微信小程序如何实现自定义picker选择器弹窗内容

<view class="free-btns" >
 <button class="free-btn" bindtap="toggleDialog">
 选定国家：{{value}}
 </button>
 </view>

 <view class="free-dialog {{ showDialog &#63; 'free-dialog--show' : '' }}">
 <view class="free-dialog__mask" bindtap="toggleDialog" />
 <view class="free-dialog__container">
 <view >
 <form bindsubmit='submit' bindreset="reset">
 <view bindtap='freetoBack' class="free-button free-dialog-reset">取消</view>
 <view bindtap='freeBack' class="free-button free-dialog-submit">确定</view>

 <radio-group class='free-radios' bindchange="radioChange">
 <label class="free-radio" bindtap="click" wx:for="{{items}}" wx:key="{{items}}" data-id="{{index}}" >
 <radio value="{{item.name}}" name="{{item.value}}"></radio>
 <label class="free-text">{{item.value}}</label>
 </label>
 </radio-group>
 </form>

 </view>
 </view>
</view>

.free-dialog__mask {
 position: fixed;
 top: 0;
 left: 0;
 right: 0;
 bottom: 0;
 z-index: 10;
 background: rgba(0, 0, 0, 0.7);
 display: none;
}
.free-dialog__container {
 position: fixed;
 left: 0;
 bottom: 0;
 width: 750rpx;
 background: white;
 transform: translateY(150%);
 transition: all 0.4s ease;
 z-index: 11;
}
.free-dialog--show .free-dialog__container {
 transform: translateY(0);
}
.free-dialog--show .free-dialog__mask {
 display: block;
}
/*模态框中的内容*/
.free-button{
 display: inline-block;
 width:50px;
 text-align: center;
 font-size:20px;
 color:#707070;
 margin-bottom:20px;
}
.free-dialog-submit{
 float: right;
 color:#48c23d;
}
radio-group{
 margin:10rpx 0rpx;
}
radio-group>label{
 width:22.5%;
 display: inline-block;
 border:1px solid #ddd;
 padding:10px 0px;
 margin:0px 2px 2px;
}

radio-group label radio{
 width:100%;
 z-index: 3;
 display: none;
}
.checked{
 background:#48c23d;
 color:#fff;
}
radio-group label .free-text{
 width:100%;
 text-align: center;
 display: inline-block;
}

Page({
 data: {
 showDialog: false,
 items: [
 { name: '中国', value: '中国' },
 { name: '美国', value: '美国' },
 { name: '巴西', value: '巴西' },
 { name: '日本', value: '日本' },
 { name: '英国', value: '英国' },
 { name: '法国', value: '法国' },
 { name: '韩国', value: '韩国' },
 { name: '俄罗斯', value: '俄罗斯' },]

 },
 /*点击变色*/
 click:function(e){
 var id = e.currentTarget.dataset.id
 var that = this
 that.setData({
 id:id
 })
 },
 onLoad: function (options) {
 var that = this
 that.setData({
 value:'show'
 })
 },
 radioChange: function (e) {
 console.log('radio发生change事件，携带value值为：', e.detail.value)
 var that = this
 that.setData({
 value: e.detail.value
 })
 console.log(this.data.value)
 },
 toggleDialog() {
 this.setData({
 showDialog: !this.data.showDialog
 });
 },
 freeBack:function(){
 var that = this
 if(this.data.value=='show'){
 wx.showModal({
 title: '提示',
 content: '你没有选择任何内容',
 })
 }
 that.setData({
 showDialog: !this.data.showDialog
 })
 },
 freetoBack: function () {
 var that = this
 wx.showModal({
 title: '提示',
 content: '你没有选择任何内容',
 })
 that.setData({
 showDialog: !this.data.showDialog,
 value:'show',
 checked: false,
 })
 },
})