Flutter 颤振:迭代期间的并发修改:实例(长度:2)为'_可增长列表';
这是一个小矩形随机出现在屏幕上的游戏,玩家必须点击它才能摆脱它,新的矩形将出现在屏幕的另一部分。 我的代码运行正常,但每次我点击屏幕上绘制的矩形时,都会出现下面的错误。我该如何解决这个问题 Main.dart:Flutter 颤振:迭代期间的并发修改:实例(长度:2)为'_可增长列表';,flutter,Flutter,这是一个小矩形随机出现在屏幕上的游戏,玩家必须点击它才能摆脱它,新的矩形将出现在屏幕的另一部分。 我的代码运行正常,但每次我点击屏幕上绘制的矩形时,都会出现下面的错误。我该如何解决这个问题 Main.dart: import 'dart:developer'; import 'package:flutter/material.dart'; import 'package:flame/flame.dart'; import 'package:flame/util.dart'; import 'p
import 'dart:developer';
import 'package:flutter/material.dart';
import 'package:flame/flame.dart';
import 'package:flame/util.dart';
import 'package:flutter/services.dart';
import 'package:langaw/langaw-game.dart';
import 'package:flutter/gestures.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
Util flameUtil = Util();
await flameUtil.fullScreen();
await flameUtil.setOrientation(DeviceOrientation.portraitUp);
LangawGame game = LangawGame();
runApp(game.widget);
TapGestureRecognizer tapper = TapGestureRecognizer();
tapper.onTapDown = game.onTapDown;
flameUtil.addGestureRecognizer(tapper);
}
fly.dart:
import 'dart:ui';
import 'package:flutter/cupertino.dart';
import 'package:langaw/langaw-game.dart';
class Fly {
Rect flyRect;
Paint flyPaint;
bool isDead = false, isOffScreen = false;
final LangawGame game;
// initialized with the game instance, along with positions x and y
Fly({this.game, double x, double y}) {
flyRect = Rect.fromLTWH(x, y, game.tileSize, game.tileSize);
flyPaint = Paint();
flyPaint.color = Color(0xff6ab04c);
}
// needs a render and update method
// this method will do the drawing
void render(Canvas canvas) {
canvas.drawRect(flyRect, flyPaint);
}
void update(double t) {
if (isDead) {
flyRect = flyRect.translate(0, game.tileSize * 12 * t);
if (flyRect.top > game.screenSize.height) {
isOffScreen = true;
}
}
}
void onTapDown() {
flyPaint.color = Color(0xffff4757);
isDead = true;
game.spawnFly();
}
}
langaw-game.dart:
import 'dart:ui';
import 'package:flame/game.dart';
import 'package:flame/flame.dart';
import 'package:langaw/components/fly.dart';
import 'dart:math';
import 'package:flutter/gestures.dart';
class LangawGame extends Game {
Size screenSize;
double tileSize;
List<Fly> flies;
Random rnd;
LangawGame() {
initialize();
}
void initialize() async {
flies = List<Fly>();
rnd = Random();
resize(await Flame.util.initialDimensions());
spawnFly();
}
// this method will do the drawing
void render(Canvas canvas) {
Rect bgRect = Rect.fromLTWH(0, 0, screenSize.width, screenSize.height);
Paint bgPaint = Paint();
bgPaint.color = Color(0xff576574);
canvas.drawRect(bgRect, bgPaint);
// now the flies are rendered on top of the background
flies.forEach((Fly fly) => fly.render(canvas));
// print(screenSize.toString());
}
void update(double t) {
flies.forEach((Fly fly) => fly.update(t));
flies.removeWhere((Fly fly) => fly.isOffScreen);
}
void spawnFly() {
double xPos = rnd.nextDouble() * (screenSize.width - tileSize);
double yPos = rnd.nextDouble() * (screenSize.height - tileSize);
flies.add(Fly(game: this, x: xPos, y: yPos));
}
void resize(Size size) {
screenSize = size;
tileSize = screenSize.width / 9;
}
void onTapDown(TapDownDetails d) {
flies.forEach((Fly fly) {
if (fly.flyRect.contains(d.globalPosition)) {
fly.onTapDown();
}
});
}
}
导入“dart:ui”;
进口“包装:火焰/游戏.飞镖”;
进口“包装:火焰/火焰.飞镖”;
导入“包:langaw/components/fly.dart”;
导入“dart:math”;
导入“package:flatter/signatures.dart”;
类LangawGame扩展了这个游戏{
屏幕大小;
双层瓷砖;
列出苍蝇;
随机rnd;
LangawGame(){
初始化();
}
void initialize()异步{
flies=List();
rnd=随机();
调整大小(wait Flame.util.initialDimensions());
产卵蝇();
}
//此方法将完成绘图
void渲染(画布){
Rect bgRect=Rect.fromLTWH(0,0,screenSize.width,screenSize.height);
Paint bgPaint=Paint();
bgPaint.color=color(0xff576574);
canvas.drawRect(bgRect,bgPaint);
//现在,苍蝇在背景上渲染
flies.forEach((Fly-Fly)=>Fly.render(canvas));
//打印(screenSize.toString());
}
无效更新(双t){
flies.forEach((Fly-Fly)=>Fly.update(t));
flies.removehere((Fly-Fly)=>Fly.isOffScreen);
}
空产卵蝇(){
double xPos=rnd.nextDouble()*(screenSize.width-tileSize);
double yPos=rnd.nextDouble()*(screenSize.height-tileSize);
添加(Fly(游戏:this,x:xPos,y:yPos));
}
空心调整大小(大小){
屏幕大小=大小;
tileSize=屏幕大小。宽度/9;
}
void onTapDown(tappdown详细信息d){
flies.forEach((Fly-Fly){
if(fly.flyRect.contains(d.globalPosition)){
fly.onTapDown();
}
});
}
}
处理手势时抛出以下ConcurrentModificationError:
迭代期间的并发修改:“\u GrowtableList”的实例(长度:2)。
引发异常时,这是堆栈:
#0 List.forEach(dart:core patch/growtable_array.dart:286:36)
#1 LangawGame.onTapDown(包:langaw/langaw game.dart:57:11)
#2 t手势识别器。把手放下。(包装:颤振/src/signatures/tap.省道:463:51)
#3 GestureRecognizer.invokeCallback(包:flatter/src/signatures/recognizer.dart:182:24)
#4 TapGestureRecognizer.handleTapDown(包:颤振/src/手势/tap.dart:463:11)
...
处理程序:“onTapDown”
识别器:TapGestureRecognizer#a4e24
国家:可能
按钮:1
我今天在上学习教程时遇到了同样的问题(顺便说一句,不错的教程,除了这个小错误,我会在有时间的时候发表评论)
问题是LangawGame.onTapDown在flies列表上迭代,在迭代过程中调用Fly.onTapDown(),后者在spawnFly方法中将元素添加到列表中
所以列表在迭代时会被修改。。。听起来像个虫子
简单的解决方案是制作列表的副本,以便使用list.from进行迭代:
游戏中的ie:
void onTapDown(TapDownDetails d) {
List<Fly>.from(flies).forEach((Fly fly) {
if (fly.flyRect.contains(d.globalPosition)) {
fly.onTapDown();
}
});
void onTapDown(tappdown详细信息d){
List.from(flies).forEach((Fly-Fly){
if(fly.flyRect.contains(d.globalPosition)){
fly.onTapDown();
}
});
有更多高性能的解决方案,但有更多的代码:)我今天在上的教程之后遇到了相同的问题(顺便说一句,不错的教程,除了我认为这个小错误,我会在有时间的时候发表评论) 问题是LangawGame.onTapDown在flies列表上迭代,在迭代过程中调用Fly.onTapDown(),后者在spawnFly方法中将元素添加到列表中 因此,列表在迭代时会被修改……这听起来像个bug 简单的解决方案是制作列表的副本,以便使用list.from进行迭代: 游戏中的ie:
void onTapDown(TapDownDetails d) {
List<Fly>.from(flies).forEach((Fly fly) {
if (fly.flyRect.contains(d.globalPosition)) {
fly.onTapDown();
}
});
void onTapDown(tappdown详细信息d){
List.from(flies).forEach((Fly-Fly){
if(fly.flyRect.contains(d.globalPosition)){
fly.onTapDown();
}
});
有更多高性能的解决方案,但有更多的代码:)删除类中的以下代码Fly:
game.spawnFly();
在langaw游戏中添加以下代码.dart->更新()
if(flies.length
game.spawnFly();
在langaw游戏中添加以下代码.dart->更新()
if(flies.length