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/private/chat.vue

@@ -1,6 +1,7 @@
 <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}">
                 <view v-for="(item, index) in popButton" :key="index" @click="pickerMenu(item)">
@@ -10,7 +11,8 @@
         </view>
         <!-- chat -->
         <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" @messageAction="messageAction" />
                 </view>
@@ -26,11 +28,11 @@
     import showMessageCell from '../components/showMessageCell'
     import utils from '@/utils/index.js'
     import imBase from '../mixins/imBase.js'
-    import messageActions from '../mixins/messageActions.js'
-    
+    import messageActions from '../mixins/messageActions.js'
+
     export default {
         mixins: [
-            imBase,
+            imBase,
             messageActions
         ],
         components: {
@@ -46,7 +48,9 @@
                     name: '',
                     userId: '',
                     portraitUrl: ''
-                }
+                },
+                placeHeight: uni.getSystemInfoSync().windowHeight,
+                bottomHeihgt: 56
             }
         },
         computed: {
@@ -59,13 +63,27 @@
                     }
                 }
             }
-        },
-        onShow() {
-            uni.setNavigationBarTitle({
-                title: this.contact(this.targetId).name
-            })
         },
-        onLoad(e) {
+        onShow() {
+            uni.setNavigationBarTitle({
+                title: this.contact(this.targetId).name
+            })
+        },
+        onLoad(e) {
+            const query = uni.createSelectorQuery().in(this);
+            this.$nextTick(function() {
+                query.select('#msgbar').boundingClientRect(bottom => {
+                    this.bottomHeihgt = bottom.height
+                }).exec();
+            })
+            // 监听键盘高度变化
+            uni.onKeyboardHeightChange(keyboard => {
+                query.select('#scroll').boundingClientRect(scroll => {
+                    const placeHeight = this.windowHeight - scroll.height - keyboard.height - this
+                        .bottomHeihgt
+                    this.placeHeight = placeHeight > 0 ? placeHeight : 0
+                }).exec();
+            })
             this.targetId = e.targetId
             this.userInfo = this.$store.getters.contactInfo(this.targetId)
             // 获取消息列表
@@ -106,16 +124,19 @@
             })
         },
         onUnload() {
+            uni.offKeyboardHeightChange(res => {
+                console.log('卸载监听键盘高度变化', res);
+            })
             uni.$off('onUserDelete_' + this.targetId)
             uni.$off('onReceiveMessage_' + this.targetId)
             uni.$off('onRecallMessage_' + this.targetId)
             uni.$off('onRecallMessage')
             uni.$off('onReadReceiptReceived')
-        },
-        onNavigationBarButtonTap() {
-            uni.navigateTo({
-                url:'/pages/im/friends/info?targetId='+this.targetId
-            })
+        },
+        onNavigationBarButtonTap() {
+            uni.navigateTo({
+                url: '/pages/im/friends/info?targetId=' + this.targetId
+            })
         },
         methods: {
             getNewMessage() {
@@ -160,6 +181,8 @@
 </script>
 
 <style scoped lang="scss">
+    .place {}
+
     /* 窗口 */
     .chat {
         background: $window-color;