有个需求，就是需要超出视图部分上面的按钮能够响应点击事件，大概如图所示：

Paste_Image.png

说一下大概情况，就是有一个容器v1(红色)，上面又一个元素v2（绿色）。v2的上面又有一个元素v3（蓝色）,v3有一部分超出了v2的边界，并且超出部分上面还存在一个按钮（右下角）。现在要求点击右下角按钮，能够让按钮响应事件。

绘制界面的代码如下：

 do {
        View1 *v = [View1 new];
        self.v1 = v;
        v.backgroundColor = [UIColor redColor];
        [self.view addSubview:v];
        [v makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(300);
            make.height.equalTo(300);
            make.top.equalTo(self.view);
            make.centerX.equalTo(self.view);
        }];
    } while (0);
    do {
        View2 *v = [View2 new];
        self.v2 = v;
        v.backgroundColor = [UIColor greenColor];
        [_v1 addSubview:v];
        [v makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(100);
            make.height.equalTo(100);
            make.top.equalTo(self.view);
            make.centerX.equalTo(self.view);
        }];
    } while (0);
    do {
        View3 *v = [View3 new];
        self.v3 = v;
        v.backgroundColor = [UIColor blueColor];
        [_v2 addSubview:v];
        [v makeConstraints:^(MASConstraintMaker *make) {
            make.width.equalTo(100);
            make.height.equalTo(100);
            make.centerX.equalTo(self.view).offset(50);
            make.bottom.equalTo(_v2).offset(20);
        }];
    } while (0);
    UIButton  *btn = [UIButton new];
    [btn setBackgroundImage:[WJCommonUtils imageFromColor:RGBCOLOR(200, 100, 100)] forState:UIControlStateNormal];
     [btn setBackgroundImage:[WJCommonUtils imageFromColor:RGBCOLOR(100, 100, 200)] forState:UIControlStateHighlighted];
    [_v3 addSubview:btn];
    [btn makeConstraints:^(MASConstraintMaker *make) {
        make.width.height.equalTo(20);
        make.right.equalTo(_v3);
        make.bottom.equalTo(_v3);
    }];

我们知道了iOS下的事件传递机制，因此可以通过重写view的hitTest方法来控制事件传递。因为可以这样改：

重写v1的hittest方法:

#import "View1.h"
#import "choose.h"

@implementation View1

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    NSLog(@"View1 hitTest start ");
    UIView *item = [super hitTest:point withEvent:event];
    if (item == self) {
        NSArray *array = [choose choose:@"View3"];
        if (array.count>0) {
            UIView *v = (UIView *)array.lastObject;
            CGPoint p = [self convertPoint:point toView: v];
            item = [v hitTest:p withEvent:event];
        }
    }
    NSLog(@"View1 hitTest - %@",item);
    return item;
}

@end

搞定!