Question

出于某种原因，我第一次在我的应用程序中以相机模式打开UIImagePickerController时，它显示为空白。我必须关闭并重新打开该视图才能让相机进纸开始工作。我正在使用适用于iOS 6的标准代码来完美捕捉相机。从下面的示例中，我正在触发capturePhoto:方法。还有其他人在使用iOS 7相机时遇到这种尴尬吗？我检查了Apple dev论坛，但几乎不可能在那里找到答案。

- (IBAction)capturePhoto:(id)sender {
    [self doImagePickerForType:UIImagePickerControllerSourceTypeCamera];
}

- (void)doImagePickerForType:(UIImagePickerControllerSourceType)type {
    if (!_imagePicker) {
        _imagePicker = [[UIImagePickerController alloc] init];
        _imagePicker.mediaTypes = @[(NSString*)kUTTypeImage];
        _imagePicker.delegate = self;
    }
    _imagePicker.sourceType = type;
    [self presentViewController:_imagePicker animated:YES completion:nil];
}

why so empty?

Answer 1

我也在使用UIImagePickerController，并在空白屏幕上遇到了同样的问题。我想稍微介绍一下klaudz提到的关于相机的iOS 7授权的内容。

参考： https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html

“录制音频始终需要用户明确许可;录制视频还需要用户在某些地区销售的设备的许可。”

以下是一些代码片段，您可以查看是否拥有相机的权限，并在您的应用先前未请求时请求它。如果您因先前的请求而被拒绝，您的应用可能需要向用户发出通知，进入设置以手动启用访问权限，正如klaudz所指出的那样。

iOS 7示例

NSString *mediaType = AVMediaTypeVideo; // Or AVMediaTypeAudio

AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:mediaType];

// This status is normally not visible—the AVCaptureDevice class methods for discovering devices do not return devices the user is restricted from accessing.
if(authStatus == AVAuthorizationStatusRestricted){
    NSLog(@"Restricted");
}

// The user has explicitly denied permission for media capture.
else if(authStatus == AVAuthorizationStatusDenied){
    NSLog(@"Denied");
}

// The user has explicitly granted permission for media capture, or explicit user permission is not necessary for the media type in question.
else if(authStatus == AVAuthorizationStatusAuthorized){
    NSLog(@"Authorized");
}

// Explicit user permission is required for media capture, but the user has not yet granted or denied such permission.
else if(authStatus == AVAuthorizationStatusNotDetermined){

    [AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) {

        // Make sure we execute our code on the main thread so we can update the UI immediately.
        //
        // See documentation for ABAddressBookRequestAccessWithCompletion where it says
        // "The completion handler is called on an arbitrary queue."
        //
        // Though there is no similar mention for requestAccessForMediaType, it appears it does
        // the same thing.
        //
        dispatch_async(dispatch_get_main_queue(), ^{

            if(granted){
                // UI updates as needed
                NSLog(@"Granted access to %@", mediaType);
            }
            else {
                // UI updates as needed
                NSLog(@"Not granted access to %@", mediaType);
            }
        });

    }];

}

else {
    NSLog(@"Unknown authorization status");
}

Answer 2

在iOS 7中，应用可以在获得用户授权之前访问相机。当应用程序第一次访问摄像头时，iOS会显示警告视图以询问用户。用户还可以在Settings--Privacy--Camera--[Your app's name]中设置授权。

如果开关关闭，相机将保持黑色空白视图。

如果使用AVCaptureDeviceInput来调用相机，可以查看：

NSError *inputError = nil;
AVCaptureDeviceInput *captureInput =
    [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&inputError];
if (inputError &&
    inputError.code == AVErrorApplicationIsNotAuthorizedToUseDevice)
{
    // not authorized
}

如果您使用UIImagePickerController致电，我仍在寻找检查是否获得授权的方法。

我试过这两种方法：
```
[UIImagePickerController isSourceTypeAvailable:]
[UIImagePickerController isCameraDeviceAvailable:]
```
但他们没有工作，他们都返回YES。

<强>更新

感谢Scott的扩张。 [AVCaptureDevice authorizationStatusForMediaType:]是一种更好的检查方法。

AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
if (authStatus == AVAuthorizationStatusAuthorized) {
    // successful
} else {
    // failed, such as
    // AVAuthorizationStatusNotDetermined
    // AVAuthorizationStatusRestricted
    // AVAuthorizationStatusNotDetermined
}

但请记得查看iOS版本，因为iOS 7上方可以使用[AVCaptureDevice authorizationStatusForMediaType:]和AVAuthorizationStatus。

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0) {
    // code for AVCaptureDevice auth checking
}

Answer 3

我遇到了完全相同的问题，并尝试了互联网上的每一个解决方案，没有运气。但最后我发现背景线程阻止了相机预览显示。如果您在尝试打开相机时碰巧有后台线程运行，请尝试阻止后台线程，看看会发生什么。希望你能解决它。

Answer 4

我遇到了这个控件AQPhotoPicker。它很容易使用，希望它能帮到你

iOS 7 UIImagePickerController相机无图像

4 个答案: