compile 'com.squareup.okhttp3:okhttp:3.3.0'

String url = "https://www.baidu.com/";

OkHttpClient okHttpClient = new OkHttpClient();

Request request = new Request.Builder()

    .url(url)

    .build();

Call call = okHttpClient.newCall(request);

try {

    Response response = call.execute();

    System.out.println(response.body().string());

} catch (IOException e) {

    e.printStackTrace();

}

private void DownloadFile() {

        OkHttpClient.Builder client = new OkHttpClient.Builder();

        //设置超时

        client.connectTimeout(20, TimeUnit.SECONDS).writeTimeout(20, TimeUnit.SECONDS).readTimeout(20, TimeUnit.SECONDS).build();

        OkhttpUtil.allowAllSSL(client);

        //传递的参数通过add连接

        RequestBody formBody = new FormBody.Builder().add("key1", value1)

                .add("key2", key2).add("key3", key3).build();

        okhttp3.Request request = new okhttp3.Request.Builder().url(downloadString).post(formBody).build();

        call = client.build().newCall(request);

        call.enqueue(new Callback() {

            //失败的回调

            @Override

            public void onFailure(Call call, IOException e) {

                e.printStackTrace();

                if (m_pDialog.isShowing()) {

                    AlertText("网络连接超时，请检查您的网络连接。");

                }

            }

            //成功的回调

            @Override

            public void onResponse(Call call, okhttp3.Response response) throws IOException {

                InputStream is = null;

                FileOutputStream fos = null;

                Headers responseHeaders = response.headers();

                for (int i = 0; i < responseHeaders.size(); i++) {

                    if (responseHeaders.name(i).equals("Content-Disposition")) {

                        fileName = new String(responseHeaders.value(i)).substring(21, responseHeaders.value(i).length());

                    }

                }

                try {

                    is = response.body().byteStream();

                    String dir = Environment.getExternalStorageDirectory()

                            + "/sss/";

                    if (FileUtil.makeFolder(dir)) {

                        File file = new File(dir, fileName);

                        fos = new FileOutputStream(file);

                        byte[] buf = new byte[1024];

                        int ch = -1;

                        while ((ch = is.read(buf)) != -1) {

                            fos.write(buf, 0, ch);

                        }

                        fos.flush();

                        if (fos != null) {

                            fos.close();

                        }

                        OpenFile();

                    } else {

                        AlertText("程序自动试图创建文件夹失败");

                    }

                } catch (Exception e) {

                    e.printStackTrace();

                    if (m_pDialog.isShowing()) {

                        AlertText("您所下载的内容不存在。");

                    }

                } finally {

                    try {

                        if (is != null)

                            is.close();

                    } catch (IOException e) {

                        e.printStackTrace();

                    }

                    try {

                        if (fos != null)

                            fos.close();

                    } catch (IOException e) {

                        e.printStackTrace();

                    }

                }

            }

        });

    }