代码如下：

html代码：
<view class="chat-box" style="{{keyboardHeight != 0 ? 'bottom:' + keyboardHeight + 'px;' : ''}}" bindtap="keyboardClick">
  <textarea auto-height class="chat-input" show-confirm-bar="{{false}}" bindfocus="focusInput" bindblur="bindblur" adjust-position="{{false}}" maxlength="70" value="{{textAreaValue}}" bindinput="bindTextarea" placeholder="请输入短信内容" />
  <text class="chat_box_num">{{textAreaValue.length}}/70</text>
  <view class="sendMsg" bindtap="sendSms">
    发送
  </view>
</view>

css代码：


.chat-box {
  position: fixed;
  left: 0;
  width: calc(100% - 10rpx);
  bottom: constant(safe-area-inset-bottom); /*兼容 IOS<11.2*/
  bottom: env(safe-area-inset-bottom); /*兼容 IOS>11.2*/
  background: #FFFFFF;
  padding: 11rpx 25rpx;
  display: flex;
  align-items: center;
}

.chat_box_num {
  position: absolute;
  right: 88px;
  bottom: 10px;
  color: #9a9a9a;
  font-size: 24rpx;
}

.chat-input {
  /*width: calc(580rpx - 10rpx - 12rpx);*/
  /*margin-right: 10rpx;*/
  /*overflow: scroll;*/
  /*background: #F4F4F4;*/
  /*border-radius: 8rpx;*/
  /*padding: 11rpx 24rpx;*/
  width: calc(580rpx - 10rpx - 12rpx);
  margin-right: 10rpx;
  overflow: scroll;
  background: #F4F4F4;
  border-radius: 8rpx;
  padding: 11rpx 24rpx 40rpx;
  min-height: 44rpx!important;
}
.sendMsg {
  padding: 12rpx 21rpx;
  background: #007AFF;
  border-radius: 6rpx;
  border: 1rpx solid rgba(5, 5, 5, 0.08);
  font-size: 27rpx;
  font-family: PingFangSC-Regular, PingFang SC;
  font-weight: 400;
  color: #FFFFFF;
  text-align: center;
}

js代码：


focusInput(e) {
  console.log('获取键盘', e)
  setTimeout(() => {
    if (!this.data.keyboardStatus) {
      return
    }
    this.setData({
      keyboardHeight: e.detail.height
    })
  }, 100)

},
bindblur(e) {
  console.log('失去焦点', e)
  this.setData({
    keyboardHeight: 0
  })
}

出现问题的手机型号： ios 13，软件版本： 15.5

微信版本号： 8.0.23