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
    }
} 

您可以使用WebServer类POST一个HttpRequest，并在其侦听器接口中跟踪响应。

WebServer server=new WebServer(getApplicationContext());

server.setOnServerStatusListner(new WebServer.OnServerStatusListner() {
    @Override
    public void onServerResponded(String responce) {

    }

    @Override
    public void onServerRevoked() {

    }
});

现在创建一个DataRack来绑定数据

List<DataRack> racks=new ArrayList<DataRack>();
racks.add(new DataRack("name","Simon"));
racks.add(new DataRack("age","40"));
racks.add(new DataRack("location","Canada"));

现在只需发送带有该机架的POST请求

server.connectWithPOST(MainActivity.this,"http://sangeethnandakumar.esy.es/PROJECTS/PUBLIC_SERVICE/posttest.php",racks);

你需要包括我的库。文件在这里

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;
}

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());
       }
    }

如果你只是想把数据附加到Url，你可以通过使用httppurlconnection来实现，因为HttpClient现在已经弃用了。 更好的方法是使用像-这样的库

凌空抽射 改造

我们可以将数据发送到php脚本，并通过使用AsyncTask类执行的代码来获取结果并显示它。

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

    // Required initialization


    private String Content;
    private String Error = null;
    private ProgressDialog Dialog = new ProgressDialog(Login.this);
    String data ="";
    int sizeData = 0;



    protected void onPreExecute() {
        // NOTE: You can call UI Element here.

        //Start Progress Dialog (Message)

        Dialog.setMessage("Please wait..");
        Dialog.show();
        Dialog.setCancelable(false);
        Dialog.setCanceledOnTouchOutside(false);

        try{
            // Set Request parameter
            data +="&" + URLEncoder.encode("username", "UTF-8") + "="+edittext.getText();



        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    // Call after onPreExecute method
    protected Void doInBackground(String... urls) {

        /************ Make Post Call To Web Server ***********/
        BufferedReader reader=null;

        // Send data
        try
        {

            // Defined URL  where to send data
            URL url = new URL(urls[0]);

            // Send POST data request

            URLConnection conn = url.openConnection();

            conn.setConnectTimeout(5000);//define connection timeout 
            conn.setReadTimeout(5000);//define read timeout
            conn.setDoOutput(true);
            OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
            wr.write( data );
            wr.flush();

            // Get the server response

            reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            StringBuilder sb = new StringBuilder();
            String line = null;



            // Read Server Response
            while((line = reader.readLine()) != null)
            {
                // Append server response in string
                sb.append(line + " ");
            }

            // Append Server Response To Content String
            Content = sb.toString();


        }
        catch(Exception ex)
        {
            Error = ex.getMessage();
        }
        finally
        {
            try
            {

                reader.close();
            }

            catch(Exception ex) {}
        }


        return null;
    }

    protected void onPostExecute(Void unused) {
        // NOTE: You can call UI Element here.

        // Close progress dialog
        Dialog.dismiss();

        if (Error != null) {

                Toast.makeText(getApplicationContext(),"Error encountered",Toast.LENGTH_LONG).show();



        }
        else {




            try {

                JSONObject jsonRootObject = new JSONObject(Content);


                JSONObject json2 =jsonRootObject.getJSONObject("jsonkey");//pass jsonkey here


                String id =json2.optString("id").toString();//parse json to string through parameters


     //the result is stored in string id. you can display it now


            } catch (JSONException e) {e.printStackTrace();}


        }

    }

}

但是使用诸如volley或retrofit之类的库是更好的选择，因为Asynctask类和HttpurlConnection相比库更慢。此外，库将获取所有内容，也更快。

@primpop的答案，我会添加如何转换字符串中的响应:

HttpResponse response = client.execute(request);
HttpEntity entity = response.getEntity();
if (entity != null) {
    InputStream instream = entity.getContent();

    String result = RestClient.convertStreamToString(instream);
    Log.i("Read from server", result);
}

下面是一个convertStramToString的例子。