           <div class="col-3">
                    <button class="btn btn-dim btn-outline-secondary btn-block card-link" @click="exchange">
                        <em class="icon ni ni-exchange-v"></em>交换
                    </button>
                </div>
                <div class="col-3">
                    <button class="btn btn-dim btn-outline-secondary btn-block card-link" @click="reset">
                        <em class="icon ni ni-trash-empty"></em>清空
                    </button