Question

我是Java ME新手，我想创建一个可以在线获取特定货币最新汇率的应用程序，我该如何完成？

我已经能够创建一个HttpConnection对象并从URL中检索数据，但它不适用于谷歌。

我在一个标题为here的问题中看到了一个示例How to get a live exchange rate data and apply it to an Android App。但是，如果我在移动应用程序上尝试它，它会返回nothings。我该如何解决这个问题？

String url = "http://www.google.com/ig/calculator?hl=en&q=1USD%3D%3FCAD";//test URL
c = (HttpConnection)Connector.open(url);
s = c.openInputStream();//open an input stream
if( l != -1 ) {
  for (i =0 ; i < l ; i++ )
  if((ch = s.read()) != -1){
     b.append((char) ch);
    }
}
stringItem2.setText("\n " + b.toString());

用

String url = "http://developers.sun.com/mobility/midp/articles/event/EventEx1.java";

我可以获取网站数据，但是

String url = "http://www.google.com/ig/calculator?hl=en&q=1USD%3D%3FCAD";

我什么都没得到

Answer 1

我会使用http://xurrency.com/api/来检索最新的汇率，如果您每天查询超过10次，则需要支付29.99。该页面的文档部分介绍了如何使用API。例如。要使用http://xurrency.com/api/usd/eur/1检索美国到EURO的兑换。如果您在浏览器中输入此内容并查看源，您将看到检索到的响应。响应是JSON。

您需要使用GSON之类的东西将JSON数据转换为Java对象。执行此操作的代码应该非常简单，例如：

    URL url = new URL("http://xurrency.com/api/usd/eur/1");
    URLConnection yc = url.openConnection();
    BufferedReader in = new BufferedReader(
                            new InputStreamReader(
                            yc.getInputStream()));
    String jsonObject = "";
    String line;
    while ((line = in.readLine()) != null) 
        jsonObject += line;

    in.close();
    Gson gson = new Gson();
    ExchangeRate = gson.fromJson(jsonObject, ExchangeRate.class);

ExchnageRate类是一个自定义类，用于封装从此JSON API检索的数据。

您可以使用您正在使用的链接使上述代码正常工作。请尝试以下代码：

  import com.google.gson.Gson;
  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.net.URL;
  import java.net.URLConnection;

  public class Main {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://www.google.com/ig/calculator?hl=en&q=1USD%3D%3FCAD");
        URLConnection yc = url.openConnection();
        BufferedReader in = new BufferedReader(
                            new InputStreamReader(
                            yc.getInputStream()));
        String jsonObject = "";
        String line;
        while ((line = in.readLine()) != null) 
            jsonObject += line;

        in.close();
        System.out.println(jsonObject);
        Gson gson = new Gson();
        GoogleCurrency another = gson.fromJson(jsonObject, GoogleCurrency.class);
        another.print();
    }

  }


  public class GoogleCurrency {
     private String lhs;
     private String rhs;
     private String error;
     private String icc;

   public GoogleCurrency() {
    lhs = "0 U.S Dollar";
    rhs = "0 U.S Dollar";
    error = "true";
    icc = "false";
   }

   public GoogleCurrency(String lhs,String rhs,String error,String icc) {
    this.lhs = lhs;
    this.rhs = rhs;
    this.error = error;
    this.icc = icc;
   }

   public void print() {
    System.out.println(lhs + " = " + rhs);
   }
 }

Answer 2

请找到以下代码，该代码返回json响应以获取转换率。

    HttpClient client = new HttpClient();       

    NameValuePair arg1 = new NameValuePair("method","runJob");

    //Change your currency types here in which you would want to convert

    NameValuePair arg2 = new NameValuePair("from","USD");
    NameValuePair arg3 = new NameValuePair("to", "PKR");

    //getting the method
    GetMethod method = new GetMethod("http://rate-exchange.appspot.com/currency");
    method.setQueryString(new NameValuePair[]{arg1, arg2, arg3});

    //executes the link
    client.executeMethod(method);

    //getting response in string
    JSONObject obj = new JSONObject(method.getResponseBodyAsString());

    //getting rate from the json response
    double rate = obj.getDouble("rate");

    //closing conncetion
    method.releaseConnection();     


    //returning value
    return rate;

如何在java-me中获取最新的汇率数据

2 个答案: