UIImagePickerController：忽略拍照请求；相机尚未准备好

Question

我在我的应用程序中使用相机。

我想3秒后自动拍照。 对于一种情况，代码工作绝对正常。

如果应用程序在相机滴答声以任何方式进行时进入后台，例如如果中间有呼叫或用户按主页键...那么当应用程序恢复时它不会继续相机勾选，并在控制台中给出此警告

UIImagePickerController：忽略拍照请求；相机尚未准备好。

发生这种情况时我想重新启动相机 我应该怎么办？

Answer 1

我们可以使用这些应用程序委托函数

- (void)applicationWillResignActive:(UIApplication *)application
{
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

Answer 2

我为解决这个问题做了什么：

- (void)viewDidAppear:(BOOL)animated {
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(cameraIsReady:)
                                                 name:AVCaptureSessionDidStartRunningNotification object:nil];

    self.ready = NO;
    if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        // There is not a camera on this device, so don't show the camera button.
        [self showImagePickerForSourceType:UIImagePickerControllerSourceTypePhotoLibrary];
    } else {
        [self showImagePickerForSourceType:UIImagePickerControllerSourceTypeCamera];
    }
}

- (void)cameraIsReady:(NSNotification *)notification {
    self.ready = YES;
}

- (IBAction)takePhoto:(id)sender {
    if (self.ready) {
        [self.imagePickerController takePicture];
    }
    self.ready = NO;
}