- (void)applicationDidEnterBackground:(UIApplication *)application {
  // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
  // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
  [[NSNotificationCenter defaultCenter]postNotificationName:UIApplicationDidEnterBackgroundNotification object:nil];
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
  // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
  [[NSNotificationCenter defaultCenter]postNotificationName:UIApplicationWillEnterForegroundNotification object:nil];
}

//
// YTHandlerEnterBackground.h
// 分時租賃
//
// Created by 柯其譜 on 17/2/24.
// Copyright © 2017年 柯其譜. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
/** 進入后臺block typedef */
typedef void(^YTHandlerEnterBackgroundBlock)(NSNotification * _Nonnull note, NSTimeInterval stayBackgroundTime);
/** 處理進入后臺并計算留在后臺時間間隔類 */
@interface YTHandlerEnterBackground : NSObject
/** 添加觀察者并處理后臺 */
+ (void)addObserverUsingBlock:(nullable YTHandlerEnterBackgroundBlock)block;
/** 移除后臺觀察者 */
+ (void)removeNotificationObserver:(nullable id)observer;
@end

//
// YTHandlerEnterBackground.m
// 分時租賃
//
// Created by 柯其譜 on 17/2/24.
// Copyright © 2017年 柯其譜. All rights reserved.
//
#import "YTHandlerEnterBackground.h"
@implementation YTHandlerEnterBackground
+ (void)addObserverUsingBlock:(YTHandlerEnterBackgroundBlock)block {
  __block CFAbsoluteTime enterBackgroundTime;
  [[NSNotificationCenter defaultCenter]addObserverForName:UIApplicationDidEnterBackgroundNotification object:nil queue:nil usingBlock:^(NSNotification * _Nonnull note) {
    if (![note.object isKindOfClass:[UIApplication class]]) {
      enterBackgroundTime = CFAbsoluteTimeGetCurrent();
    }
  }];
  __block CFAbsoluteTime enterForegroundTime;
  [[NSNotificationCenter defaultCenter]addObserverForName:UIApplicationWillEnterForegroundNotification object:nil queue:nil usingBlock:^(NSNotification * _Nonnull note) {
    if (![note.object isKindOfClass:[UIApplication class]]) {
      enterForegroundTime = CFAbsoluteTimeGetCurrent();
      CFAbsoluteTime timeInterval = enterForegroundTime-enterBackgroundTime;
      block? block(note, timeInterval): nil;
    }
  }];
}
+ (void)removeNotificationObserver:(id)observer {
  if (!observer) {
    return;
  }
  [[NSNotificationCenter defaultCenter]removeObserver:observer name:UIApplicationDidEnterBackgroundNotification object:nil];
  [[NSNotificationCenter defaultCenter]removeObserver:observer name:UIApplicationWillEnterForegroundNotification object:nil];
}
@end

- (void)viewWillAppear:(BOOL)animated {
  [super viewWillAppear:animated];
  [YTHandlerEnterBackground addObserverUsingBlock:^(NSNotification * _Nonnull note, NSTimeInterval stayBackgroundTime) {
    self.rentTimerInterval = self.rentTimerInterval-stayBackgroundTime;
  }];
}
- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
  [self.timer invalidate];
  [YTHandlerEnterBackground removeNotificationObserver:self];
}

- (void)viewWillAppear:(BOOL)animated {
  [super viewWillAppear:animated];
  self.locService.delegate = self;
  [self.locService startUserLocationService];
  //進入后臺再進入前臺重新開始定位
  [YTHandlerEnterBackground addObserverUsingBlock:^(NSNotification * _Nonnull note, NSTimeInterval stayBackgroundTime) {
    [self.locService startUserLocationService];
  }];
}
- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
  //停止定位
  self.locService.delegate = nil;
  [self.locService stopUserLocationService];
  //移除后臺監(jiān)聽
  [YTHandlerEnterBackground removeNotificationObserver:self];
}