对，我有5个意见。视图之一称为RecordViewController。 （RecordViewController导致错误）我可以在视图之间切换。但是一旦进入recordviewcontroller，就可以切换到另一个视图。但是如果我想切换回recordviewcontroller。它把我赶出了我的应用程序，并给我这个错误：
2011-08-27 19:52:00.358 app[1737:707] *** Assertion failure in +[RecordViewController alloc], /Users/user/Desktop/app/Classes/RecordViewController.m:111
2011-08-27 19:52:00.373 app[1737:707] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Attempted to allocated second singleton RecordViewController'
*** Call stack at first throw:
(
0 CoreFoundation 0x36fd064f __exceptionPreprocess + 114
1 libobjc.A.dylib 0x34229c5d objc_exception_throw + 24
2 CoreFoundation 0x36fd0491 +[NSException raise:format:arguments:] + 68
3 Foundation 0x353d0573 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 62
4 app 0x00014bdd +[RecordViewController alloc] + 212
5 app 0x00013fd3 -[EffectsViewController goRecord:] + 34
6 CoreFoundation 0x36f40571 -[NSObject(NSObject) performSelector:withObject:withObject:] + 24
7 UIKit 0x35dd2ec9 -[UIApplication sendAction:to:from:forEvent:] + 84
8 UIKit 0x35dd2e69 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 32
9 UIKit 0x35dd2e3b -[UIControl sendAction:to:forEvent:] + 38
10 UIKit 0x35dd2b8d -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 356
11 UIKit 0x35dd283b -[UIControl touchesBegan:withEvent:] + 186
12 UIKit 0x35dd1bb1 -[UIWindow _sendTouchesForEvent:] + 300
13 UIKit 0x35dd156f -[UIWindow sendEvent:] + 262
14 UIKit 0x35dba313 -[UIApplication sendEvent:] + 298
15 UIKit 0x35db9c53 _UIApplicationHandleEvent + 5090
16 GraphicsServices 0x366f4e77 PurpleEventCallback + 666
17 CoreFoundation 0x36fa7a97 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 26
18 CoreFoundation 0x36fa983f __CFRunLoopDoSource1 + 166
19 CoreFoundation 0x36faa60d __CFRunLoopRun + 520
20 CoreFoundation 0x36f3aec3 CFRunLoopRunSpecific + 230
21 CoreFoundation 0x36f3adcb CFRunLoopRunInMode + 58
22 GraphicsServices 0x366f441f GSEventRunModal + 114
23 GraphicsServices 0x366f44cb GSEventRun + 62
24 UIKit 0x35de4d69 -[UIApplication _run] + 404
25 UIKit 0x35de2807 UIApplicationMain + 670
26 app 0x00002e73 main + 70
27 app 0x00002e28 start + 40
)
terminate called after throwing an instance of 'NSException'
这是recordviewcontroller的代码
-(void)countUp {
mainInt += 1;
seconds.text = [NSString stringWithFormat:@"%02d", mainInt];
}
-(IBAction)goBack:(id)sender; {
[self dismissModalViewControllerAnimated:YES];
}
static RecordViewController *sharedInstance = nil;
+(RecordViewController *) sharedInstance {
@synchronized([RecordViewController class])
{
if (!sharedInstance)
{
[[self alloc]init];
}
return sharedInstance;
}
return nil;
}
+(id) alloc
{
@synchronized([RecordViewController class])
{
NSAssert(sharedInstance == nil, @"Attempted to allocated second singleton RecordViewController");
sharedInstance = [super alloc];
return sharedInstance;
}
return nil;
}
- (id)autorelease {
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
toggle = YES;
btnPlay.hidden = YES;
AVAudioSession * audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error: &error];
[audioSession setActive:YES error: &error];
}
- (IBAction) start_button_pressed{
if(toggle)
{
toggle = NO;
[actSpinner startAnimating];
[btnStart setImage:[UIImage imageNamed:@"recordstop.png"] forState:UIControlStateNormal];
mainInt = 0;
theTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countUp) userInfo:nil repeats:YES];
btnPlay.enabled = toggle;
btnPlay.hidden = !toggle;
NSMutableDictionary* recordSetting = [[NSMutableDictionary alloc] init];
[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatAppleIMA4] forKey:AVFormatIDKey];
[recordSetting setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey];
[recordSetting setValue:[NSNumber numberWithInt: 2] forKey:AVNumberOfChannelsKey];
recordedTmpFile = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent: [NSString stringWithFormat: @"%.0f.%@", [NSDate timeIntervalSinceReferenceDate] * 1000.0, @"caf"]]];
NSLog(@"Using File called: %@",recordedTmpFile);
recorder = [[ AVAudioRecorder alloc] initWithURL:recordedTmpFile settings:recordSetting error:&error];
[recorder setDelegate:self];
[recorder prepareToRecord];
[recorder record];
}
else
{
toggle = YES;
[actSpinner stopAnimating];
[btnStart setImage:[UIImage imageNamed:@"recordrecord.png"] forState:UIControlStateNormal];
btnPlay.enabled = toggle;
btnPlay.hidden = !toggle;
[theTimer invalidate];
NSLog(@"Using File called: %@",recordedTmpFile);
[recorder stop];
}
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
-(IBAction) play_button_pressed{
AVAudioPlayer * avPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:recordedTmpFile error:&error];
[avPlayer prepareToPlay];
[avPlayer play];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationLandscapeLeft || interfaceOrientation == UIInterfaceOrientationLandscapeRight);
}
- (void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
//Clean up the temp file.
NSFileManager * fm = [NSFileManager defaultManager];
[fm removeItemAtPath:[recordedTmpFile path] error:&error];
//Call the dealloc on the remaining objects.
[recorder dealloc];
recorder = nil;
recordedTmpFile = nil;
}
- (void)dealloc {
[super dealloc];
}
@end
谢谢
最佳答案
RecordViewController声明为单例（Apple docs on Singletons）。拥有单例视图控制器绝对没有任何意义，但我将忽略它，只是为您提供帮助。
得到该异常的原因是因为您两次调用[RecordViewController alloc]。因为它是单例，所以只能调用一次。
要解决该问题，您需要在每次要与该类进行交互时调用[RecordViewController sharedInstance]，而不是像您习惯的那样[[RecordViewController alloc] init]。