UIImagePickerController在iPhone和iPad上的区别

在iPhone中获取照片库的常用方法如下：

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;imagePicker.delegate = self;[imagePicker setAllowsEditing:NO];[self presentModalViewController:imagePicker animated:YES];[imagePicker release];} else {UIAlertView *alert = [[UIAlertView alloc]initWithTitle:nil message:@"Error accessing photo library!" delegate:nil cancelButtonTitle:@"Close" otherButtonTitles:nil];[alert show];[alert release];}

这在iPhone下操作是没有问题的，但在iPad下就会有问题了，运行时会报出下面的错误：Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'On iPad, UIImagePickerController must be presented via UIPopoverController'所以，我们必须通过UIPopoverController来实现才行。具体的实现如下：

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;imagePicker.delegate = self;[imagePicker setAllowsEditing:NO];UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:imagePicker];self.popoverController = popover;[popoverController presentPopoverFromRect:CGRectMake(0, 0, 300, 300) inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];[popover release];[imagePicker release];} else {UIAlertView *alert = [[UIAlertView alloc]initWithTitle:nil message:@"Error accessing photo library!" delegate:nil cancelButtonTitle:@"Close" otherButtonTitles:nil];[alert show];[alert release];}