HttpGet 为特定 url 返回 null

Question

当 URL="http://rest.riob.us/v3/search/474" 时，我的以下代码可以正常工作。

但是对于 URL="http://dadosabertos.rio.rj.gov.br/apiTransporte/apresentacao/rest/index.cfm/onibus/474" 返回 null。

两个 URL 在 webbrowser 上都可以正常工作。

这是我的代码：

public class HttpGetAsyncTask  extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... urls) {

    return GET(urls[0]);
}
// onPostExecute displays the results of the AsyncTask.
@Override
protected void onPostExecute(String result) {

    Log.w("TAG", "result: " + result);
}

public static String GET(String url){
    InputStream inputStream = null;
    String result = "";
    try {

        // create HttpClient
        HttpClient httpclient = new DefaultHttpClient();

        // make GET request to the given URL
        HttpResponse httpResponse = httpclient.execute(new HttpGet(url));

        // receive response as inputStream
        inputStream = httpResponse.getEntity().getContent();

        Log.v("TAG", "inputStream: " + inputStream);
        Log.e("TAG", "httpResponse.getEntity().getContentLength(): " + httpResponse.getEntity().getContentLength());

        // convert inputstream to string
        if(inputStream != null)
            result = convertInputStreamToString(inputStream);
        else
            result = "Did not work!";

    } catch (Exception e) {
        Log.d("TAG", e.getLocalizedMessage());
    }

    return result;
} 

private static String convertInputStreamToString(InputStream inputStream) throws IOException{
    BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(inputStream));
    String line = "";
    String result = "";
    while((line = bufferedReader.readLine()) != null)
        result += line;

    inputStream.close();
    return result;

}

}

可能出了什么问题？提前谢谢

Answer 1

如果您正在为 API 或 JSON 执行网络请求，请查看 VOLLEY 库。它使用起来超级简单，它为您处理队列、异步和缓存。示例：

RequestQueue queue = Volley.newRequestQueue(this);

JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, URL, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            //DO WITH RESPONSE
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            //CRAP ERROR
            Log.e("Volley", error.toString());
        }
    });
queue.add(request);

说真的，如果您要请求 JSON 数据，使用 Volley 就简单多了！这是 JSON 请求所需的所有代码，它还提供其他内置的图像或字符串请求类型，甚至允许自定义类型。