Modify for async

Signed-off-by: Nzhang-xiaobo1997 <tony.zhangxiaobo@huawei.com>

zh-cn/application-dev/media/image.md

@@ -276,21 +276,24 @@ imageSourceIncrementalSApi.updateData(array, false, 0, 10,(error,data )=> {})
 示例场景：camera作为客户端将拍照数据传给服务端
 
 ```js
-//服务端代码，创建ImageReceiver
-var receiver = image.createImageReceiver(8 * 1024, 8, image.ImageFormat.JPEG, 1);
+public async init(surfaceId: any) {
 
-//获取Surface ID
-var surfaceId = await receiver.getReceivingSurfaceId();
+  //服务端代码，创建ImageReceiver
+  var receiver = image.createImageReceiver(8 * 1024, 8, image.ImageFormat.JPEG, 1);
 
-//注册Surface的监听，在suface的buffer准备好后触发
-receiver.on('imageArrival', () => {
+  //获取Surface ID
+  var surfaceId = await receiver.getReceivingSurfaceId();
+
+  //注册Surface的监听，在suface的buffer准备好后触发
+  receiver.on('imageArrival', () => {
     //去获取Surface中最新的buffer
     receiver.readNextImage((err, img) => {
 	    img.getComponent(4, (err, componet) => {
 			//消费componet.byteBuffer，例如：将buffer内容保存成图片。
 		})
 	})
-})
+  })
 
-//调用Camera方法将surfaceId传递给Camera。camera会通过surfaceId获取surface，并生产出surface buffer。
+  //调用Camera方法将surfaceId传递给Camera。camera会通过surfaceId获取surface，并生产出surface buffer。
+}
 ```
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