一个KVO 实现WKWebView加载进度条的例子 （注意最后移除观察者）

//// ?OpenWebViewController.m// ?Treasure//// ?Created by 蓝蓝色信子 on 16/7/29.// ?Copyright ? 2016年 GY. All rights reserved.//#import "ZTOpenWebViewController.h"#import <WebKit/WebKit.h>@interface ZTOpenWebViewController ()<WKNavigationDelegate>//{// ???//网页视图// ???UIWebView * _webView;//}@property (strong, nonatomic) WKWebView *webView;@property (strong, nonatomic) UIProgressView *progressView;@end@implementation ZTOpenWebViewController- (void)viewDidLoad { ???[super viewDidLoad]; ???// ???//取消导航栏的影响 ???self.automaticallyAdjustsScrollViewInsets = NO; ???self.view.backgroundColor = [UIColor whiteColor]; ???????//[SVProgressHUD show]; ???//实例化 ???[self createWebView]; ???????[self creatCustomProgressView];}-(void)creatCustomProgressView{ ???????//增加加载进度条 ???// KVO，监听webView属性值得变化(estimatedProgress,title为特定的key) ???[_webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil]; ???[_webView addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:nil]; ???????// UIProgressView初始化 ???self.progressView = [[UIProgressView alloc] initWithProgressViewStyle:UIProgressViewStyleDefault]; ???self.progressView.frame = CGRectMake(0, 0, _webView.frame.size.width, 5); ???self.progressView.trackTintColor = [UIColor clearColor]; // 设置进度条的色彩 ???self.progressView.progressTintColor = [UIColor magentaColor]; ???// 设置初始的进度，防止用户进来就懵逼了（微信大概也是一开始设置的10%的默认值） ???[self.progressView setProgress:0.1 animated:YES]; ???[_webView addSubview:self.progressView];}- (void)viewWillAppear:(BOOL)animated{ ???[self.navigationController setNavigationBarHidden:NO animated:NO]; ???[super viewWillAppear:YES];}- (void)viewWillDisappear:(BOOL)animated{ ???[SVProgressHUD dismiss]; ???[super viewWillDisappear:animated];}- (void)createWebView{ ???_webView = [[WKWebView alloc]initWithFrame:self.view.bounds]; ???????[self.view addSubview:_webView]; ???????//调整适应比例 ???//_webView.scalesPageToFit = YES; ???//设置代理 ???_webView.navigationDelegate = self; ???[[NSURLCache sharedURLCache] removeAllCachedResponses]; ???[_webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:self.urlStr] cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10.0]]; ???}#pragma mark - WKWebView NavigationDelegate//WKNavigationDelegate- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler { ???//NSLog(@"是否允许这个导航"); ???decisionHandler(WKNavigationActionPolicyAllow);}- (void)webView:(WKWebView *)webView decidePolicyForNavigationResponse:(WKNavigationResponse *)navigationResponse decisionHandler:(void (^)(WKNavigationResponsePolicy))decisionHandler { ???// ???Decides whether to allow or cancel a navigation after its response is known. ???????//NSLog(@"知道返回内容之后，是否允许加载，允许加载"); ???decisionHandler(WKNavigationResponsePolicyAllow);}- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(null_unspecified WKNavigation *)navigation { ???//NSLog(@"开始加载"); ???//self.progress.alpha ?= 1; ???????//[SVProgressHUD show]; ???[UIApplication sharedApplication].networkActivityIndicatorVisible = YES; ???}- (void)webView:(WKWebView *)webView didReceiveServerRedirectForProvisionalNavigation:(null_unspecified WKNavigation *)navigation { ???//NSLog(@"跳转到其他的服务器"); ???}- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(null_unspecified WKNavigation *)navigation withError:(NSError *)error { ???//NSLog(@"网页由于某些原因加载失败"); ???//[SVProgressHUD dismiss]; ???//self.progress.alpha ?= 0; ???[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;}- (void)webView:(WKWebView *)webView didCommitNavigation:(null_unspecified WKNavigation *)navigation { ???//NSLog(@"网页开始接收网页内容");}- (void)webView:(WKWebView *)webView didFinishNavigation:(null_unspecified WKNavigation *)navigation { ???//NSLog(@"网页导航加载完毕"); ???//[SVProgressHUD dismiss]; ???[UIApplication sharedApplication].networkActivityIndicatorVisible = NO; ???????self.title = webView.title; ???[webView evaluateJavaScript:@"document.title" completionHandler:^(id _Nullable ss, NSError * _Nullable error) { ???????//NSLog(@"----document.title:%@---webView title:%@",ss,webView.title); ???}]; ???//self.progress.alpha ?= 0; ???}- (void)webView:(WKWebView *)webView didFailNavigation:(null_unspecified WKNavigation *)navigation withError:(NSError *)error { ???//NSLog(@"加载失败,失败原因:%@",[error description]); ???//self.progress.alpha = 0;}- (void)webViewWebContentProcessDidTerminate:(WKWebView *)webView { ???//NSLog(@"网页加载内容进程终止");}#pragma mark - KVO监听// 第三部：完成监听方法- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { ???????if ([object isEqual:_webView] && [keyPath isEqualToString:@"estimatedProgress"]) { // 进度条 ???????????????CGFloat newprogress = [[change objectForKey:NSKeyValueChangeNewKey] doubleValue]; ???????//NSLog(@"打印测试进度值：%f", newprogress); ???????????????if (newprogress == 1) { // 加载完成 ???????????// 首先加载到头 ???????????[self.progressView setProgress:newprogress animated:YES]; ???????????// 之后0.3秒延迟隐藏 ???????????__weak typeof(self) weakSelf = self; ???????????dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.3 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{ ???????????????????????????????weakSelf.progressView.hidden = YES; ???????????????[weakSelf.progressView setProgress:0 animated:NO]; ???????????}); ???????????????????} else { // 加载中 ???????????self.progressView.hidden = NO; ???????????[self.progressView setProgress:newprogress animated:YES]; ???????} ???} else if ([object isEqual:_webView] && [keyPath isEqualToString:@"title"]) { // 标题 ???????????????//self.title = _webView.title; ???} else { // 其他 ???????????????[super observeValueForKeyPath:keyPath ofObject:object change:change context:context]; ???}}-(void)dealloc{ ???NSLog(@"webVC dealloc = %@",self); ???[_webView removeObserver:self forKeyPath:@"estimatedProgress"]; ???[_webView removeObserver:self forKeyPath:@"title"];}- (void)didReceiveMemoryWarning { ???[super didReceiveMemoryWarning]; ???// Dispose of any resources that can be recreated.}/* #pragma mark - Navigation ?// In a storyboard-based application, you will often want to do a little preparation before navigation - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { // Get the new view controller using [segue destinationViewController]. // Pass the selected object to the new view controller. } */@end