UIScroView 3倍的contentSize，左右Scroll时，懒惰加载View

UIScroView 3倍的contentSize，左右Scroll时，懒惰添加左右的View

用途：分段加载数据

 

定义枚举：

typedefenum {



    ViewPositionLeft = 101,



    ViewPositionCenter,



    ViewPositionRight



} ViewPosition;

 

变量定义：

    NSInteger _currnetPage;



    CGRect _leftFrame;



    CGRect _centerFrame;



    CGRect _rightFrame;



    UIScrollView *_sv;

 

初始化变量：

-(void)createView



{



 



    _currnetPage = 0;



    



    _sv = [[UIScrollView alloc] init];



    _sv.frame = CGRectMake(0, 0, 320, 424);



    _sv.pagingEnabled = YES;



    _sv.backgroundColor = [UIColorwhiteColor];



    _sv.contentSize = CGSizeMake(_sv.frame.size.width*3, _sv.frame.size.height);



    



    _sv.showsHorizontalScrollIndicator = YES;



    _sv.showsVerticalScrollIndicator = NO;



 



    



    for (int i = 2; i > -1; i--) {



        CGRect frame;



        frame.origin.x = _sv.frame.size.width * (2 - i);



        frame.origin.y = 0;



        frame.size = _sv.frame.size;



        



        UIView *lbl = [selfcreateLabeViewWithCurrentPage:i];



        lbl.frame = frame;



        



        if (i == 2) {



            _leftFrame = frame;



            lbl.tag = ViewPositionLeft;



            



        }



        if (i == 1) {



            _centerFrame = frame;



            lbl.tag = ViewPositionCenter;



        }



        if (i == 0) {



            _rightFrame = frame;



            lbl.tag = ViewPositionRight;



        }



        



        



        [_sv addSubview:lbl];



        



        



    }



    _sv.delegate = self;            



    



    [_svscrollRectToVisible:_rightFrameanimated:NO];



    



    [self.view addSubview:_sv];



}

 

创建新View的方法（selfcreateLabeViewWithCurrentPage）：

- (UIView *)createLabeViewWithCurrentPage:(int)Page



{



    



    UILabel *textView = [[UILabel alloc] init];



    textView.text = [NSString stringWithFormat:@"Page %d",Page];



    textView.font = [UIFont systemFontOfSize:38];



    textView.textColor = [UIColor blackColor];



    textView.backgroundColor = [UIColorwhiteColor];



    textView.textAlignment = UITextAlignmentCenter;



 



    [_sv addSubview:textView];



    return textView;



}



UIScrollViewDelegate方法：



- (void)scrollViewDidEndDecelerating:(UIScrollView *)sv



{



    



    



    BOOL towardsToLeft = NO;



    CGFloat width = _sv.frame.size.width;



    



    if (_sv.contentOffset.x == width) {



        if (_currnetPage == 0) {



            _currnetPage++;



        }



        



        return;



    }



    if (_sv.contentOffset.x > width) {



        towardsToLeft = YES;



        if(_currnetPage == 0){



//            NSLog(@"currentPage = 0;  向左");



            return;



        }



//        NSLog(@"向左");



    }



    else{



//        NSLog(@"向右");



    }



    



    



//    _previousPage = _currnetPage;



    if (towardsToLeft == YES) {



        _currnetPage--;



    }



    else{



        _currnetPage++;



    }



    



    



    if (_currnetPage == 0) {



        



        



    }



    else  {



        [sv scrollRectToVisible:_centerFrameanimated:NO];



        UIView *view = [_sv viewWithTag:_currnetPage];



        view.frame = _centerFrame;



        



        if (towardsToLeft == YES) {



            UIView *viewRLeft = [_sv viewWithTag:ViewPositionLeft];



            [viewRLeft removeFromSuperview];



            



            UIView *viewRCenter = [_sv viewWithTag:ViewPositionCenter];



            viewRCenter.frame = _leftFrame;



            viewRCenter.tag = ViewPositionLeft;



            



            UIView *viewRRight = [_sv viewWithTag:ViewPositionRight];



            viewRRight.frame = _centerFrame;



            viewRRight.tag = ViewPositionCenter;



            



            UIView *viewRight = [self createLabeViewWithCurrentPage:_currnetPage - 1];



            viewRight.frame = _rightFrame;



            viewRight.tag = ViewPositionRight;



            [sv addSubview:viewRight];



        }



        else{



            UIView *viewRRight = [_sv viewWithTag:ViewPositionRight];



            [viewRRight removeFromSuperview];



            



            UIView *viewRCenter = [_sv viewWithTag:ViewPositionCenter];



            viewRCenter.frame = _rightFrame;



            viewRCenter.tag = ViewPositionRight;



            



            UIView *viewRLeft = [_sv viewWithTag:ViewPositionLeft];



            viewRLeft.frame = _centerFrame;



            viewRLeft.tag = ViewPositionCenter;



            



            UIView *viewLeft = [self createLabeViewWithCurrentPage:_currnetPage + 1];



            viewLeft.frame = _leftFrame;



            viewLeft.tag = ViewPositionLeft;



            [sv addSubview:viewLeft];



            



            



            



        }



    }



 



}



 

 

 希望对用到的朋友有用。