iOS 子視圖超過了父視圖沒法響應事件

當按鈕超過了父視圖範圍，點擊是沒有反應的。由於消息的傳遞是從最下層的父視圖開始調用hittest方法

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {  
    UIView *view = [super hitTest:point withEvent:event];  
    return view;  
}

須要重寫這個方法

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {  
    UIView *view = [super hitTest:point withEvent:event];  
    if (view == nil) {  
    CGPoint tempoint = [btn convertPoint:point fromView:self];  
        if (CGRectContainsPoint(btn.bounds, tempoint))   
    {  
           view = btn;  
        }  
     }             
    return view;  
}