On iPad, UIImagePickerController must be presented via UIPopoverController

[code]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

[code]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];
}

[code]

[code]

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];
}
[/code]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！