要在Android中获取Web表单中的隐藏值并进行POST请求，可以使用以下步骤和代码示例：

1. 使用Jsoup库解析网页并获取隐藏字段的值。

Document doc = Jsoup.connect(url).get();
Element hiddenField = doc.select("input[type=hidden]").first();
String hiddenValue = hiddenField.attr("value");

2. 构建POST请求并添加隐藏字段的值。

String postUrl = "your_post_url";
HttpPost httpPost = new HttpPost(postUrl);

List params = new ArrayList<>();
params.add(new BasicNameValuePair("hiddenField", hiddenValue));

UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params);
httpPost.setEntity(formEntity);

HttpClient httpClient = new DefaultHttpClient();
HttpResponse response = httpClient.execute(httpPost);

这里假设您已经包含了Apache HttpClient库。

3. 处理POST请求的响应。

BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
String line;
StringBuilder stringBuilder = new StringBuilder();
while ((line = reader.readLine()) != null) {
    stringBuilder.append(line);
}
String responseBody = stringBuilder.toString();

这将把响应的内容读取到一个字符串中。

完整的示例代码如下：

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;

public class Main {
    public static void main(String[] args) {
        try {
            // Step 1: Parse web page and get hidden field value
            String url = "your_web_page_url";
            Document doc = Jsoup.connect(url).get();
            Element hiddenField = doc.select("input[type=hidden]").first();
            String hiddenValue = hiddenField.attr("value");

            // Step 2: Build POST request and add hidden field value
            String postUrl = "your_post_url";
            HttpPost httpPost = new HttpPost(postUrl);

            List params = new ArrayList<>();
            params.add(new BasicNameValuePair("hiddenField", hiddenValue));

            UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(params);
            httpPost.setEntity(formEntity);

            HttpClient httpClient = new DefaultHttpClient();
            HttpResponse response = httpClient.execute(httpPost);

            // Step 3: Handle POST request response
            BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
            String line;
            StringBuilder stringBuilder = new StringBuilder();
            while ((line = reader.readLine()) != null) {
                stringBuilder.append(line);
            }
            String responseBody = stringBuilder.toString();

            // Do something with the response body
            System.out.println(responseBody);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

请注意，上述代码示例仅用于说明目的，并且可能需要根据您的实际情况进行适当的修改。