UIPickerView在UIPopoverController中正确显示方法

开发iPad应用程序与iPhone有一点小差别，就是iPad支持弹出框。这个示例展示如何在UIPopoverController上显示一个UIPickerView,当然你可以显示任何的UIView到UIPopover上面。原理就是构建一个UIViewController，然后将这个UIViewController加在UIPopoverController上，最近显示UIPopoverController，即显示出我们的UIViewController的内容。

首先，要我们的controller支持UIPickerViewDelegate，UIPopoverControllerDelegate协议，

@interface myViewController : UIViewController<UIPickerViewDelegate，UIPopoverControllerDelegate>

然后开始显示uipickerview
- (void)showPickerInPopover:(CGRect)rect
{

UIViewController *sortViewController = [[UIViewController alloc] init];
UIView *theView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
UIPickerView *thePicker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
thePicker.delegate = self;
thePicker.dataSource = self;
thePicker.showsSelectionIndicator = YES;
[theView addSubview:thePicker];
sortViewController.view = theView;
[theView release];

popViewController = [[UIPopoverController alloc] initWithContentViewController:sortViewController];
[popViewController setPopoverContentSize:CGSizeMake(320, 216) animated:NO];
[popViewController presentPopoverFromRect:rect inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
popViewController.delegate = self;
;
[sortViewController release];
}

注意内存管理，要释放UIPopoverController：
- (void)popoverControllerDidDismissPopover:(UIPopoverController *)popoverController
{
[popViewController release];
}

还有实现UIPickerDelegate
- (void)pickerView:(UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent:(NSInteger)component {
// Handle the selection
}

// tell the picker how many rows are available for a given component
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
NSUInteger numRows = 5;

return numRows;
}

// tell the picker how many components it will have
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
return 1;
}

// tell the picker the title for a given component
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
NSString *title;
title = [@"" stringByAppendingFormat:@"%d",row];

return title;
}

// tell the picker the width of each row for a given component
- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
int sectionWidth = 300;

return sectionWidth;
}

UIPickerView里的内容自行修改。