display:flex white-space: nowrap 横向布局不换行

<view class="section">
  <view class="section__title">vertical scroll</view>
  <scroll-view scroll-y="true" style="height: 200px;" bindscrolltoupper="upper" bindscrolltolower="lower" bindscroll="scroll" scroll-into-view="{{toView}}" scroll-top="{{scrollTop}}">
    <view id="green" class="scroll-view-item bc_green"></view>
    <view id="red" class="scroll-view-item bc_red"></view>
    <view id="yellow" class="scroll-view-item bc_yellow"></view>
    <view id="blue" class="scroll-view-item bc_blue"></view>
  </scroll-view>

  <view class="btn-area">
    <button size="mini" bindtap="tap">click me to scroll into view </button>
    <button size="mini" bindtap="tapMove">click me to scroll</button>
  </view>
</view>


<view class="section section_gap">
  <view class="section__title">horizontal scroll</view>
  <scroll-view class="scroll-view_H" scroll-x="true" style="width: 100%">
    <view id="green" class="scroll-view-item_H bc_green"></view>
    <view id="red" class="scroll-view-item_H bc_red"></view>
    <view id="yellow" class="scroll-view-item_H bc_yellow"></view>
    <view id="blue" class="scroll-view-item_H bc_blue"></view>
  </scroll-view>
</view>

var order = ['red', 'yellow', 'blue', 'green', 'red']
Page({
  data: {
    toView: 'red',
    scrollTop: 100
  },
  upper: function (e) {
    console.log(e)
  },
  lower: function (e) {
    console.log(e)
  },
  scroll: function (e) {
    console.log(e)
  },
  tap: function (e) {
    for (var i = 0; i < order.length; ++i) {
      if (order[i] === this.data.toView) {
        this.setData({
          toView: order[i + 1]
        })
        break
      }
    }
  },
  tapMove: function (e) {
    this.setData({
      scrollTop: this.data.scrollTop + 10
    })
  }
})

.bc_green{
    background-color: green;
}
.bc_red{
background-color: red;
}
.bc_yellow{
background-color: yellow;
}
.bc_blue{
background-color: blue;
}
.scroll-view-item{
    height: 100px;
}
/* .scroll-view_H{
    height: 100px; 
     white-space: nowrap;
    display:flex;
    flex-direction: row;
    flex-wrap:nowrap;

} */
.scroll-view-item_H{    
    height: 100px;
    width: 200px;
    display: inline-block;
}

.bc_green{
    background-color: green;
}
.bc_red{
background-color: red;
}
.bc_yellow{
background-color: yellow;
}
.bc_blue{
background-color: blue;
}
.scroll-view-item{
    height: 100px;
}
.scroll-view_H{
    height: 100px; 
     white-space: nowrap;
    display:flex;
    flex-direction: row;
    flex-wrap:nowrap;

} 
.scroll-view-item_H{    
    height: 100px;
    width: 200px;
    display: inline-block;
}

display:flex white-space: nowrap 横向布局不换行

这样就横向显示了