代码实现：
//创建手机内存文件夹（Environment用来管理手机SDcard内存的）
File file = new File(Environment.getExternalStorageDirectory() + "/H1706A");
//设置文件夹内存大小
long maxSize = 8 * 1024 * 1024;
Cache cache = new Cache(file, maxSize);
//OKHTTPClient两种写法 第二种就是通过构造者模式也可以使用
okHttpClient = new OkHttpClient.Builder().cache(cache).build();
//获取request对象并设置缓存保存时间
Request request = new Request.Builder().url(url).cacheControl(new CacheControl.Builder().maxStale(24 * 60 * 60, TimeUnit.SECONDS).build()).build();
//通过okHttpClient.newCall(request).execute()获取response对象
Response response = okHttpClient.newCall(request).execute();
String str = response.body().string();
