最好使用Apache Commons HttpClient，它已经包含在android中了。 看一看 Android开发人员:Apache HTTP客户端包摘要 一般API信息。

方法将数据作为HTTP请求发布，

public static InputStream callPostService(String Url,
        List<NameValuePair> data) {
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost(Url);
    try {
        httppost.setEntity(new UrlEncodedFormEntity(data));
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        return entity.getContent();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

注(2020年10月):以下答案中使用的AsyncTask已在Android API级别30中弃用。有关更新的示例，请参考官方文档或本博客文章

更新(2017年6月)答案，适用于Android 6.0+。感谢@Rohit Suthar， @Tamis Bolvari和@sudhiskr的评论。

    public class CallAPI extends AsyncTask<String, String, String> {
    
        public CallAPI(){
            //set context variables if required
        }
    
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
    
         @Override
         protected String doInBackground(String... params) {
            String urlString = params[0]; // URL to call
            String data = params[1]; //data to post
            OutputStream out = null;

            try {
                URL url = new URL(urlString);
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                out = new BufferedOutputStream(urlConnection.getOutputStream());

                BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
                writer.write(data);
                writer.flush();
                writer.close();
                out.close();

                urlConnection.connect();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
        }
    }

引用:

https://developer.android.com/reference/java/net/HttpURLConnection.html 如何使用NameValuePair使用POST添加参数到HttpURLConnection

原答案(2010年5月)

注意:此解决方案已过时。它只能在5.1版本以下的安卓设备上运行。Android 6.0及以上版本不包括本回答中使用的Apache http客户端。

来自Apache Commons的Http Client是可行的。它已经包含在android中。下面是一个简单的例子，说明如何使用它来执行HTTP Post。

public void postData() {
    // Create a new HttpClient and Post Header
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost("http://www.yoursite.com/script.php");

    try {
        // Add your data
        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
        nameValuePairs.add(new BasicNameValuePair("id", "12345"));
        nameValuePairs.add(new BasicNameValuePair("stringdata", "Hi"));
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

        // Execute HTTP Post Request
        HttpResponse response = httpclient.execute(httppost);
        
    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
    } catch (IOException e) {
        // TODO Auto-generated catch block
    }
} 

下面是一个完整的解决方案，它运行在后台线程中，向Web API发送一个HTTPS POST多部分请求。实际测试和工作代码。注意:“\n”字符需要在顶部的“最终字符串”中进行正确的请求格式化。

我有困难要么理解，转换，或完成以上解决方案，我的多部分POST需求。

    @Override
    protected Integer doInBackground(String... files) {

        final String MULTIPART_BOUNDARY = "xxYYzzSEPARATORzzYYxx";
        final String MULTIPART_SEPARATOR = "--" + MULTIPART_BOUNDARY + "\n";
        final String MULTIPART_FORM_DATA = "Content-Disposition: form-data; name=\"%s\"\n\n";
        final String FORM_DATA_FILE1 = "file1";
        final String FORM_DATA_FILE2 = "file2";

        OutputStream outputStream;
        Integer responseCode = 0;
        try {
            URL url = new URL("https://www.example.com/api/endpoint?n1=v1&n2=v2");
            HttpsURLConnection urlConnection = (HttpsURLConnection) url.openConnection();
            urlConnection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + MULTIPART_BOUNDARY);
            urlConnection.setConnectTimeout(6000);
            urlConnection.setRequestMethod("POST");
            urlConnection.setDoOutput(true);
            outputStream = new BufferedOutputStream(urlConnection.getOutputStream());
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream, StandardCharsets.UTF_8));
            writer.write(MULTIPART_SEPARATOR);
            writer.write(String.format(MULTIPART_FORM_DATA, FORM_DATA_FILE1));
            writer.write(files[0]);
            writer.write(MULTIPART_SEPARATOR);
            writer.write(String.format(MULTIPART_FORM_DATA, FORM_DATA_FILE2));
            writer.write(files[1]);
            writer.write(MULTIPART_SEPARATOR);
            writer.flush();
            writer.close();
            outputStream.close();
            urlConnection.connect();
            responseCode = urlConnection.getResponseCode();
            Log.d("ResponseCode:", String.valueOf(responseCode));
            urlConnection.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return responseCode;
    }

下面的方法适用于最新的Android库和使用okhttp。

    OkHttpClient client = new OkHttpClient();
    RequestBody formBody = new FormBody.Builder()
            .add("key1", "value1")
            .add("key2", "value2")  //optional
            .add("key3", "value3")  //optional
            .add("key4", "value4")  //optional
            .build();


    Request request = new Request.Builder()
    .url("http://.....")   //URL
    .post(formBody)
    .build();


    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(@NonNull Call call, @NonNull IOException e) {
            e.getStackTrace();
        }

        @Override
       public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
            if(response.isSuccessful()){
                ResponseBody responseBody = response.body();
                Log.e("TAG_", responseBody.string());
       }
    }

对我来说，接下来的工作是:

 private sendData() {
     JSONObject jsonObject = new JSONObject();
     jsonObject.accumulate("key1", value1);
     jsonObject.accumulate("key2", value2);

     boolean success = sendPost(SERVER_URL + "/v1/auth", jsonObject);
 }

 private boolean sendPost(String url, JSONObject parameters) {
        boolean requestResult = false;
        InputStream inputStream = null;
        String result = "";
        try {

            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            String json = "";

            json = parameters.toString();

            StringEntity se = new StringEntity(json);
            httpPost.setEntity(se);

            httpPost.setHeader("Accept", "application/json");
            httpPost.setHeader("Content-type", "application/json");

            HttpResponse httpResponse = httpclient.execute(httpPost);

            inputStream = httpResponse.getEntity().getContent();

            if (inputStream != null) {
                result = convertInputStreamToString(inputStream);
                requestResult = true;
            } else {
                result = "Did not work!";
                requestResult = false;
            }
            System.out.println(result);
        } catch (Exception e) {
            Log.d("InputStream", e.getLocalizedMessage());
            requestResult = false;
        }
        return requestResult;
    }