroller(mContext);
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
	}

	public void moveToLeftSide() {
		if (curScreen >= getChildCount() - 1) {
			return;
		}

		curScreen++;
		mScroller.startScroll((curScreen - 1) * getWidth(), 0, getWidth(), 0, 3000);
		scrollTo(curScreen * getWidth(), 0);
		invalidate();
		PageChage(curScreen);
	}

	public void moveToRightSide() {
		if (curScreen <= 0) {
			return;
		}
		curScreen--;
		mScroller.startScroll((curScreen + 1) * getWidth(), 0, -getWidth(), 0, 3000);
		scrollTo(curScreen * getWidth(), 0);
		invalidate();
		PageChage(curScreen);
	}

	public void stopMove() {

		if (mScroller != null) {
			if (!mScroller.isFinished()) {
				int scrollCurX = mScroller.getCurrX();
				// calculate destination screen
				int descScreen = (scrollCurX + getWidth() / 2) / getWidth();
				mScroller.abortAnimation();
				scrollTo(descScreen * getWidth(), 0);
				mScroller.forceFinished(true);
				curScreen = descScreen;
			}
		}
	}

	@Override
	public void computeScroll() {
		// TODO Auto-generated method stub
		if (mScroller.computeScrollOffset()) {
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			postInvalidate();
		}
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		// TODO Auto-generated method stub

		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(mLastionMotionX - x);
			if (xDiff > mTouchSlop) {
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;

		case MotionEvent.ACTION_DOWN:
			mLastionMotionX = 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;
	}

	public boolean onTouchEvent(MotionEvent event) {

		// TODO Auto-generated method stub
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}

		mVelocityTracker.addMovement(event);
		super.onTouchEvent(event);

		float x = event.getX();
		float y = event.getY();

		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN:
			if (mScroller != null) {
				if (!mScroller.isFinished()) {
					mScroller.abortAnimation();
				}
			}

			mLastionMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			int deltaX = (int) (mLastionMotionX - x);
			int deltaY = (int) (mLastMotionY - y);

			if (Math.abs(deltaX) < Math.abs(deltaY)) {
				break;
			}
			scrollBy(deltaX, 0);

			mLastionMotionX = x;
			break;
		case MotionEvent.ACTION_UP:
			final VelocityTracker velocityTracker = mVelocityTracker;
			velocityTracker.computeCurrentVelocity(1000);
			int velocityX = (int) velocityTracker.getXVelocity();

			if (velocityX > SNAP_VELOCITY && curScreen > 0) {
				// Fling enough to move left
				snapToScreen(curScreen - 1);
			} else if (velocityX < -SNAP_VELOCITY && curScreen < (getChildCount() - 1)) {
				snapToScreen(curScreen + 1);
			} else {
				snapToDestination();
			}

			if (mVelocityTracker != null) {
				mVelocityTracker.recycle();
				mVelocityTracker = null;
			}
			mTouchState = TOUCH_STATE_REST;
			break;
		case MotionEvent.ACTION_CANCEL:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return true;
	}

	private void snapToDestination() {
		int scrollX = getScrollX();
		int scrollY = getScrollY();
		int destScreen = (getScrollX() + getWidth() / 2) / getWidth();
		snapToScreen(destScreen);
	}

	// 滑动到相应的View
	private void snapToScreen(int whichScreen) {
		
		
		//Log.i(TAG, curScreen+" "+whichScreen+" "+flag);
		
		if (whichScreen > getChildCount() - 1)
			whichScreen = getChildCount() - 1;
		
		boolean flag = curScreen != whichScreen;
		curScreen = whichScreen;

		int dx = curScreen * getWidth() - getScrollX();

		mScroller.startScroll(getScrollX(), 0, dx, 0, Math.abs(dx) * 2);
		invalidate();
		//如果界面变化，就执行
		if (flag) {
			PageChage(curScreen);
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

		int width = MeasureSpec.getSize(widthMeasureSpec);
		int height = MeasureSpec.getSize(heightMeasureSpec);
		setMeasuredDimension(width, height);

		int childCount = getChildCount();
		for (int i = 0; i < childCount; i++) {
			View child = getChildAt(i);
			child.measure(getWidth(), height);
		}
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		// TODO Auto-generated method stub
		int startLeft = 0;
		int startTop = 0;
		int childCount = getChildCount();

		for (int i = 0; i < childCount; i++) {
			View child = getChildAt(i);

			if (child.getVisibility() != View.GONE)
				child.layout(startLeft, startTop, startLeft + getWidth(), startTop + getHeight());

			startLeft = startLeft + getWidth();
		}
	}
}