来自新闻 API 的 Json 结果为空

Posted 2023-04-19

【中文标题】来自新闻 API 的 Json 结果为空

【英文标题】：Json Result from News API is null

【发布时间】：2020-10-20 16:50:24

【问题描述】：

 @Override
    protected String doInBackground(String... strings) 
        String result = HttpRequest.getExecute("http://newsapi.org/v2/everything?q=bitcoin&from=2020-05-30&sortBy=publishedAt&apiKey=myAPIkey");
        return result;
    

即使在浏览器上打开相同的 URL 时显示很多内容，我在传递此 URL 时仍收到空响应。我收到空指针异常。请帮忙。下面是我的 HttpRequest 类。

HTTPRequest 类：

public class HttpRequest   
public static String getExecute(String targetUrl)

    URL url;
    HttpURLConnection httpURLConnection = null;
    try
    
        url = new URL(targetUrl);
        httpURLConnection = (HttpURLConnection) url.openConnection();
        httpURLConnection.setRequestMethod("GET");

        InputStream inputStream;
        if (httpURLConnection.getResponseCode() != HttpURLConnection.HTTP_OK)

            inputStream = httpURLConnection.getErrorStream();
        else
            inputStream = httpURLConnection.getInputStream();

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String line;
        StringBuffer response = new StringBuffer();
        while ( (line = bufferedReader.readLine()) != null)
        
            response.append(line);
            response.append('\r');

        
        bufferedReader.close();
        return  response.toString();


    
    catch (Exception e)
    
     e.printStackTrace();
     return  null;
    
    finally 
        if(httpURLConnection != null)
        
            httpURLConnection = null;
        
    

【问题讨论】：

这能回答你的问题吗？ What is a NullPointerException, and how do I fix it?

你在哪里得到空值？

在方法 doInBackground..结果为空。我记录了结果并检查了它。

你在 catch 块中返回 null，所以应该有一个异常，尝试打印异常并找出问题的原因

【参考方案1】：

您必须在读取结果或响应代码之前调用 connect 方法。设置请求方法后添加以下行

httpURLConnection.connect()