我正在开发一个非常简单的视频应用程序。我使用官方控件：UIImagePickerController。
问题在于，当首次展示UIImagePickerController时，iOS会询问是否允许访问相机。用户可以选择允许或拒绝。如果用户选择了拒绝，控件不会被关闭。接着，如果用户一直点击开始按钮，计时器会继续运行，但屏幕始终是黑色的，用户无法停止计时器或返回。用户只能强行关闭应用程序。下一次展示UIImagePickerController时，仍然是黑屏，用户无法通过点击开始按钮返回。
我想知道这是否是一个bug。是否有办法来检测相机访问权限，以便我们可以决定是否显示UIImagePickerController？
检查AVAuthorizationStatus并适当处理各种情况。
NSString *mediaType = AVMediaTypeVideo;
AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:mediaType];
if(authStatus == AVAuthorizationStatusAuthorized) {
// do your logic
} else if(authStatus == AVAuthorizationStatusDenied){
// denied
} else if(authStatus == AVAuthorizationStatusRestricted){
// restricted, normally won't happen
} else if(authStatus == AVAuthorizationStatusNotDetermined){
// not determined?!
[AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {
if(granted){
NSLog(@"Granted access to %@", mediaType);
} else {
NSLog(@"Not granted access to %@", mediaType);
}
}];
} else {
// impossible, unknown authorization status
}
#import <AVFoundation/AVFoundation.h> 或类似的内容。 - toblerpwn请确保：
import AVFoundation
以下代码检查所有可能的权限状态：
let cameraMediaType = AVMediaType.video
let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(for: cameraMediaType)
switch cameraAuthorizationStatus {
case .denied: break
case .authorized: break
case .restricted: break
case .notDetermined:
// Prompting user for the permission to use the camera.
AVCaptureDevice.requestAccess(for: cameraMediaType) { granted in
if granted {
print("Granted access to \(cameraMediaType)")
} else {
print("Denied access to \(cameraMediaType)")
}
}
}
自从iOS 10后，你需要在你的Info.plist文件中指定NSCameraUsageDescription键才能请求相机访问权限，否则你的应用程序将在运行时崩溃。请参见需要使用说明的APIs。
来自Apple开发者论坛的有趣侧记：
如果用户在设置中切换了对您应用程序的相机访问权限，系统会实际上终止您的应用程序。对于任何受保护的数据类别，在“设置→隐私”部分也是如此。
extension AVCaptureDevice {
enum AuthorizationStatus {
case justDenied
case alreadyDenied
case restricted
case justAuthorized
case alreadyAuthorized
case unknown
}
class func authorizeVideo(completion: ((AuthorizationStatus) -> Void)?) {
AVCaptureDevice.authorize(mediaType: AVMediaType.video, completion: completion)
}
class func authorizeAudio(completion: ((AuthorizationStatus) -> Void)?) {
AVCaptureDevice.authorize(mediaType: AVMediaType.audio, completion: completion)
}
private class func authorize(mediaType: AVMediaType, completion: ((AuthorizationStatus) -> Void)?) {
let status = AVCaptureDevice.authorizationStatus(for: mediaType)
switch status {
case .authorized:
completion?(.alreadyAuthorized)
case .denied:
completion?(.alreadyDenied)
case .restricted:
completion?(.restricted)
case .notDetermined:
AVCaptureDevice.requestAccess(for: mediaType, completionHandler: { (granted) in
DispatchQueue.main.async {
if granted {
completion?(.justAuthorized)
} else {
completion?(.justDenied)
}
}
})
@unknown default:
completion?(.unknown)
}
}
}
然后为了使用它，你需要执行以下操作：
AVCaptureDevice.authorizeVideo(completion: { (status) in
//Your work here
})
此应用程序正在从后台线程修改自动布局引擎，而在从主线程访问引擎之后。这可能导致引擎损坏和奇怪的崩溃。
要解决此问题，请确保按以下方式处理主线程的结果（Swift 3）：private func showCameraPermissionPopup() {
let cameraMediaType = AVMediaTypeVideo
let cameraAuthorizationStatus = AVCaptureDevice.authorizationStatus(forMediaType: cameraMediaType)
switch cameraAuthorizationStatus {
case .denied:
NSLog("cameraAuthorizationStatus=denied")
break
case .authorized:
NSLog("cameraAuthorizationStatus=authorized")
break
case .restricted:
NSLog("cameraAuthorizationStatus=restricted")
break
case .notDetermined:
NSLog("cameraAuthorizationStatus=notDetermined")
// Prompting user for the permission to use the camera.
AVCaptureDevice.requestAccess(forMediaType: cameraMediaType) { granted in
DispatchQueue.main.sync {
if granted {
// do something
} else {
// do something else
}
}
}
}
}
Swift: 使用 AVFoundation
@IBAction func cameraButtonClicked(sender: AnyObject) {
let authorizationStatus = AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)
print(authorizationStatus.rawValue)
if AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo) == AVAuthorizationStatus.Authorized{
self.openCameraAfterAccessGrantedByUser()
}
else
{
print("No Access")
dispatch_async(dispatch_get_main_queue()) { [unowned self] in
AVCaptureDevice.requestAccessForMediaType(AVMediaTypeVideo, completionHandler: { (granted :Bool) -> Void in
if granted == true
{
// User granted
self.openCameraAfterAccessGrantedByUser()
}
else
{
// User Rejected
alertToEncourageCameraAccessWhenApplicationStarts()
}
});
}
}
//Open camera
func openCameraAfterAccessGrantedByUser()
{
if(UIImagePickerController .isSourceTypeAvailable(UIImagePickerControllerSourceType.Camera)){
self.cameraAndGalleryPicker!.sourceType = UIImagePickerControllerSourceType.Camera
cameraAndGalleryPicker?.delegate = self
cameraAndGalleryPicker?.allowsEditing = false
cameraAndGalleryPicker!.cameraCaptureMode = .Photo
cameraAndGalleryPicker!.modalPresentationStyle = .FullScreen
presentViewController(self.cameraAndGalleryPicker!, animated: true, completion: nil)
}
else
{
}
}
//Show Camera Unavailable Alert
func alertToEncourageCameraAccessWhenApplicationStarts()
{
//Camera not available - Alert
let cameraUnavailableAlertController = UIAlertController (title: "Camera Unavailable", message: "Please check to see if it is disconnected or in use by another application", preferredStyle: .Alert)
let settingsAction = UIAlertAction(title: "Settings", style: .Destructive) { (_) -> Void in
let settingsUrl = NSURL(string:UIApplicationOpenSettingsURLString)
if let url = settingsUrl {
dispatch_async(dispatch_get_main_queue()) {
UIApplication.sharedApplication().openURL(url)
}
}
}
let cancelAction = UIAlertAction(title: "Okay", style: .Default, handler: nil)
cameraUnavailableAlertController .addAction(settingsAction)
cameraUnavailableAlertController .addAction(cancelAction)
self.window?.rootViewController!.presentViewController(cameraUnavailableAlertController , animated: true, completion: nil)
}
UIImageViewController被注释为在 iOS 2.0 中添加，并且文档从未注明应该使用 AVAuthorizationStatus，但是它位于另一个框架中。 - benc