这里有一个简单的解决方案，以确保你的应用程序可以访问互联网:

static final String CHECK_INTERNET_ACCESS_URL = "https://www.google.com";

public static void isInternetAccessWorking(Context context) {

    StringRequest stringRequest = new StringRequest(Request.Method.GET, CHECK_INTERNET_ACCESS_URL,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    // Internet access is OK
                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            // NO internet access
        }
    });

    Volley.newRequestQueue(context).add(stringRequest);
}

这个解决方案使用Android的Volley库，必须在build.gradle中声明:

implementation 'com.android.volley:volley:1.1.1'

看一下ConnectivityManager类。您可以使用这个类来获取主机上活动连接的信息。http://developer.android.com/reference/android/net/ConnectivityManager.html

编辑:你可以使用

Context.getSystemService(Context.CONNECTIVITY_SERVICE)
    .getNetworkInfo(ConnectivityManager.TYPE_MOBILE) 

or

Context.getSystemService(Context.CONNECTIVITY_SERVICE)
    .getNetworkInfo(ConnectivityManager.TYPE_WIFI) 

并解析返回NetworkInfo对象的DetailedState枚举

EDIT EDIT:查看是否可以访问主机

Context.getSystemService(Context.CONNECTIVITY_SERVICE)
    .requestRouteToHost(TYPE_WIFI, int hostAddress)

显然，我使用Context.getSystemService(Context.CONNECTIVITY_SERVICE)作为代理来表示

ConnectivityManager cm = Context.getSystemService(Context.CONNECTIVITY_SERVICE);
cm.yourMethodCallHere();

如果设备处于飞行模式(或者假设在没有可用网络的其他情况下)，cm.getActiveNetworkInfo()将为空，因此您需要添加一个空检查。

修改(Eddie的解决方案)如下:

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();
}

在AndroidManifest.xml中添加以下权限:

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

还有一点，如果你在给定的时间点绝对需要一个网络连接，那么使用netInfo.isConnected()而不是netInfo.isConnectedOrConnecting可能会更好。不过，我想这取决于个人用例。

public static boolean isNetworkAvailable(Context ctx) {
ConnectivityManager connMgr = (ConnectivityManager)ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
if(connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI).isConnected() ||
    connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).isConnected()){
        return true;
}

return false;
 } 

用户这

这对我很有用。试试吧。

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    try {
        URL url = new URL("http://stackoverflow.com/posts/11642475/edit" );
        //URL url = new URL("http://www.nofoundwebsite.com/" );
        executeReq(url);
        Toast.makeText(getApplicationContext(), "Webpage is available!", Toast.LENGTH_SHORT).show();
    }
    catch(Exception e) {
        Toast.makeText(getApplicationContext(), "oops! webpage is not available!", Toast.LENGTH_SHORT).show();
    }
}

private void executeReq(URL urlObject) throws IOException
{
    HttpURLConnection conn = null;
    conn = (HttpURLConnection) urlObject.openConnection();
    conn.setReadTimeout(30000);//milliseconds
    conn.setConnectTimeout(3500);//milliseconds
    conn.setRequestMethod("GET");
    conn.setDoInput(true);

    // Start connect
    conn.connect();
    InputStream response =conn.getInputStream();
    Log.d("Response:", response.toString());
}}

public class Network {

Context context;

public Network(Context context){
    this.context = context;
}

public boolean isOnline() {
    ConnectivityManager cm =
            (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    return activeNetwork != null &&
                          activeNetwork.isConnectedOrConnecting();
}

}