AsyncTask：DoInBackground(String...) 与 DoInBackground(Params...) 冲突？

Question

当尝试使用 Async task 执行 HTTP 发布时，我得到以下信息：

ASyncTask: DoInBackground(String...) clashes with DoInBackground(Params...) in Android.os.AsyncTask; attempting to use incompatible return type

我该如何解决这个问题？这是我第一次使用 AsyncTask。

导致错误的特定行：

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

来自完整 AsyncTask 的代码：

private class MyTask extends AsyncTask<String, Void, Void>
    {
        boolean success = false;

        @Override
        protected String doInBackground(String... params) {
            StringBuilder respData = new StringBuilder();
            URL url = new URL("MY_URL");
            URLConnection conn = url.openConnection();
            HttpURLConnection httpUrlConnection = (HttpURLConnection) conn;

            httpUrlConnection.setUseCaches(false);
            httpUrlConnection.setRequestProperty("User-Agent", "App");
            httpUrlConnection.setConnectTimeout(30000);
            httpUrlConnection.setReadTimeout(30000);

            httpUrlConnection.setRequestMethod("POST");
            httpUrlConnection.setDoOutput(true);

            OutputStream os = httpUrlConnection.getOutputStream();
            //InputStream postStream = toInputStream(toSubmit, "UTF-8");
            InputStream stream = new ByteArrayInputStream(toSubmit.getBytes(StandardCharsets.UTF_8));
            try {
                copy(stream, os);
            } finally {
                stream.close();
                os.flush();
                os.close();
            }

            httpUrlConnection.connect();

            int responseCode = httpUrlConnection.getResponseCode();

            if (200 == responseCode) {
                InputStream is = httpUrlConnection.getInputStream();
                InputStreamReader isr = null;
                try {
                    isr = new InputStreamReader(is);
                    char[] buffer = new char[1024];
                    int len;
                    while ((len = isr.read(buffer)) != -1) {
                        respData.append(buffer, 0, len);
                    }
                } finally {
                    if (isr != null)
                    {
                        isr.close();
                        success = true;
                    }
                }
                is.close();
            }
            else {
                // use below to get error stream
                // inputStream = httpUrlConnection.getErrorStream();
            }
            return "done";
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);

            Toast toast = Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT);

        }
    }

Answer 1

像这样声明你的课

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

最后一个参数是您将从 doInBackground 返回的类型，它也是 onPostExecute 的输入。

Answer 2

来自AsyncTask 的文档：

异步任务由 3 种泛型类型定义，称为 Params， 进展与结果

您的doInBackground() 方法返回一个String 值，但您的代码中的Result 参数是Void。将doInBackground() 的return 值从String 更改为Void 将解决问题 - 或者，您可以将<String, Void, Void> 替换为<String, Void, String>