Question

我正在练习TabViewcontroller的工作原理。现在我有2个UIViewcontroller的子类。一个是HypnosisViewController，另一个是TimeViewController。我想检查的是当IOS模拟器获取内存警告时 - （void）viewDidLoad 的工作原理。我做了

构建并运行应用
控制台说“HypnosisViewcontroller加载了它的视图。”
切换其他标签（TimeViewController）
在控制台中看到该消息。它说“TabViewcontroller加载了它的视图”
IOS模拟器中的模拟器内存警告命令
控制台说“HypnoTime收到内存警告。”
切换回HypnosisViewcontroller以查看控制台是否显示“HypnosisViewcontroller加载了它的视图”。试。

所以这里的问题是HypnosisViewcontroller没有被销毁并再次创建。（因为当我切换回HypnosisViewcontroller时，我看不到日志消息。）但是我倾向于在内存警告期间不应该在屏幕上销毁视图。

我错过了什么吗？提前谢谢！

HypnosisViewController.m：

#import "HypnosisViewController.h"
#import "HypnosisView.h"

@implementation HypnosisViewController

-(void)loadView
{
    //Create a view

    CGRect frame = [[UIScreen mainScreen] bounds];
    HypnosisView *v = [[HypnosisView alloc] initWithFrame:frame];

    // Set it as *the* view of this view controller
    [self setView:v];


}

-(id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)bundle
{

    self = [super initWithNibName:nil
                           bundle:nil];

    if(self){
        //Get the tab bar item
        UITabBarItem *tbi = [self tabBarItem];

        //Give it a label
        [tbi setTitle:@"Hypnosis"];

        //Create a UIImage from a file
        //This will use Hypno@2x.png on retina display devices
        UIImage *i = [UIImage imageNamed:@"Hypno.png"];

        // Put that image on the tab bar item
        [tbi setImage:i];

    }
    return self;

}

-(void)viewDidLoad
{

    // Always call the super implmetaion of viewDidload
    [super viewDidLoad];
    NSLog(@"HypnosisViewcontroller loaded its view");


}

@end

TimeViewController.m：

#import "TimeViewController.h"

@implementation TimeViewController

-(IBAction)showCurrentTime:(id)sender
{
    NSDate *now = [NSDate date];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setTimeStyle:NSDateFormatterMediumStyle];


    [timeLabel setText:[formatter stringFromDate:now]];
    [timeLabel2 setText:[formatter stringFromDate:now]];

}

-(id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)bundle
{
    // Call the superclass's designated initializer
   self = [super initWithNibName:nil
                          bundle:nil];

    //Get a pointer to the application bundle object
   // NSBundle *appBundle = [NSBundle mainBundle];

   // self = [super initWithNibName:@"TimeViewController"
                           //bundle:appBundle];

    if(self){
        //Get the tab bar item
        UITabBarItem *tbi = [self tabBarItem];

        //Give it a label
        [tbi setTitle:@"Time"];


        //Create a UIImage from a file
        //This will use Time@2x.png on retina display devices
        UIImage *i = [UIImage imageNamed:@"Time.png"];

        // Put that image on the tab bar item
        [tbi setImage:i];




    }
    return self;
}

-(void)viewDidLoad
{

    // Always call the super implmetaion of viewDidload
    [super viewDidLoad];
    NSLog(@"TimeViewcontroller loaded its view");

   // [[self view] setBackgroundColor:[UIColor greenColor]];


}

@end

enter image description here

Answer 1

内存警告不会导致控制器再破坏/卸载他们的视图。

Answer 2

工作正常。 HypnosisViewcontroller被销毁并再次创建，因为只有在启动所有视图时才会调用viewDidLoad。因此，当您切换回HypnosisViewcontroller时，您会再次看到日志消息，表示HypnosisViewcontroller已从内存中清除并再次启动。您可以尝试在这两个视图控制器之间切换而不模拟内存警告，并且您只能看到一次日志消息。

内存警告无法正常工作

2 个答案: