Android-判断当前网络是否可用

public class NetworkDetector {

    /** 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;

    /** Unknown network class. {@hide} */
    public static final int NETWORK_CLASS_UNKNOWN = 0;
    /** Class of broadly defined "2G" networks. {@hide} */
    public static final int NETWORK_CLASS_2_G = 1;
    /** Class of broadly defined "3G" networks. {@hide} */
    public static final int NETWORK_CLASS_3_G = 2;
    /** Class of broadly defined "4G" networks. {@hide} */
    public static final int NETWORK_CLASS_4_G = 3;
    /** Class of broadly defined "WIFI" networks. {@hide} */
    public static final int NETWORK_CLASS_WIFI = 4;
    /** Class of broadly defined "NONET" networks. {@hide} */
    public static final int NETWORK_CLASS_NONET = 5;

    /**
     * 判断当前网络是否可用
     * 
     * @param context
     * @return true：可用，false:不可用；
     */
    public static boolean isAvailable(Context context) {
        ConnectivityManager manager = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);

        if (manager == null) {
            return false;
        }
        NetworkInfo networkinfo = manager.getActiveNetworkInfo();
        // NetworkInfo.isAvailable() 如果网络可用返回true，否则返回false。
        if (networkinfo == null || !networkinfo.isAvailable()) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * 判断当前的网络状态
     * 
     * @param context
     * @return 0、未知， 1、2G， 2、3G， 3、4G， 4、wifi， 5、noNet；
     */
    public static int getNetWorkType(Context context) {
        ConnectivityManager manager = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        if (manager == null) {
            return NETWORK_CLASS_NONET;
        }
        NetworkInfo networkinfo = manager.getActiveNetworkInfo();
        if (networkinfo == null || !networkinfo.isAvailable()) {
            return NETWORK_CLASS_NONET;
        }

        if (networkinfo.getType() == ConnectivityManager.TYPE_WIFI) {
            return NETWORK_CLASS_WIFI;
        } else {
            return getNetworkClass(((TelephonyManager) context
                    .getSystemService(Context.TELEPHONY_SERVICE))
                    .getNetworkType());
        }
    }

    public static int getNetworkClass(int networkType) {
        switch (networkType) {
        case NETWORK_TYPE_GPRS:
        case NETWORK_TYPE_EDGE:
        case NETWORK_TYPE_CDMA:
        case NETWORK_TYPE_1xRTT:
        case NETWORK_TYPE_IDEN:
            return NETWORK_CLASS_2_G;

        case NETWORK_TYPE_UMTS:
        case NETWORK_TYPE_EVDO_0:
        case NETWORK_TYPE_EVDO_A:
        case NETWORK_TYPE_HSDPA:
        case NETWORK_TYPE_HSUPA:
        case NETWORK_TYPE_HSPA:
        case NETWORK_TYPE_EVDO_B:
        case NETWORK_TYPE_EHRPD:
        case NETWORK_TYPE_HSPAP:
            return NETWORK_CLASS_3_G;

        case NETWORK_TYPE_LTE:
            return NETWORK_CLASS_4_G;

        default:
            return NETWORK_CLASS_UNKNOWN;
        }
    }
}