iOS UI入门——Objective-C和Swift下UIPageControl的使用

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UIPageControl就是我们常说的小白点，常用于轮播图，与UIScrollView一起使用。效果如图：

Objective-C代码：

#import "ViewController.h"

@interface ViewController ()<UIScrollViewDelegate>

@property(nonatomic,strong) UIScrollView * scrollView;
@property(nonatomic,strong) UIPageControl * pageControl;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.view.backgroundColor = [UIColor whiteColor];
    [self setupView];
}

-(void)setupView{

    [self.view addSubview:self.scrollView];
    [self.view addSubview:self.pageControl];
    for (int i = 0; i < 4; i ++) {
        UIView * view = [[UIView alloc] initWithFrame:CGRectMake(self.view.frame.size.width*i, 0, self.view.frame.size.width, self.view.frame.size.height)];
        if (i == 0) {
            view.backgroundColor = [UIColor orangeColor];
        }else if (i == 1){
            view.backgroundColor = [UIColor yellowColor];
        }else if (i == 2){
            view.backgroundColor = [UIColor magentaColor];
        }else{
            view.backgroundColor = [UIColor cyanColor];
        }
        [self.scrollView addSubview:view];
    }
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    //设置当前显示的小点的索引
    self.pageControl.currentPage = scrollView.contentOffset.x/self.view.frame.size.width;
}

-(UIScrollView *)scrollView{
    if (!_scrollView) {
        _scrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
        _scrollView.contentSize = CGSizeMake(self.view.frame.size.width*4, self.view.frame.size.height);
        _scrollView.showsHorizontalScrollIndicator = NO;
        _scrollView.pagingEnabled = YES;
        _scrollView.delegate = self;
    }
    return _scrollView;
}

-(UIPageControl *)pageControl{
    if (!_pageControl) {
        //初始化
        _pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, self.view.frame.size.height - 80, self.view.frame.size.width, 20)];
        //设置总数量，一般与ScrollView的页数相同
        _pageControl.numberOfPages = 4;
        //设置不是当前页的小点颜色
        _pageControl.pageIndicatorTintColor = [UIColor whiteColor];
        //设置当前页的小点颜色
        _pageControl.currentPageIndicatorTintColor = [UIColor redColor];
    }
    return _pageControl;
}

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

@end

Swift代码：

import UIKit

class ViewController: UIViewController,UIScrollViewDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        self.setupView()
    }

    func setupView() {
        self.view.addSubview(self.scrollView)
        self.view.addSubview(self.pageControl)
        let viewSize = self.view.frame.size

        for i in 0...3 {
            let view = UIView.init(frame: CGRect.init(x:viewSize.width*CGFloat(i), y: 0, width: viewSize.width, height: viewSize.height))
            if i == 0{
                view.backgroundColor = UIColor.orange
            }else if i == 1{
                view.backgroundColor = UIColor.yellow
            }else if i == 2{
                view.backgroundColor = UIColor.magenta
            }else{
                view.backgroundColor = UIColor.cyan
            }
            self.scrollView.addSubview(view)
        }
    }

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        //设置当前显示的小点的索引
        self.pageControl.currentPage = Int(self.scrollView.contentOffset.x/self.view.frame.size.width)
    }

    lazy var scrollView: UIScrollView = {
        let sc = UIScrollView.init(frame: self.view.frame)
        sc.contentSize = CGSize.init(width: self.view.frame.size.width*4, height: self.view.frame.size.height)
        sc.showsHorizontalScrollIndicator = false
        sc.isPagingEnabled = true
        sc.delegate = self
        return sc
    }()

    lazy var pageControl: UIPageControl = {
        //初始化
        let page = UIPageControl.init(frame: CGRect.init(x: 0, y: self.view.frame.size.height - 80, width: self.view.frame.size.width, height: 20))
        //设置总数量，一般与ScrollView的页数相同
        page.numberOfPages = 4
        //设置不是当前页的小点颜色
        page.pageIndicatorTintColor = UIColor.white
        //设置当前页的小点颜色
        page.currentPageIndicatorTintColor = UIColor.red
        return page
    }()

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}