一：確認網絡環境3G/WIFI
1. 添加源文件和framework
開發Web等網絡應用程序的時候，需要確認網絡環境，連接情況等信息。如果沒有處理它們，是不會通過Apple的審查的。
Apple 的 例程 Reachability 中介紹了取得/檢測網絡狀態的方法。要在應用程序程序中使用Reachability，首先要完成如下兩部：
1.1. 添加源文件：
在你的程序中使用 Reachability 只須將該例程中的 Reachability.h 和 Reachability.m 拷貝到你的工程中。如下圖：
1.2.添加framework：
將SystemConfiguration.framework 添加進工程。如下圖：
2. 網絡狀態
Reachability.h中定義了三種網絡狀態：
typedef enum {
NotReachable = 0, //無連接
ReachableViaWiFi, //使用3G/GPRS網絡
ReachableViaWWAN //使用WiFi網絡
} NetworkStatus;
因此可以這樣檢查網絡狀態：
Reachability *r = [Reachability reachabilityWithHostName:@“www.apple.com”];
switch ([r currentReachabilityStatus]) {
case NotReachable:
// 沒有網絡連接
break;
case ReachableViaWWAN:
// 使用3G網絡
break;
case ReachableViaWiFi:
// 使用WiFi網絡
break;
}
3.檢查當前網絡環境
程序啓動時，如果想檢測可用的網絡環境，可以像這樣
// 是否wifi
+ (BOOL) IsEnableWIFI {
return ([[Reachability reachabilityForLocalWiFi] currentReachabilityStatus] != NotReachable);
}
// 是否3G
+ (BOOL) IsEnable3G {
return ([[Reachability reachabilityForInternetConnection] currentReachabilityStatus] != NotReachable);
}
例子：
- (void)viewWillAppear:(BOOL)animated {
if (([Reachability reachabilityForInternetConnection].currentReachabilityStatus == NotReachable) &&
([Reachability reachabilityForLocalWiFi].currentReachabilityStatus == NotReachable)) {
self.navigationItem.hidesBackButton = YES;
[self.navigationItem setLeftBarButtonItem:nil animated:NO];
}
}
4. 鏈接狀態的實時通知
網絡連接狀態的實時檢查，通知在網絡應用中也是十分必要的。接續狀態發生變化時，需要及時地通知用戶：
Reachability 1.5版本
// My.AppDelegate.h
#import "Reachability.h"
@interface MyAppDelegate : NSObject <UIApplicationDelegate> {
NetworkStatus remoteHostStatus;
}
@property NetworkStatus remoteHostStatus;
@end
// My.AppDelegate.m
#import "MyAppDelegate.h"
@implementation MyAppDelegate
@synthesize remoteHostStatus;
// 更新網絡狀態
- (void)updateStatus {
self.remoteHostStatus = [[Reachability sharedReachability] remoteHostStatus];
}
// 通知網絡狀態
- (void)reachabilityChanged:(NSNotification *)note {
[self updateStatus];
if (self.remoteHostStatus == NotReachable) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"AppName", nil)
message:NSLocalizedString (@"NotReachable", nil)
delegate:nil cancelButtonTitle:@"OK" otherButtonTitles: nil];
[alert show];
[alert release];
}
}
// 程序啓動器，啓動網絡監視
- (void)applicationDidFinishLaunching:(UIApplication *)application {
// 設置網絡檢測的站點
[[Reachability sharedReachability] setHostName:@"www.apple.com"];
[[Reachability sharedReachability] setNetworkStatusNotificationsEnabled:YES];
// 設置網絡狀態變化時的通知函數
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:)
name:@"kNetworkReachabilityChangedNotification" object:nil];
[self updateStatus];
}
- (void)dealloc {
// 刪除通知對象
[[NSNotificationCenter defaultCenter] removeObserver:self];
[window release];
[super dealloc];
}
Reachability 2.0版本
// MyAppDelegate.h
@class Reachability;
@interface MyAppDelegate : NSObject <UIApplicationDelegate> {
Reachability *hostReach;
}
@end
// MyAppDelegate.m
- (void)reachabilityChanged:(NSNotification *)note {
Reachability* curReach = [note object];
NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
NetworkStatus status = [curReach currentReachabilityStatus];
if (status == NotReachable) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"AppName""
message:@"NotReachable"
delegate:nil
cancelButtonTitle:@"YES" otherButtonTitles:nil];
[alert show];
[alert release];
}
}
- (void)applicationDidFinishLaunching:(UIApplication *)application {
// ...
// 監測網絡情況
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(reachabilityChanged:)
name: kReachabilityChangedNotification
object: nil];
hostReach = [[Reachability reachabilityWithHostName:@"www.google.com"] retain];
hostReach startNotifer];
// ...
}
二：使用NSConnection下載數據
1.創建NSConnection對象，設置委託對象
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[self urlString]]];
[NSURLConnection connectionWithRequest:request delegate:self];
2. NSURLConnection delegate委託方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection;
3. 實現委託方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
// store data
[self.receivedData setLength:0]; //通常在這裏先清空接受數據的緩存
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
/* appends the new data to the received data */
[self.receivedData appendData:data]; //可能多次收到數據，把新的數據添加在現有數據最後
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
// 錯誤處理
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// disconnect
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
NSString *returnString = [[NSString alloc] initWithData:self.receivedData encoding:NSUTF8StringEncoding];
NSLog(returnString);
[self urlLoaded:[self urlString] data:self.receivedData];
firstTimeDownloaded = YES;
}
三：使用NSXMLParser解析xml文件
1. 設置委託對象，開始解析
NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; //或者也可以使用initWithContentsOfURL直接下載文件，但是有一個原因不這麼做：
// It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable
// because it gives less control over the network, particularly in responding to connection errors.
[parser setDelegate:self];
[parser parse];
2. 常用的委託方法
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName
attributes:(NSDictionary *)attributeDict;
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName;
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string;
- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError;
static NSString *feedURLString = @"http://www.yifeiyang.net/test/test.xml";
3. 應用舉例
- (void)parseXMLFileAtURL:(NSURL *)URL parseError:(NSError **)error
{
NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:URL];
[parser setDelegate:self];
[parser setShouldProcessNamespaces:NO];
[parser setShouldReportNamespacePrefixes:NO];
[parser setShouldResolveExternalEntities:NO];
[parser parse];
NSError *parseError = [parser parserError];
if (parseError && error) {
*error = parseError;
}
[parser release];
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString*)qName attributes:(NSDictionary *)attributeDict{
// 元素開始句柄
if (qName) {
elementName = qName;
}
if ([elementName isEqualToString:@"user"]) {
// 輸出屬性值
NSLog(@"Name is %@ , Age is %@", [attributeDict objectForKey:@"name"], [attributeDict objectForKey:@"age"]);
}
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName
{
// 元素終了句柄
if (qName) {
elementName = qName;
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
// 取得元素的text
}
NSError *parseError = nil;
[self parseXMLFileAtURL:[NSURL URLWithString:feedURLString] parseError:&parseError];