检查当前网络是否连上

ConnectivityManager con=(ConnectivityManager)getSystemService(Activity.CONNECTIVITY_SERVICE);  

boolean wifi=con.getNetworkInfo(ConnectivityManager.TYPE_WIFI).isConnectedOrConnecting();  

boolean internet=con.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).isConnectedOrConnecting();

在AndroidManifest.xml 增加权限：

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