iPhone的scrollView使用id动态添加元素
我想用很多不同的 UI 元素填充滚动视图。 因此，我想我应该编写一个方法来记住滚动视图中的当前位置，并将元素添加到滚动视图的当前位置。
像这样的事情：
- (void)addUIElement:(id)element withWidth:(CGFloat)width andHeight:(CGFloat)height andYGap:(CGFloat)YGap {
element.frame = CGRectMake(currentScrollPos.x, (currentScrollPos.y + YGap), width, height);
[scrolly addSubview:element];
//And then set the current scroll position here
}
不幸的是，当我尝试访问 element.frame = ... 时，我收到对非结构或联合中的成员的请求。当我尝试执行 [element frame] = ... 需要左值作为赋值的左操作数。
现在，首先我不确定将对象动态添加到滚动视图的最佳方法是什么。也许任何人都有更好或更简单的方法。
另一方面，我不明白为什么上面的方法不起作用？！我是否必须将我的元素投射到实际的班级中？我以为我不必这样做......而且那样我的方法就不再有意义了。或者至少需要更多步骤......
I want to populate a scrollView with quite a few different UI elements.
Therefore I thought I would write a method that remembers the current Position in the scrollView and just adds the element to the scrollView at the current Position.
Something like:
- (void)addUIElement:(id)element withWidth:(CGFloat)width andHeight:(CGFloat)height andYGap:(CGFloat)YGap {
element.frame = CGRectMake(currentScrollPos.x, (currentScrollPos.y + YGap), width, height);
[scrolly addSubview:element];
//And then set the current scroll position here
}
Unfortunately when I try to do access element.frame = ..., I get request for member in something not a structure or union. When I try to do [element frame] = ... Lvalue required as left operand of assignment.
Now, first of all I am not sure what's the best way to dynamically add objects to a scrollview. Maybe anyone has a better or easier approach.
Then on the other hand, I don't get why the above does not work?! Would I have to cast my element to the actual class? I thought I would not have to do so... Also then my method would not make that much sense anymore. Or at least would require some more steps...
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我认为这应该有效：
但是，如果您在方法中使用不同的 UI 元素，您可以将元素参数设置为 UIView* 而不是 id 吗？这样你的代码将适用于所有 UIView 子类（我想这就是你真正需要的）
This should work I think:
However if you work with different UI elements in your method may be you can make your elements parameter UIView* instead of id? This way your code will work for all UIView subclasses (which is what you actually need I suppose)
不同之处在于“id”没有任何对框架的引用。它可以是任何东西。您想在方法声明中执行
(UIView *)element，或者在对 element.frame 的调用中执行((UIView *)element).frame。（是的，您放在屏幕上的所有内容都继承自
UIView-UIButton、UIImageView等）The difference is that "id" doesn't have any kind of reference to a frame. It could be anything. You want to instead do
(UIView *)elementin the method declaration, or alternatively in the call to element.frame, you would do((UIView *)element).frame.(And yeah, all things that you put on the screen are inheriting from
UIView--UIButton,UIImageView, etc.)