addSubview:

Adds a view to the end of the receiver’s list of subviews.

译：增加一个视图到接收者的子视图列表中。

- (void)addSubview:(UIView *)view

Parameters

view

The view to be added. This view is retained by the receiver. After being added, this view appears on top of any other subviews.

译：view参数代表被增加的view，这个view会被它的接收者retain一次（即引用计数+1）。增加完成之后，这个view将出现在接收者的其他子视图的上面。

ps：关于子视图的出现的层次的问题，可以从这些子视图被保存的数据结构来探寻答案 ，每个视图都有个数组的属性，subviews，这个就是保存的它的子视图的引用。而这个数组的顺序就是代表了各个子视图被加入时的顺序。index=0 的就是最先被加入进去的，以此类推。所以，索引值越高的视图越不容易被覆盖。

Discussion

This method retains view and sets its next responder to the receiver, which is its new superview.

译：这个方法会retain一次view，并且设置它的下一个响应者是receiver，即它的新的父视图。

ps：在removeFromSuperview里已经说过，其实视图直接的操作往往牵涉到两个方面的操作，一个是视图的数据结构，一个是响应者链。当然，addsubview也不例外。

Views can have only one superview. If view already has a superview and that view is not the receiver, this method removes the previous superview before making the receiver its new superview.

译：每一个视图只能有唯一的一个父视图。如果当前操作视图已经有另外的一个父视图，则addsubview的操作会把它先从上一个父视图中移除（包括响应者链），再加到新的父视图上面。

Availability

• Available in iOS 2.0 and later.

See Also

• • – insertSubview:atIndex:
  • – insertSubview:aboveSubview:
  • – insertSubview:belowSubview:
  • – exchangeSubviewAtIndex:withSubviewAtIndex:

addSubview和insertSubview的区别？

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IMGView *imgView = [[IMGView alloc] initWithFrame:CGRectMake(10, 0, 300, 300)];
[self.view addSubview:imgView];
[imgView release];