新增catch error demo

Author: xuyisheng

lib/backend/catcherror.dart

@@ -1,24 +1,53 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_dojo/common/main_title_widget.dart';
+import 'package:flutter_dojo/common/multi_selection_widget.dart';
 
 class CatchErrorWidget extends StatefulWidget {
   @override
   _CatchErrorWidgetState createState() => _CatchErrorWidgetState();
 }
 
 class _CatchErrorWidgetState extends State<CatchErrorWidget> {
+  String url = '';
+  String msg = '';
+
   @override
   Widget build(BuildContext context) {
-    return Column(
-      children: <Widget>[
-        MainTitleWidget('Catch error'),
-        RaisedButton(
-          onPressed: () {
-            throw Exception();
-          },
-          child: Text('Throw exception'),
-        )
-      ],
+    return SingleChildScrollView(
+      child: Column(
+        children: <Widget>[
+          MainTitleWidget('Catch Image Error'),
+          MultiSelectionWidget(
+            'Image Url',
+            [
+              'https://img.favpng.com/25/9/1/dart-google-developers-flutter-android-png-favpng-vi7iwNmVaBCVr91EF35XrnFfc.jpg',
+              'xuyisheng',
+              'https://www.baidu.com',
+            ],
+            [
+              '正确URL',
+              '错误URL',
+              '非图片URL',
+            ],
+            (value) {
+              setState(() => url = value);
+            },
+          ),
+          safeImageWidget(url),
+          Text(msg),
+        ],
+      ),
     );
   }
+
+  safeImageWidget(String url) {
+    Image image = Image.network(url);
+    final ImageStream stream = image.image.resolve(ImageConfiguration.empty);
+    stream.addListener(ImageStreamListener((_, __) {
+      msg = '';
+    }, onError: (e, trace) {
+      msg = '$e-$trace';
+    }));
+    return image;
+  }
 }