[iOS学习]WKWebView类的学习

WKWebView是在iOS8中发布的新的Web视图，旨在替换iOS中的UIWebView和macOS中的WebView。WKWebView很好的解决了UIWebView的内存占用大和加载速度慢的问题。

WKWebView可以加载本地HTML代码或者网络资源

//加载网络资源时我们一般采用的是异步的加载方式，则使用以下这个方法来加载：
//该方法需要的参数是NSURLRequest对象，必须要严格遵守某种协议
//日常上网的时候我们会把网址前的http://给省略，这个就是HTTP协议，在这里绝对不能省略
//由于采用异步请求加载网络资源，所以还要实现相应的WKNavigationDelegate委托协议。请求加载网络资源的不用阶段会触发委托对象不同的方法
- (nullable WKNavigation *)loadRequest:(NSURLRequest *)request;

//加载本地资源一般用同步方式，数据可以来源于本地文件或者是硬编码的的HTML字符串，相关方法如下：
//只用这两个方法时，我们需要注意字符集问题，而采用什么字符集取决于HTML文件
- (nullable WKNavigation *)loadHTMLString:(NSString *)string baseURL:(nullable NSURL *)baseURL;

- (nullable WKNavigation *)loadData:(NSData *)data MIMEType:(NSString *)MIMEType characterEncodingName:(NSString *)characterEncodingName baseURL:(NSURL *)baseURL API_AVAILABLE(macosx(10.11), ios(9.0));

下面这个案例展示了WKWebView的三种方法的用法，我通过三个按钮改变三种加载方式

#import "ViewController.h"
#import 

@interface ViewController ()

@property(nonatomic,strong)WKWebView *webView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    CGRect screen = [UIScreen mainScreen].bounds;
    
    ///按钮栏
    //按钮栏宽度
    CGFloat buttonBarWidth = 316;
    UIView *buttonBar = [[UIView alloc]initWithFrame:CGRectMake((screen.size.width - buttonBarWidth)/2, 20, buttonBarWidth, 30)];
    [self.view addSubview:buttonBar];
    
    ///添加LoadHTMLString按钮
    UIButton *buttonLoadHTMLString = [UIButton buttonWithType:UIButtonTypeSystem];
    [buttonLoadHTMLString setTitle:@"LoadHTMLString" forState:UIControlStateNormal];
    buttonLoadHTMLString.frame = CGRectMake(0, 0, 117, 30);
    [buttonLoadHTMLString addTarget:self action:@selector(testLoadHTMLString:) forControlEvents:UIControlEventTouchUpInside];
    [buttonBar addSubview:buttonLoadHTMLString];
    
    ///添加LoadData按钮
    UIButton *buttonLoadData = [UIButton buttonWithType:UIButtonTypeSystem];
    [buttonLoadData setTitle:@"LoadData" forState:UIControlStateNormal];
    buttonLoadData.frame = CGRectMake(137, 0, 67, 30);
    [buttonLoadData addTarget:self action:@selector(testLoadData:) forControlEvents:UIControlEventTouchUpInside];
    [buttonBar addSubview:buttonLoadData];
    
    ///添加LoadRequest按钮
    UIButton *buttonLoadRequest = [UIButton buttonWithType:UIButtonTypeSystem];
    [buttonLoadRequest setTitle:@"LoadRequest" forState:UIControlStateNormal];
    buttonLoadRequest.frame = CGRectMake(224, 0, 92, 30);
    [buttonLoadRequest addTarget:self action:@selector(testLoadRequest:) forControlEvents:UIControlEventTouchUpInside];
    [buttonBar addSubview:buttonLoadRequest];
    
    //添加WKWebView
    self.webView = [[WKWebView alloc]initWithFrame:CGRectMake(0, 60, screen.size.width, screen.size.height - 80)];
    
    [self.view addSubview:self.webView];
    
}

- (void)testLoadHTMLString:(id)sender{
    NSString *htmlPath = [[NSBundle mainBundle] pathForResource:@"index.html" ofType:nil];
    NSURL *bundleURl = [NSURL fileURLWithPath:[[NSBundle mainBundle] bundlePath]];
    NSError *error = nil;
    
    NSString *html = [[NSString alloc]initWithContentsOfFile:htmlPath encoding:NSUTF8StringEncoding error:&error];
    if (error == nil) {
        [self.webView loadHTMLString:html baseURL:bundleURl];
    }
}

- (void)testLoadData:(id)sender{
    NSString *htmlPath = [[NSBundle mainBundle] pathForResource:@"index.html" ofType:nil];
    NSURL *bundleUrl = [NSURL fileURLWithPath:[[NSBundle mainBundle]bundlePath]];
    NSData *htmlData = [[NSData alloc]initWithContentsOfFile:htmlPath];
    
    [self.webView loadData:htmlData MIMEType:@"text/html" characterEncodingName:@"UTF-8" baseURL:bundleUrl];
}

- (void)testLoadRequest:(id)sender{
    NSURL *url = [NSURL URLWithString:@"https://www.baidu.com"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    [self.webView loadRequest:request];
    self.webView.navigationDelegate = self;
}

#pragma mark - WKNavigationDelegate委托协议
//开始加载时调用
- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(null_unspecified WKNavigation *)navigation{
    NSLog(@"开始加载");
}
//当内容开始返回时调用
- (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation{
    NSLog(@"开始返回内容");
}
//加载完成后调用
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{
    NSLog(@"加载完成");
}
//加载失败的时候调用
- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation withError:(NSError *)error{
    NSLog(@"加载失败 error:%@",error.description);
}

@end

在iOS9中Xcode引入了新的特性，在LoadRequest方法中请求网络资源时，必须使用HTTPS协议，但是很多情况下我们所访问的都是HTTP协议，所以需要去Info.plist文件中修改属性。如下图所示修改：

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