Okhttp如何在主线程上自定义回应回调？

我创建了一个帮助程序类来处理我的应用程序中的所有http调用。这是一个okhttp的简单单例包装，看起来像这样（我省略了一些不重要的部分）：

public class HttpUtil {

    private OkHttpClient client;
    private Request.Builder builder;

    ...

    public void get(String url, HttpCallback cb) {
        call("GET", url, cb);
    }

    public void post(String url, HttpCallback cb) {
        call("POST", url, cb);
    }

    private void call(String method, String url, final HttpCallback cb) {
        Request request = builder.url(url).method(method, method.equals("GET") ? null : new RequestBody() {
            // don't care much about request body
            @Override
            public MediaType contentType() {
                return null;
            }

            @Override
            public void writeTo(BufferedSink sink) throws IOException {

            }
        }).build();

        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Request request, Throwable throwable) {
                cb.onFailure(null, throwable);
            }

            @Override
            public void onResponse(Response response) throws IOException {
                if (!response.isSuccessful()) {
                    cb.onFailure(response, null);
                    return;
                }
                cb.onSuccess(response);
            }
        });
    }


    public interface HttpCallback  {

        /**
         * called when the server response was not 2xx or when an exception was thrown in the process
         * @param response - in case of server error (4xx, 5xx) this contains the server response
         *                 in case of IO exception this is null
         * @param throwable - contains the exception. in case of server error (4xx, 5xx) this is null
         */
        public void onFailure(Response response, Throwable throwable);

        /**
         * contains the server response
         * @param response
         */
        public void onSuccess(Response response);
    }

}

然后使用方法：

        HttpUtil.get(url, new HttpUtil.HttpCallback() {
            @Override
            public void onFailure(Response response, Throwable throwable) {
                // handle failure
            }

            @Override
            public void onSuccess(Response response) {
                // <-------- Do some view manipulation here
            }
        });

-onSuccess- 代码运行时引发异常：

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
Only the original thread that created a view hierarchy can touch its views.
都是因为http请求是在子线程进行的，ui绘制和 Toast 都是在主线程
解决方法：
在相关代码前加上

Looper.prepare();
Toast.makeText(getContext(),"请求成功 ：" + response.body().string() ,Toast.LENGTH_LONG).show();
//do ……
Looper.loop();

即可