逍遙文工作室

總是三不五時就上臉書的我們，一定很清楚知道Facebook APP是即時判斷網路連線狀態 (Detect Network Status on Real-Time)，如果是「無法連線上網」的狀態，就會暫停需要網路才能運作的功能。

為了demo這個題目，只好出賣我的女性友人＞＿＜。

這裡我們直接使用Apple提供的Reachability程式碼，請到iOS Developer Library Reachability下載。然後將Reachability.h和Reachability.m加到專案裡。

編譯執行它專案的樣子～

其實只要幾行程式碼，就能將它應用自如，一旦偵測到無法連結網路的狀態，可以做相對應的處理，我這裡則是跳出提示。

/**
 Theme: Detect Network Status on Real-Time
 IDE: Xcode 5
 Language: Objective C
 Date: 103/03/25
 Author: HappyMan
 Blog: https://cg2010studio.wordpress.com/
 */

// 在HTAppDelegate.h
#import <UIKit/UIKit.h>
#import "Reachability.h"

@interface HTAppDelegate : UIResponder <UIApplicationDelegate>
{
    Reachability *reachabilty;
}
@property (strong, nonatomic) UIWindow *window;

@end

// 在HTAppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //  Register notification for Network status change
    [[NSNotificationCenter defaultCenter] addObserver:self selector: @selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];

    //  Initialize the listener for network status
    reachabilty = [Reachability reachabilityForInternetConnection];
    [reachabilty startNotifier];

    UIViewController *vc = [[HTMapViewController alloc] init];
    UINavigationController *nc = [[UINavigationController alloc] initWithRootViewController:vc];
    nc.navigationBarHidden = YES;
    self.window.rootViewController = nc;
    return YES;
}
// Called by Reachability whenever status changes.
- (void)reachabilityChanged:(NSNotification *)note
{
    Reachability* curReach = [note object];
    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
    [self updateInterfaceWithReachability: curReach];
}

//  Implementation for Network status notification
- (void)updateInterfaceWithReachability:(Reachability *)curReach
{
    NetworkStatus curStatus;

    BOOL m_bReachableViaWWAN;
    BOOL m_bReachableViaWifi;
    BOOL m_bReachable;
    //  According to curReach, modify current internal flags

    //  Internet reachability
    //  Need network status to know real reachability method
    curStatus = [curReach currentReachabilityStatus];

    //  Modify current network status flags
    if (curStatus == ReachableViaWWAN) {
        m_bReachableViaWWAN = true;
    } else {
        m_bReachableViaWWAN = false;
    }

    if (curStatus == ReachableViaWiFi) {
        m_bReachableViaWifi = true;
    } else {
        m_bReachableViaWifi = false;
    }

    //  Reachable is the OR result of two internal connection flags
    m_bReachable = (m_bReachableViaWifi || m_bReachableViaWWAN);

    if (!m_bReachable) {
        UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"注意" message:@"無法連結網路" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [av show];
    }
}

現在上網有兩種方式，一是3G二是WiFi，只要其中之一是連線狀態，就判定為有上網！

這程式技術使用到通知（Notification），首先註冊(add)觀察kReachabilityChangedNotification，因為Reachability將會發送(post)通知到kReachabilityChangedNotification，所以APP一旦收到通知，就會去執行reachabilityChanged這個方法。

我們關掉WiFi來測試⋯⋯

屢試不爽，會跳出提示！

參考：iOS 上偵測網路連線狀態的做法、GitHub – Reachability。