Android 7.1.1中captive portal检测导致网络不可用的状态

Android 7.1.1后 连接wifi后 可以上网 但是网络状态显示 网络不可用 ，这是由于连接wifi后系统会自动检测 captive portal 服务器地址，由于大部分国内用户访问不到 google网站 ，所以即使可以上网 但网络状态显示不可用

在android framework源码里面我们发现服务器地址为

    // Default configuration values for captive portal detection probes.
    // TODO: append a random length parameter to the default HTTPS url.
    // TODO: randomize browser version ids in the default User-Agent String.
    private static final String DEFAULT_HTTPS_URL     = "https://www.google.com/generate_204";                                                                                                                    
    private static final String DEFAULT_HTTP_URL      =
            "http://connectivitycheck.gstatic.com/generate_204";

    private static String getCaptivePortalServerHttpsUrl(Context context) {
        return getSetting(context, Settings.Global.CAPTIVE_PORTAL_HTTPS_URL, DEFAULT_HTTPS_URL);                                                                                                                  
    }

    public static String getCaptivePortalServerHttpUrl(Context context) {
        return getSetting(context, Settings.Global.CAPTIVE_PORTAL_HTTP_URL, DEFAULT_HTTP_URL);
    }

我们用可以通过命令改数据库的默认地址
AOSP issue tracker
v2ex的generate_204网址的如下：

adb shell "settings put global captive_portal_http_url http://captive.v2ex.co/generate_204"

adb shell "settings put global captive_portal_https_url https://captive.v2ex.co/generate_204"

也可以直接用命令关闭网络检测上网

adb shell settings put global captive_portal_mode 0

在源码frameworks/base/services/core/java/com/android/server/ConnectivityService.java里面

                case NetworkMonitor.EVENT_PROVISIONING_NOTIFICATION: {
                    final int netId = msg.arg2;
                    final boolean visible = (msg.arg1 != 0);
                    final NetworkAgentInfo nai;
                    synchronized (mNetworkForNetId) {
                        nai = mNetworkForNetId.get(netId);
                    }
                    // If captive portal status has changed, update capabilities or disconnect.
                    if (nai != null && (visible != nai.lastCaptivePortalDetected)) {
                        final int oldScore = nai.getCurrentScore();
                        nai.lastCaptivePortalDetected = visible;
                        nai.everCaptivePortalDetected |= visible;
                        if (nai.lastCaptivePortalDetected &&
                            Settings.Global.CAPTIVE_PORTAL_MODE_AVOID == getCaptivePortalMode()) {
                            if (DBG) log("Avoiding captive portal network: " + nai.name());
                            nai.asyncChannel.sendMessage(
                                    NetworkAgent.CMD_PREVENT_AUTOMATIC_RECONNECT);
                            teardownUnneededNetwork(nai);
                            break;
                        }
                        updateCapabilities(oldScore, nai, nai.networkCapabilities);
                    }
                    if (!visible) {
                        mNotifier.clearNotification(netId);
                    } else {
                        if (nai == null) {
                            loge("EVENT_PROVISIONING_NOTIFICATION from unknown NetworkMonitor");
                            break;
                        }
                        if (!nai.networkMisc.provisioningNotificationDisabled) {
                            mNotifier.showNotification(netId, NotificationType.SIGN_IN, nai, null,
                                    (PendingIntent) msg.obj, nai.networkMisc.explicitlySelected);
                        }
                    }

        private int getCaptivePortalMode() {
            return Settings.Global.getInt(mContext.getContentResolver(),
                    Settings.Global.CAPTIVE_PORTAL_MODE,
                    Settings.Global.CAPTIVE_PORTAL_MODE_PROMPT);
        }

我们改变 Settings.Global.CAPTIVE_PORTAL_MODE_PROMPT默认值就可以