我们在有多个 UIView 层叠时，比如一个按钮被一个 UIView 遮盖时，想要在点击最上层的 UIView 时能触发按钮的相应事件，我们该如何实现呢，初步可以想到几种办法：
1. 把按钮上层的所有 UIView 的 userInteractionEnabled 属性设置为 NO，要是 UIView 有自己的交互事件该如何办呢？而且这个 userInteractionEnabled 不能动态设置，等到点击后决定设置它的 NO 是没用的
2. UIView 接受到点击事件后主动去触发下面按钮的点击，这时的关题有三，按钮没有点击过程中的交换效果、多层 UIView 时不切实际，逐层下传吗、还有就是其他双击、三击或别的手势如何处理
我也一直被前面两种方式纠缠着，同时也让 UIPopoverController 的 NSArray *passthroughViews 属性提醒着，因为对于 UIPopoverController，设置到它的 passthoughViews 属性中的控件事件可以完全从 UIDimmingView 下透出来。但苦于不可能看到 UIPopoverController 的源码，还是后面一而再的 Google 终于发现了 UIView 的方法：
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event; // recursively calls -pointInside:withEvent:. point is in the receiver's coordinate system
只要实现了最顶层的 UIView 的 hitTest 方法，在某些情况返回下层的某个按钮实例，即相当于把那个按钮的事件透出来了，比如在点击落在该按钮上时，不管这个按钮在 UIView 下多少层都可以把它挖出来。
先看效果图：
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三个图分别是：
1. 所见到的，按钮被半透明红色 View 遮住了一部分
2. 可点击未遮住的按钮部分，可看到按钮被点下未抬起的效果
3. 在红色的 View 中点击按钮被遮住部分，同样触发了按钮的相应事件，且有中间效果，也就是说按钮穿透出来了
再看代码实现，有两部分代码，分别是 ViewController 和 CustomController
ViewController.h
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//// ViewController.h//// Created by Unmi on 11/15/11.// Copyright (c) 2011 http://unmi.cc. All rights reserved.//#import <UIKit/UIKit.h>@interface ViewController : UIViewController{}@end |
ViewController.h
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//// ViewController.m//// Created by Unmi on 11/15/11.// Copyright (c) 2011 http://unmi.cc. All rights reserved.//#import "ViewController.h"#import "CustomView.h"@implementation ViewController{ UIButton *passthroughButton;}#pragma mark - View lifecycle- (void)viewDidLoad{ [super viewDidLoad]; passthroughButton = [UIButton buttonWithType:UIButtonTypeRoundedRect]; [passthroughButton setTitle:@"Passthrough" forState:UIControlStateNormal]; [self.view addSubview:passthroughButton]; passthroughButton.frame = CGRectMake(20, 50, 120, 28); [passthroughButton release]; CustomView *customView = [[CustomView alloc] initWithFrame:CGRectMake(80, 10, 300, 200)]; customView.backgroundColor = [UIColor colorWithRed:1 green:0 blue:0 alpha:.5]; customView.passthroughViews = [NSArray arrayWithObject:passthroughButton]; [self.view addSubview:customView]; [customView release];}- (void)dealloc { [super dealloc];}@end |
CustomView.h
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//// CustomView.h// TestPopover//// Created by Unmi on 2/19/12.// Copyright (c) 2012 http://unmi.cc. All rights reserved.//#import <UIKit/UIKit.h>@interface CustomView : UIView@property (nonatomic, copy) NSArray *passthroughViews;@end |
CustomView.m
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//// CustomView.m//// Created by Unmi on 2/19/12.// Copyright (c) 2012 http://unmi.cc. All rights reserved.//#import "CustomView.h"@interface CustomView()-(BOOL) isPassthroughView: (UIView*) view;@end@implementation CustomView{ BOOL testHits; }@synthesize passthroughViews=_passthroughViews;-(UIView*) hitTest:(CGPoint)point withEvent:(UIEvent *)event{ if(testHits){ return nil; } if(!self.passthroughViews || (self.passthroughViews && self.passthroughViews.count == 0)){ return self; } else { UIView *hitView = [super hitTest:point withEvent:event]; if (hitView == self) { //Test whether any of the passthrough views would handle this touch testHits = YES; CGPoint superPoint = [self.superview convertPoint:point fromView:self]; UIView *superHitView = [self.superview hitTest:superPoint withEvent:event]; testHits = NO; if ([self isPassthroughView:superHitView]) { hitView = superHitView; } } return hitView; }}- (BOOL)isPassthroughView:(UIView *)view { if (view == nil) { return NO; } if ([self.passthroughViews containsObject:view]) { return YES; } return [self isPassthroughView:view.superview];} -(void) dealloc{ self.passthroughViews = nil;}@end |
关键要理解 hitTest 方法的作用，可参考：
1. http://blog.sina.com.cn/s/blog_677089db01012wpg.html
2. https://github.com/werner77/WEPopover