When building applications with Dart and Flutter, you might come across the frustrating issue of losing data on a TextInput field when the keyboard is dismissed. This typically occurs because the state of the input field is not being managed correctly. By utilizing a TextEditingController, you can ensure that the value users type into the text field remains intact even after they click 'Ok' or use the back button to hide the keyboard.
Understanding TextEditingController
In Flutter, a TextEditingController is an object that can be used to control a text field. It helps in retrieving the current value of the text field, listening to changes, and manipulating it. If you don’t initialize a TextEditingController, the text field will not maintain its state after interactions.
Why the Value Disappears
When a Flutter app is built without a TextEditingController, the state of the input field is not preserved upon keyboard dismissal because there’s no reference to the text that users input. When the keyboard is hidden, the widget is rebuilt, and without the controller, the text field resets to its initial state.
Implementing TextEditingController
Here’s how to implement a TextEditingController in your Flutter app effectively:
Step 1: Create the TextEditingController
Begin by initializing a TextEditingController in your widget. This can be achieved as follows:
class ChatCepBottomSheet extends StatelessWidget {
final TextEditingController _cepController = TextEditingController();
@override
Widget build(BuildContext context) {
return Column(
children: [
TextFormField(
controller: _cepController,
),
SizedBox(height: 32),
ElevatedButton(
onPressed: () {
// You can now retrieve the text from the controller
String inputText = _cepController.text;
print(inputText); // Example action with input text
},
child: Text('Search'),
)
],
);
}
}
Step 2: Use the Controller
By adding a controller: property to your TextFormField, you can capture the user’s input as they type. Upon clicking the 'Search' button, you can access the current value of the input field by using TextEditingController.text. This is vital for processing the input later, such as making a search request:
onPressed: () {
String inputText = _cepController.text;
// Implement your search logic using inputText
}
Step 3: Dispose of the Controller Properly
It’s important to manage memory and resources effectively by disposing of your TextEditingController when it’s no longer needed. In a stateful widget, you would do this in the dispose method:
@override
void dispose() {
_cepController.dispose();
super.dispose();
}
This step is crucial in preventing memory leaks in your application. However, since the example provided uses a stateless widget, you might manage the lifecycle differently.
Frequently Asked Questions (FAQ)
Q1: What happens if I don’t use a TextEditingController?
A1: Without a TextEditingController, the input value is lost every time the widget is rebuilt, particularly when dismissing the keyboard.
Q2: Can I use TextEditingController in Stateless Widgets?
A2: Yes, but be cautious about how you manage the controller lifecycle, as stateless widgets do not have the dispose method to clean up resources.
Q3: What if I want to use predefined values in the TextFormField?
A3: You can set the initial text of the TextEditingController directly by passing a string to its constructor: TextEditingController(text: 'Initial Value').
By adding a TextEditingController to your text fields, you can ensure that user input is preserved, leading to a smoother and more reliable user experience in your Dart applications.
