Question

我在我的应用中使用navigationController。在我推动并弹出一个视图控制器3次后，我的应用程序因内存不足而崩溃。这是我的代码。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
        HomePageVC *homePage = [[ViewController alloc] homePage = [[ViewController alloc] initWithNibName:@"MainView-iPad" bundle:nil];
        navigationController = [[UINavigationController alloc] initWithRootViewController:homePage];
        self.window.rootViewController = navigationController;
        [self.window makeKeyAndVisible];
        return YES;
}

当用户按下按钮时，我将他发送到另一个视图控制器。

 -(IBAction)showMap:(id)sender
 {
    MapViewController *mapViewController = Nil;
    mapViewController = [[MapViewController alloc] initWithNibName:@"MapView-iPad" bundle:nil];
    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    [appDelegate.navigationController pushViewController:mapViewController animated:YES];
 }

当他想回到rootView Controller时，我做

-(IBAction)goBack:(id)sender
{
    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    [appDelegate.navigationController popToRootViewControllerAnimated:YES];
}

现在这几次之后，逐渐调用didReceiveLowMemory并且应用程序崩溃了。

为了进行更多调试，我在循环中打印了内存使用情况。

-(void) report_memory {
    struct task_basic_info info;
    mach_msg_type_number_t sizeM = sizeof(info);
    kern_return_t kerr = task_info(mach_task_self(),
                               TASK_BASIC_INFO,
                               (task_info_t)&info,
                               &sizeM);
    if( kerr == KERN_SUCCESS ) {
        NSLog(@"Memory usage: %.4lf MB", info.resident_size/1000000.0);
    } else {
        NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
    }
}

输出

When the app Launches    : Memory usage: 137.8263 MB
After showMap First Time : Memory usage: 206.2172 MB
Gone Back Home           : Memory usage: 223.6580 MB   ==> MapVC didn't release

After showMap Second Time: Memory usage: 227.2172 MB
Press Go Back Home       : Memory usage: 250.2172 MB   ==> MapVC didn't release

After showMap Third Time : App Crashes

我的lowMemory写成

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    NSLog(@"Got Low Memory From %@",[self class]);
}

为了增加更多惊喜，我从HomePageVC和MapVC获得了低内存警告。如果我得到了MapVC，我是如何从中获得lowMemory的呢？为什么MapVC消耗的内存没有被释放？我正在使用ARC。

Answer 1

我的代码中遇到了同样的问题（使用ARC），在调用popToRootViewControllerAnimated后我的UIViewController没有被释放：

我的错误原因是由于UIViewController中的NSTimer。我试图在dealloc中使计时器无效，但因为我的NSTimer使用了target：self（即保留指向我的UIViewController的指针）dealloc从未被调用过。

要解决此问题，我在viewWillDisappear中使计时器无效。

Answer 2

看起来iOS除非需要，否则不会释放内存。我添加了一些代码来分配大量内存。弹出视图控制器时，内存从未发布。但是当调用didReceiveMemorywarning时，实际上我得到了回忆。我通过本练习学到的另一件事是，当它不是来自apple tutorial here的活动窗口时，释放视图。

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    if ([self.view window] == nil)
        self.view = nil;
}

popToRootViewControllerAnimated之后内存未释放

2 个答案: