On iPad, UIImagePickerController must be presented via UIPopoverController

On iPad, UIImagePickerController must be presented via UIPopoverController 可以用以下方法来判断设备的类型选择不同的Controller

if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) { // We are using an iPhone UIActionSheet *alertSheet = [[UIActionSheet alloc] initWithTitle:@"Where do you want to get your daily image?" delegate:(self) cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Camera", @"Library", nil]; [alertSheet setTag:0]; [alertSheet setDelegate:self]; [alertSheet showFromTabBar:[[self tabBarController] tabBar]]; [alertSheet release]; }else { // We are using an iPad UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init]; imagePickerController.delegate = self; UIPopoverController *popoverController=[[UIPopoverController alloc] initWithContentViewController:imagePickerController]; popoverController.delegate=self; [popoverController presentPopoverFromRect:((UIButton *)sender).bounds inView:sender permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES]; }

iPad与iPhone调用UIImagePickerViewController方法略有不同是本文要介绍的内容，文中很详细的讲述了iPad与iphone各自的调用方法，来看详细内容。
我们知道，在iPhone中获取照片库常用的方法如下：
UIImagePickerController *m_imagePicker = [[UIImagePickerController alloc] init];
    if ([UIImagePickerController isSourceTypeAvailable:
         UIImagePickerControllerSourceTypePhotoLibrary]) {
        m_imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        m_imagePicker.delegate = self;
        //        [m_imagePicker.navigationBar.subviews];
        [m_imagePicker setAllowsEditing:NO];
        //m_imagePicker.allowsImageEditing = NO;
        [self presentModalViewController:m_imagePicker animated:YES];
        [m_imagePicker release];
    }else {
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:nil message:
@"Error accessing photo library!" delegate:nil cancelButtonTitle:@"Close" otherButtonTitles:nil];
        [alert show];
        [alert release];
    }
这对iPhone的操作是没有问题的。但是当我们在iPad环境中却有问题了，当我们运行时会报如下错误：
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。具体实现如下：
UIImagePickerController *m_imagePicker = [[UIImagePickerController alloc] init];
    if ([UIImagePickerController isSourceTypeAvailable:
         UIImagePickerControllerSourceTypePhotoLibrary]) {
        m_imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
        m_imagePicker.delegate = self;
        [m_imagePicker setAllowsEditing:NO];
        UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:m_imagePicker];
        self.popoverController = popover;
        //popoverController.delegate = self;

        [popoverController presentPopoverFromRect:CGRectMake(0, 0, 300, 300) inView:self.
 view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];

        //[self presentModalViewController:m_imagePicker animated:YES];
        [popover release];
        [m_imagePicker release];
    }else {
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:nil message:@"Error accessing photo library!"
 delegate:nil cancelButtonTitle:@"Close" otherButtonTitles:nil];
        [alert show];
        [alert release];
    }
这里需要注意，对局部UIPopoverController对象popover我们赋给了一个全局的UIPopoverController对象popoverController。而不能直接调用popover。因为在popover对象还可见时，是不能够被释放的。
小结：iPad与iphone调用UIImagePickerViewController方法略有不同的内容介绍完了，希望本文对你有所帮助！