dart - Flutter TextField value always uppercase & debounce

Dart - Flutter TextField value always uppercase & debounce

To ensure that the text entered into a TextField is always uppercase, you can use a TextEditingController and a listener to modify the text as it's being typed. For debouncing the text changes, you can use a delay before updating the state. Here's an example of how you can achieve both:

import 'dart:async'; import 'package:flutter/material.dart'; void main() { runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( home: MyHomePage(), ); } } class MyHomePage extends StatefulWidget { @override _MyHomePageState createState() => _MyHomePageState(); } class _MyHomePageState extends State<MyHomePage> { TextEditingController _controller = TextEditingController(); Timer? _debounce; @override void dispose() { _controller.dispose(); _debounce?.cancel(); super.dispose(); } void _onTextChanged(String value) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(Duration(milliseconds: 500), () { setState(() { _controller.value = _controller.value.copyWith( text: value.toUpperCase(), selection: TextSelection.collapsed(offset: value.length), ); }); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar( title: Text('TextField Debounce & Uppercase'), ), body: Center( child: Padding( padding: EdgeInsets.all(20.0), child: TextField( controller: _controller, onChanged: _onTextChanged, decoration: InputDecoration( hintText: 'Enter text', ), ), ), ), ); } }

In this example, the TextEditingController _controller is used to control the text field. The _onTextChanged method is called whenever the text in the TextField changes. It cancels the previous _debounce timer (if it exists) and starts a new one. After a delay of 500 milliseconds (adjustable as needed), it updates the _controller's value to the uppercase of the entered text, ensuring that it's always uppercase. The selection is also maintained at the end of the text.

Examples

  1. Query: "Flutter TextField convert to uppercase"

    • Description: This query discusses how to ensure that the text entered into a TextField is automatically converted to uppercase.
    • Code:
      TextField( onChanged: (text) { text = text.toUpperCase(); // Converts to uppercase }, decoration: InputDecoration( labelText: 'Enter text', ), )

  2. Query: "Flutter TextField with text transformation"

    • Description: This query explores how to implement custom text transformations for a TextField, such as converting text to uppercase as the user types.
    • Code:
      TextEditingController _controller = TextEditingController(); TextField( controller: _controller, onChanged: (text) { _controller.value = TextEditingValue( text: text.toUpperCase(), // Transform to uppercase selection: TextSelection.collapsed(offset: text.length), ); }, decoration: InputDecoration( labelText: 'Enter text', ), )

  3. Query: "Flutter debounce for TextField"

    • Description: This query addresses how to implement a debounce mechanism for a TextField to reduce the frequency of onChanged events and avoid excessive function calls.
    • Code:
      import 'dart:async'; Timer? _debounce; TextField( onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(const Duration(milliseconds: 500), () { print("Debounced value: $text"); }); }, decoration: InputDecoration( labelText: 'Debounced TextField', ), )

  4. Query: "Flutter TextField debounce with uppercase transformation"

    • Description: This query explores combining a debounce mechanism with text transformation in a TextField, ensuring text is always uppercase while avoiding excessive onChanged events.
    • Code:
      import 'dart:async'; TextEditingController _controller = TextEditingController(); Timer? _debounce; TextField( controller: _controller, onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(const Duration(milliseconds: 500), () { _controller.value = TextEditingValue( text: text.toUpperCase(), // Convert to uppercase selection: TextSelection.collapsed(offset: text.length), ); }); }, decoration: InputDecoration( labelText: 'Uppercase & Debounce', ), )

  5. Query: "Flutter TextField debounce to avoid rapid API calls"

    • Description: This query focuses on using a debounce mechanism in a TextField to avoid rapid API calls or database queries as the user types.
    • Code:
      import 'dart:async'; Timer? _debounce; TextField( onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(const Duration(milliseconds: 500), () { // Call API or query database here print("API Call with value: $text"); }); }, decoration: InputDecoration( labelText: 'Debounced API Call', ), )

  6. Query: "Flutter TextField value uppercase with focus change"

    • Description: This query explores how to convert text to uppercase when the focus is lost, ensuring the final value is always uppercase.
    • Code:
      TextEditingController _controller = TextEditingController(); TextField( controller: _controller, onSubmitted: (text) { _controller.text = text.toUpperCase(); // Uppercase on submit }, decoration: InputDecoration( labelText: 'Uppercase on Submit', ), )

  7. Query: "Flutter TextField debounce with focus change"

    • Description: This query discusses how to use a debounce mechanism in a TextField to delay actions until the focus is lost or a timeout occurs.
    • Code:
      import 'dart:async'; Timer? _debounce; TextField( onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(const Duration(milliseconds: 500), () { // Action after debounce delay print("Debounced action after focus change or delay"); }); }, decoration: InputDecoration( labelText: 'Debounced on Focus Change', ), )

  8. Query: "Flutter TextField uppercase with debounce on specific key press"

    • Description: This query explores implementing a debounce mechanism in a TextField that triggers on a specific key press, such as "Enter," while ensuring text is always uppercase.
    • Code:
      import 'dart:async'; Timer? _debounce; TextEditingController _controller = TextEditingController(); TextField( controller: _controller, onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(const Duration(milliseconds: 500), () { _controller.text = text.toUpperCase(); // Convert to uppercase print("Debounced on specific key press"); }); }, onSubmitted: (text) { _controller.text = text.toUpperCase(); // Uppercase on submit }, decoration: InputDecoration( labelText: 'Debounced on Enter Key', ), )

  9. Query: "Flutter TextField debounce with custom delay"

    • Description: This query discusses implementing a custom debounce delay for a TextField, allowing for fine-tuning of the debounce period.
    • Code:
      import 'dart:async'; Timer? _debounce; int debounceDelay = 300; // Custom delay in milliseconds TextField( onChanged: (text) { if (_debounce?.isActive ?? false) _debounce!.cancel(); _debounce = Timer(Duration(milliseconds: debounceDelay), () { print("Custom debounce delay: $text"); }); }, decoration: InputDecoration( labelText: 'TextField with Custom Debounce Delay', ), )

  10. Query: "Flutter TextField debounce and uppercase with controller"

More Tags

geometry text-parsing nsurlprotocol ssms-2012 contentsize saga unions formatexception move data-access

More Programming Questions

More Mortgage and Real Estate Calculators

More Cat Calculators

More Date and Time Calculators

More Pregnancy Calculators