update doc

README.md

@@ -22,6 +22,7 @@ QQ Group：892398530。
 * Pay.
 * Launch Mini-Program.
 * Subscribe Message.
+* Auth By QRCode
 
 ## Sample
 [See sample here](./example)

README_CN.md

@@ -21,6 +21,7 @@ QQ群：892398530。
 * 支付。
 * 打开小程序。
 * 一次性订阅消息。
+* 二维码登录。
 
 
 ## 示例

doc/ATUH_BY_QR_CODE.md

+## AUTH BY QR CODE
+
+When WeChat not installed on devices, user can login with WeChat-QRCode.
+
+### Flutter
+
+Request QRCode by the following codes:
+
+```dart
+fluwx.authByQRCode(
+                  appId: "wxd930ea5d5a258f4f",
+                  scope: "noncestr",
+                  nonceStr: "nonceStr",
+                  timeStamp: "1417508194",
+                  signature: "429eaaa13fd71efbc3fd344d0a9a9126835e7303");
+            }
+```
+[What do the params mean?](https://open.weixin.qq.com/cgi-bin/showdocument?action=dir_list&t=resource/res_list&verify=1&id=215238808828h4XN&token=&lang=zh_CN)
+
+
+You can receive the data from WeChat through these ways:
+
+```dart
+//listening your auth status
+    fluwx.onAuthByQRCodeFinished.listen((data){
+          setState(() {
+            _status =
+                "errorCode=>${data.errorCode}\nauthCode=>${data.authCode}";
+          });
+        });
+
+    //show your qrcode after this
+    fluwx.onAuthGotQRCode.listen((image) {
+      setState(() {
+        _image = image;
+      });
+    });
+
+    //qrcode was scanned
+    fluwx.onQRCodeScanned.listen((scanned) {
+      setState(() {
+        _status = "scanned";
+      });
+    });
+    
+```
+    
+### Android
+WeChatSDK will crash due to `HttpClient` when running on Android P,see this [solution](https://cloud.tencent.com/developer/ask/146536) for help .

doc/AUTH_BY_QR_CODE_CN.md

+## 二维码登录
+
+如果用户没有安装微信，我们可以通过扫描二维码登录.
+
+### Flutter
+
+请求一个二维码:
+
+```dart
+fluwx.authByQRCode(
+                  appId: "wxd930ea5d5a258f4f",
+                  scope: "noncestr",
+                  nonceStr: "nonceStr",
+                  timeStamp: "1417508194",
+                  signature: "429eaaa13fd71efbc3fd344d0a9a9126835e7303");
+            }
+```
+[这些参数都是什么意思?](https://open.weixin.qq.com/cgi-bin/showdocument?action=dir_list&t=resource/res_list&verify=1&id=215238808828h4XN&token=&lang=zh_CN)
+
+通过以下方式监听扫描过程:
+
+```dart
+//当扫码完成
+    fluwx.onAuthByQRCodeFinished.listen((data){
+          setState(() {
+            _status =
+                "errorCode=>${data.errorCode}\nauthCode=>${data.authCode}";
+          });
+        });
+
+    //这个时候可以显示你的二维码了
+    fluwx.onAuthGotQRCode.listen((image) {
+      setState(() {
+        _image = image;
+      });
+    });
+
+    //二维码被扫描了
+    fluwx.onQRCodeScanned.listen((scanned) {
+      setState(() {
+        _status = "scanned";
+      });
+    });
+    
+```
+    
+### Android
+在Android P上，微信SDK会闪退， 查看[该文章](https://cloud.tencent.com/developer/ask/146536)以寻求帮助.

example/lib/auth_by_qr_code_page.dart

@@ -17,7 +17,6 @@ class _AuthByQRCodePageState extends State<AuthByQRCodePage> {
     super.initState();
 
     fluwx.onAuthByQRCodeFinished.listen((data){
-        print("----finished");
           setState(() {
             _status =
                 "errorCode=>${data.errorCode}\nauthCode=>${data.authCode}";