How to make a card deck with fixed width cards?

I want to make a responsive card deck using bootstrap 4 fixed width cards. Here I have posted the code below, but it's not responsive why?

<div class="card-deck">
<div class="card col-lg-2 col-md-3 col-sm-4 col-6" style="max-width: 12rem;">
    <div class="card-body">
        <h4 class="card-title">Title 1</h4>
        <p>Small text here</p>
        <small class="text-muted">3 mins ago</small>
    </div>
</div>
<div class="card col-lg-2 col-md-3 col-sm-4 col-6" style="max-width: 12rem;">
    <div class="card-body">
        <h4 class="card-title">Title 2</h4>
        <p>Small text here</p>
        <small class="text-muted">3 mins ago</small>
    </div>
</div>
<div class="card col-lg-2 col-md-3 col-sm-4 col-6" style="max-width: 12rem;">
    <div class="card-body">
        <h4 class="card-title">Title 3</h4>
        <p>Small text here</p>
        <small class="text-muted">3 mins ago</small>
    </div>
</div>
<div class="card col-lg-2 col-md-3 col-sm-4 col-6" style="max-width: 12rem;">
    <div class="card-body">
        <h4 class="card-title">Title 4</h4>
        <p>Small text here</p>
        <small class="text-muted">3 mins ago</small>
    </div>
</div>

回答1:

For a Bootstrap 4 card deck with fixed-width cards do this:

Put each card into a column with the classes col-auto mb-3 (auto-width column + margin-bottom with 3 units).

To center them add the justify-content-center class to the row.

Here's a working code snippet (click "run code snippet" below and expand to full page):

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<div class="container-fluid mt-4">
    <div class="row justify-content-center">
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
        <div class="col-auto mb-3">
            <div class="card" style="width: 18rem;">
                <div class="card-body">
                    <h5 class="card-title">Card title</h5>
                    <h6 class="card-subtitle mb-2 text-muted">Card subtitle</h6>
                    <p class="card-text">Some quick example text to build on the card title and make up the bulk of the card's content.</p>
                    <a href="#" class="card-link">Card link</a>
                    <a href="#" class="card-link">Another link</a>
                </div>
            </div>
        </div>
    </div>
</div>

回答2:

In here mentioned, these layout options are not yet responsive. So I have found simple solution. Change the parent <div class="card-deck">...</div> to <div class="row">...</div>.

Thanks for all of your feedbacks.