anchor.diff:      super.initState();
   
       _controller = AnimationController(vsync: this)
  +      ..value = 0.5
         ..addListener(() {
  -        setState(() {});
  +        setState(() {
  +          // Rebuild the widget at each frame to update the "progress" label.
  +        });
         });
     }
  -
  -  bool get _isLoaded => _controller.duration != null;
   
     @override
     void dispose() {
  
positive.code:                 });
                },
              ),
              if (_isLoaded) ...[
                Text('${_controller.value.toStringAsFixed(2)}'),
                Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    IconButton(
                      icon: Transform(
                        child: Icon(Icons.play_arrow),
                        alignment: Alignment.center,
                        transform: Matrix4.rotationY(math.pi),
                      ),
                      onPressed: () {
                        // Play the animation in reverse
  
                        if (_controller.value == 0) _controller.value = 1;
                        _controller.reverse(from: _controller.value);
                      },
                    ),
                    IconButton(
                      icon: Icon(Icons.pause),
                      onPressed: _controller.isAnimating
                          ? () {
                              _controller.stop();
                            }
                          : null,
                    ),
                    IconButton(
                      icon: Icon(Icons.play_arrow),
                      onPressed: () {
                        // Play the animation forward from where is is
  
                        if (_controller.value == 1) _controller.value = 0;
                        _controller.forward(
                            from: _controller.value == 1 ? 0 : _controller.value);
                      },
                    ),
                  ],
                ),
                const SizedBox(height: 30),
                RaisedButton(
                  child: Text('Loop between frames'),
                  onPressed: () {
                    // Loop between 2 specifics frames
  
                    var start = 0.1;
                    var stop = 0.5;
                    _controller.repeat(
                      min: start,
                      max: stop,
                      reverse: true,
                      period: _controller.duration * (stop - start),
                    );
                  },
                ),
              ],
            ],
          ),
        ),
  
negative.code: import 'package:flutter/material.dart';
  import 'package:lottie/lottie.dart';
  
  /// This example show how to play the Lottie animation in various way:
  /// - Start and stop the animation on event callback
  /// - Play the animation forward and backward
  /// - Loop between two specific frames
  ///
  /// This works by creating an AnimationController instance and passing it
  