Slider will call onChanged before onChangeStart when sliding.

[empirejames]

Is there an existing issue for this?

• I have searched the existing issues
• I have read the guide to filing a bug

Steps to reproduce

1. Create a slider bar
2. print log when drag the slider (onChangeStart, onChanged, onChangeEnd)
3. You will see also (onChanged print at first)

Expected results

Don't trigger the slider onChanged event before onChangeStart

Actual results

onChanged will called before onChangeStart every times.

Code sample

Code Sample

class SliderExample extends StatefulWidget {
  @override
  _SliderExampleState createState() => _SliderExampleState();
}

class _SliderExampleState extends State<SliderExample> {
  double _sliderValue = 0.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Slider Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('Slider Value: $_sliderValue'),
            Slider(
              value: _sliderValue,
              onChangeStart: (newValue) {
                  print("onChangeStart ......");
              },
              onChanged: (newValue) {
                  print("onChanged ......");
              },
              onChangeEnd: (newValue) {
                  print("onChangeEnd ......");
              },
              min: 0,
              max: 100,
              divisions: 100,
              label: '$_sliderValue',
            ),
          ],
        ),
      ),
    );
  }
}

Flutter Doctor output

flutter doctor -v

[✓] Flutter (Channel stable, 3.13.3, on macOS 13.5 22G74 darwin-arm64 (Rosetta), locale zh-Hant-TW)
    • Flutter version 3.13.3 on channel stable at /Users/chupa/fvm/versions/3.13.3
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 2524052335 (6 weeks ago), 2023-09-06 14:32:31 -0700
    • Engine revision b8d35810e9
    • Dart version 3.1.1
    • DevTools version 2.25.0

[✓] Android toolchain - develop for Android devices (Android SDK version 32.0.0)
    • Android SDK at /Users/chupa/Library/Android/sdk
    • Platform android-33, build-tools 32.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b829.9-10027231)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14E300c
    • CocoaPods version 1.12.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2022.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b829.9-10027231)

[✓] VS Code (version 1.82.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension can be installed from:
      🔨 https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (3 available)
    • SM T820 (mobile) • 804aec3701e8cf48 • android-arm64  • Android 9 (API 28)
    • macOS (desktop)  • macos            • darwin-arm64   • macOS 13.5 22G74 darwin-arm64 (Rosetta)
    • Chrome (web)     • chrome           • web-javascript • Google Chrome 116.0.5845.140

[✓] Network resources
    • All expected network resources are available.

• No issues found!

[dam-ease]

Hi @empirejames. Thanks for filing this. I'm able to reproduce this on the latest master and stable channels following the reproduction steps provided above.

Code Sample Used

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Slider Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: SliderExample(),
    );
  }
}

class SliderExample extends StatefulWidget {
  @override
  _SliderExampleState createState() => _SliderExampleState();
}

class _SliderExampleState extends State {
  double _sliderValue = 0.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Slider Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text('Slider Value: $_sliderValue'),
            Slider(
              value: _sliderValue,
              onChangeStart: (newValue) {
                print("onChangeStart ......");
              },
              onChanged: (newValue) {
                print("onChanged ......");
              },
              onChangeEnd: (newValue) {
                print("onChangeEnd ......");
              },
              min: 0,
              max: 100,
              divisions: 100,
              label: '$_sliderValue',
            ),
          ],
        ),
      ),
    );
  }
}

stable, master flutter doctor -v

[✓] Flutter (Channel stable, 3.13.7, on macOS 13.0 22A380 darwin-arm64, locale en-NG)
    • Flutter version 3.13.7 on channel stable at /Users/damilolaalimi/sdks/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 2f708eb839 (8 days ago), 2023-10-09 09:58:08 -0500
    • Engine revision a794cf2681
    • Dart version 3.1.3
    • DevTools version 2.25.0

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/damilolaalimi/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • ANDROID_HOME = /Users/damilolaalimi/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b802.4-9586694)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14E300c
    • CocoaPods version 1.12.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2022.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b802.4-9586694)

[!] Android Studio (version unknown)
    • Android Studio at /Users/damilolaalimi/Downloads/Android Studio Preview.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    ✗ Unable to determine Android Studio version.
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)

[✓] VS Code (version 1.82.3)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.50.0

[✓] VS Code (version 1.83.1)
    • VS Code at /Users/damilolaalimi/Downloads/Visual Studio Code.app/Contents
    • Flutter extension version 3.50.0

[✓] Connected device (4 available)
    • sdk gphone64 arm64 (mobile) • emulator-5554                        • android-arm64  • Android 14 (API 34) (emulator)
    • iPhone XS (mobile)          • 3CFD1268-0D52-486E-A12E-6E136E972D94 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-16-4 (simulator)
    • macOS (desktop)             • macos                                • darwin-arm64   • macOS 13.0 22A380 darwin-arm64
    • Chrome (web)                • chrome                               • web-javascript • Google Chrome 118.0.5993.70

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

[✓] Flutter (Channel master, 3.16.0-12.0.pre.83, on macOS 13.0 22A380 darwin-arm64, locale en-NG)
    • Flutter version 3.16.0-12.0.pre.83 on channel master at /Users/damilolaalimi/fvm/versions/master
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision d8c2539629 (4 hours ago), 2023-10-17 02:57:24 -0400
    • Engine revision 90bbe8ee4a
    • Dart version 3.3.0 (build 3.3.0-29.0.dev)
    • DevTools version 2.28.1

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/damilolaalimi/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • ANDROID_HOME = /Users/damilolaalimi/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b802.4-9586694)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14E300c
    • CocoaPods version 1.12.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2022.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b802.4-9586694)

[!] Android Studio (version unknown)
    • Android Studio at /Users/damilolaalimi/Downloads/Android Studio Preview.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    ✗ Unable to determine Android Studio version.
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)

[✓] VS Code (version 1.82.3)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.50.0

[✓] VS Code (version 1.83.1)
    • VS Code at /Users/damilolaalimi/Downloads/Visual Studio Code.app/Contents
    • Flutter extension version 3.50.0

[✓] Connected device (4 available)
    • sdk gphone64 arm64 (mobile) • emulator-5554                        • android-arm64  • Android 14 (API 34) (emulator)
    • iPhone XS (mobile)          • 3CFD1268-0D52-486E-A12E-6E136E972D94 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-16-4 (simulator)
    • macOS (desktop)             • macos                                • darwin-arm64   • macOS 13.0 22A380 darwin-arm64
    • Chrome (web)                • chrome                               • web-javascript • Google Chrome 118.0.5993.70

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

[TahaTesser]

This regressed in #121483