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UIImagePickerController虽然可以用在IPAD与IPhone，但代码有所不同。

IPhone的代码如下：

   1:  partial void SelectImage(NSObject sender, MonoTouch.UIKit.UIEvent @event) {

   2:              UIImagePickerController picker = new UIImagePickerController ();

   3:              picker.ModalPresentationStyle = UIModalPresentationStyle.FullScreen;

   4:              picker.Delegate = new MyImagePickerDelegate (this);

   5:              this.PresentModalViewController (picker,true);

   6:          }

   7:   

   8:  public class MyImagePickerDelegate : UIImagePickerControllerDelegate

   9:      {

  10:          MYTableViewController _mvc;

  11:          public MyImagePickerDelegate (MYTableViewController mvc)

  12:          {

  13:              _mvc = mvc;

  14:          }

  15:          public override void FinishedPickingImage(UIImagePickerController picker, UIImage image, NSDictionary editingInfo) {

  16:              // TODO: Implement - see: http://go-mono.com/docs/index.aspx?link=T%3aMonoTouch.Foundation.ModelAttribute

  17:          }

  18:   

  19:          public override void Canceled(UIImagePickerController picker) {

  20:              // TODO: Implement - see: http://go-mono.com/docs/index.aspx?link=T%3aMonoTouch.Foundation.ModelAttribute

  21:          }

  22:      }

这段代码在IPhone下是正常的，但在IPAD上会报如下异常

MonoTouch.Foundation.MonoTouchException: Objective-C exception thrown. Name: NSInvalidArgumentException Reason: On iPad, UIImagePickerController must be presented via UIPopoverController

为什么呢？就和异常提的一样。UIImagePickerController必须由UIPopoverController来承载。

IPAD代码：

   1:  //static UIImagePickerController imagePicker = new UIImagePickerController();

   2:  //static UIPopoverController popOver = new UIPopoverController (imagePicker);

UIImagePickerController imagePicker;

UIPopoverController popOver;

   3:  partial void SelectImage(NSObject sender, MonoTouch.UIKit.UIEvent @event) {

   4:              //UIImagePickerController picker = new UIImagePickerController ();

   5:              //picker.ModalPresentationStyle = UIModalPresentationStyle.FullScreen;

   6:              //picker.Delegate = new MyImagePickerDelegate (this);

   7:              //this.PresentModalViewController (picker,true);

   8:   

   9:              if (popOver == null || popOver.ContentViewController == null)

  10:              {

  11:                  imagePicker = new UIImagePickerController();

  12:                  popOver = new UIPopoverController(imagePicker);

  13:                  ImagePickerDelegate imgDel = new ImagePickerDelegate();

  14:                  imagePicker.Delegate = imgDel;

  15:                  imagePicker.SourceType = UIImagePickerControllerSourceType.PhotoLibrary;

  16:              }

  17:              if (popOver.PopoverVisible)

  18:              {

  19:                  popOver.Dismiss(true);

  20:                  imagePicker.Dispose();

  21:                  popOver.Dispose();

  22:                  return;

  23:              }

  24:              else

  25:              {

  26:                  popOver.PresentFromRect(((UIButton)sender).Frame, this.View, UIPopoverArrowDirection.Any, true);

  27:              }

  28:   

  29:          }

public override void ViewDidLoad()

        {

            imagePicker = new UIImagePickerController();

            popOver = new UIPopoverController(imagePicker);

            base.ViewDidLoad();

        }

注意把2个Control设置成静态的，否则会报错[UIPopoverController dealloc] reached while popover is still visible.

也可以不设置成静态变量，但要声明为类成员变量或属性，然后再ViewDidLoad方法初始化，就是避免在要使用的时候已经被GC回收了。

原因还是GC，所以一个很好的做法是UIPopoverControllers应始终保持在一个实例变量。或建立一个强类型属性。

   1:  public class ImagePickerDelegate : UIImagePickerControllerDelegate

   2:      {

   3:          public ImagePickerDelegate()

   4:          {}

   5:          

   6:          public override void FinishedPickingMedia(UIImagePickerController picker, NSDictionary info)

   7:          {

   8:              UIImage image = (UIImage)info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));

   9:              // do whatever else you'd like to with the image

  10:          }

  11:      }

总结：

1. UIImagePickerController必须由UIPopoverController来承载。
2. 如果presentModalViewController的UIImagePickerController的SourceType为设置到“UIImagePickerControllerSourceTypeCamera”时。设备必须是iPad 2的相机在全屏幕视图。最大化才是是正确的UIModalPresentationStyle.FullScreen，presentModalViewController的sourceType被设置成任何其他的情况都会崩溃。UIImagePickerController Class Reference
3. UIPopoverControllers应始终保持在一个实例变量。或建立一个强类型属性保存。

作者：Bruce Lee
出处：http://www.cnblogs.com/BruceLee521
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