英文:
Flutter doesn't delete last item in list
问题
我有一个包含小部件（messages
我已经尝试过
messages.remove(Widget);
messages.removeAt(index);
我甚至尝试过 messages.clear()|
但它也不起作用...我可以删除除最后一个之外的所有消息...我还尝试将列更改为ListView.builder...请给我一个建议..
我的页面代码：
....
StreamBuilder(
stream: _channel.stream,
builder: (context, AsyncSnapshot<dynamic> snapshot) {
if (snapshot.hasData) {
RocketChatMessage? mes;
if (snapshot.hasData) {
try {
var msg = RocketChatMessage.fromJson(
json.decode(snapshot.data));
if (msg.fields != null) {
if (msg.fields!.args![0].msg != null &&
(msg.fields!.args![0].msg!
.isNotEmpty ||
msg.fields!.args![0].file !=
null)) {
if (chat.isEmpty) {
chat.add(msg);
messages.add(generateMessage(msg));
} else {
var item = msg.fields!.args![0].sId;
var ex =
chat.last.fields!.args![0].sId;
if (item != ex) {
chat.add(msg);
messages.add(generateMessage(msg));
scrollDown();
}
}
}
}
} catch (e) {
getChatStory(false);
print("story");
}
}
}
return Expanded(
child: Stack(
children: [
SingleChildScrollView(
controller: scrollController,
child: Column(
children: messages,
),
),
],
),
);
}
),
....
英文:
I have a list which contains widgets (messages<Widget>) , the problem is that i can't delete last item from list.
I already tried
messages.remove(Widget);
messages.removeAt(index);
I even tried messages.clear()|
But it also doesn't work.... I can delete all message except last one... I also tried change column to listview.builder... Please give me an advice..
my page code:
....
StreamBuilder(
stream: _channel.stream,
builder:
(context, AsyncSnapshot<dynamic> snapshot) {
if (snapshot.hasData) {
RocketChatMessage? mes;
if (snapshot.hasData) {
try {
var msg = RocketChatMessage.fromJson(
json.decode(snapshot.data));
if (msg.fields != null) {
if (msg.fields!.args![0].msg != null &&
(msg.fields!.args![0].msg!
.isNotEmpty ||
msg.fields!.args![0].file !=
null)) {
if (chat.isEmpty) {
chat.add(msg);
messages.add(generateMessage(msg));
} else {
var item = msg.fields!.args![0].sId;
var ex =
chat.last.fields!.args![0].sId;
if (item != ex) {
chat.add(msg);
messages.add(generateMessage(msg));
scrollDown();
}
}
}
}
} catch (e) {
getChatStory(false);
print("story");
}
}
}
return Expanded(
child: Stack(
children: [
SingleChildScrollView(
controller: scrollController,
child: Column(
children: messages,
),
),
],
));
}
),
....
答案1
得分: 0
你可以使用专用命令来移除最后一个元素，假设你有类似于 List<Widget> messages 这样的东西。命令是 messages.removeLast()。如果这不能解决你的问题，请提供更多细节，比如你的变量 messages 的类型。
英文:
Assuming that you have something like List<Widget> messages, you can use the dedicated command to remove the last element. It will be messages.removeLast(). If this does not answer your questions, please provide more details like the type of your variable messages.
答案2
得分: 0
我将为您翻译以下代码部分：
我将StreamBuilder更改为常规的监听器，并似乎正在工作
_channel.stream.listen((event) {
RocketChatMessage? mes;
if (event != null) {
try {
var msg = RocketChatMessage.fromJson(json.decode(event));
if (msg.msg == "changed" && msg.fields != null) {
if (msg.fields!.args![0].msg != null &&
(msg.fields!.args![0].msg!.isNotEmpty ||
msg.fields!.args![0].file != null)) {
if (chat.isEmpty) {
chat.add(msg);
messages.add(generateMessage(msg));
} else {
var item = msg.fields!.args![0].sId;
var ex = chat.last.fields!.args![0].sId;
if (item != ex) {
chat.add(msg);
messages.add(generateMessage(msg));
}
}
setState(() {});
scrollDown();
}
}
} catch (e) {
getChatStory(false);
print("story");
}
}
});
和小部件
Expanded(
child: ListView.builder(
controller: scrollController,
itemCount: chat.length,
itemBuilder: (context, index) {
return generateMessage(chat[index]);
})),
请注意，我已将HTML实体字符（例如"和&）还原为原始文本。
英文:
i changed StreamBuilder , to usual listener , and seems like working
_channel.stream.listen((event) {
RocketChatMessage? mes;
if (event != null) {
try {
var msg = RocketChatMessage.fromJson(json.decode(event));
if (msg.msg == "changed" && msg.fields != null) {
if (msg.fields!.args![0].msg != null &&
(msg.fields!.args![0].msg!.isNotEmpty ||
msg.fields!.args![0].file != null)) {
if (chat.isEmpty) {
chat.add(msg);
messages.add(generateMessage(msg));
} else {
var item = msg.fields!.args![0].sId;
var ex = chat.last.fields!.args![0].sId;
if (item != ex) {
chat.add(msg);
messages.add(generateMessage(msg));
}
}
setState(() {});
scrollDown();
}
}
} catch (e) {
getChatStory(false);
print("story");
}
}
});
and widget
Expanded(
child: ListView.builder(
controller: scrollController,
itemCount: chat.length,
itemBuilder: (context, index) {
return generateMessage(chat[index]);
})),
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