在调用相机后idleTimerDisabled失效的问题

在调用相机后idleTimerDisabled失效的问题

相关资料:

• http://stackoverflow.com
• https://github.com/jamiemcd

问题

• 前几天有人在群里边说，设置idleTimerDisabled=YES后，在使用相机后不会阻止锁屏(很好奇怎么回事)。

解决

• 1、完全不了解情况，先试了一下（代码来源）：

    - (void)viewDidLoad
    {
    	[super viewDidLoad];
  
    	self.button = [UIButton buttonWithType:UIButtonTypeSystem];
    	[self.button setTranslatesAutoresizingMaskIntoConstraints:NO];
    	[self.button setTitle:@"Show ImagePicker" forState:UIControlStateNormal];
    	[self.button addTarget:self action:@selector(buttonTouchHandler:) forControlEvents:UIControlEventTouchUpInside];
    	[self.view addSubview:self.button];
    	[self.view setNeedsUpdateConstraints];
    }
  
    - (void)buttonTouchHandler:(UIButton *)button
    {
    	[self logIdleTimerDisabled];
    	UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
    	imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera;
    	imagePickerController.delegate = self;
    	[self presentViewController:imagePickerController animated:YES completion:nil];
    }
  
    - (void)updateViewConstraints
    {
    	[super updateViewConstraints];
  
    	if (self.viewConstraints)
    	{
    		[self.view removeConstraints:self.viewConstraints];
    	}
  
    	NSMutableDictionary *views = [@{ @"button": self.button} mutableCopy];
    	NSMutableArray *constraints = [NSMutableArray array];
    	[constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-20-[button]-20-|" options:0 metrics:nil views:views]];
    	[constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[button]-|" options:0 metrics:nil views:views]];
  
    	self.viewConstraints = [constraints copy];
    	[self.view addConstraints:self.viewConstraints];
    }
  
    - (void)logIdleTimerDisabled
    {
    	BOOL idleTimerDisabled = [UIApplication sharedApplication].idleTimerDisabled;
    	NSLog(@"idleTimerDisabled = %d", idleTimerDisabled);
    }
  
    #pragma mark - UIImagePickerControllerDelegate
    - (void)imagePickerController:(UIImagePickerController *)picker  didFinishPickingMediaWithInfo:(NSDictionary *)info
    {
    	[self logIdleTimerDisabled];
    	[self dismissViewControllerAnimated:YES completion:^{
    		[self logIdleTimerDisabled];
    	}];
    }
  
    - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
    {
    	[self logIdleTimerDisabled];
    	[self dismissViewControllerAnimated:YES completion:^{
    		[self logIdleTimerDisabled];
    	}];
    }   
  

  注：Appdelegate中已近设置idleTimerDisabled为YES，Xcode会阻止设备休眠。
  Log:

    2017-03-23 13:22:25.594 UIImagePickerControllerBug[30239:3267578] idleTimerDisabled = 1
    2017-03-23 13:22:28.476 UIImagePickerControllerBug[30239:3267578] Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates.
    2017-03-23 13:22:32.312 UIImagePickerControllerBug[30239:3267578] idleTimerDisabled = 1
    2017-03-23 13:22:32.846 UIImagePickerControllerBug[30239:3267578] idleTimerDisabled = 0   
  

• 2、上边的『代码来源』原文中有作者的一些猜测：

    I have attached a simplified Xcode project to demonstrate the bug.
  
    	1. Run UIImagePickerControllerBug on a device not connected to Xcode (because Xcode always keeps the device from sleeping).  
    	2. Observe that the app does not fall asleep.
    	3. Press the Show ImagePicker Button.
    	4. Take a photo or just press cancel
    	5. Observe that the app will now fall asleep.   
  

• 3、在『stackoverflow.com』查找的时候，发现其中有人在很早以前就提出了这个问题（由于是前些天的事情有些链接找不到了），不知道是出于什么原因官方一直没有解决。

解决

• 解决办法就是相机的完成或者取消代理中延时设置，详见:

    - (void)resetIdleTimerDisabled
    {
    	[[UIApplication sharedApplication] setIdleTimerDisabled:YES];
    }
  
    #pragma mark - UIImagePickerControllerDelegate
  
    - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
    {
    	[self dismissViewControllerAnimated:YES completion:^{
    		[self performSelector:@selector(resetIdleTimerDisabled) withObject:nil afterDelay:1.0];
    	}];
    }
  
    - (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
    {
    	[self dismissViewControllerAnimated:YES completion:^{
    		[self performSelector:@selector(resetIdleTimerDisabled) withObject:nil afterDelay:1.0];
    	}];
    }  
  

备注

• Xcode会阻止设备休眠。