统一聊天页的头像大小，改用rpx2px的计算，84rpx

pages/im/components/messageCell.vue

@@ -2,7 +2,7 @@
     <view class="message--cell">
         <view class="avatar">
             <u-badge max="99" shape="horn" absolute :offset="[-5, -8]" :value="item.unreadMessageCount" />
-            <u-avatar :src="contact(item.targetId).portraitUrl" shape="square" size="44" />
+            <u-avatar :src="contact(item.targetId).portraitUrl" shape="square" :size="avatarSize" />
         </view>
         <view class="content">
             <view class="header">
@@ -18,6 +18,7 @@
 
 <script>
     import messagePreview from './messagePreview'
+    import utils from '@/utils/index.js'
 
     export default {
         props: {
@@ -27,8 +28,16 @@
                     return {}
                 }
             }
-        },
+        },
+        data() {
+            return {
+                avatarRpx: 84
+            }
+        },
         computed: {
+            avatarSize() {
+                return utils.rpx2px(this.avatarRpx)
+            },
             contact() {
                 return function(targetId) {
                     return this.$store.getters.contactInfo(targetId)
@@ -48,6 +57,7 @@
 
         .avatar {
             position: relative;
+            padding-top: 5rpx;
 
             .u-badge {
                 z-index: 998;
@@ -59,8 +69,6 @@
             box-sizing: border-box;
             position: relative;
             flex: 1;
-
-
             border-bottom-width: 0.5px !important;
             border-color: #f9f9f9 !important;
             border-bottom-style: solid;