//先设定sourceType为相机，然后判断相机是否可用（ipod）没相机，不可用将sourceType设定为相片库

    UIImagePickerControllerSourceType sourceType = UIImagePickerControllerSourceTypeCamera;

//    if (![UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypeCamera]) {

//        sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

//    }

    //sourceType = UIImagePickerControllerSourceTypeCamera; //照相机

    //sourceType = UIImagePickerControllerSourceTypePhotoLibrary; //图片库

    //sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum; //保存的相片

    UIImagePickerController *picker = [[UIImagePickerController alloc] init];//初始化

    picker.delegate = self;

    picker.allowsEditing = YES;//设置可编辑

    picker.sourceType = sourceType;

    [self presentModalViewController:picker animated:YES];//进入照相界面

    [picker release];

UIImagePickerController *pickerImage = [[UIImagePickerController alloc] init];

    if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {

        pickerImage.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

        //pickerImage.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;

        pickerImage.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:pickerImage.sourceType];

    }

    pickerImage.delegate = self;

    pickerImage.allowsEditing = NO;

    [self presentModalViewController:pickerImage animated:YES];

    [pickerImage release];

UIImagePickerControllerSourceType sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

    //sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum; //保存的相片

    UIImagePickerController *picker = [[UIImagePickerController alloc] init];

    picker.delegate = self;

    picker.allowsEditing = NO;//是否允许编辑

    picker.sourceType = sourceType;

    /*

     如果从一个导航按钮处呈现，使用：

     presentPopoverFromBarButtonItem:permittedArrowDirections:animated:；

     如果要从一个视图出呈现，使用：

     presentPopoverFromRect:inView:permittedArrowDirections:animated:

     如果设备旋转以后，位置定位错误需要在父视图控制器的下面方法里面重新定位：

     didRotateFromInterfaceOrientation:（在这个方法体里面重新设置rect）

     然后再次调用：

     - (void)presentPopoverFromRect:(CGRect)rect inView:(UIView *)view permittedArrowDirections:(UIPopoverArrowDirection)arrowDirections animated:(BOOL)animated

     */

    //UIPopoverController只能在ipad设备上面使用；作用是用于显示临时内容，特点是总是显示在当前视图最前端，当单击界面的其他地方时自动消失。

    UIPopoverController *popover = [[UIPopoverController alloc]initWithContentViewController:picker];

    self.imagePicker = popover;

    //permittedArrowDirections 设置箭头方向

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

    [picker release];

    [popover release];