Question

我使用异步任务在服务器上传图像，最后我想返回上传文件的值。我怎样才能做到这一点我叫asynctask为

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

和我的asynctask函数如下：

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

尝试下面给出的代码。

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

你差不多了，你应该只做一步。正如我所看到的，您将使用doInBackground方法返回结果（作为调用uploadFile的结果）。现在，此值将传递给onPostExecute方法，该方法在主线程上执行。在其正文中，您应该通知正在等待结果的组件，结果到达。有很多方法可以做到，但是如果你不想使用第三方库，最简单的方法应该是在AsyncTask构造函数中注入监听器并在onPostExecute调用它。例如，您可以声明以下界面：

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

并在AsyncTask构造函数中注入实现它的实例：

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

现在，您可以在onPostExecute：

处使用它

@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this文章开始。

如何从android中的异步任务获取filleUploaded URL作为字符串

2 个答案: