Flutter 为 FCM 的 ShowDialog 在 null 上调用了方法“+”
Flutter The method '+' was called on null for ShowDialog for FCM
我在 flutter 中使用 FCM 在我的应用程序上推送通知，在我的设备通知栏上单击通知时一切正常，它将我路由回应用程序并显示一个对话框，其中包含通知的更多详细信息。但是，当我终止该应用程序并发送一条推送通知，该通知将我路由回该应用程序，而不是向我显示包含通知更多详细信息的对话框时，我收到以下错误“NoSuchMethodError The method '+' was called on null”。下面是我的 onMessage、onResume 和 Onlaunch。
@override
void initState() {
// TODO: implement initState
super.initState();
final FirebaseMessaging firebaseMessaging = FirebaseMessaging();
firebaseMessaging.configure(
onMessage: (Map<String, dynamic> message) async {
item_id= message['data']['item_id'].toString();
type_id= message['data']['type_id'].toString();
item_title= message['data']['item_title'].toString();
item_description= message['data']['item_description'].toString();
item_thumbnail_name= message['data']['item_thumbnail_name'].toString();
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
}
onResume: (Map<String, dynamic> message) async {
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
} onLaunch: (Map<String, dynamic> message) async {
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
}
}
我的最佳猜测是您正在此处创建 item_description 变量：
item_description= message['data']['item_description'].toString();
但是 message['data']['item_description'] 在地图中实际上没有值，因此 '+' was called on null 错误。
为了修复它是一个空字符串而不是空字符串，将行更新为：
item_description= message['data']['item_description'].toString() ?? '';
因此，在逐行查看我的代码并进行故障排除后，我能够在 onLaunch 中找到 item_description= message['data']['item_description']; ，因此我将其添加如下：
onLaunch: (Map<String, dynamic> message) async {
item_description= message['data']['item_description'];
}
将此添加到我的 onLaunch 后，我再次收到错误并显示我的 showdialog。
我在 flutter 中使用 FCM 在我的应用程序上推送通知，在我的设备通知栏上单击通知时一切正常，它将我路由回应用程序并显示一个对话框，其中包含通知的更多详细信息。但是，当我终止该应用程序并发送一条推送通知，该通知将我路由回该应用程序，而不是向我显示包含通知更多详细信息的对话框时，我收到以下错误“NoSuchMethodError The method '+' was called on null”。下面是我的 onMessage、onResume 和 Onlaunch。
@override
void initState() {
// TODO: implement initState
super.initState();
final FirebaseMessaging firebaseMessaging = FirebaseMessaging();
firebaseMessaging.configure(
onMessage: (Map<String, dynamic> message) async {
item_id= message['data']['item_id'].toString();
type_id= message['data']['type_id'].toString();
item_title= message['data']['item_title'].toString();
item_description= message['data']['item_description'].toString();
item_thumbnail_name= message['data']['item_thumbnail_name'].toString();
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
}
onResume: (Map<String, dynamic> message) async {
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
} onLaunch: (Map<String, dynamic> message) async {
if(type_id=='1' ){
showGeneralDialog(
barrierLabel: "General Information",
barrierDismissible: false,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 1200),
context: context,
pageBuilder: (context, anim1, anim2) {
return Align(
alignment: Alignment.bottomCenter,
child: Container(
height: 400,
child: SingleChildScrollView(child:Column(children: [
SizedBox(height: 10,),
Center(child:Container(
padding: EdgeInsets.all(10),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Container(
padding: EdgeInsets.all(0),
child:Material(
color: Colors.white,
child:Text("Information!",style:TextStyle(
fontFamily: 'Montserrat', fontSize: 20.0, color: Colors.black,fontWeight: FontWeight.bold)
))),
],))),
Container(
padding: EdgeInsets.all(5),
child:Material(
color: Colors.white,
child:Column(
mainAxisSize: MainAxisSize.min,
children: [
Stack(children: [
Image.asset("assets/640x360.png",fit: BoxFit.cover,
height: 180,),
Image.network(item_thumbnail_name),
],),
Center(child:Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_title,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.pink,
fontSize: 15,fontWeight: FontWeight.bold),
))),
Padding(
padding: EdgeInsets.only(top: 5, bottom: 5),
child: Text(item_description+"...",
maxLines: 4,
style: TextStyle(
fontFamily: 'Montserrat',
color: Colors.grey,
fontSize: 12,fontWeight: FontWeight.normal),
)),
],))),
Container(
padding: EdgeInsets.only(left:5,right:5),
child:Row(
children: <Widget>[
Expanded(child:RaisedButton(
color: Colors.blue,
onPressed: () { Navigator.pop(context, false);
},
textColor: Colors.white,
padding: const EdgeInsets.all(0.0),
child: Container(
decoration: const BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(3)),
color: Colors.blue,
),
padding: const EdgeInsets.all(10.0),
child:
const Text('Close',),
),
)),
],
)),
],)),
margin: EdgeInsets.only(bottom: 50, left: 12, right: 12),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(20),
),
),
);
},
transitionBuilder: (context, anim1, anim2, child) {
return SlideTransition(
position: Tween(begin: Offset(0, 1), end: Offset(0, 0)).animate(anim1),
child: child,
);
},
);
}
}
}
我的最佳猜测是您正在此处创建 item_description 变量：
item_description= message['data']['item_description'].toString();
但是 message['data']['item_description'] 在地图中实际上没有值，因此 '+' was called on null 错误。
为了修复它是一个空字符串而不是空字符串，将行更新为：
item_description= message['data']['item_description'].toString() ?? '';
因此，在逐行查看我的代码并进行故障排除后，我能够在 onLaunch 中找到 item_description= message['data']['item_description']; ，因此我将其添加如下：
onLaunch: (Map<String, dynamic> message) async {
item_description= message['data']['item_description'];
}
将此添加到我的 onLaunch 后，我再次收到错误并显示我的 showdialog。