连通状态改变(包括wifi,3G等移动网络):
android.net.conn.CONNECTIVITY_CHANGE
ConnectivityManager.CONNECTIVITY_ACTION
wifi连接改变:
android.net.wifi.RSSI_CHANGED
 
判断网络连通状态(包括wifi,3G等):
public boolean isNetworkConnected(Context context) {  
    if (context != null) {  
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context  
                .getSystemService(Context.CONNECTIVITY_SERVICE);  
        NetworkInfo mNetworkInfo = mConnectivityManager.getActiveNetworkInfo();  
        if (mNetworkInfo != null) {  
            return mNetworkInfo.isAvailable();  
        }  
    }  
    return false;  
}
wifi连通状态:
public boolean isWifiConnected(Context context) {  
    if (context != null) {  
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context  
                .getSystemService(Context.CONNECTIVITY_SERVICE);  
        NetworkInfo mWiFiNetworkInfo = mConnectivityManager  
                .getNetworkInfo(ConnectivityManager.TYPE_WIFI);  
        if (mWiFiNetworkInfo != null) {  
            return mWiFiNetworkInfo.isAvailable();  
        }  
    }  
    return false;  
}
3G等移动的连通状态:
public boolean isMobileConnected(Context context) {  
    if (context != null) {  
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context  
                .getSystemService(Context.CONNECTIVITY_SERVICE);  
        NetworkInfo mMobileNetworkInfo = mConnectivityManager  
                .getNetworkInfo(ConnectivityManager.TYPE_MOBILE);  
        if (mMobileNetworkInfo != null) {  
            return mMobileNetworkInfo.isAvailable();  
        }  
    }  
    return false;  
}
     
获取当前网络连接类型:
public static int getConnectedType(Context context) {  
    if (context != null) {  
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context  
                .getSystemService(Context.CONNECTIVITY_SERVICE);  
        NetworkInfo mNetworkInfo = mConnectivityManager.getActiveNetworkInfo();  
        if (mNetworkInfo != null && mNetworkInfo.isAvailable()) {  
            return mNetworkInfo.getType();  
        }  
    }  
    return -1;  
}