关键类

ConnectivityManager类，可以获取网络状态信息。

权限

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
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基本使用

1. 获取ConnectivityManager的实例

Context context = getApplicationContext();
ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
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1. 获取NetworkInfo对象

NetworkInfo networkInfo = manager.getActiveNetworkInfo();
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1. 调用NetworkInfo的相应方法

NetworkInfo类：isConnected、isAvailable、getType等。

isConnected和isAvailable的区别

代码

/*** 网络工具类* Created by zhoujingxin on 2018/1/23.*/public class NetworkUtils {public static final int NETWORK_TYPE_NONE = 0;public static final int NETWORK_TYPE_WIFI = 1;public static final int NETWORK_TYPE_2G = 2;public static final int NETWORK_TYPE_3G = 3;public static final int NETWORK_TYPE_4G = 4;/*** 判断当前是否有网络连接** @param context* @return true：数据网络或者wifi；false：没有开启任何网络*/public static boolean isNetworkConnected(Context context) {if (context != null) {ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo networkInfo = manager.getActiveNetworkInfo();if (networkInfo != null) {return networkInfo.isAvailable() && networkInfo.isConnected();}}return false;}/*** Wifi网络当前是否连接** @param context* @return 只开启wifi时，返回true；同时开启wifi和数据网络时，返回true；*/public static boolean isWifiConnected(Context context) {if (context != null) {ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo networkInfo = manager.getActiveNetworkInfo();if (networkInfo != null && networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {return networkInfo.isAvailable() && networkInfo.isConnected();}}return false;}/*** 数据网络当前是否连接** @param context* @return 只开启数据网络时，返回true；同时开启wifi和数据网络时会返回false；*/public static boolean isMobileConnected(Context context) {if (context != null) {ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo networkInfo = manager.getActiveNetworkInfo();if (networkInfo != null && networkInfo.getType() == ConnectivityManager.TYPE_MOBILE) {return networkInfo.isAvailable() && networkInfo.isConnected();}}return false;}/*** 通过反射获取数据网络是否连接* 可以在wifi和数据网络同时开启时使用* @param context* @return*/public static boolean isMobileDataEnabled(Context context) {try {ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);Method getMobileDataEnabled = ConnectivityManager.class.getDeclaredMethod("getMobileDataEnabled");getMobileDataEnabled.setAccessible(true);boolean dataEnabled = (boolean) getMobileDataEnabled.invoke(connectivityManager);return dataEnabled;} catch (NoSuchMethodException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}return false;}/*** 获取当前连接的网络的类型* 原生** @param context* @return*/public static int getConcreteNetworkType(Context context) {if (context != null) {ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo networkInfo = manager.getActiveNetworkInfo();if (networkInfo != null && networkInfo.isAvailable()) {return networkInfo.getType();}}return -1;}/*** 获取当前的网络状态 ：没有网络-0：WIFI网络1：4G网络-4：3G网络-3：2G网络-2* 自定义** @param context* @return*/public static int getSimpleNetworkType(Context context) {//结果返回值int netType = NETWORK_TYPE_NONE;//获取手机所有连接管理对象ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);//获取NetworkInfo对象NetworkInfo networkInfo = manager.getActiveNetworkInfo();//NetworkInfo对象为空 则代表没有网络if (networkInfo == null) {return netType;}//否则 NetworkInfo对象不为空 则获取该networkInfo的类型int nType = networkInfo.getType();if (nType == ConnectivityManager.TYPE_WIFI) {//WIFInetType = NETWORK_TYPE_WIFI;} else if (nType == ConnectivityManager.TYPE_MOBILE) {int nSubType = networkInfo.getSubtype();TelephonyManager telephonyManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);//3G   联通的3G为UMTS或HSDPA 电信的3G为EVDOif (nSubType == TelephonyManager.NETWORK_TYPE_LTE&& !telephonyManager.isNetworkRoaming()) {netType = NETWORK_TYPE_4G;} else if (nSubType == TelephonyManager.NETWORK_TYPE_UMTS|| nSubType == TelephonyManager.NETWORK_TYPE_HSDPA|| nSubType == TelephonyManager.NETWORK_TYPE_EVDO_0&& !telephonyManager.isNetworkRoaming()) {netType = NETWORK_TYPE_3G;//2G 移动和联通的2G为GPRS或EGDE，电信的2G为CDMA} else if (nSubType == TelephonyManager.NETWORK_TYPE_GPRS|| nSubType == TelephonyManager.NETWORK_TYPE_EDGE|| nSubType == TelephonyManager.NETWORK_TYPE_CDMA&& !telephonyManager.isNetworkRoaming()) {netType = NETWORK_TYPE_2G;} else {netType = NETWORK_TYPE_2G;}}return netType;}}
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注意：

• isWifiConnected和isMobileConnected方法只能用于判断当前所使用的网络；也就是说，如果当前wifi和数据网络同时开启，isWifiConnected会返回true，而isMobileConnected会返回false；
• 如果希望同时判断数据网络是否也连接的话，可以调用isMobileDataEnabled方法；该方法通过反射调用ConnectivityManager中@hide标记的getMobileDataEnabled的方法来进行判断。

监听网络状态变化

1. 自定义广播接收器
   可能用到WifiManager类。
2. 静态注册广播

<receiver android:name=".NetWorkStateReceiver"><intent-filter><action android:name="android.net.conn.CONNECTIVITY_CHANGE"/><action android:name="android.Net.wifi.WIFI_STATE_CHANGED" /><action android:name="android.net.wifi.STATE_CHANGE" /></intent-filter>
</receiver>
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如果只使用CONNECTIVITY_CHANGE的话，在7.0以上会收不到广播。

1. 动态注册广播

IntentFilter filter = new IntentFilter();
filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
filter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
filter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
registerReceiver(netWorkStateReceiver, filter);
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参考资料

• http://www.cnblogs.com/ccdc/p/4432583.html
• https://www.jianshu.com/p/10ed9ae02775
• http://www.10tiao.com/html/227/201612/2650238011/1.html