如何从安卓中的异步任务中获取字符串形式的填充上传的 URL

Question

我正在使用异步任务在服务器上上传图像，最后我想返回上传的文件 url 的值。我该怎么做我将异步任务称为

new Config.UploadFileToServer(loginUserInfoId, uploadedFileURL).execute();

我的异步任务函数是：

public static final class UploadFileToServer extends AsyncTask<Void, Integer, String> {
            String loginUserInfoId = "";
            String filePath = "";
            long totalSize = 0;
            public UploadFileToServer(String userInfoId, String url){
                loginUserInfoId = userInfoId;
                filePath = url;
            }
            @Override
            protected void onPreExecute() {
                // setting progress bar to zero
                super.onPreExecute();
            }
            @Override
            protected void onProgressUpdate(Integer... progress) {
                // Making progress bar visible
                // updating progress bar value
            }
            @Override
            protected String doInBackground(Void... params) {
                return uploadFile();
            }
            @SuppressWarnings("deprecation")
            private String uploadFile() {
                String responseString = null;
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(Config.HOST_NAME +     "/AndroidApp/AddMessageFile/"+loginUserInfoId);
                try {
                    AndroidMultiPartEntity entity = new AndroidMultiPartEntity(
                            new AndroidMultiPartEntity.ProgressListener() {
                                @Override
                                public void transferred(long num) {
                                    publishProgress((int) ((num / (float) totalSize) * 100));
                                }
                            });
                    File sourceFile = new File(filePath);
                    // Adding file data to http body
                    entity.addPart("file", new FileBody(sourceFile));
                    totalSize = entity.getContentLength();
                    httppost.setEntity(entity);
                    // Making server call
                    HttpResponse response = httpclient.execute(httppost);
                    HttpEntity r_entity = response.getEntity();
                    int statusCode = response.getStatusLine().getStatusCode();
                    if (statusCode == 200) {
                        // Server response
                        responseString = EntityUtils.toString(r_entity);
                    } else {
                        responseString = "Error occurred! Http Status Code: "
                                + statusCode;
                    }
                } catch (ClientProtocolException e) {
                    responseString = e.toString();
                } catch (IOException e) {
                    responseString = e.toString();
                }
                responseString = responseString.replace(""","");
                return responseString;
            }
            @Override
            protected void onPostExecute(String result) {
                super.onPostExecute(result);
            }
        }

Answer 1

尝试我的代码，如下所示。

public Result CallServer(String params)
{
try
{
    MainAynscTask task = new MainAynscTask();
    task.execute(params);
    Result aResultM = task.get();  //Add this
}
catch(Exception ex)
{
     ex.printStackTrace();
}
 return aResultM;//Need to get back the result

}

Answer 2

你几乎已经明白了，你应该只做一步。如我所见，您正在doInBackground方法返回结果（作为调用uploadFile的结果）。现在，此值传递给在主线程上执行的 onPostExecute 方法。在其正文中，您应该通知正在等待结果的组件，该结果已到达。有很多方法可以做到这一点，但是如果您不想使用第三方库，最简单的方法应该是在AsyncTask构造函数中注入侦听器并在onPostExecute调用它。例如，可以声明以下接口：

public interface MyListener {
    void onDataArrived(String data);
}

并在AsyncTask构造函数中注入一个实现它的实例：

public UploadFileToServer(String userInfoId, String url, MyListener listener){
    loginUserInfoId = userInfoId;
    filePath = url;
    mListener = listener;
}

现在，您可以简单地在onPostExecute使用它：

@Override
protected void onPostExecute(String result) {
    listener.onDataArrived(result);
    super.onPostExecute(result); //actually `onPostExecute` in base class does nothing, so this line can be removed safely
}

如果您正在寻找更复杂的解决方案，可以从阅读本文开始。