Flutter:flame, ComposedComponent cant be mixed onto PositionComponent - flutter

Question

I am making a game in flutter, and i found this link in github https://github.com/g0rdan/Flutter.Bird and i tried to run it in my computer and i encounter this error error: 'ComposedComponent' can't be mixed onto 'PositionComponent' because 'PositionComponent' doesn't implement 'HasGameRef'. (mixin_application_not_implemented_interface at [myfirstgame] lib\game\bird.dart:16)
enum BirdStatus { waiting, flying}
enum BirdFlyingStatus { up, down, none }
class Bird extends PositionComponent with ComposedComponent { == from this line
int _counter = 0;
int _movingUpSteps = 15;
Size _screenSize;
double _heightDiff = 0.0;
double _stepDiff = 0.0;
BirdGround ground;
BirdStatus status = BirdStatus.waiting;
BirdFlyingStatus flyingStatus = BirdFlyingStatus.none;
Bird(Image spriteImage, Size screenSize)
{
_screenSize = screenSize;
List<Sprite> sprites = [
Sprite.fromImage(
spriteImage,
width: SpriteDimensions.birdWidth,
height: SpriteDimensions.birdHeight,
y: SpritesPostions.birdSprite1Y,
x: SpritesPostions.birdSprite1X,
),
Sprite.fromImage(
spriteImage,
width: SpriteDimensions.birdWidth,
height: SpriteDimensions.birdHeight,
y: SpritesPostions.birdSprite2Y,
x: SpritesPostions.birdSprite2X,
),
Sprite.fromImage(
spriteImage,
width: SpriteDimensions.birdWidth,
height: SpriteDimensions.birdHeight,
y: SpritesPostions.birdSprite3Y,
x: SpritesPostions.birdSprite3X,
)
];
var animatedBird = new Animation.spriteList(sprites, stepTime: 0.15);
this.ground = BirdGround(animatedBird);
this..add(ground);
}
void setPosition(double x, double y) {
this.ground.x = x;
this.ground.y = y;
}
void update(double t) {
if (status == BirdStatus.flying) {
_counter++;
if (_counter <= _movingUpSteps) {
flyingStatus = BirdFlyingStatus.up;
this.ground.showAnimation = true;
this.ground.angle -= 0.01;
this.ground.y -= t * 100 * getSpeedRatio(flyingStatus, _counter);
}
else {
flyingStatus = BirdFlyingStatus.down;
this.ground.showAnimation = false;
if (_heightDiff == 0)
_heightDiff = (_screenSize.height - this.ground.y);
if (_stepDiff == 0)
_stepDiff = this.ground.angle.abs() / (_heightDiff / 10);
this.ground.angle += _stepDiff;
this.ground.y += t * 100 * getSpeedRatio(flyingStatus, _counter);
}
this.ground.update(t);
}
}
double getSpeedRatio(BirdFlyingStatus flyingStatus, int counter){
if (flyingStatus == BirdFlyingStatus.up) {
var backwardCounter = _movingUpSteps - counter;
return backwardCounter / 10.0;
}
if (flyingStatus == BirdFlyingStatus.down) {
var diffCounter = counter - _movingUpSteps;
return diffCounter / 10.0;
}
return 0.0;
}
void jump() {
Flame.audio.play('wing.wav');
status = BirdStatus.flying;
_counter = 0;
this.ground.angle = 0;
}
}
class BirdGround extends AnimationComponent {
bool showAnimation = true;
BirdGround(Animation animation)
: super(ComponentDimensions.birdWidth, ComponentDimensions.birdHeight, animation);
#override
void update(double t){
if (showAnimation) {
super.update(t);
}
}
}

Answer 1

This uses a very old Flame version, so I would recommend not building anything on top of it.
But to your problem, it is missing the HasGameRef mixin on your component, so if you write something like this it should work:
class Bird extends PositionComponent with HasGameRef<YourGameClass>, ComposedComponent { ...