调整新信息的获取模式，以前是刷新整体列表，更改为concat

pages/im/group/chat.nvue

@@ -16,7 +16,7 @@
             </cell>
             <cell class="cell-footer" ref="chatBottom"></cell>
         </list>
-        <sent-message-bar :conversationType="conversationType" :targetId="targetId" @onSuccess="getMessageList()" />
+        <sent-message-bar :conversationType="conversationType" :targetId="targetId" @onSuccess="getNewMessage()" />
     </view>
 </template>
 
@@ -59,7 +59,7 @@
             this.getMessageList()
             uni.$on('onReceiveMessage', (msg) => {
                 if (msg.targetId == this.targetId) {
-                    this.getMessageList()
+                    this.getNewMessage()
                 }
             })
             uni.$once('cleanGroupMessage', this.getMessageList)
@@ -87,6 +87,18 @@
                        url: '/pages/im/friends/info?targetId=' + item.senderUserId
                    }) 
                 }
+            },
+            getNewMessage() {
+                im.getMessageList(
+                    this.conversationType,
+                    this.targetId,
+                    new Date().getTime(),
+                    10,
+                    false,
+                    (messages) => {
+                        this.messages = this.messages.concat(messages)
+                        this.scrollBottom()
+                    })
             },
             // 获取消息列表
             getMessageList() {
@@ -94,7 +106,7 @@
                     this.conversationType,
                     this.targetId,
                     new Date().getTime(),
-                    20,
+                    100,
                     true,
                     (messages) => {
                         this.messages = messages.reverse()