如何在Android中了解服务器是否可达？

Question

嗨，我想知道我的网站可访问或可用吗？

我知道我的设备是否在线：

protected boolean isOnline() {

        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnectedOrConnecting()) {
            Toast.makeText(this, "You are connecting to Internet!", Toast.LENGTH_LONG).show();
            return true;
        } else {
            Toast.makeText(this, "You are not connecting to Internet!", Toast.LENGTH_LONG).show();
            return false;
        }
    }

使用这种方法，我想知道URL是否可用：

public boolean isServerReachable(String serverURL) {

        ConnectivityManager connMan = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = connMan.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnected()) {
            try {
                URL urlServer = new URL(serverURL);
                HttpURLConnection urlConn = (HttpURLConnection) urlServer.openConnection();
                urlConn.setConnectTimeout(3000); //<- 3Seconds Timeout
                urlConn.connect();
                if (urlConn.getResponseCode() == 200) {
                    Toast.makeText(this, "Server is Available", Toast.LENGTH_LONG).show();
                    return true;
                } else {
                    Toast.makeText(this, "Server is not Available", Toast.LENGTH_LONG).show();
                    return false;
                }
            } catch (MalformedURLException e1) {
                return false;
            } catch (IOException e) {
                return false;
            }
        }
        return false;
    }

然后我创建一个Button，单击时将调用这两个方法，如下所示：

if (isOnline()) {
    isServerReachable("https://www.google.com/");
 }

如果WiFi关闭，当我单击按钮时，此消息将显示：

您没有连接到互联网！

当WiFi开启时，此错误将显示：

> Process: com.rastari.salar.salytest, PID: 3864
>     android.os.NetworkOnMainThreadException
>             at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1147)
>             at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
>             at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
>             at java.net.InetAddress.getAllByName(InetAddress.java:215)
>             at com.android.okhttp.HostResolver$1.getAllByName(HostResolver.java:29)
>             at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:232)
>             at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:124)
>             at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:272)
>             at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:211)
>             at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:382)
>             at com.android.okhttp.internal.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:106)
>             at com.android.okhttp.internal.http.DelegatingHttpsURLConnection.connect(DelegatingHttpsURLConnection.java:89)
>             at com.android.okhttp.internal.http.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:25)
>             at com.rastari.salar.salytest.MainActivity.isServerReachable(MainActivity.java:78)
>             at com.rastari.salar.salytest.MainActivity$1.onClick(MainActivity.java:37)
>             at android.view.View.performClick(View.java:4780)
>             at android.view.View$PerformClick.run(View.java:19866)
>             at android.os.Handler.handleCallback(Handler.java:739)
>             at android.os.Handler.dispatchMessage(Handler.java:95)
>             at android.os.Looper.loop(Looper.java:135)
>             at android.app.ActivityThread.main(ActivityThread.java:5254)
>             at java.lang.reflect.Method.invoke(Native Method)
>             at java.lang.reflect.Method.invoke(Method.java:372)
>             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
>             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 06-25
> 06:14:16.845    1557-1557/? E/EGL_emulation﹕ tid 1557:
> eglCreateSyncKHR(1207): error 0x3004 (EGL_BAD_ATTRIBUTE) 06-25
> 06:14:17.614    1708-1891/? E/WifiStateMachine﹕ CMD_START_SCAN :
> connected mode and no configuration

如何确定服务器可用？

感谢你。

Answer 1

从Asynctask调用方法isServerReachable() 。

由于您是在应用程序的主线程上进行网络调用，因此崩溃。

Answer 2

该错误是由于isServerReachable()方法引起的，因为您正在UI线程中进行联网操作，这将导致NetworkOnMainThreadException 。 而不是直接运行它们，而是在AsyncTask或另一个辅助Thread执行该方法。

 public class MyAsyncTask extends AsyncTask<Void, Void, Boolean> {
        @Override
        protected Boolean doInBackground(Void... params) {
            return isServerReachable(URl);
        }

        @Override
        protected void onPostExecute(Boolean aBoolean) {
            super.onPostExecute(aBoolean);
            //Perform operations.
        }
    }