ConnectivityManager是网络连接相关的管理器，它主要用于查询网络状态并在网络发生改变时发出状态变化通知。

这个类主要负责的下列四个方面：

     1.  监控网络状态（包括WiFi, GPRS, UMTS等）。

     2.  当网络连接改变时发送广播Intent。

     3.  当一种网络断开时，试图连接到另一种网络进行故障处理。

     4.  提供一系列接口让应用程序查询可获得的网络的粗粒度和细粒度状态。

   比较重要的几个类常量

int

TYPE_BLUETOOTH

The Bluetooth data connection. 蓝牙数据连接

int

TYPE_ETHERNET

The Ethernet data connection. 以太网数据连接

int

TYPE_MOBILE

The Mobile data connection. 移动数据链接

int

TYPE_WIFI

The WIFI data connection. wifi链接

String

CONNECTIVITY_ACTION

网络连接发生改变

int

DEFAULT_NETWORK_PREFERENCE

默认网络连接偏好，建议在config.xml中进行配置.并通过调用 getNetworkPreference()

String

EXTRA_EXTRA_INFO

The lookup key for a string that provides optionally supplied extra information about the network state.

查询关键字，提供关于网络状态的信息

String

EXTRA_NETWORK_INFO

getActiveNetworkInfo() or getAllNetworkInfo()获取网络连接信息

String

EXTRA_NETWORK_TYPE

触发 CONNECTIVITY_ACTION广播的网络类型

比较重要的方法

NetworkInfo

getActiveNetworkInfo() 获取当前连接可用的网络

NetworkInfo[]

getAllNetworkInfo()  获取设备支持的所有网络类型的链接状态信息。

NetworkInfo

getNetworkInfo(int networkType)   获取特定网络类型的链接状态信息

int

getNetworkPreference()   获取当前偏好的网络类型。

boolean

isActiveNetworkMetered() 



Returns if the currently active data network is metered.

static boolean

isNetworkTypeValid(int networkType)    判断给定的数值是否表示一种网络

boolean

requestRouteToHost(int networkType, int hostAddress)



Ensure that a network route exists to deliver traffic to the specified host via the specified network interface.

void

setNetworkPreference(int preference)



Specifies the preferred network type.

int

startUsingNetworkFeature(int networkType,  String



Tells the underlying networking system that the caller wants to begin using the named feature.

int

stopUsingNetworkFeature(int networkType,  String



Tells the underlying networking system that the caller is finished using the named feature.

 二. NetworkInfo详解

        NetworkInfo是一个描述网络状态的接口，可通过ConnectivityManager调用getActiveNetworkInfo()获得当前连接的网络类型。

        NetworkInfo有两个枚举类型的成员变量NetworkInfo.DetailedState和NetworkInfo.State，用于查看当前网络的状态。其中NetworkInfo.State的值包括：

NetworkInfo.State

CONNECTED 

已连接

NetworkInfo.State

CONNECTING 

正在连接

NetworkInfo.State

DISCONNECTED 


NetworkInfo.State

DISCONNECTING 


NetworkInfo.State

SUSPENDED 


NetworkInfo.State

UNKNOWN 


        NetworkInfo.DetailedState则状态描述更为详细。    

        NetworkInfo还包括一系列可用的方法用于判断当前网络是否可用，如下：

Public Methods

NetworkInfo.DetailedState

getDetailedState()



Reports the current fine-grained state of the network.

String

getExtraInfo()



Report the extra information about the network state, if any was provided by the lower networking layers., if one is available.

String

getReason()  如果数据网络连接可用，但是连接失败，则通过此方法可获得尝试链接失败的原因



Report the reason an attempt to establish connectivity failed, if one is available.

NetworkInfo.State

getState()   获取网络连接的粗粒度状态



Reports the current coarse-grained state of the network.

int

getSubtype()  



Return a network-type-specific integer describing the subtype of the network.

String

getSubtypeName()



Return a human-readable name describing the subtype of the network.

int

getType()报告当前网络从属的网络类型


NetworkInfo

String

getTypeName() 报告当前网络从属的网络类型，更明确的方式如wifi,和mobile等。



Return a human-readable name describe the type of the network, for example "WIFI" or "MOBILE".

boolean

isAvailable()   判断当前网络是否可用



Indicates whether network connectivity is possible.

boolean

isConnected()   判断当前网络是否存在，并可用于数据传输



Indicates whether network connectivity exists and it is possible to establish connections and pass data.

boolean

isConnectedOrConnecting()  



Indicates whether network connectivity exists or is in the process of being established.

boolean

isFailover()



Indicates whether the current attempt to connect to the network resulted from the ConnectivityManager trying to fail over to this network following a disconnect from another network.

boolean

isRoaming()   判断设备当前是否在网络上漫游



Indicates whether the device is currently roaming on this network.

String

toString( )  返回一个包含该网络的简单的易懂的字符串描述。



Returns a string containing a concise, human-readable description of this object.




以上摘自网络，下面代码判断系统网络状态

public enum NetType {
        NONE, WIFI, CELLULAR
    }
 /**
     * 判断网络状态
     *
     * @param context
     * @return
     */
    public static NetType getNetType(Context context){
        ConnectivityManager conManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        Trace.i("Tools", "conManger:" + conManger);
        if(conManager == null){
            return NetType.NONE;
        }

        NetworkInfo networkInfo = conManager.getActiveNetworkInfo();
        if(networkInfo == null || ! networkInfo.isAvailable()){
            return NetType.NONE;//网络未连接
        }

        if(networkInfo.getType() == ConnectivityManager.TYPE_WIFI){
            return NetType.WIFI;//连接WIFI
        }

        return NetType.CELLULAR;//连接移动网络
    }