Android 判断网络是不是可用

import android.app.Activity;import android.content.Context;import android.net.ConnectivityManager;import android.net.NetworkInfo;public class NetworkDetector { /**  * 判断网络是否可用  * @param act  * @return  */ public static Boolean detect(Activity act) {  ConnectivityManager manager = (ConnectivityManager) act    .getApplicationContext().getSystemService(      Context.CONNECTIVITY_SERVICE);  if (manager == null) {   return false;  }  NetworkInfo networkinfo = manager.getActiveNetworkInfo();  if (networkinfo == null || !networkinfo.isAvailable()) {   return false;  }  return true; }}

因为以上代码用到了权限，需要在AndroidManifest文件中加入如下权限代码：

    <uses-permission

       android:name="android.permission.ACCESS_NETWORK_STATE" />