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

objectivec 复制代码

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

objectivec 复制代码

#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

less 复制代码

@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

objectivec 复制代码

[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

objectivec 复制代码

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

@oubijiexi