作為3D Touch的一部分，peek and pop （預(yù)覽和彈出）個(gè)人覺(jué)得還是很有意思的，今天就說(shuō)說(shuō)如何去實(shí)現(xiàn)這一小功能恋昼。

一、遵守協(xié)議

@interface ViewController ()<UIViewControllerPreviewingDelegate>

@end

二赶促、注冊(cè)代理液肌，并傳入響應(yīng)3D Touch的視圖，并實(shí)現(xiàn)三個(gè)通知中心（分別為刪除鸥滨、置頂嗦哆、未讀功能）。

注意:注冊(cè)代理應(yīng)該放在viewDidLoad里面婿滓，而看了很多文章都把registerForPreviewingWithDelegate方法放在tableView的cellForRowAtIndexPath代理方法中老速，這樣寫(xiě)非常不好，因?yàn)樽?cè)只需要執(zhí)行一次凸主。

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(deleteActionClick:) name:MessageDeleteNoti object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(stickActionClick:) name:MessageStickNoti object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(noReadActionClick:) name:MessageNoReadNoti object:nil];
    
    if (@available(iOS 9.0, *)) {
        
        if ([self check3DTouchAvailable]) { // 判斷3d touch是否可用
            
            [self registerForPreviewingWithDelegate:(id)self sourceView:self.tableView];
        }
    }
}

- (BOOL)check3DTouchAvailable {
    
    if (self.traitCollection.forceTouchCapability == UIForceTouchCapabilityAvailable) {
        
        return YES;
    }
    return NO;
}

- (void)dealloc{
    
    [[NSNotificationCenter defaultCenter] removeObserver:self name:MessageDeleteNoti object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:MessageStickNoti object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:MessageNoReadNoti object:nil];
}

三橘券、實(shí)現(xiàn)UIViewControllerPreviewingDelegate協(xié)議

可以看看官方API，只有需實(shí)現(xiàn)以下兩個(gè)方法

NS_CLASS_AVAILABLE_IOS(9_0) @protocol UIViewControllerPreviewingDelegate <NSObject>

// If you return nil, a preview presentation will not be performed
- (nullable UIViewController *)previewingContext:(id <UIViewControllerPreviewing>)previewingContext viewControllerForLocation:(CGPoint)location NS_AVAILABLE_IOS(9_0);
- (void)previewingContext:(id <UIViewControllerPreviewing>)previewingContext commitViewController:(UIViewController *)viewControllerToCommit NS_AVAILABLE_IOS(9_0);

@end

3.1 當(dāng)系統(tǒng)察覺(jué)到足夠的壓力時(shí)，會(huì)調(diào)用previewingContext:commitViewController:代理方法：

- (void)previewingContext:(id<UIViewControllerPreviewing>)previewingContext commitViewController:(UIViewController *)viewControllerToCommit {
    
    // 將配置好的控制器推入導(dǎo)航棧
    [self.navigationController pushViewController:viewControllerToCommit animated:YES];
}

3.2 當(dāng)用戶重壓區(qū)域的出現(xiàn)預(yù)覽界面旁舰，其他區(qū)域則會(huì)變模糊,在此方法中我們可以把需要的數(shù)據(jù)傳入到下一個(gè)界面锋华。

- (UIViewController *)previewingContext:(id<UIViewControllerPreviewing>)previewingContext viewControllerForLocation:(CGPoint)location {
    
    NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
    if (!indexPath) {
        return nil;
    }
    //防止重復(fù)加入
    if ([self.presentedViewController isKindOfClass:[nextViewController class]]){
        return nil;
    }
    else {
        
        NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
        listCell *cell = (listCell *)[self.tableView cellForRowAtIndexPath:indexPath];
        CGRect rect = cell.frame;
        previewingContext.sourceRect = rect;
        NIMRecentSession *recentSession = self.conversationArr[indexPath.row];
        if (recentSession.unreadCount > 0) {
            
            [recentSession setValue:@"0" forKey:@"unreadCount"];
        }
        
        [self sort];
        [self testDataIsNull];
        nextViewController *vc = [[nextViewController alloc] initWithSession:recentSession.session];
        vc.indexPath = indexPath;
        vc.isTop = [recentSession isTop];
        vc.isOfficeNotiAccount = recentSession.isOfficeNotiAccount;
        return vc;
    }
}

四、實(shí)現(xiàn)通知方法

- (void)deleteActionClick:(NSNotification *)noti {
    
    NSIndexPath *indexPath = noti.userInfo[@"index"];
    NIMRecentSession *recentSession = self.conversationArr[indexPath.row];
    [self onDeleteRecentAtIndexPath:recentSession atIndexPath:indexPath];
}

- (void)stickActionClick:(NSNotification *)noti {
    
    NSIndexPath *indexPath = noti.userInfo[@"index"];
    NSInteger isTop = [noti.userInfo[@"isTop"] integerValue];
    NIMRecentSession *recentSession = self.conversationArr[indexPath.row];

    if (isTop) { // 點(diǎn)擊了取消置頂
        
        [recentSession setTopFlag:0];
        [self sort];
        [self testDataIsNull];
    }else { // 點(diǎn)擊了置頂
        
        [recentSession setTopFlag:1];
        [self sort];
        [self testDataIsNull];
    }
}

- (void)noReadActionClick:(NSNotification *)noti {
    
    NSIndexPath *indexPath = noti.userInfo[@"index"];
    NIMRecentSession *recentSession = self.conversationArr[indexPath.row];
    
    [recentSession setValue:@"1" forKey:@"unreadCount"];
    [self testDataIsNull];
}

五鬓梅、添加Peek狀態(tài)下供置，上劃時(shí)的快速操作谨湘，即在nextViewController重寫(xiě)方法绽快，通過(guò)發(fā)送通知告訴上一個(gè)界面需要執(zhí)行的操作。

#pragma mark - UIPreviewActionItem
- (NSArray<id<UIPreviewActionItem>> *)previewActionItems {
    
    UIPreviewAction *noReadAction = [UIPreviewAction actionWithTitle:@"標(biāo)為未讀" style:UIPreviewActionStyleDefault handler:^(UIPreviewAction * _Nonnull action, UIViewController * _Nonnull previewViewController) {
        
        NSLog(@"標(biāo)為未讀");
        [[NSNotificationCenter defaultCenter] postNotificationName:MessageNoReadNoti object:nil userInfo:@{@"index":self.indexPath}];
    }];
    
    UIPreviewAction *stickAction = [UIPreviewAction actionWithTitle:@"置頂" style:UIPreviewActionStyleDefault handler:^(UIPreviewAction * _Nonnull action, UIViewController * _Nonnull previewViewController) {
        
        NSLog(@"置頂");
        [[NSNotificationCenter defaultCenter] postNotificationName:MessageStickNoti object:nil userInfo:@{@"index":self.indexPath,@"isTop":@(self.isTop)}];
    }];
    
    UIPreviewAction *cancelStickAction = [UIPreviewAction actionWithTitle:@"取消置頂" style:UIPreviewActionStyleDefault handler:^(UIPreviewAction * _Nonnull action, UIViewController * _Nonnull previewViewController) {
        
        NSLog(@"取消置頂");
        [[NSNotificationCenter defaultCenter] postNotificationName:MessageStickNoti object:nil userInfo:@{@"index":self.indexPath,@"isTop":@(self.isTop)}];
    }];
    
    UIPreviewAction *deleteAction = [UIPreviewAction actionWithTitle:@"刪除" style:UIPreviewActionStyleDestructive handler:^(UIPreviewAction * _Nonnull action, UIViewController * _Nonnull previewViewController) {
        
        NSLog(@"刪除");
        [[NSNotificationCenter defaultCenter] postNotificationName:MessageDeleteNoti object:nil userInfo:@{@"index":self.indexPath}];
    }];
    
    if (self.isOfficeNotiAccount) {
        return @[noReadAction, deleteAction];
    }
    
    return self.isTop ? @[noReadAction, cancelStickAction, deleteAction] : @[noReadAction, stickAction, deleteAction];
}