HttpURLConnection错误

Question

我想从一个网站获取HTML，因为我使用的是这代码。当我尝试从文档中添加这代码时，我得到了这一错误

            //Get HTML
            URL url = new URL("http://www.android.com/");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try {
                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                readStream(in);
                finally {
                    urlConnection.disconnect();
                }
            }

哪里出了问题？我忘了进口一些东西了吗？

Answer 1

你没有忘记进口任何东西。

密码有几处问题。

1)您丢失了catch块以配合try，并且您的finally语句在if中不正确。它应该如下所示：

try {
    InputStream in = new BufferedInputStream(urlConnection.getInputStream());
    readStream(in);
} catch (Exception e) { // best practice is to be more specific with the Exception type
    urlConnection.disconnect();
    Log.w("Login", "Error downloading HTML from " + url);        
} finally {
    if(urlConnection != null) {
                urlConnection.disconnect();
    }
}

2)在文档中所跟踪的示例中，一旦流从urlConnection中检索到，它们将由您来决定如何处理它。

因此，在您的活动中创建您自己的void readStream(InputStream in)方法，然后可以使用InputStream。把它写到磁盘上，显示在屏幕上，由你来决定。

Answer 2

您缺少了catch子句。将其放在finally子句之前如下：

} catch (Exception e) { //it's bad practice to catch Exception, specify it more if you can, i just don't know what errors InputStream throws
    Log.e("ClassTag", e.getMessage(), e);
} finally { /* ... */ }

Answer 3

finally块不进入try块，将其更改为：

 try {
     InputStream in = new BufferedInputStream(urlConnection.getInputStream());
     readStream(in);
 }
 finally {
    urlConnection.disconnect();
}

还要确保您已经导入了java.net.URL。