檢查網站是否在線

Question

我試圖檢查website是否在線。我已經嘗試過這樣的：

public static boolean checkisonline(String targetUrl) { 

    if (android.os.Build.VERSION.SDK_INT > 9) { 
     StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
     StrictMode.setThreadPolicy(policy); 
    } 

    HttpURLConnection httpUrlConn; 
    try { 
     httpUrlConn = (HttpURLConnection) new URL(targetUrl) 
       .openConnection(); 

     httpUrlConn.setRequestMethod("HEAD"); 

     // Set timeouts in milliseconds 
     httpUrlConn.setConnectTimeout(30000); 
     httpUrlConn.setReadTimeout(30000); 

     // Print HTTP status code/message for your information. 
     System.out.println("Response Code: " 
       + httpUrlConn.getResponseCode()); 
     System.out.println("Response Message: " 
       + httpUrlConn.getResponseMessage()); 

     return (httpUrlConn.getResponseCode() == HttpURLConnection.HTTP_OK); 
    } catch (Exception e) { 
     System.out.println("Error: " + e.getMessage()); 
     return false; 
    } 
} 

但我總是得到Error: null在輸出中，即使該網站是在線。

Stackdrace：
03-05 14:51:30.931 8409-8460/de.treevo.app I/System.out﹕ Error: null 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ java.io.EOFException 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at java.util.zip.GZIPInputStream.readFully(GZIPInputStream.java:202) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:98) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at java.util.zip.GZIPInputStream.<init>(GZIPInputStream.java:81) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at com.android.okhttp.internal.http.HttpEngine.initContentStream(HttpEngine.java:468) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at com.android.okhttp.internal.http.HttpEngine.readResponse(HttpEngine.java:666) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:347) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponseCode(HttpURLConnectionImpl.java:503) 03-05 14:51:30.931 8409-8460/de.treevo.app W/System.err﹕ at de.treevo.core.functions.checkisonline(functions.java:79) 03-05 14:51:30.941 8409-8460/de.treevo.app W/System.err﹕ at de.treevo.app.add_series$1.run(add_series.java:167) 03-05 14:51:30.941 8409-8460/de.treevo.app W/System.err﹕ at java.lang.Thread.run(Thread.java:841)

Answer 1

存在，你可以用它來實現這一目標的java.net.InetAddress中的類中的方法：

http://developer.android.com/reference/java/net/InetAddress.html#isReachable%28java.net.NetworkInterface,%20int,%20int%29