[iOS开发]从 UIWebView 到 WKWebView

UIWebView自iOS2就有，WKWebView从iOS8才有，毫无疑问WKWebView将逐步取代笨重的UIWebView。通过简单的测试即可发现UIWebView占用过多内存，且内存峰值更是夸张。WKWebView网页加载速度也有提升，但是并不像内存那样提升那么多

WKWebView优势:
占用内存可能只有 UIWebView 的1/3~1/4
更多的支持HTML5的特性
官方宣称的高达60fps的滚动刷新率以及内置手势
Safari相同的JavaScript引擎
将UIWebViewDelegate与UIWebView拆分成了14类与3个协议(官方文档说明)
另外用的比较多的，增加加载进度属性:estimatedProgress

iOS网络—UIWebView、WKWebView使用详解

说下怎么使用增加加载进度属性estimatedProgress,直接上代码:

- (void)viewDidLoad {
[super viewDidLoad];
_webView = [[WKWebView alloc] initWithFrame:self.view.bounds];
_webView.UIDelegate = self;
_webView.navigationDelegate = self;
[self.view addSubview:_webView];

_progressView = [[UIProgressView alloc]initWithFrame:CGRectMake(0, 65, CGRectGetWidth(self.view.frame),2)];
[self.view addSubview:_progressView];

[_webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew| NSKeyValueObservingOptionOld context:nil];
[_webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]]];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
NSLog(@" %s,change = %@",__FUNCTION__,change);
if ([keyPath isEqual: @"estimatedProgress"] && object == _webView) {
    [self.progressView setAlpha:1.0f];
    [self.progressView setProgress:_webView.estimatedProgress animated:YES];
        if(_webView.estimatedProgress >= 1.0f)
        {
            [UIView animateWithDuration:0.3 delay:0.3 options:UIViewAnimationOptionCurveEaseOut animations:^{
                [self.progressView setAlpha:0.0f];
            } completion:^(BOOL finished) {
                [self.progressView setProgress:0.0f animated:NO];
            }];
        }
}
else {
    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
  }
}

- (void)dealloc {
[_webView removeObserver:self forKeyPath:@"estimatedProgress"];

// if you have set either WKWebView delegate also set these to nil here
[_webView setNavigationDelegate:nil];
[_webView setUIDelegate:nil];
}