android 如何判斷有沒有網絡

//從項目取出來的代碼，android  如何判斷有沒有網絡，分享一下

protected static int getAPNType(Context context) {
//給網絡設置值
int netType = -2;
//得到網絡管理器
ConnectivityManager connMgr = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);


NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo == null) {
return netType;
}

int nType = networkInfo.getType();
if (nType == ConnectivityManager.TYPE_MOBILE) {

Log.e("e"," , networkInfo.getExtraInfo() =  "
+  networkInfo.getExtraInfo());
if (networkInfo.getExtraInfo().toLowerCase().equals("cmnet")) {
netType = 1; // CMNET;
} else {
netType = 2; // CMWAP;
}
} else if (nType == ConnectivityManager.TYPE_WIFI) {
netType = 3;// WIFI
}


return netType;
}