如果没有互联网连接，如何加载本地 html 文件

Question

我的应用中有许多 uiwebview，它们显示托管在服务器上的 html 文件。如果没有互联网连接，我还想拥有将显示的 html 文件的本地副本，但我不明白该怎么做。我拥有的 .m 文件与下面类似。

目前uiwebview 将显示远程托管页面（在下面的“contact.html”示例中。有谁能解释如果没有可用的互联网，我如何加载文件的本地副本？

#import "ContactMeViewController.h"
@interface ContactMeViewController ()
@end
@implementation ContactMeViewController
- (void)viewDidLoad
{
NSString *urlAddress = @"http://www.domain.co.nz/apppages/contact.html";
    //Create a URL object.
NSURL *url = [NSURL URLWithString:urlAddress];
    //URL Request Object
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
    //Load the request in the UIWebView.
[webview loadRequest:requestObj];
webview.scalesPageToFit = YES;
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
@end

我已按如下方式更新了 .m 文件，但得到一个没有互联网连接的空白屏幕，而不是本地文件加载：

#import "ContactMeViewController.h"
@interface ContactMeViewController (UIWebViewDelegate)
@end
@implementation ContactMeViewController
- (void)viewDidLoad
{
NSString *urlAddress = @"http://www.kuranimarsters.co.nz/apppages/contact.html";

//Create a URL object.
NSURL *url = [NSURL URLWithString:urlAddress];

//URL Request Object
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];

//Load the request in the UIWebView.
[webview loadRequest:requestObj];
webview.scalesPageToFit = YES;
}
-(void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
if (-1009 == kCFURLErrorNotConnectedToInternet) {
    // if we can identify the error i.e, no internet connection
    [self loadHtmlFile];
}
}
-(void)loadHtmlFile
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"contact.html"];
NSString *content = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:NULL];

NSString* htmlString = [NSString stringWithContentsOfFile:content encoding:NSUTF8StringEncoding error:nil];
[webview loadHTMLString:htmlString baseURL:nil];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
@end

Answer 1

为UIWebView 应用代理并在-(void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error 中加载本地html 文件。

默认情况下，如果有互联网 -(void)webViewDidFinishLoad:(UIWebView *)webView，将被执行，您将看到按照 URL 的页面。

Answer 2

您可以将html文件的数据作为.html文件存储到应用程序的文档目录中，并在下次使用该文件加载webview，例如

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *filePath = [NSString stringWithFormat:@"%@/%@", [paths objectAtIndex:0],@"index.html"];   

// Download and write to file
NSURL *url = [NSURL URLWithString:@"http://www.domain.co.nz/apppages/contact.html"];
NSData *urlData = [NSData dataWithContentsOfURL:url];
[urlData writeToFile:filePath atomically:YES];

// Load file in UIWebView
 [web loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:filePath]]];    

Answer 3

使用webView的委托方法并在ContactMeViewController.m中实现

在 didFailLoadWithError 方法中，您可以使用 [错误代码] 来识别错误代码。您可以使用 kCFURLErrorNotConnectedToInternet = -1009。

-(void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error {
    if ([error code] == kCFURLErrorNotConnectedToInternet) {
        // if we can identify the error i.e, no internet connection
        [self loadHtmlFile];
    }
}

-(void)loadHtmlFile
{
    NSString *htmlFile = [[NSBundle mainBundle] pathForResource:@"contact" ofType:@"html"];
NSString* htmlString = [NSString stringWithContentsOfFile:htmlFile encoding:NSUTF8StringEncoding error:nil];
[webview loadHTMLString:htmlString baseURL:nil];
}