//index.xml

<form bindsubmit="formBindsubmit" bindreset="formReset">
  <view style="display:flex;">
    <label>用户名：</label>
    <input name="userName" placeholder="请输入用户名！" />
  </view>
  <view style="display:flex;">
    <label>密码：</label>
    <input name="psw" placeholder="请输入密码！" password="true" />
  </view>
  <view style="display:flex;margin-top:30px;">
    <button style="width:30%;" formType="submit" >登录</button>
    <button style="width:30%" formType="reset" >重置</button>
  </view>
</form>
<view>{{userName}}</view>
<view>{{psw}}</view>
<toast duration="2000" hidden="{{toastHidden}}" bindchange="toastBindChange">用户名或密码不能为空！</toast>

//index.js

Page({
  data:{
    // text:"这是一个页面"
    toastHidden:true,
    userName:\'\',
    psw:\'\'
  },
  formBindsubmit:function(e){
    if(e.detail.value.userName.length==0||e.detail.value.psw.length==0){
      this.setData({
        toastHidden:!this.data.toastHidden
      })
    }else{
      this.setData({
        tip:\'\',
        userName:\'用户名：\'+e.detail.value.userName,
        psw:\'密码：\'+e.detail.value.psw
      })
    }
  },
  formReset:function(){
    this.setData({
      userName:\'\',
      psw:\'\'
    })
  },
  toastBindChange:function(){
    this.setData({
        toastHidden:!this.data.toastHidden
    })
  }
})