您可以使用广播接收器，并等待操作 ConnectivityManager.CONNECTIVITY_ACTION

You can use a Broadcast receiver and wait for the action ConnectivityManager.CONNECTIVITY_ACTION

下面的doc

例如：

broadcastReceiver = new BroadcastReceiver() {

                @Override
                public void onReceive(Context context, Intent intent) {

                    ConnectivityManager connectivity = (ConnectivityManager) context
                            .getSystemService(Context.CONNECTIVITY_SERVICE);


                        NetworkInfo[] info = connectivity.getAllNetworkInfo();
                        //Play with the info about current network state


                    }

                }
            };

            intentFilter = new IntentFilter();
            intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
            registerReceiver(broadcastReceiver, intentFilter);