Vue $emit()不能触发父组件方法的原因及解决

<div id="app">
 <button v-on:click="IncrHandle">增加</button>
 <input v-model="total" placeholder="请输入内容" />
 <child v-bind:count="total" v-on:onIncr="IncrHandle"></child>
</div>
Vue.component("child",{
 props:['count'],
 template:"<button v-on:click='incr'>增加{{count}}</button>",
 data: function(){
 return {
  count: 0
 }
 },
 methods:{
 incr: function(){
  this.$emit('onIncr')
  this.count += 1
 }
 }
})
new Vue({
 el:"#app",
 data:{
 total: 0
 },
 methods:{
 IncrHandle:function(){
  this.total += 1
  total("增加1")
 },
 DncrHandle:function(){
  this.total -= 1
 }
 }
})