详解flutter engine 那些没被释放的东西
由于flutter一直存在内存泄漏的问题,导致很多开发者不胜困扰,博主在0.9.4就开始对其代码内部内存问题在engine层面修改代码,得到解决,但是对于每个版本都需要跟随官方打包,对于开发者并不是很友好。
然而喜出望外的是,在后来的几个版本中,官方内置开发了手动释放内存的方式:smile_cat:
/** * Destroy running context for an engine. * * This method can be used to force the FlutterEngine object to release all resources. * After sending this message, the object will be in an unusable state until it is deallocated. * Accessing properties or sending messages to it will result in undefined behavior or runtime * errors. */ - (void)destroyContext;
翻译如下:
销毁引擎的运行上下文。 此方法可用于强制FlutterEngine对象释放所有资源。 发送此消息后,对象将处于不可用状态,直到解除分配为止。 访问属性或向其发送消息将导致未定义的行为或运行时错误。
但是
, 但是
, 但是
,(重要的事说三遍) 在Flutter engine开发群里面,有群友反馈还有很多问题
- 无法完全释放内存
- 偶现崩溃
偶现崩溃的是什么鬼,暂时没有遇到,不好说。 之前博主遇到的崩溃是自己使用方式的问题,在fluttervc关闭之后还有任务在执行methodchannel,即还在调用plugin,这个可以在开发上避免。 值得注意的是,flutter中使用c++实现,自己对于内存管理并不是很好
内存问题自测如下
确实存在问题,还有将近30M没有被释放,查看一下当前内存对象,如下图
一个一个看还有那些没有被释放吧
android:LruCache
Least Recently Used 近期最少使用算法。 内存管理的一种页面置换算法,对于在内存中但又不用的数据块(内存块)叫做LRU,flutter engine 会根据哪些数据属于LRU而将其移出内存而腾出空间来加载另外的数据。
dart::BackgroundComplier 对isolate编译优化的类
BackgroundCompiler 在后台线程中运行优化编译的类。 实现:每个隔离一个任务,它与拥有isolate一起消失,后台编译器中没有OSR编译。
dart::bin::socket
vm和开发平台通信的机制,比如jit即时编译的dill文件,通过socket传递给dart vm,vm通过rpc加载文件,重置线程,从而实现hotreload热重载
dart::BoolPrameter
- dart::EnumParameter
- dart::IdParameter
- dart::IdParameter
- dart::xxxPrameter
定义在dart vm,service.cc中,都继承自MethodParameter,做对应参数校验,参数解析用。编译dart文件用的
dart::OSThread
在dart 运行时负责操作系统线程,创建线程,移除线程,线程查找与管理。 如下图
FlutterEngineRegistrar 注册使用key注册plugin的地方,所有plugin调用dart底层的方法都会通过 handlemethodcall 回调给使用者, 其初始化的地方是引起内存泄漏的地方
- (instancetype)initWithPlugin:(NSString*)pluginKey flutterEngine:(FlutterEngine*)flutterEngine { self = [super init]; NSAssert(self, @"Super init cannot be nil"); _pluginKey = pluginKey;// [pluginKey retain]; _flutterEngine = flutterEngine;// [flutterEngine retain]; return self; }
此处有一篇文章介绍,解决engine的循环引用文章
FlutterStandardMethodCodec 标准方法编解码
FlutterStringCodec string编解码 FlutterJsonMessageCodec json编解码
不看不知道,一看吓一跳,也竟然是个单例,当然不会被释放了,也能理解,在flutter中用到jsonmssage的地方很多,用不着每次都初始化
代码实现的地方
@implementation FlutterJSONMessageCodec + (instancetype)sharedInstance { static id _sharedInstance = nil; if (!_sharedInstance) { _sharedInstance = [FlutterJSONMessageCodec new]; } return _sharedInstance; }
std:share_ptrxxx 共享指针
指针获取 flutter isolate service dartvm symbolmapping
~~ 文章完 ~~
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完整测试代码如下
#import "FlutterTesterViewController.h" #import <Flutter/Flutter.h> #import "GeneratedPluginRegistrant.h" @interface FlutterTesterViewController () @property (nonatomic, weak) FlutterViewController * ctr; @property (nonatomic, weak) FlutterEngine * engine; @end @implementation FlutterTesterViewController - (void)viewDidLoad { [super viewDidLoad]; float Y = 210; [self createButton:@"加载boundle资源" frame:CGRectMake(80.0, Y, 160.0, 40.0) action:@selector(handleBoundleResource )]; Y += 40.0 + 10; [self createButton:@"autorelease" frame:CGRectMake(80.0, Y, 160.0, 40.0) action:@selector(handleAutoRelase)]; NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString * path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"flutter_assets"] ; NSLog(@"path: %@",path); } -(void)handleNetWorkResource:(UIButton *)button{ } /** * 加载boundle资源 */ - (void)handleBoundleResource { FlutterDartProject * dart = [[FlutterDartProject alloc] init]; FlutterEngine * engine = [[FlutterEngine alloc] initWithName:@"ios.dart.flutter" project:dart]; [engine runWithEntrypoint:nil]; FlutterViewController* flutterViewController = [[FlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil]; [GeneratedPluginRegistrant registerWithRegistry:flutterViewController]; [self addBackButton:flutterViewController]; [flutterViewController setInitialRoute:@"route1"]; [self presentViewController:flutterViewController animated:YES completion:nil]; self.engine = engine; } -(void)handleAutoRelase{ FlutterBasicMessageChannel* channel; FlutterEngine * engine; @autoreleasepool { FlutterViewController* flutterViewController = [[FlutterViewController alloc] init]; channel = flutterViewController.engine.systemChannel; engine = flutterViewController.engine; NSLog(@"engine111:%@",engine); } NSLog(@"engine222:%@",engine); [channel sendMessage:@"Hello!"]; [channel setMessageHandler:^(id _Nullable message, FlutterReply _Nonnull callback) { }]; } -(void)addBackButton:(UIViewController *)flutterViewController{ dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ UIButton * btn = [UIButton buttonWithType:UIButtonTypeSystem]; [btn setTitle:@"关闭" forState:UIControlStateNormal]; btn.frame = CGRectMake(10, 100, 50, 30); [btn addTarget:self action:@selector(buttonTap:) forControlEvents:UIControlEventTouchUpInside]; [flutterViewController.view addSubview:btn]; self.ctr = flutterViewController; }); } -(void)buttonTap:(id)sender{ // [self.navigationController popViewControllerAnimated:YES]; __weak __typeof(self)weakSelf = self; [self.ctr dismissViewControllerAnimated:YES completion:^{ [weakSelf.engine destroyContext]; }]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } -(UIButton *)createButton:(NSString *)title frame:(CGRect)frame action:(SEL)selector{ UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; [button addTarget:self action:selector forControlEvents:UIControlEventTouchUpInside]; [button setTitle:title forState:UIControlStateNormal]; UIColor * bgcolor = [UIColor colorWithRed:arc4random()%256/255. green:arc4random()%256/255. blue:arc4random()%256/255. alpha:1]; [button setBackgroundColor:bgcolor]; button.frame = frame; [self.view addSubview:button]; return button; } @end
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