Flutter 颤振更新给了我这个错误:方法'*';被调用为空
我有一个使用Flutter 颤振更新给了我这个错误:方法'*';被调用为空,flutter,dart,flame,Flutter,Dart,Flame,我有一个使用flame库的flatter应用程序。我想让一个物体在颤振游戏中移动。运行update函数时,出现以下错误: The method '*' was called on null. Receiver: null Tried calling: *(0.0) 似乎有些东西没有初始化,而update函数是在初始化之前运行的。当我注释出player.update(t)时,它可以工作,但不会调用update函数。我做错了什么?我怎样才能修复它?这是我的密码: 游戏控制器类 class Game
flame
库的flatter应用程序。我想让一个物体在颤振游戏中移动。运行update
函数时,出现以下错误:
The method '*' was called on null.
Receiver: null
Tried calling: *(0.0)
似乎有些东西没有初始化,而update
函数是在初始化之前运行的。当我注释出player.update(t)时,它可以工作,但不会调用update函数。我做错了什么?我怎样才能修复它?这是我的密码:
游戏控制器类
class GameController extends Game {
Size screenSize;
Player player;
GameController() {
initialize();
}
void initialize() async {
final initDimetion = await Flame.util.initialDimensions();
resize(initDimetion);
player = Player(this);
}
void render(Canvas c) {
Rect bgRect = Rect.fromLTWH(0, 0, screenSize.width, screenSize.height);
Paint bgPaint = Paint()..color = Color(0xFFFAFAFA);
c.drawRect(bgRect, bgPaint);
player.render(c);
}
void update(double t) {
if (player is Player) { // Tried adding this if statement but it didn't work
player.update(t);
}
}
void resize(Size size) {
screenSize = size;
}
}
玩家等级
class Player {
final GameController gameController;
Rect playerRect;
double speed;
Player(this.gameController) {
final size = 40.0;
playerRect = Rect.fromLTWH(gameController.screenSize.width / 2 - size / 2,
gameController.screenSize.height / 2 - size / 2, size, size);
}
void render(Canvas c) {
Paint color = Paint()..color = Color(0xFF0000FF);
c.drawRect(playerRect, color);
}
void update(double t) {
double stepDistance = speed * t;
Offset stepToSide = Offset.fromDirection(90, stepDistance);
playerRect = playerRect.shift(stepToSide);
}
}
您从未将玩家的速度属性初始化为值。因此Player.update中的
speed*t
会导致此错误
只需在构造函数中初始化speed属性
Player(this.gameController) {
final size = 40.0;
this.speed = 0;
playerRect = Rect.fromLTWH(gameController.screenSize.width / 2 - size / 2,
gameController.screenSize.height / 2 - size / 2, size, size);
}