ios - addSubview 改变一个对象在 scroll.subviews 中的索引

Question

我在循环 FOR 内的 UIScrollView 中添加了对象，但是在第二次交互之后 subviews 的索引发生了变化。

当我创建 ScrollView 时:

scroll.subviews :(
"<UIImageView: 0x147aeee0; frame = (1017 186; 7 5); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x147aef50>>",
"<UIImageView: 0x147aefa0; frame = (1019 184; 5 7); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x147af010>>"

)

在我使用 [scroll addSubview:btn];

进行循环后

首先

scroll.subviews :(
"<UIImageView: 0x147aeee0; frame = (1017 186; 7 5); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x147aef50>>",
"<UIImageView: 0x147aefa0; frame = (1019 184; 5 7); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x147af010>>",
"<ContentButton: 0x13fdc610; baseClass = UIButton; frame = (15 10; 221 173); opaque = NO; tag = 1; layer = <CALayer: 0x1034cc00>>"

)

第二个(将最后一个对象更改为索引 0)

scroll.subviews :(
"<ContentButton: 0x13fdc610; baseClass = UIButton; frame = (15 10; 221 173); opaque = NO; tag = 1; layer = <CALayer: 0x1034cc00>>",
"<UIImageView: 0x147aefa0; frame = (1019 184; 5 7); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x147af010>>",
"<UIImageView: 0x147aeee0; frame = (1017 186; 7 5); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x147aef50>>",
"<ContentButton: 0x105ddf70; baseClass = UIButton; frame = (246 10; 221 173); opaque = NO; tag = 149; layer = <CALayer: 0x105523e0>>"

)

第三次以此类推，对象会正常添加(在最后一个索引中)

scroll.subviews :(
"<ContentButton: 0x13fdc610; baseClass = UIButton; frame = (15 10; 221 173); opaque = NO; tag = 1; layer = <CALayer: 0x1034cc00>>",
"<UIImageView: 0x147aefa0; frame = (1019 184; 5 7); alpha = 0; opaque = NO; autoresize = LM; userInteractionEnabled = NO; layer = <CALayer: 0x147af010>>",
"<UIImageView: 0x147aeee0; frame = (1017 186; 7 5); alpha = 0; opaque = NO; autoresize = TM; userInteractionEnabled = NO; layer = <CALayer: 0x147aef50>>",
"<ContentButton: 0x105ddf70; baseClass = UIButton; frame = (246 10; 221 173); opaque = NO; tag = 149; layer = <CALayer: 0x105523e0>>",
"<ContentButton: 0x13f1dc80; baseClass = UIButton; frame = (477 10; 221 173); opaque = NO; tag = 3; layer = <CALayer: 0x13f1dd20>>"

)

问题出在第二次交互中，为什么最后一个对象(ContentButton)在索引 2 中并变为索引 0？

for (obj * objScroll in arrayChaObj)
    {                
        // UIButton
        ContentButton * btn = [[ContentButton alloc] initWithFrame:CGRectMake(btContentPosXChaObj,
                                                                    10,
                                                                    imgButtonScroll.size.width,
                                                                    imgButtonScroll.size.height)];

        btContentPosXChaObj += 10 + imgButtonScroll.size.width;
        [scroll addSubview:btn];

        NSLog(@"scroll.subviews :%@",scroll.subviews);
        [scroll setContentSize:CGSizeMake(btContentPosXChaObj, imgButtonScroll.size.height+10)];
    }

Answer 1

这只是一个大胆的猜测。

当您第一次调用 setContentSize: 时会发生什么？好吧，这两个 ImageView 最终都在内容区域之外。它们永远不会显示。

我想 scrollview 然后优化 subview 的顺序并将不可见的放在最后，这可能会改进其剪裁(重绘)功能。

目前我没有时间检查和实验，但这对我来说是一个合理的解释。