如何知道UnknownHostException的原因？ [英] How to know the cause of UnknownHostException?

问题描述

如果服务器关闭或没有互联网连接，则会抛出 UnknownHostException 。如何确定是否由于服务器关闭或没有互联网连接而抛出 UnknownHostException ？

An UnknownHostException is thrown if a server is down or if there is no internet connection. How can I determine if the UnknownHostException is thrown because the server is down or there is no internet connection?

原因是我需要通知用户有关错误的原因。而且我必须显示类似抱歉。该服务当前不可用。请稍后再试或您没有互联网连接。

The reason for this is I need to notify the user about the cause of the error. And I have to display something like this "Sorry. The service is currently not available. Please try again later" or "You do not have an internet connection".

推荐答案

您可以检查网络状态以确定是否可以使用Internet连接（尽管并非100％可靠）：

You could check the network state to determine if an internet connection is available (not 100% reliable though):

ConnectivityManager conMgr =  (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);

if ( conMgr.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTED 
    ||  conMgr.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTING  ) {
...
}

编辑：

EDIT :

恕我直言，无法告诉确定电话互联网连接已断开。
但是，除了检查网络状态之外，您还可以进行简单的测试，例如从Internet上的网站下载一个小页面（选择一些可靠的服务器）。

IMHO, there is no way to tell for sure that the phone internet connectivity is down. But you could, in addition to checking the network state, make a simple test like downloading a small page from a website on the internet (pick some reliable server).

此双重测试的结果应该在99％的时间内都是准确的。

The result of this double test should be accurate 99% of the time.

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