public class OkSingle {
    protected static Context context;
    private static OkSingle okSingle;
    private static OkHttpClient mOkHttpClient;
    private static Gson gson;

    private static final int SUCCESS = 1;
    private static final int FAILED = 0;

    public OkSingle(OkHttpClient okHttpClient) {
        if 
 
(okHttpClient == null) {
            mOkHttpClient = new OkHttpClient();
        } else {
            mOkHttpClient = okHttpClient;
        }
        //獲取MyApplication的context
context = MyApplication.context;
        gson = new Gson();

    }

    public static OkSingle initClient(OkHttpClient okHttpClient) {
        if 
 
(okSingle == null) {
            synchronized (OkSingle.class) {
                if (okSingle == null) {
                    okSingle = new OkSingle(okHttpClient);
                }
            }
        }
        return okSingle;

    }

    //獲得單例的物件
public static OkSingle getInstance() {
        return 
 
initClient(null);

    }

    public <T> void getRequestAsync(String url,
                                    final GetResponse.ErrorListener errorListener,
                                    final GetResponse.Listener<T> listener,
                                    final Class<T> tClass) {
        Request request = new Request.Builder().url(url).build();
        //這種寫法,可以讓Handler指定屬於主執行緒
final Handler handler = new Handler(Looper.getMainLooper()) {

            @Override
public void handleMessage(Message msg) {
                super.handleMessage(msg);
                switch (msg.what) {
                    case SUCCESS:
                        //成功時候的回撥
listener.onResponse((T) msg.obj);
                        break;
                    case FAILED:
                        errorListener.onErrorResponse();
                        break;
                }

            }
        };

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

            @Override
public void onFailure(Call call, IOException e) {
                errorListener.onErrorResponse();
            }

            @Override
public void onResponse(Call call, Response response) throws IOException {
                try {
                    String result = response.body().string();
                    T t = gson.fromJson(result, tClass);
                    Message message = handler.obtainMessage();//這種寫法比較省記憶體
message.what = SUCCESS;
                    message.obj = t;
                    handler.sendMessage(message);
                } catch (IOException e) {
                    e.printStackTrace();
                    //因為是失敗,所以返回失敗,在主執行緒中判斷
handler.sendEmptyMessage(FAILED);
                }
            }


        });


    }

    
    
    //自定義介面
public interface GetResponse {
        
        //成功的介面
interface Listener<T> {
            void onResponse(T response);
        }
        //失敗的介面
interface ErrorListener {
            void onErrorResponse();
        }
    }

}