Question

我有一个iPad应用，使用Storyboards，XCode 4.6和iOS 6.1。我有一个包含UIViewController的场景。在UIViewController里面，我有一个UIScrollController，都是使用IB创建的。以编程方式，在viewDidLoad我创建了两个（2）UIViews（一个名为subViewGrid，另一个名为subViewData）并将其添加到UIViewController;它们都在模拟器中正确显示。这是代码：

- (void)viewDidLoad  {

[super viewDidLoad];

// notify me when calendar has been tapped and CFGregorianDate has been updated
[[NSNotificationCenter defaultCenter] removeObserver:self];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(calendarTapNotification:)
                                             name:@"calendarDateSelected" object:nil ];

//   UIScrollVIew settings
CGSize scrollableSize = CGSizeMake(760, 1379);  //  set size of scheduleView
[self.schedScrollView setContentSize:scrollableSize];
self.schedScrollView.contentInset = UIEdgeInsetsMake(0,0,44,44);  //  allow for scroll bar
self.schedScrollView.directionalLockEnabled = YES;  //  prevents diagonal scrolling

//  create a sub-view to hold the appointment GRID
CGRect frame = CGRectMake(0,0,760,1390);  //  110,48,760,1390
subViewGrid = [[UIView alloc] initWithFrame:frame];
subViewGrid.tag = 12;  //  use tag to get correct sub-view
subViewGrid.backgroundColor = [UIColor grayColor];
subViewGrid.alpha = 1.0;  //  make it opaque
[self.schedScrollView addSubview:subViewGrid];

//  create a sub-view to hold the appointment DATA
frame = CGRectMake(110,48,670,750); 
subViewData = [[UIView alloc] initWithFrame:frame];
subViewData.tag = 22;  //  use tag to get correct sub-view
subViewData.backgroundColor = [UIColor redColor];
subViewData.alpha = 0.2;  //  make it sort of transparent
[self.schedScrollView addSubview:subViewData];

[self.subViewGrid setNeedsDisplay];  //  ****  UPDATED ****

}

以下是.h的<{1}}文件内容：

UIViewController

在我的@interface CalendarViewController : UIViewController { UIView *subViewGrid; UIView *subViewData; } @property (strong, nonatomic) IBOutlet UIScrollView *schedScrollView; - (void) calendarTapNotification:(NSNotification *) notification; -(NSDate *)beginningOfDay:(NSDate *)date; -(NSDate *)endOfDay:(NSDate *)date; @end方法中，我有一些代码应该在subViewGrid上绘制一个“网格”。问题是drawRect永远不会被调用。

我已阅读drawRect程序员指南，并查看了SO并进行了Google搜索，但没有找到解决该问题的任何内容，即：UIView为什么不会[self.subViewGrid setNeedsDisplay]致电drawRect从哪里放到它？

Answer 1

您的视图控制器需要为其控制的视图调用setNeedsDisplay，而不是为自己调用。所以，你想要

 [self.subViewGrid setNeedsDisplay]

Answer 2

这只是您阅读文档时的错误。理解文档对于Objective-C编程至关重要，因此我将尽力帮助您掌握它。

如果查看setNeedsDisplay的文档，您会发现它是CALayer或UIView类方法。如果您继续查看继承，则会看到UIView为UIResponder:NSObject且CALayer为NSObject。这些都不会从UIViewController继承，这就是您收到错误的原因。您需要致电[self.subViewGrid setNeedsDisplay]

在UIViewController的代码中，[self.subViewGrid setNeedsDisplay]没有调用-drawRect

2 个答案: