android okhttpclient设置编码,请问OkHttp 3如何设置post请求的编码呢？

我用下面的方式服务器获取的登录的账号和密码都是null，但是我直接砸url拼接的话会获取到值。我想请教下这是为什么。

public static String sendByPostMap(String url, Map params) {

String result;

OkHttpClient client = new OkHttpClient();

StringBuilder content = new StringBuilder();

Set> entrys = params.entrySet();

Iterator> iterator = params.entrySet().iterator();

while (iterator.hasNext()) {

Map.Entry entry = iterator.next();

content.append(entry.getKey()).append("=").append(entry.getValue());

if (iterator.hasNext()) {

content.append("&");

}

}

RequestBody requestBody = RequestBody.create(MEDIA_TYPE_TEXT, content.toString());

Request request = new Request.Builder().url(url).post(requestBody).build();

Response response = null;

try {

response = client.newCall(request).execute();

assert response.body() != null;

result = response.body().string();

System.out.println("result = " + result);

return result;

} catch (IOException e) {

e.printStackTrace();

}

return null;

}

public static void main(String[] args) {

//String url = "http://172.18.9.166:8080/user/login.kq";

//String url = "http://172.18.9.166:8899/demo/postByMap?loginName=admin&loginPassword=Hans1107laser";

String url = "http://172.18.9.166:8899/demo/postByMap";

Map params = new HashMap<>();

params.put("loginName", "admin");

params.put("loginPassword", "123456");

String result = sendByPostMap(url, params);

System.out.println("result = " + result);

}