public class HttpUtil {
    static HttpUtil util;
    private final OkHttpClient client;

//  私有化構造方法
    private HttpUtil(){
        client = new OkHttpClient();
    }

    public static HttpUtil getInstance(){
        if(util == null){
            synchronized (HttpUtil.class){
                util 
 
= new HttpUtil();
            }
        }

        return util;
    }



    public void httRequest(String url,final HttpRespon respon) {

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

        client.newCall(request).enqueue(new Callback() {

            
 
//              請求失敗
            @Override
            public void onFailure(Call call, IOException e) {
                e.printStackTrace();
                respon.onError("請求網絡失敗");
            }

            //              有響應
            @Override
            public void onResponse(Call call, Response response) throws
 
 IOException {

                if (!response.isSuccessful()) {
                    respon.onError("請求網絡失敗");
                }

//                  獲取響應body
                    String json = response.body().string();
//                  解析Json
                    respon.parse(json);


            }
        });
    }


}

定義的回調接口:

public abstract class HttpRespon<T> {
    //http返回的類型的泛型
    Class<T> t;

    public HttpRespon(Class<T> t){
        this.t = t;
    }

//  請求失敗時，回調的方法
    public abstract void onError(String msg);
//  請求成功時，回調的方法
    public abstract void onSuccess(T t);

    public void parse(String json){
        if(TextUtils.isEmpty(json)){
            //請求失敗
            onError("連接網絡失敗");
            return;
        }
        if(t == String.class){
            onSuccess((T) json);
            return;
        }

        T result = JsonUtil.parse(json, this.t);
        if(result == null){
            onError("Json解析失敗");
        }else{
            onSuccess(result);
        }
    }
}

調用的事例:

            HttpUtil.getInstance().httRequest(Constant.SPLASH_URL, new HttpRespon<Ad>(Ad.class) {
                @Override
                public void onError(String msg) {
                    Log.i("fjl", msg);
                }

                @Override
                public void onSuccess(Ad ad) {
                    Intent intent = new Intent();
                    intent.setClass(AdsActivity.this, AdDownloadService.class);
                    intent.putExtra(AdDownloadService.AD_DATA, ad);
                    startService(intent);
                }
            });

Okhttp的封裝和回調