java - 如何在Java/Android中访问AsyncTask中的不同URL

Question

尝试使用同一类中的不同 URL 时遇到问题。我会多次访问类似下面的网页。

我查找了许多不同的 Q/As 和教程，但似乎找不到如何将 URL 作为参数传递，因此在 doInBackground 方法中使用它。我这样调用执行方法:

new RetrieveFeedTask().execute();

private class RetrieveFeedTask extends AsyncTask<Void, Void, String> {

    protected void onPreExecute() {
    }

    protected String doInBackground(Void... urls) {
        try {
            URL url = new URL(API_URL_COMPETITIONS); // this is url http://api.football-data.org/v1/competitions
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try {
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReadelConnection.getInputStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    stringBuilder.append(line).append("\n");
                }
                bufferedReader.close();
                return stringBuilder.toString();
            } finally {
                urlConnection.disconnect();
            }
        } catch (Exception e) {
            Log.e("ERROR", e.getMessage(), e);
            return null;
        }
    }

    //entire JSON page is saved in response
    protected void onPostExecute(String response) {
        if(response == null) {
            response = "THERE WAS AN ERROR";
        }
        Log.i("INFO", response);
        try {
            JSONArray comps = new JSONArray(response);
            JSONObject second = comps.getJSONObject(1); //this is array element PremierLeague2016/2017
            compArray.add("Competition");
            compArray.add(second.getString("caption"));
             //i then set this to an ArrayAdapter and show the results in a Spinner.                 adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            competition.setAdapter(adapter);
            adapter.notifyDataSetChanged();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

感谢任何帮助!

Answer 1

can't seem find how to pass a URL as a parameter so it is used in the doInBackground method

AsyncTask 类是 AsyncTask<Params, Progress, Result> 。你想要一个String参数，不是 Void范围。

private class RetrieveFeedTask extends AsyncTask<String, Void, String> 

然后你可以使用protected String doInBackground(String... urls) (因为无效网址没有意义)

并更新您的通话

String url1 = "http://...";
String url2 = "http://...";
new RetrieveFeedTask().execute(url1, url2);

在 doInBackground 中

for (String url : urls) {
     try { 
         URL url = new URL(url);
         HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

或者，忘记循环...您可以简单地访问 urls[0]例如，要获取第一个 String 值，只需小心 IndexOutOfBoundsException