Day9

1 UIScrollView 与 delegate的通讯

   1.1 用户开始拖拽时，调用scrollViewWillBeginDragging

   1.2 具体滚动到某个位置，调用scrollViewDidScroll

   1.3 调用scrollViewDidEndDragging:willDecelerate 

(1) 声明协议 <UIScrollViewDelegate>

(2) 设置代理

(3) 实现对应的方法

//
//  ViewController.m
//  
//
//  Created by xin on 15-4-4.
//  Copyright (c) 2015年 Jackey. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property (weak, nonatomic) IBOutlet UIButton *lastContent;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    CGFloat height = CGRectGetMaxY(self.lastContent.frame)+44.f;
    self.scrollView.contentSize = CGSizeMake(0, height);
    
    //声明协议
    self.scrollView.delegate = self;
}

//设置代理
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    //实现方法
    NSLog(@"start dragging");
}


@end

　　

2 用户使用捏合手势时调用

  viewForZoomingInScrollView

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    CGFloat height = CGRectGetMaxY(self.lastContent.frame)+44.f;
    self.scrollView.contentSize = CGSizeMake(0, height);
    
    //声明协议
    self.scrollView.delegate = self;
    
    //定义缩放的范围
    self.scrollView.maximumZoomScale = 2.f;
    self.scrollView.minimumZoomScale = .5f;
}

//返回uiview
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    return self.imageView;
}

　　

3 pageControl 的2个属性

self.pageControl.numberOfPages = ImageCount;
self.pageControl.currentPage = pageNum;

4 scrollView的图片滚动需要注意的点

// 让动画一页一页的效果
    self.scrollView.pagingEnabled = YES;


-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    CGPoint offSet = self.scrollView.contentOffset;
    CGFloat offsetX = offSet.x;
    CGFloat width = self.scrollView.frame.size.width;
    //加多0.5width，提前预判
    int pageNum = (offsetX + 0.5f * width) / width ;
    
    self.pageControl.currentPage = pageNum;
}

所有的code

//
//  ViewController.m
//  scrollPicture
//
//  Created by xin on 15/4/7.
//  Copyright (c) 2015年 Jackey. All rights reserved.
//

#import "ViewController.h"
#define ImageCount 5

@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property (weak, nonatomic) IBOutlet UIPageControl *pageControl;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    CGFloat width = self.scrollView.bounds.size.width;
    CGFloat height = self.scrollView.bounds.size.height;
    //image draw
    for (int i=0; i<ImageCount+1; i++) {
        UIImageView *imageView = [[UIImageView alloc]init];
        CGFloat imageX = (i-1)*width;
        imageView.frame = CGRectMake(imageX, 0.f, width, height);
        imageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"img_%02d",i]];
        [self.scrollView addSubview:imageView];
        
    }
    
    self.scrollView.contentSize = CGSizeMake((ImageCount*width), 0);
    // 让动画一页一页的效果
    self.scrollView.pagingEnabled = YES;
    self.scrollView.delegate = self;
    self.pageControl.numberOfPages = ImageCount;
    
}

#pragma mark - UIScrollViewDelegate实现方法
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    CGPoint offSet = self.scrollView.contentOffset;
    CGFloat offsetX = offSet.x;
    CGFloat width = self.scrollView.frame.size.width;
    //加多0.5width，提前预判
    int pageNum = (offsetX + 0.5f * width) / width ;
    
    self.pageControl.currentPage = pageNum;
}


@end

　　

4 NSTimer

//usage
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.f target:self selector:@selector(nextPage) userInfo:nil repeats:YES];

//invalidate
[self.timer invalidate];
    self.timer =  nil;

　上面的写法会引发冲突，如果存在其它的dragging事件

所以

self.timer = [NSTimer timerWithTimeInterval:1.f target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];