uitableview 向下拖动到屏幕外

Question

我基本上是在尝试实现这个效果：http://youtu.be/VBW2i0P11iI

tableview 是一个基本的，通过自动布局固定到它的 superview。下面的视图添加了经典的 insertSubview:belowSubview:/addChildViewController 组合。

我尝试了几种方法。我现在拥有的是：

if (scrollOffset >= -scrollView.contentInset.top) {
        self.resultsTableViewContainerTopConstraint.constant = 0;
    } else {
        self.resultsTableViewContainerTopConstraint.constant = MAX(self.resultsTableViewContainerTopConstraint.constant, self.resultsTableViewContainerTopConstraint.constant - scrollDiff);
    }
}

所以我基本上是根据 contentOffset 的增量来更改顶部约束。这样做的问题是 uitableview 反弹回来，所以它总是进入 if 的第一个分支。但即使我解决了这个问题，我也觉得我只会修补它。我确信有一种更优雅的方式可以在具有相同响应能力的视频中实现效果。

任何建议将不胜感激。 谢谢

Answer 1

我不确定这是否是你想要的，但我做了一个快速演示：

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UITableViewDataSource, UITableViewDelegate, UIScrollViewDelegate>

@property (nonatomic, strong) UIView *headerView;
@property (nonatomic, strong) UILabel *lblTitle;

@property (nonatomic, strong) UIButton *btnReset;

@property (nonatomic, strong) UIImageView *imageView;

@property (nonatomic, strong) UIScrollView *scrollView;
@property (nonatomic, strong) UITableView *tableView;

@property (nonatomic, strong) NSLayoutConstraint *scrollViewTopConstraint;

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    //self.view.backgroundColor = [UIColor whiteColor];

    [self initViews];
    [self initConstraints];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(void)initViews
{
    self.view.backgroundColor = [UIColor colorWithRed:43.0/255.0 green:39.0/255.0 blue:55.0/255.0 alpha:1.0];

    self.scrollView = [[UIScrollView alloc] init];
    self.scrollView.backgroundColor = [UIColor clearColor];
    self.scrollView.alwaysBounceVertical = YES;
    self.scrollView.delegate = self;

    self.headerView = [[UIView alloc] init];
    self.headerView.backgroundColor = [UIColor colorWithRed:43.0/255.0 green:39.0/255.0 blue:55.0/255.0 alpha:1.0];
    self.headerView.layer.shadowColor = [UIColor blackColor].CGColor;
    self.headerView.layer.shadowOffset = CGSizeMake(0,0);
    self.headerView.layer.shadowOpacity = 0.25;
    self.headerView.layer.shadowRadius = 4;

    self.lblTitle = [[UILabel alloc] init];
    self.lblTitle.text = @"HEADER VIEW";
    self.lblTitle.textColor = [UIColor whiteColor];
    self.lblTitle.textAlignment = NSTextAlignmentCenter;

    self.btnReset = [[UIButton alloc] init];
    [self.btnReset setTitle:@"Reset" forState:UIControlStateNormal];
    self.btnReset.backgroundColor = [UIColor colorWithRed:0.75 green:0.0 blue:0.0 alpha:1.0];
    self.btnReset.layer.cornerRadius = 5.0;
    [self.btnReset addTarget:self action:@selector(resetView) forControlEvents:UIControlEventTouchUpInside];

    self.imageView = [[UIImageView alloc] init];
    self.imageView.backgroundColor = [UIColor colorWithRed:43.0/255.0 green:39.0/255.0 blue:55.0/255.0 alpha:1.0];

    self.tableView = [[UITableView alloc] init];
    self.tableView.delegate = self;
    self.tableView.dataSource = self;
    self.tableView.rowHeight = 150.0;
    self.tableView.layer.shadowColor = [UIColor blackColor].CGColor;
    self.tableView.layer.shadowOffset = CGSizeMake(0,-5);
    self.tableView.layer.shadowOpacity = 0.5;
    self.tableView.layer.shadowRadius = 20;
    self.tableView.backgroundColor = [UIColor clearColor];
    self.tableView.scrollEnabled = NO;
    self.tableView.clipsToBounds = NO;


    [self.headerView addSubview:self.lblTitle];
    [self.headerView addSubview:self.btnReset];

    [self.scrollView addSubview:self.tableView];

    [self.view addSubview:self.imageView];
    [self.view addSubview:self.scrollView];
    [self.view addSubview:self.headerView];

}

-(void)initConstraints
{
    self.scrollView.translatesAutoresizingMaskIntoConstraints = NO;
    self.headerView.translatesAutoresizingMaskIntoConstraints = NO;
    self.lblTitle.translatesAutoresizingMaskIntoConstraints = NO;
    self.btnReset.translatesAutoresizingMaskIntoConstraints = NO;
    self.imageView.translatesAutoresizingMaskIntoConstraints = NO;
    self.tableView.translatesAutoresizingMaskIntoConstraints = NO;

    id views = @{
                 @"scrollView": self.scrollView,
                 @"headerView": self.headerView,
                 @"lblTitle": self.lblTitle,
                 @"btnReset": self.btnReset,
                 @"imageView": self.imageView,
                 @"tableView": self.tableView
                 };

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[scrollView]|" options:0 metrics:nil views:views]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[scrollView]" options:0 metrics:nil views:views]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.scrollView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0]];



    self.scrollViewTopConstraint = [NSLayoutConstraint constraintWithItem:self.scrollView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1.0 constant:0.0];

    [self.view addConstraint:self.scrollViewTopConstraint];




    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:self.scrollView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[headerView(320)]|" options:0 metrics:nil views:views]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[headerView(50)]" options:0 metrics:nil views:views]];

    [self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[tableView(320)]|" options:0 metrics:nil views:views]];

    [self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-150-[tableView(300)]|" options:0 metrics:nil views:views]];

    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[imageView(320)]|" options:0 metrics:nil views:views]];
    [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[imageView(320)]" options:0 metrics:nil views:views]];

    [self.headerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[lblTitle]|" options:0 metrics:nil views:views]];
    [self.headerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[lblTitle]|" options:0 metrics:nil views:views]];

    [self.headerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[btnReset(80)]-5-|" options:0 metrics:nil views:views]];
    [self.headerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[btnReset]-8-|" options:0 metrics:nil views:views]];
}

-(BOOL)prefersStatusBarHidden
{
    return YES;
}

#pragma mark - TableView Methods -

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return 2;
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellID = @"cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellID];

    if(cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID];
    }

    cell.backgroundColor = [UIColor colorWithRed:0.5 green:0.5 blue:0.5 alpha:1.0];

    return cell;
}

#pragma mark - ScrollView Delegate -

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //NSLog(@"scrollView offset = %lf", scrollView.contentOffset.y);

    if(scrollView.contentOffset.y <= -145)
    {
        //self.scrollView.scrollEnabled = NO;

        self.scrollViewTopConstraint.constant = self.view.bounds.size.height;

        [UIView animateWithDuration:0.5 delay:0.0 options:UIViewAnimationOptionCurveEaseOut animations:^{

            [self.scrollView layoutIfNeeded];

        } completion:^(BOOL finished) {

        }];
    }
}

-(void)resetView
{
    self.scrollViewTopConstraint.constant = 0;

    [UIView animateWithDuration:0.5 delay:0.0 options:UIViewAnimationOptionCurveEaseIn animations:^{

        [self.scrollView layoutIfNeeded];

    } completion:^(BOOL finished) {

    }];
}

打开应用后得到的结果：

然后你向下拖动到边缘，视图会突然打开：

按下红色的重置按钮将其恢复：D