UIScrollView 节省空间

//
//  ViewController.m
//  MG货仓
//
//  Created by ＦＣ on 16/1/26.
//  Copyright © 2016年 fchl. All rights reserved.
//
#define WIDTH [UIScreen mainScreen].bounds.size.width
#define HEIGHT [UIScreen mainScreen].bounds.size.height

#import "ViewController.h"

@interface ViewController ()<UIScrollViewDelegate>
{
UICollectionView *_collectionView;

UIScrollView *_scrollView;
UIView       *_firstView;
UIView       *_secondView;
UIView       *_thirdView;

UIColor      *_color[5];

int  _count;
int  _index;
int  _currentType;

BOOL _isDecelerating;
}

- (void)createIndexView;
- (void)createFirstView;
- (void)createLastView;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];

_count = 5;
_index = 0;
_currentType = 0;
_scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT)];
_scrollView.delegate = self;
_scrollView.showsHorizontalScrollIndicator = NO;
_scrollView.showsVerticalScrollIndicator = NO;
_scrollView.directionalLockEnabled = YES;
_scrollView.pagingEnabled = YES;

_color[0] = [UIColor redColor];
_color[1] = [UIColor greenColor];
_color[2] = [UIColor blueColor];
_color[3] = [UIColor cyanColor];
_color[4] = [UIColor yellowColor];

[self.view addSubview:_scrollView];
[self createFirstView];

}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
CGFloat pageWidth = scrollView.frame.size.width;
int pageIndex = floor((scrollView.contentOffset.x - pageWidth/2)/pageWidth) + 1;
switch (_currentType) {
case 0:
{
_index = _index + pageIndex;
if (pageIndex == 1) {
[self createIndexView];
}
break;
}
case 1:
{
_index = _index + pageIndex - 1;
if (pageIndex == 0) {
[self createIndexView];
}
break;
}
case 2:
{
_index = _index + pageIndex - 1;
if (_index == 0) {
[self createFirstView];
}else if (_index == _count - 1){
[self createLastView];
}else{
[self createIndexView];
}
break;
}
default:
break;
}
NSLog(@"_index = %d",_index);
scrollView.userInteractionEnabled = YES;
}

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
{
scrollView.userInteractionEnabled = NO;
}

- (void)createIndexView
{
[_firstView removeFromSuperview];
[_secondView removeFromSuperview];
[_thirdView removeFromSuperview];

_firstView = [[UIView alloc] initWithFrame:CGRectMake(0, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_firstView];
_firstView.backgroundColor = _color[_index -1];

_secondView = [[UIView alloc] initWithFrame:CGRectMake(WIDTH, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_secondView];
_secondView.backgroundColor = _color[_index];

_thirdView = [[UIView alloc] initWithFrame:CGRectMake(WIDTH*2, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_thirdView];
_thirdView.backgroundColor = _color[_index + 1];

[_scrollView scrollRectToVisible:CGRectMake(WIDTH, 50, WIDTH, HEIGHT) animated:NO];
_scrollView.contentSize = CGSizeMake(WIDTH*3, HEIGHT);
_currentType = 2;
}

- (void)createLastView
{
[_firstView removeFromSuperview];
[_secondView removeFromSuperview];
[_thirdView removeFromSuperview];

_firstView = [[UIView alloc] initWithFrame:CGRectMake(0, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_firstView];
_firstView.backgroundColor = _color[_index - 1];

_secondView = [[UIView alloc] initWithFrame:CGRectMake(WIDTH, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_secondView];
_secondView.backgroundColor = _color[_index];

_scrollView.contentSize = CGSizeMake(WIDTH*2, H
9d93
EIGHT);
[_scrollView scrollRectToVisible:CGRectMake(WIDTH, 50, WIDTH, HEIGHT) animated:NO];
_currentType = 1;
}

- (void)createFirstView
{
[_firstView removeFromSuperview];
[_secondView removeFromSuperview];
[_thirdView removeFromSuperview];

_firstView = [[UIView alloc] initWithFrame:CGRectMake(0, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_firstView];
_firstView.backgroundColor = _color[_index];

_secondView = [[UIView alloc] initWithFrame:CGRectMake(WIDTH, 50, WIDTH, HEIGHT)];
[_scrollView addSubview:_secondView];
_secondView.backgroundColor = _color[_index + 1];

_scrollView.contentSize = CGSizeMake(WIDTH*2, HEIGHT);
[_scrollView scrollRectToVisible:CGRectMake(0, 50, WIDTH, HEIGHT) animated:NO];
_currentType = 0;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end