PlatformNetworksManager.java 文件源码

/**
 * Returns a CellInfo object representing the currently registered base stations, containing
 * its identity fields and signal strength. Null if no base station is active.
 */
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
@Nullable
private static CellInfo getActiveCellInfo(TelephonyManager telephonyManager) {
    int numRegisteredCellInfo = 0;
    List<CellInfo> cellInfos = telephonyManager.getAllCellInfo();

    if (cellInfos == null) {
        return null;
    }
    CellInfo result = null;

    for (int i = 0; i < cellInfos.size(); i++) {
        CellInfo cellInfo = cellInfos.get(i);
        if (cellInfo.isRegistered()) {
            numRegisteredCellInfo++;
            if (numRegisteredCellInfo > 1) {
                return null;
            }
            result = cellInfo;
        }
    }
    // Only found one registered cellinfo, so we know which base station was used to measure
    // network quality
    return result;
}