Disable dropDown value in Flutter
policyDropdown = ['Platinum', 'Gold', 'Sr. Citizen'],
child: Container(
height: 50.0,
child: ListTile(
title: Text('Policy Type'),
trailing: DropdownButtonHideUnderline(
child: DropdownButton(
value: policyDropdownData,
items: policyDropdown.map((String value) {
return DropdownMenuItem(
child: Text(value),
value: value,
);
}).toList(),
onChanged: (String? value) {
setState(() {
policyDropdownData = value.toString();
});
},
),
disable the first data of the policyDropdown... What can I do?
You can use the enable property of the DropdownMenuItem and enable every other option than the first one of your policyDropdown list i.e."Platinum".
for example:
return DropdownMenuItem(
value: value,
child: Text(value),
enabled: value != 'Platinum',
);
Additionally, If you want users to know that the option is disabled you can change the color of the text using the same logic.
return DropdownMenuItem(
value: value,
child: Text(
value,
style: TextStyle(
color: value != 'Platinum'
? Colors.white
: Colors.white60,
),
),
enabled: value != 'Platinum',
);
Related
so i aim to use a dropDownButton if already i have selected an option i find it selected ( the value is saved in DataBase) and of course it can be modified else if i didn't choose any option i choose . so this is using the attribute value : value: box.read("optioSaved") ?? dropDownValue, but here if the user has already choose a value he can't modified it
how can i do ?
this is the full code :
child: DropdownButton<String>(
icon: const Icon(Icons.keyboard_arrow_down),
isExpanded: true,
style: const TextStyle(
color: Colors.black,
fontSize: 17,
fontFamily: 'SFProRegular',
),
underline: Container(
height: 1,
color: Colors.black,
),
onChanged: (String? newValue) {
setState(() {
dropDownValue = newValue;
});
},
items: <String>[
"option1",
"option 2",
].map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
value: box.read("optioSaved") ?? dropDownValue,
hint: const Text("choose"),
),
assign box.read("optioSaved") to dropDownValue in initState and then just value: dropDownValue
I have a DropDownButtonFormField I need to check this. If the dropdown value is not selected by the user then assign the initial value when submitting.
Custom DropDown
Container myDropDownContainer(String initialVal, List<String> listItems,
String text, Function myFunc, Function validate) {
return Container(
margin: const EdgeInsets.all(8),
child: Row(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.start,
children: [
SizedBox(
width: 120,
child: Text(
text,
style: kTextStyle,
),
),
const SizedBox(
width: 20,
),
Expanded(
child: Container(
height: 50,
decoration: BoxDecoration(
color: Colors.orangeAccent,
borderRadius: BorderRadius.circular(5)),
child: DropdownButtonFormField<String>(
autovalidateMode: AutovalidateMode.always,
//menuMaxHeight: 300,
validator: (value) {
if(value!.isEmpty) {
return "485s4a8sd4as85";
}
} ,
decoration: const InputDecoration(border: InputBorder.none),
isExpanded: true,
onTap: () => myFunc,
//borderRadius: BorderRadius.circular(5),
value: initialVal,
icon: const Icon(
Icons.arrow_downward,
color: Colors.black38,
),
iconSize: 24,
elevation: 16,
dropdownColor: Colors.deepOrange,
style: kTextStyle.copyWith(color: Colors.black),
onChanged: (val) => myFunc(val),
items: listItems.map<DropdownMenuItem<String>>((String? val) {
return DropdownMenuItem(
//TODO: Set default values
value: val,
child: Text(
val,
style: kTextStyle.copyWith(color: Colors.black),
),
);
}).toList(),
),
),
)
],
),
);
}
This is my onChanged property that assigns the selected value by the user. I added some explanations about what I am trying to do.
String _valueCinsiyet = "Diğer"; // initial value
void onChangedCinsiyet(String? newVal) {
setState(() {
if(newVal==null) {
_formData.setCinsiyet(_valueCinsiyet);
/*
'if newVal is null' means that if the value is not selected by the user
then set the initialValue( _valueCinsiyet)
*/
} else {
/*
if newVal is not null then assign the newVal( which means the selected value)
into my initialValue, then set the data to use it on different pages. What is missing?
*/
_valueCinsiyet = newVal;
_formData.setCinsiyet(_valueCinsiyet);
}
});
}
You can use nullable data to track DropdownButtonFormField changes. Being nullable you can check if it is null or not, no need to anything extra on onChanged: just assign new value usual way.
On state before build method: String? value; // value to keep track
child: DropdownButtonFormField<String>(
value: value,
onChanged: (val) {
setState(() {
value = val;
});
},
Now onSaved/submit button you can pass value by checking null, simple way is
value?? "default Value". In your case, it is value??Diğer
I`m creating a dropdown button in flutter, but i have a problem
when i use dropdown it shows the name of the first item but i want to change it(default value) to categories and idk how to do that, also i tried to use hint(as you see in codes)but it didn't work.
here is my codes:
Container(
height: pageHeight / 15,
padding: EdgeInsets.all(20),
child:DropdownButton(
value: _value,
items: const [
DropdownMenuItem(
child: Text("First Item"),
value: 1,
),
DropdownMenuItem(
child: Text("Second Item"),
value: 2,
),
],
onChanged: (value) {
setState(() {
_value = value as int ;
});
},
hint:Text("Select item")
),
)
I want to change this First Item to categories
Make value nullable. DropdownButton can have null value and while it is null it will show hint widget.
int? _value;
DropdownButton(
value: _value,
items: const [
DropdownMenuItem(
child: Text("First Item"),
value: 1,
),
DropdownMenuItem(
child: Text("Second Item"),
value: 2,
),
],
onChanged: (value) {
setState(() {
_value = value as int;
});
},
hint: Text("categories"),
),
Just Asign on initState()
selectedDropDownValue = "categories";
Container(
height: pageHeight / 15,
padding: EdgeInsets.all(20),
child:DropdownButton(
value: _value,
items: const [
DropdownMenuItem(
child: Text("First Item"),
value: 1,
),
DropdownMenuItem(
child: Text("Second Item"),
value: 2,
),
],
value: selectedDropDownValue,
onChanged: (value) {
setState(() {
selectedDropDownValue = value;
});
},
hint:Text("Select item")
),
)
I am using FutureBuilder in flutter to fill up a drop down menu DropdownButtonFormField, i have the method
onChanged: (String? newValue) {
setState(() {
dropdownBrokers = newValue!;
});
},
Which allows the widget to rebuild and then assign the new value selected from the dropdown list. However, i am now experiencing a problem from my research stating that whenever the setState() is called, the future builder runs again, which makes my dropdown menu populate again. This is the full code snippet
FutureBuilder <List<Broker>>(
future: brokerData,
builder: (context, snapshot){
if(snapshot.hasData){
//do what needs to be done here
List<Broker>? data = snapshot.data;
for(var i = 0; i< data!.length; i++){
_brokers.add(data[i].firmName);
print(data[i].firmName);
}
return Container(
padding: EdgeInsets.all(10),
child: InputDecorator(
decoration: InputDecoration(
labelStyle: TextStyle(
color: Colors.grey
),
isDense: true,
contentPadding: EdgeInsets.all(7.0),
errorStyle: TextStyle(color: Colors.redAccent, fontSize: 16.0),
hintText: 'Select Broker',
border: OutlineInputBorder(borderRadius: BorderRadius.circular(5.0))),
child: DropdownButtonHideUnderline(
child: DropdownButtonFormField<String>(
alignment: Alignment.center,
value: dropdownBrokers,
icon: const Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: const TextStyle(color: Colors.indigo),
onChanged: (String? newValue) {
setState(() {
dropdownBrokers = newValue!;
});
},
items: _brokers.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
),
),
),
),
);
Also i get an error when i reselect an item.
How do i prevent the FutureBuilder from running twice
FutureBuilder will always be rendered once unless recreated in the build method. So the solution to this can be done in two ways:
1: Only calling brokerData in the FutureBuilder method or
2: Only calling brokerData in the initState override.
You can not do both.
And I assume the data to be populated in the dropdown comes from the future builder. Then use snapshot.data of the future instead of an already created value in this case:
items: _brokers.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
Change to:
items: snapshot.data.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
How can I change the height of a DropdownButton in flutter.
I have tried to use Padding and SizedBox but none is realy working.
SizedBox just increases the container size while the DropdownButton is clamped to top left and therefore is not centered anymore.
Padding is ignored or moves the content outside of the button.
I do not want to change the size of the dropdown overlay but the button itself.
build(BuildContext context) {
return ThemeData(
data: ThemeData(canvasColor: Colors.white),
child: DropdownButton(
items: _items.map((item) => DropdownMenuItem(child: Text(item), value: item)).toList(),
isExpanded: true,
selectedItemBuilder: (_) {
return _items.map<Widget>((String lang) {
return Center(
widthFactor: 1,
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 12),
child: Text(lang, style: TextStyle(color: Colors.black))
),
);
}).toList();
}
)
)
}
Wrap it in a Container, give a height, width as per your need and set isExpanded true in DropDownButton. Also change dropdownbutton text font size as per your need.
Container(
height: 50.0,
width: 200.0,
child: DropdownButton(
value: dropdownValue,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
isExpanded: true,
style: TextStyle(color: Colors.deepPurple, fontSize: 20.0),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (String newValue) {
setState(() {
dropdownValue = newValue;
});
},
items: <String>['One', 'Two', 'Free', 'Four']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
)
)
End product should look something like this,
Looks like the 'itemHeight' property for the DropdownButton class should do the trick. I tried it and it increased the height of my DropdownButton.
Here is some sample code I have from a previous project using the itemHeight:
DropdownButton<String>(
itemHeight: 100.0,
value: selectedCurrency,
items: dropdownItems,
onChanged: (value) {
setState(() {
selectedCurrency = value;
getData();
});
},
);
Note: Just make sure the value you provide isn't less than 48.0, since it will give an error.
Docs:
itemHeight property: https://api.flutter.dev/flutter/material/DropdownButton/itemHeight.html
Minimum itemHeight defined by 'kMinInteractiveDimension':
https://api.flutter.dev/flutter/material/kMinInteractiveDimension-constant.html
itemHeight: null,
You just need to leave the itemHeight with the null value.
It will make the height of the DropdownButton with the menu item's intrinsic height.
Use SizedBox Widget
SizedBox(
height: 30,
child:DropdownButton<String>(
value: selectedCurrency,
items: dropdownItems,
onChanged: (value) {},
))
The easiest of all methods is using DropDownButton2 which is built over DropDownButton
And just change the buttonHeight attribute
Not just buttonHeight , you can even change itemHeight , buttonwidth and many more customize
String? selectedValue;
List<String> items = [
'Item1',
'Item2',
'Item3',
'Item4',
];
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: DropdownButtonHideUnderline(
child: DropdownButton2(,
items: items
.map((item) =>
DropdownMenuItem<String>(
value: item,
child: Text(
item,
),
))
.toList(),
value: selectedValue,
onChanged: (value) {
setState(() {
});
},
buttonHeight: 40,
buttonWidth: 140,
itemHeight: 40,
),
),
),
);
}
checkout : DropDownButton2 for more examples.
Hope it helps !!
You need to use menuMaxHeight property of DropdownButton Widget.
child: DropdownButton(
menuMaxHeight: 500.0,
value: '1',
items: setTotalPages(),
onChanged: (String? newValue) {
setState(() {
dropdownvalue = newValue!;
});
},
)
Add this property menuMaxHeight: 200, to DropdownButton