键盘高度计算，改善聊天页面内容少的时候推屏的问题，但是有点卡断

pages/im/group/chat.vue

@@ -1,6 +1,6 @@
 <template>
     <view class="chat">
-        <sent-message-bar :conversationType="conversationType" :targetId="targetId" @onSuccess="getNewMessage()" />
+        <sent-message-bar id="msgbar" :conversationType="conversationType" :targetId="targetId" @onSuccess="getNewMessage()" />
 
         <view class="shade" @click="hidePop" v-show="showPop">
             <view class="pop" :style="popStyle" :class="{'show':showPop}">
@@ -11,7 +11,8 @@
         </view>
 
         <view class="body">
-            <view class="scroll">
+            <view class="place" :style="{ height: placeHeight + 'px' }"></view>
+            <view class="scroll" id="scroll">
                 <view class="cell" v-for="(message, index) in messages" :key="index">
                     <show-message-cell :message="message" isGroup @messageAction="messageAction" />
                 </view>
@@ -51,7 +52,9 @@
                 messages: [],
                 groupInfo: {
                     name: ''
-                }
+                },
+                placeHeight: uni.getSystemInfoSync().windowHeight,
+                bottomHeihgt: 56
             }
         },
         computed: {
@@ -68,7 +71,21 @@
         onShow() {
             this.initGroupInfo()
         },
-        onLoad(e) {
+        onLoad(e) {
+            const query = uni.createSelectorQuery().in(this);
+            this.$nextTick(function() {
+                query.select('#msgbar').boundingClientRect(bottom => {
+                    this.bottomHeihgt = bottom.height
+                }).exec();
+            })
+            // 监听键盘高度变化
+            uni.onKeyboardHeightChange(keyboard => {
+                query.select('#scroll').boundingClientRect(scroll => {
+                    const placeHeight = this.windowHeight - scroll.height - keyboard.height - this
+                        .bottomHeihgt
+                    this.placeHeight = placeHeight > 0 ? placeHeight : 0
+                }).exec();
+            })
             this.targetId = e.targetId
             // 获取历史消息列表
             this.getMessageList()