仿抖音评论手势拖拽 iOS

 

通过观察可以发现抖音的评论视图是从底部弹出的，包括顶部视图和UITableView视图，

1.经过分析可以知道评论视图最底部是一个透明的UIView，并且添加了手势UIPanGestureRecognizer。

2.当UITableView滑动到最顶部时，下拉白色背景视图可以滑动消失

3.当UITableView滑动时，白色背景视图不滑动

4.当手指点击或者拖动上面的空白区域或关闭按钮，视图消失

下面来说说具体的实现：

1.初始化视图并添加手势，需要遵循代理 UIGestureRecognizerDelegate

@property (nonatomic, strong) UIView *bgView;//白色背景视图

- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        self.initOriginY = 100;
        self.needReplaceY = 120;
        self.backgroundColor = [UIColor clearColor];
        
        self.bgView = [[UIView alloc] initWithFrame:CGRectMake(0, self.initOriginY, UIScreenWidth, UIScreenHeight - self.initOriginY)];
        self.bgView.backgroundColor = [UIColor whiteColor];
        [self.bgView setCorner:UIRectCornerTopLeft | UIRectCornerTopRight cornerRadius:7];
        [self addSubview:self.bgView];//添加手势
        UIPanGestureRecognizer *panGesture = [UIPanGestureRecognizer new];
        panGesture.delegate = self;
        //cancelsTouchesInView 默认 YES，自定义的手势响应后，系统手势不再响应，但自定义手势识别前，会先执行系统手势。设置为 NO 后，自定义手势和系统手势会同时识别响应。
        panGesture.cancelsTouchesInView = NO;
        [panGesture addTarget:self action:@selector(panGestureAction:)];
        [self addGestureRecognizer:panGesture];
    }
    return self;
}

将列表加到白色背景视图上，我这儿用的是 UICollectionView，因为列表是瀑布流 ，如果您们用的是UITableView，作相应的变化即可。

@property (nonatomic, strong) UICollectionView *collectionView;

[self.bgView addSubview:self.collectionView];

2.手势代理处理

@property (nonatomic, assign) CGFloat beginContentOffsetY;//self.collectionView 偏移的y坐标
@property (nonatomic, assign) CGFloat lastTouchPointY;//记录一下开始拖动时的y坐标
@property (nonatomic, assign) BOOL isUpPan;//是否上拉
@property (nonatomic, assign) CGFloat initOriginY;//白色背景视图顶部y坐标
@property (nonatomic, assign) CGFloat needReplaceY;//拖动距离超过此距离时才识别手势

- (void)panGestureAction:(UIPanGestureRecognizer *)gestureRecognizer {
    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view];
    
    //self.collectionView拖动时
    if (self.collectionView.panGestureRecognizer.state != UIGestureRecognizerStatePossible) {
        //self.collectionView拖动时如果 contentOffset.y > 0 就不走自定义手势
        if (self.collectionView.contentOffset.y > 0) {
            return;
        }
    }

    if (translation.y > self.beginContentOffsetY) {
        self.bgView.top = translation.y - self.beginContentOffsetY  + self.initOriginY;
    } else {
        self.bgView.top = self.initOriginY;
    }
    
    if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {
        //是否上拉
        self.isUpPan = ([gestureRecognizer locationInView:self].y - self.lastTouchPointY < 0 && fabs([gestureRecognizer velocityInView:self].y) > 10);
        if (translation.y > self.needReplaceY && !self.isUpPan) {
            //大于需求拖动的距离并且是下拉才取消视图
            [self dissmis];
        } else {
            //复位
            [UIView animateWithDuration:0.2f animations:^{
                self.bgView.top = self.initOriginY;
            }];
        }
    } else if (gestureRecognizer.state == UIGestureRecognizerStateBegan) {
        //
        self.beginContentOffsetY = self.collectionView.contentOffset.y;
        //记录一下开始拖动时的y坐标
        self.lastTouchPointY = [gestureRecognizer locationInView:self].y;
    }
}

- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [super touchesEnded:touches withEvent:event];
    UITouch * aTouch = touches.anyObject;
    CGPoint aPoint = [aTouch locationInView:self];
    //点击透明背景取消视图
    if (aPoint.y < self.initOriginY) {
        [self dissmis];
    }
}

3.展示、取消视图实现

- (void)show {
    [UIView animateWithDuration:0.3f animations:^{
        self.top = 0;
    }];
}

- (void)dissmis {
    [UIView animateWithDuration:0.2f animations:^{
        self.bgView.top = UIScreenHeight;
    } completion:^(BOOL finished) {
        [self removeFromSuperview];
    }];
}

4.UIView的扩展设置圆角

/// 设置圆角
/// @param corner 圆角类型
/// @param cornerRadius 圆角大小
- (void)setCorner:(UIRectCorner)corner cornerRadius:(CGFloat)cornerRadius {
    CAShapeLayer *mask = [CAShapeLayer layer];
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:self.bounds byRoundingCorners:corner cornerRadii:CGSizeMake(cornerRadius*2, cornerRadius*2)];
    mask.path = path.CGPath;
    self.layer.mask = mask;
}

 5.调用方式

        RecommendView *recommendView = [[RecommendView alloc] initWithFrame:CGRectMake(0, UIScreenHeight, UIScreenWidth, UIScreenHeight)];
        self.view addSubview:recommendView];
        [recommendView show];

备注：

translationInView : 手指在视图上移动的位置（x,y）向下和向右为正，向上和向左为负。

locationInView ： 手指在视图上的位置（x,y）就是手指在视图本身坐标系的位置。

velocityInView： 手指在视图上移动的速度（x,y）, 正负也是代表方向，值得一体的是在绝对值上|x| > |y| 水平移动， |y|>|x| 竖直移动。