小程序 顶部区域弹出picker的下拉框代码

以下是小程序中顶部区域弹出picker的下拉框代码示例：

WXML部分：

<view class="container">
  <view class="picker">
    <view class="picker-btn" bindtap="showPicker">
      <text>{{selectedValue}}</text>
      <image src="/images/down.png"></image>
    </view>
    <picker class="picker-box" value="{{selectedIndex}}" range="{{pickerData}}" bindchange="pickerChange" bindcancel="hidePicker">
      <view class="picker-item">{{pickerData[selectedIndex]}}</view>
    </picker>
  </view>
</view>

CSS部分：

.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.picker {
  position: relative;
  width: 200rpx;
  height: 50rpx;
  border: 1rpx solid #ccc;
  border-radius: 5rpx;
  background-color: #fff;
}

.picker-btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 10rpx;
  height: 100%;
}

.picker-btn image {
  width: 20rpx;
  height: 20rpx;
}

.picker-box {
  position: absolute;
  top: 50rpx;
  left: 0;
  width: 100%;
  background-color: #fff;
  z-index: 10;
}

.picker-item {
  text-align: center;
  font-size: 14rpx;
  padding: 10rpx;
  line-height: 1.5;
  color: #333;
  border-top: 1rpx solid #ccc;
}

JS部分：

Page({
  data: {
    pickerData: ['选项1', '选项2', '选项3', '选项4'],
    selectedIndex: 0,
    selectedValue: '选项1',
    isPickerShow: false
  },

  showPicker() {
    this.setData({
      isPickerShow: true
    });
  },

  hidePicker() {
    this.setData({
      isPickerShow: false
    });
  },

  pickerChange(e) {
    const selectedIndex = e.detail.value;
    const selectedValue = this.data.pickerData[selectedIndex];
    this.setData({
      selectedIndex,
      selectedValue,
      isPickerShow: false
    });
  }
})

在上面的代码中，我们首先定义了一个picker组件，然后在picker-box里面定义了picker-item，用来展示每个选项。在picker-btn中，我们绑定了一个showPicker事件，点击该按钮时，会显示picker-box，选择完成后，我们监听了picker的change事件，获取选中的值，并更新selectedValue的值，然后再将picker-box隐藏起来。