Monotouch在IPAD與IPhone使用UIImagePickerController的圖片選擇不同的代碼

UIImagePickerController雖然可以用在IPAD與IPhone，但代碼有所不同。

IPhone的代碼如下：

partial void SelectImage(NSObject sender, MonoTouch.UIKit.UIEvent @event) {
            UIImagePickerController picker = new UIImagePickerController ();
            picker.ModalPresentationStyle = UIModalPresentationStyle.FullScreen;
            picker.Delegate = new MyImagePickerDelegate (this);
            this.PresentModalViewController (picker,true);
        }

public class MyImagePickerDelegate : UIImagePickerControllerDelegate
    {
        MYTableViewController _mvc;
        public MyImagePickerDelegate (MYTableViewController mvc)
        {
            _mvc = mvc;
        }
        public override void FinishedPickingImage(UIImagePickerController picker, UIImage image, NSDictionary editingInfo) {
            // TODO: Implement - see: http://go-mono.com/docs/index.aspx?link=T%3aMonoTouch.Foundation.ModelAttribute
        }

        public override void Canceled(UIImagePickerController picker) {
            // TODO: Implement - see: http://go-mono.com/docs/index.aspx?link=T%3aMonoTouch.Foundation.ModelAttribute
        }
    }

這段代碼在IPhone下是正常的，但在IPAD上會報如下異常

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

為什么呢？就和異常提的一樣。UIImagePickerController必須由UIPopoverController來承載。

IPAD代碼：

   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個Control設置成靜態的，否則會報錯[UIPopoverController dealloc] reached while popover is still visible.

也可以不設置成靜態變量，但要聲明為類成員變量或屬性，然后再ViewDidLoad方法初始化，就是避免在要使用的時候已經被GC回收了。

原因還是GC，所以一個很好的做法是UIPopoverControllers應始終保持在一個實例變量。或建立一個強類型屬性。

public class ImagePickerDelegate : UIImagePickerControllerDelegate
    {
        public ImagePickerDelegate()
        {}

        public override void FinishedPickingMedia(UIImagePickerController picker, NSDictionary info)
        {
            UIImage image = (UIImage)info.ObjectForKey(new NSString("UIImagePickerControllerOriginalImage"));
            // do whatever else you'd like to with the image
        }
    }

總結：

1. UIImagePickerController必須由UIPopoverController來承載。
2. 如果presentModalViewController的UIImagePickerController的SourceType為設置到“UIImagePickerControllerSourceTypeCamera”時。設備必須是iPad 2的相機在全屏幕視圖。最大化才是是正確的UIModalPresentationStyle.FullScreen，presentModalViewController的sourceType被設置成任何其他的情況都會崩潰。UIImagePickerController Class Reference
   
   
3. UIPopoverControllers應始終保持在一個實例變量。或建立一個強類型屬性保存。

 

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