目录

• 最小案例
• 概况
• 实践概要
  • NetworkInfo 实践详解
  • ConnectivityManager 实践详解
  • Network 浅析
• 实用工具
• 参考

最小案例

需要的权限

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

MainActivity.java

public class MainActivity extends AppCompatActivity {
 
    private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter=new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }
 
    @Override
    protected void onDestroy(){
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
 
private final  class NetworkChangeReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent){
      ConnectivityManager cm=(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
      NetworkInfo networkInfo= cm.getActiveNetworkInfo();
      if(networkInfo == null){
        // WIFI 和 移动网络都关闭 即没有有效网络
        Log.e(TAG, "当前无网络连接");
        return;
      }
      String typeName = "";
      if(networkInfo.getType()==ConnectivityManager.TYPE_WIFI){
        //WIFI网络跳转的页面.
        typeName = networkInfo.getTypeName();//==> WIFI
      }else if(networkInfo.getType()==ConnectivityManager.TYPE_MOBILE) {
        //无线网络跳转的页面
        typeName = networkInfo.getTypeName();//==> MOBILE
      }
      Log.e(TAG, "==>" + typeName);
      Log.e(TAG, "==>" + networkInfo.getDetailedState());
    }
  }
}

概况

ConnectivityManager主要职责，官方说明：

1. Monitor network connections (Wi-Fi, GPRS, UMTS, etc.)
2. Send broadcast intents when network connectivity changes
3. Attempt to "fail over" to another network when connectivity to a network is lost
4. Provide an API that allows applications to query the coarse-grained or fine-grained state of the available networks
5. Provide an API that allows applications to request and select networks for their data traffic

平民翻译：

1. 监控网络连接(Wi-Fi, GPRS, UMTS, etc.)；
2. 当网络连接改变时发送Intent；
3. 当连接到一个网络失败时，尝试用其他网络补救；
4. 提供API给应用查询有效网络粗略或者精确的状态；
5. 提供API给应用为它们的数据传输请求和选择网络；

实践概要

NetworkInfo 实践详解

<font size=10 face=STHupo color=red>注意: </font>

• isConnected() 和 isAvailable() 都为true 不能保证能正常连接到服务器，解决方案用ping命令，参考ShellUtil.execCmd：

//ShellUtil.CommandResult result = ShellUtil.execCmd(String.format("ping -c 1 %s", ip), false);
String[] command = new String[]{String.format("ping -c 1 %s", ip)};
int result = -1;
Process process = Runtime.getRuntime().exec(isRoot ? "su" : "sh");
DataOutputStream os = new DataOutputStream(process.getOutputStream());
for (String command : commands) {
    if (command == null) continue;
    os.write(command.getBytes());
    os.writeBytes(LINE_SEP);
    os.flush();
}
os.writeBytes("exit" + LINE_SEP);
os.flush();
result = process.waitFor();

• getDetailedState/getState 直接看NetworkInfo源码getState等到的值为

public enum State {
    CONNECTING, CONNECTED, SUSPENDED, DISCONNECTING, DISCONNECTED, UNKNOWN
}

• getExtrInfo() WIFI链接返回SSID名称，移动网络返回APN（Access Point Name）,电信物联网得卡到列如：ctnet或ctwap

ConnectivityManager 实践详解

ConnectivityManager类按照其主要职能，常用方法大致可分为三类：

• 获取网络链接信息getXXX如getActiveNetwork，getDefaultProxy
• 多网络链接绑定指定网络 bindsocket和bindprocesstonetwork（6.0的系统 api>23）
• 监听类型 registerDefaultNetworkCallback/registerNetworkCallback

 cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    cm.addDefaultNetworkActiveListener(new ConnectivityManager.OnNetworkActiveListener() {
      @Override public void onNetworkActive() {
        Log.e(TAG, "Active ==>"); //无论是否成功链接外网，只要有一定量的数据传输就会间隔有回调
      }
    });

应用场景：

• 手机同时连接移动网络和本地局域网，手机所有的连接默认访问移动网络，需要手机连接本地局域网：
  Okhttp,picasso与glidez指定网络访问的案例

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP/*5.0*/) {
      ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
      // 请注意这里会有一个版本适配bug，所以请在这里添加非空判断
      if (connectivityManager != null) {
        NetworkRequest.Builder builder = new NetworkRequest.Builder();

        NetworkRequest request = builder.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
            .addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR)
            .build();

        connectivityManager.registerNetworkCallback(request,new ConnectivityManager.NetworkCallback(){

          /**
           * 网络可用的回调连接成功
           * */
          @Override public void onAvailable(Network network) {
            super.onAvailable(network);
            Log.e(TAG, "onAvailable ==>" + network.toString());
          }

          /**
           * 实践中在网络连接正常的情况下，丢失数据会有回调
           * */
          @Override public void onLosing(Network network, int maxMsToLive) {
            super.onLosing(network, maxMsToLive);
            Log.e(TAG, "onLosing ==>" + network.toString() + " max==>" + maxMsToLive);
          }

          /**
           * 网络不可用时调用和onAvailable成对出现
           */
          @Override public void onLost(Network network) {
            super.onLost(network);
            Log.e(TAG, "onLost ==>" + network.toString());
          }

          @Override public void onUnavailable() {
            super.onUnavailable();
            Log.e(TAG, "onUnavailable ==>");
          }

          /**
           * 字面直接能理解
           * @param network 新连接网络
           * @param networkCapabilities 新连接网络的一些能力参数
           */
          @Override
          public void onCapabilitiesChanged(Network network, NetworkCapabilities networkCapabilities) {
            super.onCapabilitiesChanged(network, networkCapabilities);
            Log.e(TAG, "onCapabilitiesChanged ==>" + networkCapabilities.toString());
            //WIFI -> CELLULAR
            //[ Transports: CELLULAR Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN&VALIDATED LinkUpBandwidth>=51200Kbps LinkDnBandwidth>=102400Kbps Specifier: <3>]
            //CELLULAR -> WIFI
            //==>[ Transports: WIFI Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN&VALIDATED LinkUpBandwidth>=1048576Kbps LinkDnBandwidth>=1048576Kbps SignalStrength: -42]
          }
        
          /**
           * 和上面类似，但是没有试出效果
           */
          @Override
          public void onLinkPropertiesChanged(Network network, LinkProperties linkProperties) {
            super.onLinkPropertiesChanged(network, linkProperties);
            Log.e(TAG, "onLinkPropertiesChanged ==>" + linkProperties.toString());
          }
        });
      }
    }

更多监听内容设置请访问官网NetworkRequest 科学上网

Network 浅析

从源码中可以得出Network就是一个Parcelable数据，最重要的参数是

public final int netId;

在回想一下Network什么时候第一次获得

@Override public void onAvailable(Network network)

如果到这里还啥都不get代码意图，那看Network提供的方法

public InetAddress[] getAllByName(String host) throws UnknownHostException {
    return InetAddress.getAllByNameOnNet(host, netId);
}

public InetAddress getByName(String host) throws UnknownHostException {
    return InetAddress.getByNameOnNet(host, netId);
}

bindSocket(Socket socket)
getSocketFactory()
openConnection(URL url)
openConnection(URL url, Proxy proxy)

好到此我的理解是在网络连接onAvailable成功后,返回基于netId的底层网络标识，可以基于这个Network建立一些特殊的URL访问；

实用工具

NetUtil.java

//NetUtils.java
 private static final int NETWORK_TYPE_GSM = 16;
  private static final int NETWORK_TYPE_TD_SCDMA = 17;
  private static final int NETWORK_TYPE_IWLAN = 18;
 /**
   * 判断网络是否可用
   * <p>需要异步 ping，如果 ping 不通就说明网络不可用</p>
   *
   * @param ip ip 地址（自己服务器 ip），如果为空，ip 为阿里巴巴公共 ip
   * @return {@code true}: 可用<br>{@code false}: 不可用
   */
  public static boolean isAvailableByPing(String ip) {
    if (ip == null || ip.length() <= 0) {
      // 阿里巴巴公共 ip
      ip = "223.5.5.5";
    }
    ShellUtil.CommandResult result = ShellUtil.execCmd(String.format("ping -c 1 %s", ip), false);
    boolean ret = result.result == 0;
    if (result.successMsg != null) {
      Log.d("NetUtil", "isAvailableByPing() called" + result.successMsg);
    }
    if (result.errorMsg != null) {
      Log.d("NetUtil", "isAvailableByPing() called" + result.errorMsg);
    }
    return ret;
  }

  /**
   * 判断移动数据是否打开
   *
   * @return {@code true}: 是<br>{@code false}: 否
   */
  public static boolean isMobileDataEnabled() {
    try {
      TelephonyManager tm = (TelephonyManager) Utils.getApp().getSystemService(Context.TELEPHONY_SERVICE);
      Method getMobileDataEnabledMethod = tm.getClass().getDeclaredMethod("getDataEnabled");
      if (getMobileDataEnabledMethod != null) {
        return (boolean) getMobileDataEnabledMethod.invoke(tm);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
    return false;
  }

  /**
   * 打开或关闭移动数据
   *
   * @param enabled {@code true}: 打开<br>{@code false}: 关闭
   */
  public static void setMobileDataEnabled(boolean enabled) {
    try {
      TelephonyManager tm = (TelephonyManager) Utils.getApp().getSystemService(Context.TELEPHONY_SERVICE);
      Method setMobileDataEnabledMethod = tm.getClass().getDeclaredMethod("setDataEnabled", boolean.class);
      if (null != setMobileDataEnabledMethod) {
        setMobileDataEnabledMethod.invoke(tm, enabled);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  private enum NetworkType {
    // wifi
    NETWORK_WIFI,
    // 4G 网
    NETWORK_4G,
    // 3G 网
    NETWORK_3G,
    // 2G 网
    NETWORK_2G,
    // 未知网络
    NETWORK_UNKNOWN,
    // 没有网络
    NETWORK_NO
  }

  /**
   * 获取当前网络类型
   *
   * @return 网络类型
   * <ul>
   * <li>{@link NetworkType#NETWORK_WIFI   } </li>
   * <li>{@link NetworkType#NETWORK_4G     } </li>
   * <li>{@link NetworkType#NETWORK_3G     } </li>
   * <li>{@link NetworkType#NETWORK_2G     } </li>
   * <li>{@link NetworkType#NETWORK_UNKNOWN} </li>
   * <li>{@link NetworkType#NETWORK_NO     } </li>
   * </ul>
   */
  public static NetworkType getNetworkType() {
    NetworkType netType = NetworkType.NETWORK_NO;
    NetworkInfo info = getActiveNetworkInfo();
    if (info != null && info.isAvailable()) {
      if (info.getType() == ConnectivityManager.TYPE_WIFI) {
        netType = NetworkType.NETWORK_WIFI;
      } else if (info.getType() == ConnectivityManager.TYPE_MOBILE) {
        switch (info.getSubtype()) {

          case NETWORK_TYPE_GSM:
          case TelephonyManager.NETWORK_TYPE_GPRS:
          case TelephonyManager.NETWORK_TYPE_CDMA:
          case TelephonyManager.NETWORK_TYPE_EDGE:
          case TelephonyManager.NETWORK_TYPE_1xRTT:
          case TelephonyManager.NETWORK_TYPE_IDEN:
            netType = NetworkType.NETWORK_2G;
            break;

          case NETWORK_TYPE_TD_SCDMA:
          case TelephonyManager.NETWORK_TYPE_EVDO_A:
          case TelephonyManager.NETWORK_TYPE_UMTS:
          case TelephonyManager.NETWORK_TYPE_EVDO_0:
          case TelephonyManager.NETWORK_TYPE_HSDPA:
          case TelephonyManager.NETWORK_TYPE_HSUPA:
          case TelephonyManager.NETWORK_TYPE_HSPA:
          case TelephonyManager.NETWORK_TYPE_EVDO_B:
          case TelephonyManager.NETWORK_TYPE_EHRPD:
          case TelephonyManager.NETWORK_TYPE_HSPAP:
            netType = NetworkType.NETWORK_3G;
            break;

          case NETWORK_TYPE_IWLAN:
          case TelephonyManager.NETWORK_TYPE_LTE:
            netType = NetworkType.NETWORK_4G;
            break;
          default:

            String subtypeName = info.getSubtypeName();
            //  中国移动 联通 电信 三种 3G 制式
            if (subtypeName.equalsIgnoreCase("TD-SCDMA")
                || subtypeName.equalsIgnoreCase("WCDMA")
                || subtypeName.equalsIgnoreCase("CDMA2000")) {
              netType = NetworkType.NETWORK_3G;
            } else {
              netType = NetworkType.NETWORK_UNKNOWN;
            }
            break;
        }
      } else {
        netType = NetworkType.NETWORK_UNKNOWN;
      }
    }
    return netType;
  }

参考

• ConnectivityManager 官网API 科学上网
• Android多网络机制浅析
• android 5.0 以上监听网络变化