iOS - Runloop在实际开发中的应用

1. 控制线程生命周期（线程保活）

如果需要经常在子程序执行任务，可能希望一个线程可以重复使用，避免每次都要创建、销毁带来不必要的开销

ZSXPermenantThread.h

typedef void (^ZSXPermenantThreadTask)(void);@interface ZSXPermenantThread : NSObject/**开启线程*/
//- (void)run;/**在当前子线程执行一个任务*/
- (void)executeTask:(ZSXPermenantThreadTask)task;/**结束线程*/
- (void)stop;@end

ZSXPermenantThread.m

#import "ZSXPermenantThread.h"/** ZSXThread **/
@interface ZSXThread : NSThread
@end
@implementation ZSXThread
- (void)dealloc
{NSLog(@"%s", __func__);
}
@end/** ZSXPermenantThread **/
@interface ZSXPermenantThread()@property (strong, nonatomic) ZSXThread *innerThread;
@property (assign, nonatomic, getter=isStopped) BOOL stopped;@end@implementation ZSXPermenantThread#pragma mark - public methods
- (instancetype)init {if (self = [super init]) {self.stopped = NO;__weak typeof(self) weakSelf = self;self.innerThread = [[ZSXThread alloc] initWithBlock:^{[[NSRunLoop currentRunLoop] addPort:[[NSPort alloc] init] forMode:NSDefaultRunLoopMode];while (weakSelf && !weakSelf.isStopped) {[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];}}];[self.innerThread start];}return self;
}- (void)executeTask:(ZSXPermenantThreadTask)task {if (!self.innerThread || !task) return;[self performSelector:@selector(__executeTask:) onThread:self.innerThread withObject:task waitUntilDone:NO];
}- (void)stop {if (!self.innerThread) return;[self performSelector:@selector(__stop) onThread:self.innerThread withObject:nil waitUntilDone:YES];
}- (void)dealloc {NSLog(@"%s", __func__);[self stop];
}#pragma mark - private methods
- (void)__stop {self.stopped = YES;CFRunLoopStop(CFRunLoopGetCurrent());self.innerThread = nil;
}- (void)__executeTask:(ZSXPermenantThreadTask)task {task();
}@end

在 ViewController中使用

@interface ViewController ()@property (strong, nonatomic) ZSXPermenantThread *thread;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];self.thread = [[ZSXPermenantThread alloc] init];
}- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{[self.thread executeTask:^{NSLog(@"执行任务 - %@", [NSThread currentThread]);}];
}- (IBAction)stop:(UIButton *)sender {[self.thread stop];
}- (void)dealloc
{NSLog(@"%s", __func__);
}@end

运行结果：

2. 解决NSTimer在滑动时停止工作的问题

2.1. 案例

使用NSTimer创建一个定时器，循环打印

[NSTimer scheduledTimerWithTimeInterval:1.0 repeats:YES block:^(NSTimer * _Nonnull timer) {NSLog(@"%d", ++count);
}];

当scrollView 滚动时，定时器就停止了

2.2 解决

NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 repeats:YES block:^(NSTimer * _Nonnull timer) {NSLog(@"%d", ++count);}];
//    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
//    [[NSRunLoop currentRunLoop] addTimer:timer forMode:UITrackingRunLoopMode];// NSDefaultRunLoopMode、UITrackingRunLoopMode 才是真正存在的模式
// NSRunLoopCommonModes 并不是一个真的模式，它只是一个标记而已
// time 能在_commonModes数组中存放的的模式下工作。也就是包含NSDefaultRunLoopMode、UITrackingRunLoopMode
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

3. 监控应用卡顿

4. 性能优化

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