android手机信号强度检测
最近在面试的时候被问到一个问题，当手机处于弱网状态下，如何处理，如何监听网络信号强度变化。 这里先了解关于手机信号强度的相关几个概念文章出处：/fuchengbo000/article/details/42740357
Android手机信号强度介绍
android定义了2种信号单位：dBm和asu。它们之间的关系是：dBm =-113+2asu，这是google给android手机定义的特有信号单位。例如，我的信号强度为-53dBm，则对应30asu，因为-53 = -113 + (230) 。详细介绍两者：
asu：alone signal unit 独立信号单元，是一种模拟信号。ASU仅仅代表手机将它的位置传递给附近的信号塔的速率。它和dBm测量的是一样的东西，但是是以一种更加线性的方式来表示。dBm：是一个表示功率绝对值的值（也可以认为是以1mW功率为基准的一个比值），计算公式为：10log（功率值/1mw）。
[例] 如果功率P为1mw，折算为dBm后为0dBm。[例] 对于0.01mW的功率，按dBm单位进行折算后的值应为： 10log（0.01/1）=-20dBm。这个数值越大，表明信号越好。由于手机信号强度一般较小，折算成为dBm一般都是负数。中国移动的规范规定,手机接收电平>=(城市取-90dBm;乡村取-94dBm) 时,则满足覆盖要求,也就是说此处无线信号强度满足覆盖要求.-67dBm要比-90dBm信号要强20多个dB,那么它在打电话接通成功率和通话过程中的话音质量都会好的多。再引入一个相关概念dB。
dB：是一个表征相对值的值，纯粹的比值，只表示两个量的相对大小关系，没有单位，当考虑甲的功率相比于乙功率大或小多少个dB时，按下面的计算公式：10log（甲功率/乙功率），如果采用两者的电压 比计算，要用20log（甲电压/乙电压）。
[例] 甲功率比乙功率大一倍，那么10lg（甲功率/乙功率）=10lg2=3dB，即甲的功率比乙的功率大3 dB。反之，如果甲的功率是乙的功率的一半，则甲的功率比乙的功率小3 dB。
总结：dBm是负数，越接近0信号强度越高，信号越好，但不可能为0。asu为正数，值越大信号越好。dB是两个量之间的比值，表示两个量间的相对大小，而dBm则是表示功率绝对大小的值。
关于对数运算，不记得的自行复习一下了。下面再来了解一下网络类型吧，还是很多的，不过在国内只要了解国内三大运营商的网络类型大概就可以了。
电信2G CDMA3G CDMA20004G TD-LTE，FDD-LTE移动2G GSM3G TD-SCDMA4G TD-LTE，FDD-LTE联通2G GSM3G WCDMA4G TD-LTE，FDD-LTE
而谷歌API给我们提供的有19种类型，在TelephonyManager类中定义，具体如下
/** Network type is unknown */public static final int NETWORK_TYPE_UNKNOWN = 0;/** Current network is GPRS */public static final int NETWORK_TYPE_GPRS = 1;/** Current network is EDGE */public static final int NETWORK_TYPE_EDGE = 2;/** Current network is UMTS */public static final int NETWORK_TYPE_UMTS = 3;/** Current network is CDMA: Either IS95A or IS95B*/public static final int NETWORK_TYPE_CDMA = 4;/** Current network is EVDO revision 0*/public static final int NETWORK_TYPE_EVDO_0 = 5;/** Current network is EVDO revision A*/public static final int NETWORK_TYPE_EVDO_A = 6;/** Current network is 1xRTT*/public static final int NETWORK_TYPE_1xRTT = 7;/** Current network is HSDPA */public static final int NETWORK_TYPE_HSDPA = 8;/** Current network is HSUPA */public static final int NETWORK_TYPE_HSUPA = 9;/** Current network is HSPA */public static final int NETWORK_TYPE_HSPA = 10;/** Current network is iDen */public static final int NETWORK_TYPE_IDEN = 11;/** Current network is EVDO revision B*/public static final int NETWORK_TYPE_EVDO_B = 12;/** Current network is LTE */public static final int NETWORK_TYPE_LTE = 13;/** Current network is eHRPD */public static final int NETWORK_TYPE_EHRPD = 14;/** Current network is HSPA+ */public static final int NETWORK_TYPE_HSPAP = 15;/** Current network is GSM {@hide} */public static final int NETWORK_TYPE_GSM = 16;/** Current network is TD_SCDMA {@hide} */public static final int NETWORK_TYPE_TD_SCDMA = 17;/** Current network is IWLAN {@hide} */public static final int NETWORK_TYPE_IWLAN = 18;
下面通过一些实例来测试一下吧
首先记得加权限
<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"/>
实例代码
原来的方式，只通过监听信号改变来区分网络类型
public class MainActivity extends AppCompatActivity {private static final int NETWORKTYPE_WIFI = 0;private static final int NETWORKTYPE_4G = 1;private static final int NETWORKTYPE_2G = 2;private static final int NETWORKTYPE_NONE = 3;public TextView mTextView;public TelephonyManager mTelephonyManager;public PhoneStatListener mListener;/*** 网络信号强度监听** @param savedInstanceState*/@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mTextView = (TextView) findViewById(R.id.textview);//获取telephonyManagermTelephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);//开始监听mListener = new PhoneStatListener();//监听信号强度mTelephonyManager.listen(mListener, PhoneStatListener.LISTEN_SIGNAL_STRENGTHS);}@Overrideprotected void onResume() {super.onResume();mTelephonyManager.listen(mListener, PhoneStatListener.LISTEN_SIGNAL_STRENGTHS);}@Overrideprotected void onPause() {super.onPause();//用户不在当前页面时，停止监听mTelephonyManager.listen(mListener, PhoneStatListener.LISTEN_NONE);}private class PhoneStatListener extends PhoneStateListener {//获取信号强度@Overridepublic void onSignalStrengthsChanged(SignalStrength signalStrength) {super.onSignalStrengthsChanged(signalStrength);//获取网络信号强度//获取0-4的5种信号级别，越大信号越好,但是api23开始才能用// int level = signalStrength.getLevel();int gsmSignalStrength = signalStrength.getGsmSignalStrength();//获取网络类型int netWorkType = getNetWorkType(MainActivity.this);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;}}}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() == WORK_TYPE_LTE) {//这里只简单区分两种类型网络，认为4G网络为快速，但最终还需要参考信号值return true;}return false;}}
改进后的方式，wifi的信号通过wifimanager来监听，更精确，并且通过广播的方式更灵敏
package org.worksingstrange;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import .ConnectivityManager;import workInfo;import .wifi.WifiInfo;import .wifi.WifiManager;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.telephony.PhoneStateListener;import android.telephony.SignalStrength;import android.telephony.TelephonyManager;import android.widget.TextView;public class MainActivity extends AppCompatActivity {private static final intNETWORKTYPE_WIFI= 0; private static final intNETWORKTYPE_4G= 1; private static final intNETWORKTYPE_2G= 2; private static final intNETWORKTYPE_NONE= 3; public TextView mTextView; public TelephonyManager mTelephonyManager; public PhoneStatListener mListener; public int mGsmSignalStrength; private NetWorkBroadCastReciver mNetWorkBroadCastReciver; /** * 网络信号强度监听 * *@paramsavedInstanceState */ @Override protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextView = (TextView) findViewById(R.id.textview); //获取telephonyManager mTelephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); //开始监听 mListener = new PhoneStatListener(); /**由于信号值变化不大时，监听反应不灵敏，所以通过广播的方式同时监听wifi和信号改变更灵敏*/mNetWorkBroadCastReciver = new NetWorkBroadCastReciver(); IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION); intentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION); intentFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION); intentFilter.addAction(WifiManager.RSSI_CHANGED_ACTION); registerReceiver(mNetWorkBroadCastReciver, intentFilter); }@Override protected void onResume() {super.onResume(); mTelephonyManager.listen(mListener, PhoneStatListener.LISTEN_SIGNAL_STRENGTHS); }@Override protected void onPause() {super.onPause(); //用户不在当前页面时，停止监听 mTelephonyManager.listen(mListener, PhoneStatListener.LISTEN_NONE); }private class PhoneStatListener extends PhoneStateListener {//获取信号强度 @Override public void onSignalStrengthsChanged(SignalStrength signalStrength) {super.onSignalStrengthsChanged(signalStrength); //获取网络信号强度 //获取0-4的5种信号级别，越大信号越好,但是api23开始才能用// int level = signalStrength.getLevel(); mGsmSignalStrength = signalStrength.getGsmSignalStrength(); //网络信号改变时，获取网络信息 getNetWorkInfo(); }}/**暂时不用这个方法*/ public 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() ?NETWORKTYPE_4G:NETWORKTYPE_2G; }} else {mNetWorkType =NETWORKTYPE_NONE;//没有网络 }return mNetWorkType; }/** * 判断网络速度 */ private boolean isFastMobileNetwork() {if (mTelephonyManager.getNetworkType() == TelephonyManager.NETWORK_TYPE_LTE) {//这里只简单区分两种类型网络，认为4G网络为快速，但最终还需要参考信号值 return true; }return false; }//接收网络状态改变的广播 class NetWorkBroadCastReciver extends BroadcastReceiver {@Override public void onReceive(Context context, Intent intent) {getNetWorkInfo(); }}/** * 获取网络的信息 */ private void getNetWorkInfo() {ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo info = connectivityManager.getActiveNetworkInfo(); if (info != null && info.isAvailable()) {switch (info.getType()) {case ConnectivityManager.TYPE_WIFI://wifiWifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);WifiInfo connectionInfo = manager.getConnectionInfo();int rssi = connectionInfo.getRssi();mTextView.setText("当前为wifi网络，信号强度=" + rssi);break;case ConnectivityManager.TYPE_MOBILE://移动网络,可以通过TelephonyManager来获取具体细化的网络类型String netWorkStatus = isFastMobileNetwork() ? "4G网络" : "2G网络";mTextView.setText("当前为" + netWorkStatus + "，信号强度=" + mGsmSignalStrength);break; }} else {mTextView.setText("没有可用网络"); }}@Override protected void onDestroy() {super.onDestroy(); unregisterReceiver(mNetWorkBroadCastReciver); }}
关于信号获取流程，这个还需深入研究，目前只在应用层简单获取了网络信号。
