Android：未知主机异常
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Android: UnknownHostException
提问by anisbet
I am using Android SDK 2.2, testing my application with the emulator. I want to send a HTTP Post. When I do I get a UnknownHostException. I have placed the required permissions <uses-permission android:name="android.permission.INTERNET" />
in the manifest.xml. Also I can open the browser on the emulator and navigate to the URL with no problem.
我正在使用 Android SDK 2.2，用模拟器测试我的应用程序。我想发送一个 HTTP 帖子。当我这样做时，我得到一个 UnknownHostException。我已将所需的权限<uses-permission android:name="android.permission.INTERNET" />
放在 manifest.xml 中。此外，我可以在模拟器上打开浏览器并毫无问题地导航到 URL。
Here is my code:
这是我的代码：
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost( uri );
HttpResponse response = null;
try
{
// Add your data
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
2 );
nameValuePairs.add( new BasicNameValuePair( "id", "edit-name" ) );
nameValuePairs
.add( new BasicNameValuePair( "stringdata", userName ) );
httppost.setEntity( new UrlEncodedFormEntity( nameValuePairs ) );
// Execute HTTP Post Request
response = httpclient.execute( httppost );
// Log.i( "HttpManager:", "======> response: "
// + response.getEntity().getContent() );
}
catch (ClientProtocolException e)
{
Log.e( "HttpManager", "ClientProtocolException thrown" + e );
}
catch (IOException e)
{
Log.e( "HttpManager", "IOException thrown" + e );
}
回答by anisbet
Ok, I feel pretty lame... The INTERNET permission tag is a child of the manifest tag, not the application tag. Sheesh!
好吧，我觉得很蹩脚... INTERNET 权限标记是清单标记的子项，而不是应用程序标记。嘘！
回答by Frank V
For others' consideration, I ran in to this problem and a Google landed me. As mentioned by anisbet, I double checked my permission tag and it was in the right spot.
为了其他人的考虑，我遇到了这个问题，谷歌找到了我。正如 anisbet 所提到的，我仔细检查了我的许可标签，它在正确的位置。
I eventually fired up the android built in browser and was getting the same response from my web server as well as Google.com (while the computer itself was fine). I terminated the android emulator and restarted; worked on the first try.
我最终启动了内置浏览器的 android，并从我的网络服务器和 Google.com 得到了相同的响应（而计算机本身很好）。我终止了android模拟器并重新启动；第一次尝试。
After reviewing your code, it may be worth while to restart the emulator. In all fairness to the emulator, a bunch of programs crashed shortly after doing this, so perhaps something else was going on in my computer. Still, this wasted a ton of time for me so perhaps this will save someone the headache I went though.
查看您的代码后，重新启动模拟器可能是值得的。平心而论，一堆程序在执行此操作后不久就崩溃了，所以我的计算机中可能发生了其他事情。尽管如此，这对我来说还是浪费了大量时间，所以也许这可以避免我头痛的问题。
Best of Luck!
祝你好运！
回答by igo
Make sure you have an internet connection. That's what happened to me when I forgot I am testing with mobile phone with no internet connection.
确保您有互联网连接。当我忘记我正在使用没有互联网连接的手机进行测试时，这就是发生在我身上的事情。
回答by Moritz
You know what solved it for me was putting the permission just before the closing manifest tag, like so:
您知道为我解决的问题是将许可放在结束清单标签之前，如下所示：
<uses-permission android:name="android.permission.INTERNET" />
</manifest>
回答by java dev
It happens sometimes when you are running app in the emulator. Just restart the emulator will solve the problem. It worked for me !
当您在模拟器中运行应用程序时，有时会发生这种情况。只需重新启动模拟器即可解决问题。它对我有用！
回答by diadyne
If none of the above worked, try taking a step back and making sure that your device or emulator can actually reach the internet by opening up a browser.
如果上述方法均无效，请尝试退后一步，确保您的设备或模拟器可以通过打开浏览器实际访问互联网。
回答by Vijay
I ran in to the same issue. I have the correct permissions in my Android Manifest file and the Url is correct too. I am getting the response in the web browser. I restarted the IDE, Emulator, but didn't fix the problem. So i deleted the AVD using AVD manager and then started the emulator and it started to work.
我遇到了同样的问题。我在我的 Android 清单文件中拥有正确的权限，并且 URL 也是正确的。我在网络浏览器中收到响应。我重新启动了 IDE、模拟器，但没有解决问题。所以我使用 AVD 管理器删除了 AVD，然后启动了模拟器，它开始工作。
回答by metric152
I ran into a similar problem when testing an app that had a minSdkVersion set to 4 and I was trying to run it on a G1. Changing it to 3 solved the problem for me.
我在测试一个 minSdkVersion 设置为 4 的应用程序时遇到了类似的问题，我试图在 G1 上运行它。将其更改为 3 为我解决了问题。
回答by tlunter
A final check would be that your domain name is a valid domain. Having a underscore in a domain is invalid and will throw an unknown host exception.
最后的检查是您的域名是一个有效的域。在域中使用下划线是无效的，并且会抛出一个未知的主机异常。
回答by Tejaswi Yerukalapudi
One other thing: It turned out that the internet itself wasn't working for me. Launching the emulator from the commandline with these switches fixed it for me: emulator -avd your_avd_name -dns-server 8.8.8.8
另一件事：事实证明，互联网本身并不适合我。使用这些开关从命令行启动模拟器为我修复了它：emulator -avd your_avd_name -dns-server 8.8.8.8
