是否可以合并/交叉两个 UIView 而不是让它们重叠？

Question

给定两个带有UIPanGestureRecognizers 的边框的UIViews：

如果我将左侧的 UIView 拖到右侧的 UIView 上，这是通常的行为：

是否有可能让他们在看起来合并的地方执行以下行为？：

寻找最简单的方法来做到这一点！

Answer 1

一种方法是使用多个 sibling 层和​​zPosition。为了达到这个效果，你添加了两层，一层用于边框，一层用于内容。并且边框层的zPosition 比内容要小。当然，使用UIPanGestureRecognizer 移动图层。

MP4 version

斯威夫特：

import UIKit

class MergingView: UIView {

    let borderLayer = CALayer()
    let backgroundLayer = CALayer()

    override func layoutSubviews() {
        super.layoutSubviews()

        addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:))))

        borderLayer.borderWidth = 5
        borderLayer.frame = frame
        borderLayer.zPosition = 10
        borderLayer.borderColor = UIColor.black.cgColor
        superview?.layer.addSublayer(borderLayer)

        backgroundLayer.frame = CGRect(x: frame.origin.x + 5, y: frame.origin.y + 5, width: frame.width - 10, height: frame.height - 10)
        backgroundLayer.zPosition = 20
        backgroundLayer.backgroundColor = UIColor.white.cgColor
        superview?.layer.addSublayer(backgroundLayer);
    }

    @objc func handlePan(_ recognizer: UIPanGestureRecognizer) {
        CATransaction.begin()
        CATransaction.setValue(kCFBooleanTrue, forKey: kCATransactionDisableActions)

        let translation = recognizer.translation(in: self)
        frame = self.frame.offsetBy(dx: translation.x, dy: translation.y)
        recognizer.setTranslation(CGPoint.zero, in: self)

        borderLayer.frame = borderLayer.frame.offsetBy(dx: translation.x, dy: translation.y)
        backgroundLayer.frame = backgroundLayer.frame.offsetBy(dx: translation.x, dy: translation.y)

        CATransaction.commit()
    }
}

---

Objective-C 标头：

#import <UIKit/UIKit.h>

@interface MVMergingView : UIView

@end

Objective-C 实现：

#import "MVMergingView.h"

@interface MVMergingView ()

@property (strong) CALayer *borderLayer;
@property (strong) CALayer *backgroundLayer;

@end

@implementation MVMergingView

- (void)layoutSubviews {
    [super layoutSubviews];

    [self addGestureRecognizer:[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]];

    CALayer *borderLayer = [CALayer layer];
    borderLayer.borderWidth = 5.f;
    borderLayer.frame = self.frame;
    borderLayer.zPosition = 10;
    borderLayer.borderColor = UIColor.blackColor.CGColor;
    self.borderLayer = borderLayer;
    [self.superview.layer addSublayer:borderLayer];

    CALayer *backgroundLayer = [CALayer layer];
    backgroundLayer.frame = CGRectMake(self.frame.origin.x + 5.f, self.frame.origin.y + 5.f, self.frame.size.width - 10, self.frame.size.height - 10);
    backgroundLayer.zPosition = 20;
    backgroundLayer.backgroundColor = UIColor.whiteColor.CGColor;
    self.backgroundLayer = backgroundLayer;
    [self.superview.layer addSublayer:backgroundLayer];
}

- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
    [CATransaction begin];
    [CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];

    CGPoint translation = [recognizer translationInView:self];
    self.frame = CGRectOffset(self.frame, translation.x, translation.y);
    [recognizer setTranslation:CGPointZero inView:self];

    self.borderLayer.frame = CGRectOffset(self.borderLayer.frame, translation.x, translation.y);
    self.backgroundLayer.frame = CGRectOffset(self.backgroundLayer.frame, translation.x, translation.y);

    [CATransaction commit];
}

@end

---

示例回购：https://github.com/dimitarnestorov/MergingView

Answer 2

您的“合并”而不是重叠的要求似乎只是因为边界而存在。如果没有边界，就不需要合并；您只需将它们重叠。所以问题就变成了如何处理边界。

我在想也许你可以有一个特殊的 UIView 子类 (MergingView?) 作为 2 个视图的父类；边框视图和内容视图。既然边框和内容在不同的视图中，“合并”就变得微不足道了。

当我们将A 放在B 之上时，我们所要做的就是将A 的边框视图和内容视图交给B（所以它们现在是B 的子视图），然后将B 的所有边框视图发送给后面。

你可以继续与B合并更多，过程相同。

这适合您的用例吗？如果需要，很乐意发布代码。