I add a button to add a list of widget in my screen, like this:
List<Widget> timeWidget = [];
buildTime() {
setState(
() {
timeWidget.add(Padding(
padding: EdgeInsets.all(20.0),
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
HourScheduleItem(
enabled: true,
day: _day,
onRemove: () {
timeWidget.remove(data);
},
onChanged: (date, hour) {
setState(
() {
_day = date;
_hour = hour;
print(_hour);
},
);
},
)
],
),
));
},
);
}
When a click onTap button buildTime(); the return is a constructor into Column in my screen:
Column(children: timeWidget.map((data) {
return data;
}).toList()),
But when I choose an option in the next widget added, the option chosen is shown only in the first widget, I believe this must be due to the fact that it does not get an index?
enter image description here
This due to how states and widgets in the widget tree are linked together. The flutter YouTube channel has a great in depth explanation of this topic, but TL;DR flutter doesn't "know" which widget in the list you actually clicked on unless you give each widget a unique identifier to tell them apart!
In almost all cases, you can do this by adding a key: UniqueKey() parameter to the constructor of the widget you're putting in a list. In your case, you would pass it in to your HourScheduleItem which would then pass it into the super() constructor.
Related
I have an input page to create a new reminder. On this page you will select several different variables (reminder type, start date, etc.) - at this stage I am just trying to get it work for two variables.
I have a button object that I create, which takes some text, a "isSelected" value (which changes the color to show it is selected) and an onPress callback. The plan is to use a loop to create one of these buttons for each of the necessary selection options and then feed that into a ListView, so you have a scroll-able list of selection option. As you select the item the properties of the new reminder object will update and the color will change to selected.
When I click the button, the value is selected (the print statement shows this) but the button does not change to the new isSelected value, despite a SetState being used. What is it I am missing here? Is it possible to feed buttons into a ListView like this and still have their state update? Or do you need to find another work around?
class AddReminder extends StatefulWidget {
#override
_AddReminderState createState() => _AddReminderState();
}
class _AddReminderState extends State<AddReminder> {
String addReminder = "";
Reminder newReminder = Reminder();
#override
List<Widget> getReminderTypesButton(
String selectionName, List selectionOptions, var reminderVariable) {
// create new list to add widgets to
List<Widget> selectionOptionsWidgets = [];
// loop through selection options and create buttons
for (String selection in selectionOptions) {
bool isSelectedValue = false;
selectionOptionsWidgets.add(
FullWidthButton(
text: selection,
isSelected: isSelectedValue,
onPress: () {
setState(() {
reminderVariable = selection;
isSelectedValue = true;
});
print(reminderVariable);
},
),
);
}
;
// return list of widgets
return selectionOptionsWidgets;
}
Widget build(BuildContext context) {
List<List<Widget>> newList = [
getReminderTypesButton("Type", reminderTypesList, newReminder.type),
getReminderTypesButton(
"Frequency", repeatFrequencyTypesList, newReminder.repeatFrequency)
];
List<Widget> widgetListUnwrap(List<List<Widget>> inputList) {
//takes list of list of widgets and converts to widget list (to feed into list view)
List<Widget> widgetsUnwrapped = [];
for (var mainList in inputList) {
for (var widgets in mainList) {
widgetsUnwrapped.add(widgets);
}
}
return widgetsUnwrapped;
}
return SafeArea(
child: Container(
color: Colors.white,
child: Column(
children: [
Hero(
tag: addReminder,
child: TopBarWithBack(
mainText: "New reminder",
onPress: () {
Navigator.pop(context);
},
)),
Expanded(
child: Container(
child: ListView(
children: widgetListUnwrap(newList),
shrinkWrap: true,
),
),
),
],
),
),
);
}
}
Here are the lists that I reference
List<String> reminderTypesList = [
"Appointment",
"Check-up",
"Other",
];
List<String> repeatFrequencyTypesList = [
"Never",
"Daily",
"Weekly",
"Monthly",
"Every 3 months",
"Every 6 months",
"Yearly",
];
List<List<String>> selectionOptions = [
reminderTypesList,
repeatFrequencyTypesList
];
The reason your state not changing is that every time you call setState(), the whole build function will run again. If you initiate a state (in this case isSelectedValue) within the build method (since the getReminderTypesButton() got called within the build), the code will run through the below line again and again, resetting the state to the initial value.
bool isSelectedValue = false;
This line will always set the isSelectedValue to false, no matter how many time you call setState.
In order to avoid this, you need to place the state outside of the build method, ideally in the FullWidthButton like this:
class FullWidthButton extends StatefulWidget {
const FullWidthButton({Key? key}) : super(key: key);
#override
_FullWidthButtonState createState() => _FullWidthButtonState();
}
class _FullWidthButtonState extends State<FullWidthButton> {
bool isSelectedValue = false;
#override
Widget build(BuildContext context) {
return InkWell(
onTap: () => setState(() => isSelectedValue = !isSelectedValue),
// ...other lines
);
}
}
I need to implement lists of buttons in a column depending on the data entry. So, for that I have to use for loop. Each button requires two entires id, text. I can make it with List. But it accepts only string value not the integer.
This is the code I tried.
code
Widget getTextWidgets(List<String> strings)
{
List<Widget> list = new List<Widget>();
for(var i = 0; i < strings.length; i++){
list.add(new ButtonForHome(
lable: strings[i],
onPressed: (){},
));
}
return new Column(children: list);
}
I want to put id in onPressed event. How can I implement in the Flutter?
You should use Listview instead of Column
SAMPLE CODE
getTextWidgets() {
return ListView.builder(
itemCount: yourList.length,
itemBuilder: (context, itemIndex) {
return MaterialButton(
child: Text(yourList[itemIndex]),
onPressed: () {
debugPrint('Clicked index $itemIndex');
});
});
}
Now your question
I want to put id in onPressed event. How can I implement in the Flutter?
You can create a POJO class like this
class DataModel{
String name;
int id;
DataModel(this.name, this.id);
}
Now create list of your POJO class
List<DataModel> list= List<DataModel>();
Now add data in your list like this
list.add(DataModel("name", 1));
list.add(DataModel("name", 2));
list.add(DataModel("name", 3));
Now you can use it like this way
getTextWidgets() {
return ListView.builder(
itemCount: list.length,
itemBuilder: (context, itemIndex) {
return MaterialButton(
child: Text(list[itemIndex].name),
onPressed: () {
debugPrint('Clicked item name '+list[itemIndex].name);
debugPrint('Clicked item ID '+list[itemIndex].id.toString());
});
});
}
Nilesh Rathod has indeed given the descriptive answer for the same. In flutter there is also, a way to achieve this, which is quite similar to POJO class, is
To create own widget and specify the fields needs to be passed when we are using the widget
Add the widget to the list, with the data specified for passing
You can track, the id, by pressing itself also
I can clearly see that, you have created your own widget named as ButtonForHome, which takes in label for now. What you can do is, to make your widget takes in two argument, and you can do it like this:
class ButtonForHome extends StatelessWidget {
final String label;
final int id; // this will save your day
// #required will not let user to skip the specified key to be left null
ButtonForHome({#required this.label, #required this.id});
#override
Widget build(BuildContext context) {
return Container(
child: Center(
child: RaisedButton(
color: Colors.blue,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
),
child: Text(this.label),
onPressed: () => print(this.id) // Here you print your id using your button only
)
);
}
}
Now creating your button with a list, or adding via list
You can do it via ListView.builder()
You can do it via your way, i.e., List<Widget>.add()
I am gonna show the solution in your way only:
Widget getTextWidgets(List<String> strings){
List<Widget> list = new List<Widget>();
for(var i = 0; i < strings.length; i++){
list.add(ButtonForHome(
id: i, // passing the i value only, for clear int values
label: strings[i]
));
}
return Column(children: list);
}
With the new flutter in place, you don't need to do new every time while defining a widget. It understands now, so no need of const, new at all
So, wherever you populate your getTextWidget, it will show up the Widgte ButtonForHome, which has unique id, and label. Now the ButtonForHome, prints the id of that particular widget which was passed uniquely. So now, you can see your result happening.
I hope this is what you were looking for. Try it, and let me know.
In my build, I have this function that basically stacks a button and a counter, i'm also passing a function (this let's me reuse the buildbuttoncolumn for all buttons instead of copying code arround
my build:
Widget build(BuildContext context) {
List<Widget> _layouts = [
_videoInfo(),
_channelInfo(),
_comment(),
_moreInfo(),
VideoList(
channel: widget.channel,
isMiniList: true,
currentVideoId: widget.detail.id
),
];
if (MediaQuery.of(context).orientation == Orientation.landscape) {
_layouts.clear();
}
return Scaffold(
body: Column(children: <Widget>[
_buildVideoPlayer(context),
Expanded(
child: ListView(
children: _layouts,
),
)
]));
}
my videoinfo:
Widget _videoInfo() {
return Column(
children: <Widget>[
ListTile(
title: Text(widget.detail.title),
subtitle: Text(widget.detail.viewCount + ' . ' + widget.detail.publishedTime),
trailing: Icon(Icons.arrow_drop_down),
),
Container(
padding: EdgeInsets.all(8.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
_buildButtomColumn(Icons.thumb_up, widget.detail.likeCount, function: _like(widget.detail.id, true)),
_buildButtomColumn(Icons.thumb_down, widget.detail.dislikeCount, function: _like(widget.detail.id, false)),
_buildButtomColumn(CupertinoIcons.share_up, "Partilhar"), //function: share(context, widget.detail.player)
_buildButtomColumn(Icons.add_to_photos, "Guardar"),
],
),
)
],
);
}
_buildButtomColumn(Icons.thumb_up, widget.detail.likeCount, function: _like(widget.detail.id, true)),
the method then does something like this:
Widget _buildButtomColumn(IconData icon, String text, {function}) {
return GestureDetector(
onTap: () => function
child: Column(.....
oh and here's the like:
_like(String videoId, bool liked) {
youtubeAPI.likeDislikeVideo(videoId, liked);
}
when I open the page, the onTap gets triggered without me actually pressing the button.
Where is the problem?
You are calling that function yourself, there is no problem with onTap callback and it is not fired somehow without user interaction
Next snippet performs _like function invocation and pass returned result to function:... arg (refer to lang tour)
function: _like(widget.detail.id, true)
You can prevent such situations if you declare function: argument type as Function and you will get static analysis type error before you run code
_buildButtomColumn(IconData icon, String text, {Function function})
Back to you code - how to fix it?
pass function argument directly to onTap argument
Widget _buildButtomColumn(IconData icon, String text, {VoidCallback function}) {
/// here I enforced type as VoidCallback - it is typedef for `void Function()`
return GestureDetector(
onTap: function, // <-- pass function, onTap type is VoidCallback
child: Column(.....
2.a. pass anonymous function with desired payload
_buildButtomColumn(Icons.thumb_up, widget.detail.likeCount,
function: () => youtubeAPI.likeDislikeVideo(videoId, liked), // <-- this will be invoked later
)
2.b. this variant is for sake of completeness
declare callable class and pass it's instance to function:... arg ()
class LikeCommand {
final String videoId;
final bool liked;
LikeCommand(this.videoId, this.liked);
void call() => youtubeAPI.likeDislikeVideo(videoId, liked);
}
_buildButtomColumn(Icons.thumb_up, widget.detail.likeCount,
function: LikeCommand(videoId, liked),
)
PS I recommend declaring types, since dart is a strongly typed language and specifying types will save you from typical problems in the future
PPS feel free to reach me in comments
I have a TextField and an IconButton in a row like so.
I would like the IconButton to be enabled only when there is text in the TextField. I am using the provider package for state management.
Here is the ChangeNotifier implementation.
class ChatMessagesProvider with ChangeNotifier{
List<ChatMessage> chatMessages = <ChatMessage>[];
bool messageTyped = false;
ChatMessagesProvider(this.chatMessages);
void newMessage(String textMessage){
ChatMessage message = ChatMessage(textMessage);
this.chatMessages.add(message);
notifyListeners();
}
int messageCount() => chatMessages.length;
void updateMessageTyped(bool typed){
this.messageTyped = typed;
// notifyListeners(); Un-comennting this makes the Text disappear everytime I type something on the text field
}
}
Here is the actual widget:
class TextCompose extends StatelessWidget {
final TextEditingController _composeTextEditingController = new TextEditingController();
TextCompose(this.chatMessagesProvider);
final ChatMessagesProvider chatMessagesProvider;
#override
Widget build(BuildContext context) {
return Container(
margin: const EdgeInsets.all(8.0),
child: Row(
children: <Widget>[
Flexible(
child: new TextField(
controller: _composeTextEditingController,
onSubmitted: (String text) {
_onMessageSubmitted(text, context);
},
onChanged: (String text){
if(text.length > 0){
chatMessagesProvider.updateMessageTyped(true);
print(text);
}
else{
chatMessagesProvider.updateMessageTyped(false);
print("No text typed");
}
},
decoration: new InputDecoration.collapsed(
hintText: "Enter message"
),
),
),
new Container(
margin: new EdgeInsets.all(8.0),
child: new IconButton(
color: Theme.of(context).accentColor,
icon: new Icon(Icons.send),
disabledColor: Colors.grey,
onPressed:chatMessagesProvider.messageTyped // This dosen't work
? () => _onMessageSubmitted(_composeTextEditingController.text, context)
: null,
),
)
],
),
);
}
void _onMessageSubmitted(String text, BuildContext context){
if(chatMessagesProvider.messageTyped) { // This works fine.
// clear the message compose text box
_composeTextEditingController.clear();
// add the message to provider.
chatMessagesProvider.newMessage(text);
// set the message typed to false
chatMessagesProvider.messageTyped = false;
}
I am using messageTyped from ChatMessageProvider to check to see if there is any text in the TextField. It seems to work fine when I check it in the _onMessageSubmitted method but not when I check its value in the onPressed property for the IconButton.
I know this because I can see the IconButton remains disabled(colour doesn't change from grey) when I type text, whereas I can hit the submit button on the virtual keyboard and the text is cleared from the TextField(as per call to _composeTextEditingController.clear())
Question:
why does chatMessagesProvider.messageTyped return the right value when called from the _onMessageSubmitted but not when it is called from the onPrssed attribute in the IconButton?
How would I debug something like this in Flutter, I would really like to drop a breakpoint in onPressedAttribute and see the value for chatMessagesProvider.messageTyped
Let me know if you need to see any more of my code.
onPressed:chatMessagesProvider.messageTyped this line is being executed during widget build time so it is always default value and it will never get refreshed until unless you rebuild the widget using notify listener or stateful widget.
Store the currently being typed message in your provider and make your send button enable/disable depends on whether currently being typed message is empty or not.
You say you are using 'provider_package' but you actually have no Provider in your layout. Instead you have a custom built ChangeNotifier with no listeners - you are indeed calling notifyListeners() but there are actually no listeners, so no rebuild is being triggered. A rebuild is needed in order for the button to change its onPressed function reference and implicitly its color.
As for debugging, you can set a breakpoint on the line with onPressed, but it will only be hit during a rebuild.
The most important thing to understand is that the function reference you give to onPressed will be invoked correctly, but a rebuild is needed for the widget to change visually.
Although your current ChangeNotifier implementation does not make much sense, simply wrapping your calls to updateMessageTyped within setState should solve the visual problem - and your breakpoint will also be hit after each typed/deleted character.
The simplest solution you can, first of all, make your widget StatefulWidget.
You need a boolean inside State class:
bool hasText = false;
Then create initState:
#override
void initState() {
_composeTextEditingController.addListener(() {
if (_composeTextEditingController.text.isNotEmpty) {
setState(() {
hasText = true;
});
} else {
setState(() {
hasText = false;
});
}
});
super.initState();
}
Also don't forget to dispose:
#override
void dispose() {
_composeTextEditingController.dispose();
super.dispose();
}
And finally your build method:
Row(
children: <Widget>[
Expanded(
child: TextField(
controller: _composeTextEditingController,
)),
if (hasText) IconButton(icon: Icon(Icons.send), onPressed: () {})
],
),
How does setState actually work?
It seems to not do what I expect it to do when the Widget which should have been rebuilt is built in a builder function. The current issue I have is with a ListView.builder and buttons inside an AlertDialog.
One of the buttons here is an "AutoClean" which will automatically remove certain items from the list show in the dialog.
Note: The objective here is to show a confirmation with a list of "Jobs" which will be submitted. The jobs are marked to show which ones appear to be invalid. The user can go Back to update the parameters, or press "Auto Clean" to remove the ones that are invalid.
The button onTap looks like this:
GeneralButton(
color: Colors.yellow,
label: 'Clear Overdue',
onTap: () {
print('Nr of jobs BEFORE: ${jobQueue.length}');
for (int i = jobQueue.length - 1; i >= 0; i--) {
print('Checking item at $i');
Map task = jobQueue[i];
if (cuttoffTime.isAfter(task['dt'])) {
print('Removing item $i');
setState(() { // NOT WORKING
jobQueue = List<Map<String, dynamic>>.from(jobQueue)
..removeAt(i); // THIS WORKS
});
}
}
print('Nr of jobs AFTER: ${jobQueue.length}');
updateTaskListState(); // NOT WORKING
print('New Task-list state: $taskListState');
},
),
Where jobQueue is used as the source for building the ListView.
updateTaskListState looks like this:
void updateTaskListState() {
DateTime cuttoffTime = DateTime.now().add(Duration(minutes: 10));
if (jobQueue.length == 0) {
setState(() {
taskListState = TaskListState.empty;
});
return;
}
bool allDone = true;
bool foundOverdue = false;
for (Map task in jobQueue) {
if (task['result'] == null) allDone = false;
if (cuttoffTime.isAfter(task['dt'])) foundOverdue = true;
}
if (allDone) {
setState(() {
taskListState = TaskListState.done;
});
return;
}
if (foundOverdue) {
setState(() {
taskListState = TaskListState.needsCleaning;
});
return;
}
setState(() {
taskListState = TaskListState.ready;
});
}
TaskListState is simply an enum used to decide whether the job queue is ready to be submitted.
The "Submit" button should become active once the taskListState is set to TaskListState.ready. The AlertDialog button row uses the taskListState for that like this:
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
if (taskListState == TaskListState.ready)
ConfirmButton(
onTap: (isValid && isOnlineNow)
? () {
postAllInstructions().then((_) {
updateTaskListState();
// navigateBack();
});
: null),
From the console output I can see that that is happening but it isn't working. It would appear to be related to the same issue.
I don't seem to have this kind of problem when I have all the widgets built using a simple widget tree inside of build. But in this case I'm not able to update the display of the dialog to show the new list without the removed items.
This post is getting long but the ListView builder, inside the AleryDialog, looks like this:
Flexible(
child: ListView.builder(
itemBuilder: (BuildContext context, int itemIndex) {
DateTime itemTime = jobQueue[itemIndex]['dt'];
bool isPastCutoff = itemTime.isBefore(cuttoffTime);
return Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
mainAxisSize: MainAxisSize.max,
children: <Widget>[
Text(
userDateFormat.format(itemTime),
style: TextStyle(
color:
isPastCutoff ? Colors.deepOrangeAccent : Colors.blue,
),
),
Icon(
isPastCutoff ? Icons.warning : Icons.cached,
color: isPastCutoff ? Colors.red : Colors.green,
)
],
);
},
itemCount: jobQueue.length,
),
),
But since the Row() with buttons also doesn't react to setState I doubt that the problem lies within the builder function itself.
FWIW all the code, except for a few items like "GeneralButton" which is just a boilerplate widget, resides in the State class for the Screen.
My gut-feeling is that this is related to the fact that jobQueue is not passed to any of the widgets. The builder function refers to jobQueue[itemIndex], where it accesses the jobQueue attribute directly.
I might try to extract the AlertDialog into an external Widget. Doing so will mean that it can only access jobQueue if it is passed to the Widget's constructor....
Since you are writing that this is happening while using a dialog, this might be the cause of your problem:
https://api.flutter.dev/flutter/material/showDialog.html
The setState call inside your dialog therefore won't trigger the desired UI rebuild of the dialog content. As stated in the API a short and easy way to achieve a rebuild in another context would be to use the StatefulBuilder widget:
showDialog(
context: context,
builder: (dialogContext) {
return StatefulBuilder(
builder: (stateContext, setInnerState) {
// return your dialog widget - Rows in ListView in Container
...
// call it directly as part of onTap of a widget of yours or
// pass the setInnerState down to another widgets
setInnerState((){
...
})
}
);
EDIT
There are, as in almost every case in the programming world, various approaches to handle the setInnerState call to update the dialog UI. It highly depends on the general way of how you decided to manage data flow / management and logic separation. As an example I use your GeneralButton widget (assuming it is a StatefulWidget):
class GeneralButton extends StatefulWidget {
// all your parameters
...
// your custom onTap you provide as instantiated
final VoidCallback onTap;
GeneralButton({..., this.onTap});
#override
State<StatefulWidget> createState() => _GeneralButtonState();
}
class _GeneralButtonState extends State<GeneralButton> {
...
#override
Widget build(BuildContext context) {
// can be any widget acting as a button - Container, GestureRecognizer...
return MaterialButton(
...
onTap: {
// your button logic which has either been provided fully
// by the onTap parameter or has some fixed code which is
// being called every time
...
// finally calling the provided onTap function which has the
// setInnerState call!
widget.onTap();
},
);
}
If you have no fixed logic in your GeneralButton widget, you can write: onTap: widget.onTap
This would result in using your GeneralButton as follows:
...
GeneralButton(
...
onTap: {
// the desired actions like provided in your first post
...
// calling setInnerState to trigger the dialog UI rebuild
setInnerState((){});
},
)