UIView 中的控件事件穿透 Passthrough 的实现(转)

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:

![](http://unmi.cc/wp-content/uploads/2012/02/passthrough1.png "passthrough1") ![](http://unmi.cc/wp-content/uploads/2012/02/passthrough2.png "passthrough1")
![](http://unmi.cc/wp-content/uploads/2012/02/passthrough3.png "passthrough1")

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

本文原始链接 [http://unmi.cc/uiview-event-passthrough/](http://unmi.cc/uiview-event-passthrough/), 来自 [隔叶黄莺 Unmi Blog](http://unmi.cc/)
ViewController.h
//
//  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

//
//  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

//
//  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

//
//  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

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