我做了这个webservice请求URL，使用一个Gson库:

客户:

public EstabelecimentoList getListaEstabelecimentoPorPromocao(){

        EstabelecimentoList estabelecimentoList  = new EstabelecimentoList();
        try{
            URL url = new URL("http://" +  Conexao.getSERVIDOR()+ "/cardapio.online/rest/recursos/busca_estabelecimento_promocao_android");
            HttpURLConnection con = (HttpURLConnection) url.openConnection();

            if (con.getResponseCode() != 200) {
                    throw new RuntimeException("HTTP error code : "+ con.getResponseCode());
            }

            BufferedReader br = new BufferedReader(new InputStreamReader((con.getInputStream())));
            estabelecimentoList = new Gson().fromJson(br, EstabelecimentoList.class);
            con.disconnect();

        } catch (IOException e) {
            e.printStackTrace();
        }
        return estabelecimentoList;
}

对我来说，最简单的方法是使用名为Retrofit2的库

我们只需要创建一个接口，其中包含我们的请求方法，参数，我们还可以为每个请求定制头部:

    public interface MyService {

      @GET("users/{user}/repos")
      Call<List<Repo>> listRepos(@Path("user") String user);

      @GET("user")
      Call<UserDetails> getUserDetails(@Header("Authorization") String   credentials);

      @POST("users/new")
      Call<User> createUser(@Body User user);

      @FormUrlEncoded
      @POST("user/edit")
      Call<User> updateUser(@Field("first_name") String first, 
                            @Field("last_name") String last);

      @Multipart
      @PUT("user/photo")
      Call<User> updateUser(@Part("photo") RequestBody photo, 
                            @Part("description") RequestBody description);

      @Headers({
        "Accept: application/vnd.github.v3.full+json",
        "User-Agent: Retrofit-Sample-App"
      })
      @GET("users/{username}")
      Call<User> getUser(@Path("username") String username);    

    }

最好的是，我们可以使用enqueue方法轻松地进行异步操作

有一根线:

private class LoadingThread extends Thread {
    Handler handler;

    LoadingThread(Handler h) {
        handler = h;
    }
    @Override
    public void run() {
        Message m = handler.obtainMessage();
        try {
            BufferedReader in = 
                new BufferedReader(new InputStreamReader(url.openStream()));
            String page = "";
            String inLine;

            while ((inLine = in.readLine()) != null) {
                page += inLine;
            }

            in.close();
            Bundle b = new Bundle();
            b.putString("result", page);
            m.setData(b);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        handler.sendMessage(m);
    }
}

更新

这是一个非常古老的答案。我绝对不会再推荐Apache的客户端了。你可以用任意一种:

改造 OkHttp 截击 HttpUrlConnection

原来的答案

首先，申请访问网络的权限，在您的清单中添加以下内容:

<uses-permission android:name="android.permission.INTERNET" />

那么最简单的方法是使用Apache http客户端与Android捆绑:

    HttpClient httpclient = new DefaultHttpClient();
    HttpResponse response = httpclient.execute(new HttpGet(URL));
    StatusLine statusLine = response.getStatusLine();
    if(statusLine.getStatusCode() == HttpStatus.SC_OK){
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        response.getEntity().writeTo(out);
        String responseString = out.toString();
        out.close();
        //..more logic
    } else{
        //Closes the connection.
        response.getEntity().getContent().close();
        throw new IOException(statusLine.getReasonPhrase());
    }

如果你想让它在单独的线程上运行，我建议扩展AsyncTask:

class RequestTask extends AsyncTask<String, String, String>{

    @Override
    protected String doInBackground(String... uri) {
        HttpClient httpclient = new DefaultHttpClient();
        HttpResponse response;
        String responseString = null;
        try {
            response = httpclient.execute(new HttpGet(uri[0]));
            StatusLine statusLine = response.getStatusLine();
            if(statusLine.getStatusCode() == HttpStatus.SC_OK){
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                response.getEntity().writeTo(out);
                responseString = out.toString();
                out.close();
            } else{
                //Closes the connection.
                response.getEntity().getContent().close();
                throw new IOException(statusLine.getReasonPhrase());
            }
        } catch (ClientProtocolException e) {
            //TODO Handle problems..
        } catch (IOException e) {
            //TODO Handle problems..
        }
        return responseString;
    }
    
    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        //Do anything with response..
    }
}

然后，你可以通过以下方式提出请求:

   new RequestTask().execute("http://stackoverflow.com");

看看这个很棒的新库，它可以通过gradle获得:)

构建。Gradle:编译'com.apptakk.http_request:http-request:0.1.2'

用法:

new HttpRequestTask(
    new HttpRequest("http://httpbin.org/post", HttpRequest.POST, "{ \"some\": \"data\" }"),
    new HttpRequest.Handler() {
      @Override
      public void response(HttpResponse response) {
        if (response.code == 200) {
          Log.d(this.getClass().toString(), "Request successful!");
        } else {
          Log.e(this.getClass().toString(), "Request unsuccessful: " + response);
        }
      }
    }).execute();

https://github.com/erf/http-request

按照上面的建议使用凌空射击。添加以下到构建。gradle(模块:app)

implementation 'com.android.volley:volley:1.1.1'

在AndroidManifest.xml中添加以下内容:

<uses-permission android:name="android.permission.INTERNET" />

并添加以下活动代码:

public void httpCall(String url) {

    RequestQueue queue = Volley.newRequestQueue(this);

    StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    // enjoy your response
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    // enjoy your error status
                }
    });

    queue.add(stringRequest);
}

它取代了http客户端，非常简单。