fix |> 19889 疑难-竖屏直播间，评论区顶部应是渐隐效果，见截图，参考安卓。

@@ -10,6 +10,7 @@ export struct ChatItemComponent {
   }
 
   build() {
+    Row(){
       Row() {
         Text() {
           if (this.item.role == LiveMessageRole.host) {
@@ -59,5 +60,7 @@ export struct ChatItemComponent {
         right: 8
       })
       .margin({ left: 16, bottom: 4 })
+    }.width("100%")
+    .backgroundColor(Color.Transparent)
   }
 }
\ No newline at end of file

@@ -100,16 +100,22 @@ export struct PlayerCommentComponent {
           ForEach(this.liveChatList, (item: LiveRoomItemBean) => {
             ListItem() {
               ChatItemComponent({ item: item })
-            }
+            }.blendMode(BlendMode.SRC_IN, BlendApplyType.OFFSCREEN)
           })
         }
-        .width('80%')
+        .width('100%')
         .scrollBar(BarState.Off)
+        .edgeEffect(EdgeEffect.None)
 
       }
       .constraintSize({
         maxHeight: 280
+      }).width("80%")
+      .linearGradient({ angle: 0,
+        colors: [[0xff000000, 0.85], [0x01000000, 1.0]]
       })
+      .blendMode(BlendMode.SRC_OVER, BlendApplyType.OFFSCREEN)
+
 
       // 收藏、分享、点赞是否需要根据字段显隐
       LiveOperRowListView({