android - 问题 : Android's isConnected() used to get current state of WiFi often returns false even when the device is connected

Question

我的 Android 应用程序只能在连接到互联网的 WiFi 下运行。因此，我使用以下代码来检查设备是否已连接:

ConnectivityManager conMgr = (ConnectivityManager)getSystemService(Activity.CONNECTIVITY_SERVICE);
boolean wifi = conMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI).isConnected();

但是，当应用程序启动并且 WiFi 连接到 Internet 时，我经常收到仅在 wifi = false 时显示的通知。我是不是遗漏了什么，或者支票不够准确？

Answer 1

我的项目也依赖 Wifi(尽管我使用的是专用网络)。以下是我在启动时设置 Wifi 连接的代码:

private void initWIFI (WifiManager wifiMgr, String SSID, String key)
{
    WifiInfo curr;
    if (null == (curr = wifiMgr.getConnectionInfo()))  // Get current wifi state
    {
        joinNetwork (wifiMgr, SSID, key);
    }
    else switch (curr.getSupplicantState())
    {
        case DISCONNECTED:
        case DORMANT:
        case INACTIVE:
        case SCANNING:
            joinNetwork (wifiMgr, SSID, key);
            break;

        default:
            if (!curr.getSSID().equals (SSID))
                joinNetwork (wifiMgr, SSID, key);
    }

    while (wifiMgr.getConnectionInfo().getIpAddress() == 0)
    {
        try
        {
            Thread.sleep (1000);
        }
        catch (Exception e)
        { }
    }
}

/**This method is used to join the proper WiFi network when necessary.  Normally,
 * the Android retains network configuration and it is not necessary to manually
 * re-join the desired network on software startup. However, when it is determined
 * that the Android is not currently attached to the proper network, this function
 * is used to correct that situation. */
private void joinNetwork (WifiManager wifiMgr, String SSID, String key)
{
    try
    {
        WifiConfiguration wc         = new WifiConfiguration();

        wc.allowedAuthAlgorithms.set (WifiConfiguration.AuthAlgorithm.OPEN);
        wc.allowedAuthAlgorithms.set (WifiConfiguration.AuthAlgorithm.SHARED);

        wc.allowedGroupCiphers.set   (WifiConfiguration.GroupCipher.WEP40);
        wc.allowedGroupCiphers.set   (WifiConfiguration.GroupCipher.WEP104);

        wc.allowedKeyManagement.set  (WifiConfiguration.KeyMgmt.NONE);

        wc.allowedPairwiseCiphers.set (WifiConfiguration.PairwiseCipher.TKIP);
        wc.allowedPairwiseCiphers.set (WifiConfiguration.PairwiseCipher.CCMP);

        wc.allowedProtocols.set      (WifiConfiguration.Protocol.WPA);
        wc.allowedProtocols.set      (WifiConfiguration.Protocol.RSN);

        wc.hiddenSSID                = false;
        wc.priority                  = 32;

        wc.SSID                      = "\"" + SSID + "\"";
        wc.status                    = WifiConfiguration.Status.ENABLED;

        wc.wepKeys[0]                = key;
        wc.wepTxKeyIndex             = 0;

        int netID;                   
        if (-1 == (netID             = wifiMgr.addNetwork (wc)))
        {
            listener.lostConnection (true);
        }
        else
        {
            wifiMgr.enableNetwork (netID, true);
            Thread.sleep (5000);  // Delay to allow the DHCP process to work
        }
    }
    catch (Exception e)
    {
        listener.lostConnection (true);
    }
}

需要指出的是，我一直使用同一个无线接入点，joinNetwork()中的代码是专门为它配置的，所以如果你的配置需要更灵活，那么你的解决方案可能会更复杂。遗憾的是，我不记得我在哪个网站上找到了这段代码的起点，但我并不需要大量的谷歌搜索就可以找到它。最后，我非常确定您的应用程序需要具有 ACCESS_WIFI_STATE 和 CHANGE_WIFI_STATE 权限。