How to clear flexbox item?

Question

I need to clear flex box layout item so that first item is 100% width, the second is 50% centered on its own line, and 3rd and 4th are 50% width on the same line.

The clear works normal on simple block items but I can't find a way to do this with flex layout.

https://jsfiddle.net/tzx8qyjt/

.container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-flow: row wrap;
  justify-content: space-around;
}

.item {
  background: tomato;
  padding: 5px;
  width: 100%;
  height: 150px;
  margin-top: 10px;
  margin-bottom: 10px;
  line-height: 150px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
}

.container.block {
  display: block;
}

.container.block .item {
  float: left;
  box-sizing: border-box;
}

.half {
  width: 50%;
}

.container .item.centered {
  float: none;
  clear: both;
  margin-left: auto;
  margin-right: auto;
}

<ul class="container">
  <li class="item">1</li>
  <li class="item half centered">2 Clear after me</li>
  <li class="item half">3</li>
  <li class="item half">4</li>
</ul>
<br />
<br />
<br />
<br />
<br />
<ul class="container block">
  <li class="item">1</li>
  <li class="item half centered">2 Clear after me</li>
  <li class="item half">3</li>
  <li class="item half">4</li>
</ul>

Answer 1

Since clearing floats won't work the same for flex items, you could do like this, where you set box-sizing: border-box on all items (makes padding be included in the set width) and then for your 2:nd, you give it a small margin, which will force the rest to a new line

.container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-flex-flow: row wrap;
  justify-content: space-around;
}

.item {
  background: tomato;
  padding: 5px;
  width: 100%;
  height: 150px;
  margin-top: 10px;
  margin-bottom: 10px;
  line-height: 150px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
  box-sizing: border-box;
}

.half {
  width: 50%;
}
.container .item.centered {
  margin: 0 10px;
}

<ul class="container">
  <li class="item">1</li>
  <li class="item half centered">2 Clear after me</li>
  <li class="item half">3</li>
  <li class="item half">4</li>
</ul>

Answer 2

The key to the flex layout is using proper widths, flex-wrap: wrap and box-sizing: border-box.

The first item gets 100% width. That forces subsequent items off the line.

The second, third and fourth items each get 50% width.

But each item also has horizontal padding. So item 2 will force items three and four off the line.

For items three and four, if we adjust their box model from box-sizing: content-box (the default) to border-box, the padding gets included in the width calculation and both items fit perfectly on one line.

.container {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-around;
  padding: 0;
  margin: 0;
  list-style: none;
}

li:nth-child(1) { flex: 0 0 100%;} /* flex-grow, flex-shrink, flex-basis */
li:nth-child(2) { flex: 0 0 50%; }
li:nth-child(3) { flex: 0 0 50%; box-sizing: border-box; }
li:nth-child(4) { flex: 0 0 50%; box-sizing: border-box; }

.item {
  background: tomato;
  padding: 5px;
  height: 150px;
  margin-top: 10px;
  margin-bottom: 10px;
  line-height: 150px;
  color: white;
  font-weight: bold;
  font-size: 3em;
  text-align: center;
}

<ul class="container">
  <li class="item">1</li>
  <li class="item half centered">2 Clear after me</li>
  <li class="item half">3</li>
  <li class="item half">4</li>
</ul>

Answer 3

I hope that it may work for you. I am using this code.

    .clear {
      width: 100%;
      border: none;
      margin: 0;
      padding: 0;
    }

<ul class="container">
  <li class="item">1</li>
  <li class="item half">2 Clear after me</li>
  <li class='clear'><li>
  <li class="item half">3</li>
  <li class="item half">4</li>
</ul>

What we generally use in flow layout.

.clear {
  border: 0;
  clear: both;
  height: 0;
}