在android中调用httpget时出错（检索google方向）

我试图用android httpget调用此URL，以获得一个json方向数组：

基本上这就是我到目前为止所做的：

1）为了调用google directions并记录检索到的结果，我首先创建了一个asynctask：

public class MyTask extends AsyncTask<String, Integer, String> {

@Override
protected String doInBackground(String... params) {

InputStream is = null;

    String result = null;

try{

        HttpClient httpclient = new DefaultHttpClient();
         HttpGet httpget = new HttpGet(params[0]);
         HttpResponse response = httpclient.execute(httpget);
         HttpEntity entity = response.getEntity();
         int lenght = (int) entity.getContentLength();

         StringBuffer buffer = new StringBuffer(lenght);

         is = entity.getContent();
         }catch(Exception e){
             Log.e("log_tag", "Error in http connection"+e.toString());
        }

    try{
        BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);

         StringBuilder sb = new StringBuilder();
         sb.append(reader.readLine() + "\n");

         String line="0";
         while ((line = reader.readLine()) != null) {
                        sb.append(line + "\n");
          }
          is.close();
        result = sb.toString();
          }catch(Exception e){
                Log.e("log_tag", "Error converting result "+e.toString());
          }

    Log.i("Result", result);


    return result;



  }


}

其中urlString是一个StringBuilder。我尝试了几种方法来构建该地址，甚至尝试使用URLEncoder.encode（myUrl）对其进行编码但是我总是会遇到一个异常，那就是http connectionjava.lang.NegativeArraySizeException中的错误，我无法从google检索json数据。我如何正确格式化该url？我的目标是实现与这个家伙（在json部分）相同的结果：

---

谢谢！

请删除有问题的代码，因为它没有在任何地方使用

//int lenght = (int) entity.getContentLength();

//StringBuffer buffer = new StringBuffer(lenght);

---

我终于明白了！我改变了google Web服务的调用方式。基本上这部分：

     HttpClient httpclient = new DefaultHttpClient();
     HttpGet httpget = new HttpGet(params[0]);
     HttpResponse response = httpclient.execute(httpget);
     HttpEntity entity = response.getEntity();

用另一种方式调用google Web服务：

        HttpURLConnection urlConnection = null;
        url = new URL("http://maps.googleapis.com/maps/api/directions/json?origin=Adelaide,SA&destination=Adelaide,SA&waypoints=optimize:true%7cBarossa+Valley,SA%7cClare,SA%7cConnawarra,SA%7cMcLaren+Vale,SA&sensor=false");
        urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.setRequestMethod("GET");
        urlConnection.setDoOutput(true);
        urlConnection.setDoInput(true);
        is = urlConnection.getInputStream();
        urlConnection.connect();

然后我将输入流“链接”到InputStreamReader中，将InputStreamReader“链接”到缓冲读取器中，一切正常：

        InputStreamReader inputStream = new InputStreamReader(is);
        BufferedReader r = new BufferedReader(inputStream);
        String line = null;
        line = r.readLine();
        while (line!=null){

            Log.i("RESULT", line);

            line = r.readLine();

        }

---

通过这种方式，我可以记录所需的结果。我想了解的一件事是，为什么httpclient不工作，而httpURLConnection却工作。有人能帮我吗？

logcat中的Stacktrace应该指向失败的行，post；pWell它指向下一行StringBuffer=newStringBuffer（lenght）；因此来自httpget的响应似乎是空的（可能是因为请求格式错误！）。但是它仍然不能工作！

        InputStreamReader inputStream = new InputStreamReader(is);
        BufferedReader r = new BufferedReader(inputStream);
        String line = null;
        line = r.readLine();
        while (line!=null){

            Log.i("RESULT", line);

            line = r.readLine();

        }