ios - Objective-C中的EXC_BAD_ACCESS错误

Question

我正在尝试编写一个简单的iOS程序，该程序将在插入/拔出耳机时发出通知。我是Objective-C和iOS的新手，很多代码是由其他人编写的，我现在正尝试对其进行调整，因此在解决此问题时遇到了问题。代码在这里:

AppDelegate.m

#import "AppDelegate.h"

@implementation AppDelegate

static void onHeadsetChange(void *, AudioServicesPropertyID, UInt32, const void *);

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.headsetOnHandler = self.headsetOffHandler = ^{};
    NSLog(@"%lu", AudioSessionInitialize(NULL, NULL, NULL, NULL));
    NSLog(@"%lu", AudioSessionSetActive(true));
    NSLog(@"%lu", AudioSessionAddPropertyListener(kAudioSessionProperty_AudioRouteChange, &onHeadsetChange, (__bridge void *)self));
    return YES;
}

static void onHeadsetChange(void *inUserData, AudioSessionPropertyID inPropertyID, UInt32 inPropertyValueSize, const void *inPropertyValue) {
    if (inPropertyID != kAudioSessionProperty_AudioRouteChange) return;
    NSLog(@"The headset changed");
    AppDelegate *const delegate = (__bridge AppDelegate *)inUserData;

    const CFDictionaryRef routeChangeDictionary = inPropertyValue;
    const CFNumberRef routeChangeReasonRef = CFDictionaryGetValue(routeChangeDictionary, CFSTR(kAudioSession_AudioRouteChangeKey_Reason));
    SInt32 routeChangeReason;
    CFNumberGetValue(routeChangeReasonRef, kCFNumberSInt32Type, &routeChangeReason);
    switch (routeChangeReason) {
        case kAudioSessionRouteChangeReason_NewDeviceAvailable:
            //NSLog([delegate description]);
            [delegate headsetOnHandler];
            break;
        case kAudioSessionRouteChangeReason_OldDeviceUnavailable:
            [delegate headsetOffHandler];
            break;
        default:
            break;
    }
}
@end

ViewController.m

#import "ViewController.h"

@implementation ViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor redColor];
    AppDelegate *delegate = (AppDelegate *)([UIApplication sharedApplication].delegate);
    delegate.headsetOnHandler = ^{ self.view.backgroundColor = [UIColor greenColor];};
    delegate.headsetOffHandler = ^{ self.view.backgroundColor = [UIColor redColor];};
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

我正在获取EXC_BAD_ACCESS error, code=1 at [delegate headsetOnHandler] and [delegate headsetOffHandler]。如果需要为此添加.h文件，我会的，如果还有其他遗漏的地方，请告诉我。

编辑:
我添加了人们认为应该添加的声明:

@property (readwrite, assign) void (^headsetOnHandler)(void);
@property (readwrite, assign) void (^headsetOffHandler)(void);

Answer 1

如何声明headsetOnHandler和headsetOffHandler属性？

如果是assign或retain，则可能是问题的根源。由于它们是块，因此它必须是copy(即使在某些情况下，在ARC下)。如果它们是atomic和retain，那么您的getter将有效地在getter中调用[[block retain] autorelease]，这将解释您的崩溃。

有点远射。

发生当机时，请务必回溯

当您知道崩溃所在的代码行时，请始终在该行上张贴任何变量的变量声明

请注意，ARC会稍微改变这种行为，在某些情况下会自动处理这些块，但是-IIRC-在这种情况下，您仍然需要对其进行copy编码。