有时候我们需要实时监听手机的网络及其它的信号值，但是菜鸟的我在网上百度了很久，没有找到比较合适的例子，后面直接看系统的API，完成了下面的例子，在这做一下笔记：

   public static void getPhoneState(Context context) {
   final TelephonyManager telephonyManager = (TelephonyManager)     context.getSystemService(Context.TELEPHONY_SERVICE);
    PhoneStateListener MyPhoneListener = new PhoneStateListener() {
        @Override
       //获取对应网络的ID，这个方法在这个程序中没什么用处
        public void onCellLocationChanged(CellLocation location) {
            if (location instanceof GsmCellLocation) {
                int CID = ((GsmCellLocation) location).getCid();
            } else if (location instanceof CdmaCellLocation) {
                int ID = ((CdmaCellLocation) location).getBaseStationId();
            }
        }
       //系统自带的服务监听器，实时监听网络状态
        @Override
        public void onServiceStateChanged(ServiceState serviceState) {
            super.onServiceStateChanged(serviceState);
        }
       //这个是我们的主角，就是获取对应网络信号强度
        @Override
        public void onSignalStrengthsChanged(SignalStrength signalStrength) {
             //这个ltedbm 是4G信号的值
            String signalinfo = signalStrength.toString();
            String[] parts = signalinfo.split(" ");
            int ltedbm = Integer.parseInt(parts[9]);
             //这个dbm 是2G和3G信号的值
            int asu = signalStrength.getGsmSignalStrength();
            int dbm = -113 + 2 * asu;

            if (telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_LTE) {
                Log.i("NetWorkUtil", "网络：LTE 信号强度：" + ltedbm + "======Detail:" + signalinfo);
            } else if (telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_HSDPA ||
                    telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_HSPA ||
                    telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_HSUPA ||
                    telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_UMTS)                                               {
                String bin;
                if (dbm > -75) {
                    bin = "网络很好";
                } else if (dbm > -85) {
                    bin = "网络不错";
                } else if (dbm > -95) {
                    bin = "网络还行";
                } else if (dbm > -100) {
                    bin = "网络很差";
                } else {
                    bin = "网络错误";
                }
                Log.i("NetWorkUtil", "网络：WCDMA 信号值：" + dbm + "========强度：" + bin + "======Detail:" + signalinfo);
            } else {
                String bin;
                if (asu < 0 || asu >= 99) bin = "网络错误";
                else if (asu >= 16) bin = "网络很好";
                else if (asu >= 8) bin = "网络不错";
                else if (asu >= 4) bin = "网络还行";
                else bin = "网络很差";
                Log.i("NetWorkUtil", "网络：GSM 信号值：" + dbm + "========强度：" + bin + "======Detail:" + signalinfo);
            }
            super.onSignalStrengthsChanged(signalStrength);
        }
    };
    telephonyManager.listen(MyPhoneListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
}