iOS UIButton加在window上点击无效果问题

UIButton加在window上，点击没有效果，找了很久，原来是没有加上这名：[self.window makeKeyAndVisible];

self.window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
    ViewController *vc = [[ViewController alloc] init];
    self.window.rootViewController = vc;
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    view1 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view1.backgroundColor = [UIColor blueColor];
    [self.window addSubview:view1];

    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view2.backgroundColor = [UIColor yellowColor];
    [self.window addSubview:view2];

    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view3.backgroundColor = [UIColor redColor];
    [self.window addSubview:view3];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(, , , );
    button.userInteractionEnabled = YES;
    button.backgroundColor = [UIColor greenColor];
    [button setTitle:@"change" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(changeView) forControlEvents:UIControlEventTouchUpInside];
    [self.window addSubview:button];
    NSLog(@"%@",self.window.subviews);

- (void)changeView
{
    [self.window bringSubviewToFront:view1];
     NSLog(@"%@",self.window.subviews);
}

不要直接加在window上，加在ViewController view上点击有效果

view1 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view1.backgroundColor = [UIColor blueColor];
    [self.view addSubview:view1];

    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view2.backgroundColor = [UIColor yellowColor];
    view2.tag = ;
    [self.view addSubview:view2];

    UIView *view3 = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
    view3.backgroundColor = [UIColor redColor];
    [self.view addSubview:view3];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(, , , );
    button.userInteractionEnabled = YES;
    button.backgroundColor = [UIColor greenColor];
    [button setTitle:@"change" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(changeView) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    NSLog(@"%@",self.view.subviews);

- (void)changeView
{
    [self.view bringSubviewToFront:view1];
    UIView *view = [self.view viewWithTag:];
    view.backgroundColor = [UIColor purpleColor];
    NSLog(@"%@",self.view.subviews);
}