Return 来自 Asynctask 的字符串

Question

我正在尝试解析一个 json 对象，但我无法将 doInBackground 的结果转换为 onPostExecute

这是我的 AsyncTask 代码：

private class GetContacts extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Showing progress dialog
        pDialog = new ProgressDialog(MyActivity.this);
        pDialog.setMessage("Please wait...");
        pDialog.setCancelable(false);
        pDialog.show();

    }

    @Override
    protected Void doInBackground(Void... arg0) {
        // Creating service handler class instance
        ServiceHandler sh = new ServiceHandler();

        // Making a request to url and getting response
        String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

        Log.d("Response: ", "> " + jsonStr);
        if (jsonStr != null) {
            try {
                JSONObject jsonObj = new JSONObject(jsonStr);
                String auth2 = jsonObj.getString("auth");

            } catch (JSONException e) {
                e.printStackTrace();
            }
        } else {
            Log.e("ServiceHandler", "Couldn't get any data from the url");
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void auth2) {
        super.onPostExecute(auth2);
        // Dismiss the progress dialog
        if (pDialog.isShowing())
            pDialog.dismiss();
        Toast.makeText(getApplicationContext(), "String retrived:" + auth2, Toast.LENGTH_SHORT).show();
    }

}

我知道它可能是因为我在那里有 return null，但是当我制作 return 字符串时我得到错误。

我知道 jsonStr 保存 json 数据，我可以在日志中看到它： 回应：﹕ > {"user_info":{"auth":0}}

我从教程中整理了这段代码，这就是为什么我不完全理解它的原因。

我的目标是查看 auth 是 0 还是 1。

Answer 1

阅读文档： http://developer.android.com/reference/android/os/AsyncTask.html

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


    @Override
    protected String doInBackground(Void... arg0) {


        ...
        return "askdjalskdj";
    }

    @Override
    protected void onPostExecute(String auth2) {
        Log.i("Output", auth2);
    }

}

查看我在 Asynctask 的通用实现中设置的参数，查看 doInBackground 中定义的 return 值和 onPostExecute 的参数类型

AsyncTask's generic types The three types used by an asynchronous task are the following:

Params, the type of the parameters sent to the task upon execution.

Progress, the type of the progress units published during the background computation.

Result, the type of the result of the background computation.

Not all types are always used by an asynchronous task. To mark a type as unused, simply use the type Void:

private class MyTask extends AsyncTask { ... }

Answer 2

cant get the result out of doInBackground into onPostExecute

至 return auth2 来自 doInBackground 的字符串：

1. 将 doInBackground 方法的 return 类型从 Void 更改为 String:

 @Override
    protected String doInBackground(Void... arg0) {

   }

2. 将 AsyncTask 最后一个通用类型从 Void 更改为 String :

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

3. Return auth2 来自 doInBackground :

  String auth2 = jsonObj.getString("auth");
  return auth2;

4. 将 onPostExecute 参数类型从 Void 更改为 String :

@Override
    protected void onPostExecute(String auth2) {
        super.onPostExecute(auth2);
        //...
        Toast.makeText(getApplicationContext(),
            "String retrived:" + auth2, Toast.LENGTH_SHORT).show();
    }

Return 来自 Asynctask 的字符串

Return string from Asynctask

android

json

android-asynctask