判断有没有SIM卡

获取移动网络的信号，一定要判断是否插了SIM卡，没插卡肯定是没法获取的

    /**
     * 判断是否包含SIM卡
     *
     * @return 状态
     */
    public static boolean hasSimCard(Context context) {
        TelephonyManager telMgr = (TelephonyManager)
                context.getSystemService(Context.TELEPHONY_SERVICE);
        int simState = telMgr.getSimState();
        boolean result = true;
        switch (simState) {
            case TelephonyManager.SIM_STATE_ABSENT:
            case TelephonyManager.SIM_STATE_UNKNOWN:
                result = false; // 没有SIM卡
                break;
        }
        return result;
    }

获取信号强度

如果插了SIM卡，就可以通过下边方法来获取移动网络的信号强度（单位dBM），使用的是TelephonyManager 来监听

    private void getMobileNetworkSignal() {
        if (!PhoneUtils.hasSimCard(mcontext)) {
            logger.info("getMobileNetworkSignal: no sim card");
            return;
        }
        TelephonyManager mTelephonyManager = (TelephonyManager) BaseApplication.getAppContext().getSystemService(Context.TELEPHONY_SERVICE);
        if (mTelephonyManager != null) {
            mTelephonyManager.listen(new PhoneStateListener() {

                @Override
                public void onSignalStrengthsChanged(SignalStrength signalStrength) {
                    super.onSignalStrengthsChanged(signalStrength);
                    int asu = signalStrength.getGsmSignalStrength();
                    int lastSignal = -113 + 2 * asu;
                    if (lastSignal > 0) {
                        mobileNetworkSignal = lastSignal + "dBm";
                    }
                    logger.info("Current mobileNetworkSignal：" + lastSignal + " dBm");
                }
            }, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);
        }
    }

也可以添加网络类型的判断，来获取是何种网络的信号强度

int netWorkType = getNetWorkType(mContext);
switch (netWorkType) {
    case NETWORKTYPE_WIFI:
        mTextView.setText("当前网络为wifi,信号强度为：" + gsmSignalStrength);
        break;
    case NETWORKTYPE_2G:
        mTextView.setText("当前网络为2G移动网络,信号强度为：" + gsmSignalStrength);
        break;
    case NETWORKTYPE_4G:
        mTextView.setText("当前网络为4G移动网络,信号强度为：" + gsmSignalStrength);
        break;
    case NETWORKTYPE_NONE:
        mTextView.setText("当前没有网络,信号强度为：" + gsmSignalStrength);
        break;
    case -1:
        mTextView.setText("当前网络错误,信号强度为：" + gsmSignalStrength);
        break;
}

用到的获取网络类型的方法：

public static int getNetWorkType(Context context) {
    int mNetWorkType = -1;
    ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = manager.getActiveNetworkInfo();
    if (networkInfo != null && networkInfo.isConnected()) {
        String type = networkInfo.getTypeName();
        if (type.equalsIgnoreCase("WIFI")) {
            mNetWorkType = NETWORKTYPE_WIFI;
        } else if (type.equalsIgnoreCase("MOBILE")) {
            return isFastMobileNetwork(context) ? NETWORKTYPE_4G : NETWORKTYPE_2G;
        }
    } else {
        mNetWorkType = NETWORKTYPE_NONE;//没有网络
    }
    return mNetWorkType;
}

/**
 * 判断网络类型
 */
private static boolean isFastMobileNetwork(Context context) {
    TelephonyManager telephonyManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
    if (telephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_LTE) {
        return true;
    }
    return false;
}

最后添加必要权限即可

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>