UIImagePickerController在iPhone和iPad中用法的一点不同

源自：http://huchenqiang90.blog.163.com/blog/static/1125008002011018416051/

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。