android viewpager不可左滑

public class CanotSlidingViewpager extends ViewPager {    private float mLastMotionX;    private float  x;    public CanotSlidingViewpager(Context context, AttributeSet attrs) {        super(context, attrs);        // TODO Auto-generated constructor stub    }    public CanotSlidingViewpager(Context context) {        super(context);    }    @Override    public boolean dispatchTouchEvent(MotionEvent ev) {        // TODO Auto-generated method stub        switch (ev.getAction()) {            case MotionEvent.ACTION_DOWN:                x = ev.getX();                break;            case MotionEvent.ACTION_MOVE:                mLastMotionX = ev.getX() - x;                if(mLastMotionX>0){                    return true;                }

                break;        }        return super.dispatchTouchEvent(ev);    }}