Question

iOS模拟器7.1中的

，下面是简单的代码：

命令+ shift + H模拟按下主页按钮，输出逻辑上：
- activing
- 辞职
- backgrounding
双命令+ shift + H模拟双击主页按钮然后轻扫以杀死应用程序，输出“奇怪”：
- activing
- 辞职
- backgrounding
- backgrounding

在案例2中出于哪种原因，后台被调用两次？请注意，使用iOS 8.0案例2.显示： - 活动 - 辞职 - 背景

#import "ViewController.h"

@interface ViewController ()
@end

@implementation ViewController {}

- (void)backgrounding {
    NSLog(@"backgrounding");
}

- (void)resigning {
    NSLog(@"resigning");
}

- (void)activing {
    NSLog(@"activing");
}

- (void)viewDidLoad {
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(backgrounding) name:UIApplicationDidEnterBackgroundNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(resigning) name:UIApplicationWillResignActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(activing) name:UIApplicationDidBecomeActiveNotification object:nil];
}

@end

Answer 1

iOS 7（至少在模拟器中）发送两个后台事件。您只需编写应用程序即可优雅地处理多个后台事件。

我通过创建一个自定义UIApplication子类来检查这一点，该子类记录每个事件，以及其内部GraphicsServices事件（如果有）：

#import "MyApplication.h"

@interface NSObject (hack)

- (id)_gsEvent;

@end

@implementation MyApplication

- (void)sendEvent:(UIEvent *)event {
    NSLog(@"event=%@", event);
    if ([event respondsToSelector:@selector(_gsEvent)]) {
        NSLog(@"_gsEvent=%@", event._gsEvent);
    }
    [super sendEvent:event];
}

@end

这是在多任务处理屏幕中刷掉应用程序时的输出：

2014-09-15 16:14:32.894 background[19438:70b] event=<UIInternalEvent: 0x8c148e0>
2014-09-15 16:14:32.894 background[19438:70b] _gsEvent=<GSEvent 0xd9149f0>{type = 32, windowLoc = (0.000000, 0.000000)}
2014-09-15 16:14:32.895 background[19438:70b] event=<UIInternalEvent: 0x8c148e0>
2014-09-15 16:14:32.895 background[19438:70b] _gsEvent=<GSEvent 0x8f1ac20>{type = 7d7, windowLoc = (0.000000, 0.000000)}
2014-09-15 16:14:32.896 background[19438:70b] backgrounding
2014-09-15 16:14:32.943 background[19438:70b] event=<UIInternalEvent: 0x8c148e0>
2014-09-15 16:14:32.944 background[19438:70b] _gsEvent=<GSEvent 0x8b22c90>{type = 7d7, windowLoc = (0.000000, 0.000000)}
2014-09-15 16:14:32.944 background[19438:70b] backgrounding

您可以看到有两个独立的GraphicsServices事件（具有不同的地址），每个UIApplicationDidEnterBackgroundNotification一个。

杀死应用程序时有两个UIApplicationDidEnterBackgroundNotification

1 个答案: