iOS 加载webView进度条

简介##

为了项目的敏捷性和简单性,现在的app常常会嵌入不少的H5页面,而如何优雅的显示这些web页面呢,我这里参照微信显示web页面的方式,做了一个导航栏下的加载进度条.因为项目最低支持iOS7,所以不能使用WKWebView来加载网页,只能使用 UIWebView,查看 UIWebView的API可以发现,并没有代理或是通知告诉我们webView加载了多少,所以这个进度条我决定用虚拟的方式来做,就是假装知道加载了多少.

加载WebView的控制器WYWebController

@interface WYWebController : UIViewController

@property (nonatomic, copy) NSString *url;

@end


#import "WLWebController.h"
#import "WLWebProgressLayer.h"
#import "UIView+Frame.h"

@interface WLWebController ()<UIWebViewDelegate>

@end

@implementation WLWebController
{
    UIWebView *_webView;
    
    WLWebProgressLayer *_progressLayer; ///< 网页加载进度条
}

- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor whiteColor];
    [self setupUI];
}

- (void)setupUI {
    _webView = [[UIWebView alloc] initWithFrame:self.view.bounds];
    _webView.delegate = self;
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:self.url]];
    [_webView loadRequest:request];
    
    _webView.backgroundColor = [UIColor whiteColor];
    
    _progressLayer = [WLWebProgressLayer new];
    _progressLayer.frame = CGRectMake(0, 42, SCREEN_WIDTH, 2);
    
    [self.navigationController.navigationBar.layer addSublayer:_progressLayer];
    [self.view addSubview:_webView];
}

#pragma mark - UIWebViewDelegate
/// 网页开始加载
- (void)webViewDidStartLoad:(UIWebView *)webView {
    [_progressLayer startLoad];
}

/// 网页完成加载
- (void)webViewDidFinishLoad:(UIWebView *)webView {
    [_progressLayer finishedLoad];

// 获取h5的标题
    self.title = [webView stringByEvaluatingJavaScriptFromString:@"document.title"];
    
}

/// 网页加载失败
- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
    [_progressLayer finishedLoad];
}

- (void)dealloc {
    
    [_progressLayer closeTimer];
    [_progressLayer removeFromSuperlayer];
    _progressLayer = nil;
    NSLog(@"i am dealloc");
}

@end

进度条WYWebProgressLayer.h

#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width

@interface WYWebProgressLayer : CAShapeLayer

- (void)finishedLoad;
- (void)startLoad;

- (void)closeTimer;

@end

WYWebProgressLayer.m这个类主要继承自CAShapeLayer,这里我主要想要使用CAShaperLayer的strokeStart[默认0]和strokeEnd[默认1]这两个属性来对进度条进行渲染,使用定时器更改strokeEnd的值使其看起来就像在一点一点的加载一样.

#import "WYWebProgressLayer.h"
#import "NSTimer+addition.h"

static NSTimeInterval const kFastTimeInterval = 0.003;

@implementation WYWebProgressLayer {
   CAShapeLayer *_layer;
   
   NSTimer *_timer;
   CGFloat _plusWidth; ///< 增加点
}

- (instancetype)init {
   if (self = [super init]) {
       [self initialize];
   }
   return self;
}

- (void)initialize {
   self.lineWidth = 2;
   self.strokeColor = [UIColor greenColor].CGColor;
   
   _timer = [NSTimer scheduledTimerWithTimeInterval:kFastTimeInterval target:self selector:@selector(pathChanged:) userInfo:nil repeats:YES];
   [_timer pause];
   
   UIBezierPath *path = [UIBezierPath bezierPath];
   [path moveToPoint:CGPointMake(0, 2)];
   [path addLineToPoint:CGPointMake(SCREEN_WIDTH, 2)];
   
   self.path = path.CGPath;
   self.strokeEnd = 0;
   _plusWidth = 0.01;
}

- (void)pathChanged:(NSTimer *)timer {
   self.strokeEnd += _plusWidth;
   
   if (self.strokeEnd > 0.8) {
       _plusWidth = 0.002;
   }
}

- (void)startLoad {
   [_timer resumeWithTimeInterval:kFastTimeInterval];
}

- (void)finishedLoad {
   [self closeTimer];
   
   self.strokeEnd = 1.0;
   dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.25 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
       self.hidden = YES;
       [self removeFromSuperlayer];
   });
}

- (void)dealloc {
//    NSLog(@"progressView dealloc");
   [self closeTimer];
}

#pragma mark - private
- (void)closeTimer {
   [_timer invalidate];
   _timer = nil; 
}

Demo:https://github.com/wangyansnow/WYWebViewDemo

如何放到项目中用##

只需要下载demo,然后把demo中的整个web文件夹拖入到项目中,使用方式例:

WYWebController *webVC = [WYWebController new];
webVC.url = @"https://www.baidu.com";
[self.navigationController pushViewController:webVC animated:YES];