入门学习Retrofit2 碰到重复请求两次的问题

代码如下：
ApiSerice:public interface  ApiService {
    
    @GET("test.do")
    Call<String> getString(@Query("phoneNum")String phoneNum);
}
执行模块：    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.buttonOK:
                Retrofit retrofit = new Retrofit.Builder()
                        .baseUrl(LocalPropertyUtils.serverUrl(MainActivity.this))
                        .addConverterFactory(FastJsonConverterFactory.create())
                        .build();
                ApiService apiService = retrofit.create(ApiService.class);
                String phoneNum = "13948756432";
                Call<String> call = apiService.getString(phoneNum);
                call.enqueue(new Callback<String>() {
                    @Override
                    public void onResponse(Call<String> call, Response<String> response) {
                        if (response.isSuccessful()) {
                            Message message = new Message();
                            message.obj = response;
                            mHandler.sendMessage(message);
                        }
                    }
                    @Override
                    public void onFailure(Call<String> call, Throwable t) {
                        t.printStackTrace();
                    }
                });
                break;
            default:
                break;
        }
    }
HandlerHandler mHandler = new Handler() {
        Integer times = 0;
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            times++;
            //这里会弹出两次
            Toast.makeText(MainActivity.this, "Times:" + times.toString(), Toast.LENGTH_LONG).show();
        }
    };
Debug调试，发现其中onResponse()会执行两次，在短时间内发送了两次请求。