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target - action设计模式的思想

2024-07-19 18:15:32   222人阅读

不同的实例点击效果不同:点击改变自身颜色,点击改变父视图颜色,点击修改视图位置.以上效果可由target - action设计模式实现.
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor yellowColor];
    CustomView *greenView = [[CustomView alloc] initWithFrame:CGRectMake(20, 40, 280, 100)];
    greenView.backgroundColor = [UIColor greenColor];
    [greenView addTarget:self acton:@selector(changeColor:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:greenView];
    [greenView release];
    
    CustomView *redView = [[CustomView alloc] initWithFrame:CGRectMake(20, 200, 280, 100)];
    redView.backgroundColor = [UIColor redColor];
    [redView addTarget:self acton:@selector(changeSuperviewColor:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:redView];
    [redView release];
    
    CustomView *blueView = [[CustomView alloc] initWithFrame:CGRectMake(20, 360, 280, 100)];
    blueView.backgroundColor = [UIColor blueColor];
    [blueView addTarget:self acton:@selector(changelocation:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:blueView];
    [blueView release];
}

- (void)changeColor:(CustomView *)view
{
    view.backgroundColor = [UIColor randomColor];
}

- (void)changeSuperviewColor:(CustomView *)view
{
    view.superview.backgroundColor = [UIColor randomColor];
}

- (void)changelocation:(CustomView *)view
{
    view.center = CGPointMake(arc4random() % 200 + 100, arc4random() % 400 + 100);
}

@interface CustomView ()
{
    id _target;    //目标
    SEL _action;  //行为
    UIControlEvents _controlEvents;
}
@end

//为当前视图指定当视图接收到响应事件之后,由target来通过action方法进行响应.
- (void)addTarget:(id)target acton:(SEL)action forControlEvents:(UIControlEvents)controlEvents
{
    //利用实例变量存储外界传入的参数,方便在其他方法中使用
    _target = target;
    _action = action;
    _controlEvents = controlEvents;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    if (UIControlEventTouchDown == _controlEvents) {
        //当当前视图接收到触摸事件之后,交由target去处理
        [_target performSelector:_action withObject:self];
    }
 }   
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    if (UIControlEventTouchUpInside == _controlEvents) {
        [_target performSelector:_action withObject:self];
    }
}


target - action设计模式的思想


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