释放细节视图控制器导致内存问题

Question

我有一个基于拆分视图控制器的应用程序。在详细视图控制器中，将其称为 FirstViewController，当用户按下按钮时，我会使用新的视图控制器更新视图控制器，称为 SecondViewContorller，如下所示：

- (void) buttonPressed:(id)sender {
     UIViewController <SubstitutableDetailViewController> *detailViewController = nil;

     SecondViewController *secondVC = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
     ...
     detailViewController = secondVC;

     MyAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
     UINavigationController *nav = (UINavigationController *)[delegate.splitViewController.viewControllers objectAtIndex: 0];
     NSArray *viewControllers = [NSArray arrayWithObjects:nav, detailViewController, nil];
     self.splitViewController.viewControllers = viewControllers;

 ...

    [detailViewController release];

}

在 SecondViewController 中，有时我们有：

 MyAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
 UINavigationController *nav = (UINavigationController *)[delegate.splitViewController.viewControllers objectAtIndex: 0];
 NSArray *array = nav.viewControllers;
 // Retrieve the master view controller
 MasterViewController *masterVC = [array objectAtIndex:[array count] - 1];
 [masterVC selectRowManually:[NSIndexPath indexPathForRow:0 inSection:0]];

在 selectRowManually 中，我再次初始化 FirstViewController：

 UIViewController <SubstitutableDetailViewController> *detailViewController = nil;

 if (rowNo == 0) {
      FirstViewController *newDetailViewController = [[FirstViewController alloc] initWithNibName:@"FirstViewController" bundle:nil];
      detailViewController = newDetailViewController;
 }
 ...

 UINavigationController *nav = (UINavigationController *)[delegate.splitViewController.viewControllers objectAtIndex: 0];

 // Update the split view controller's view controllers array.
 NSArray *viewControllers = [[NSArray alloc] initWithObjects:nav, detailViewController, nil];
 delegate.splitViewController.viewControllers = viewControllers;
 [viewControllers release];

 ...

 [detailViewController release];

如果我在这个时间点模拟内存警告（在 FirstViewController 再次显示之后），我会得到一个

-[UIView _invalidateSubviewCache]: message sent to deallocated instance ...

有一个堆栈跟踪

#0     0x012dd057 in ___forwarding___
#1     0x012dcf22 in __forwarding_prep_0___
#2     0x00b49a55 in -[UIView dealloc]
#3     0x00bbe52a in -[UIViewController setView:]
#4     0x00bc0eec in -[UIViewController unloadViewForced:]
#5     0x00bbcb0a in -[UIViewController unloadViewIfReloadable]
#6     0x00bbc15b in -[UIViewController didReceiveMemoryWarning]
#7     0x0006aec7 in -[SecondViewController didReceiveMemoryWarning] at SecondViewController.m:385
...

第 385 行在哪里

[super didReceiveMemoryWarning];

如果在 SecondViewController 的 buttonPressed 方法中我注释了我释放 detailViewContorller 的行，一切正常，但我泄漏了内存。如果我按原样保留该行，那么如果出现内存警告，应用程序就会崩溃。

我能做什么？

谢谢， 米海

Answer 1

我很好奇您发布 detailViewController 而不是 secondVC 的第一个代码块？因为你的 secondVC 在方法结束时没有释放。您应该在 dealloc 方法中释放 detailViewController，而不是在 SplitViewAppDelegate 中释放，因为它是拆分视图的根视图的一部分。

干杯，希望对您有所帮助。