在 iPhone 上证明 UIVIews：算法帮助

Question

我一直在寻找一种方法来证明在包含视图中对齐 UIView 子类的集合。我的算法有点麻烦，希望有人能帮助发现我的错误。这是我现在所在位置的伪代码：

// 1 see how many items there are
int count = [items count];

// 2 figure out how much white space is left in the containing view
float whitespace = [containingView width] - [items totalWidth];

// 3 Figure out the extra left margin to be applied to items[1] through items[count-1]
float margin = whitespace/(count-1);

// 4 Figure out the size of every subcontainer if it was evenly split
float subcontainerWidth = [containingView width]/count;

// 5 Apply the margin, starting at the second item
for (int i = 1; i < [items count]; i++) {
    UIView *item = [items objectAtIndex:i];
    [item setLeftMargin:(margin + i*subcontainerWidth)];
}

这里的项目似乎没有均匀分布。差远了。我哪里错了？

以下是该算法的实际效果： alt text http://grab.by/1Wcg

编辑：上面的代码是伪代码。我在此处添加了实际代码，但如果您不熟悉three20 项目，则可能没有意义。

@implementation TTTabStrip (JustifiedBarCategory)
- (CGSize)layoutTabs {
    CGSize size = [super layoutTabs];

    CGPoint contentOffset = _scrollView.contentOffset;
    _scrollView.frame = self.bounds;
    _scrollView.contentSize = CGSizeMake(size.width + kTabMargin, self.height);

    CGFloat contentWidth = size.width + kTabMargin;
    if (contentWidth < _scrollView.size.width) {
        // do the justify logic

        // see how many items there are
        int count = [_tabViews count];

        // 2 figure out how much white space is left
        float whitespace = _scrollView.size.width - contentWidth;

        // 3 increase the margin on those items somehow to reflect.  it should be (whitespace) / count-1
        float margin = whitespace/(count-1);

        // 4 figure out starting point
        float itemWidth = (_scrollView.size.width-kTabMargin)/count;
        // apply the margin
        for (int i = 1; i < [_tabViews count]; i++) {
            TTTab *tab = [_tabViews objectAtIndex:i];
            [tab setLeft:(margin + i*itemWidth)];
        }

    } else {
        // do the normal, scrollbar logic
        _scrollView.contentOffset = contentOffset;
    }
    return size;
}
@end

Answer 1

我能够自己让它工作！我对元素应用了错误的边距。问题是我需要在考虑之前元素的原点和宽度时应用边距。

@implementation TTTabStrip (JustifiedBarCategory)
- (CGSize)layoutTabs {
    CGSize size = [super layoutTabs];

    CGPoint contentOffset = _scrollView.contentOffset;
    _scrollView.frame = self.bounds;
    _scrollView.contentSize = CGSizeMake(size.width + kTabMargin, self.height);

    CGFloat contentWidth = size.width + kTabMargin;
    if (contentWidth < _scrollView.size.width) {
        // do the justify logic

        // see how many items there are
        int count = [_tabViews count];

        // 2 figure out how much white space is left
        float whitespace = _scrollView.size.width - contentWidth;

        // 3 increase the margin on those items somehow to reflect.  it should be (whitespace) / count-1
        float margin = whitespace/(count-1);

        // apply the margin
        for (int i = 1; i < [_tabViews count]; i++) {
            // 4 figure out width from the left edge to the right of the 1st element
            float start = [[_tabViews objectAtIndex:i-1] frame].origin.x + [[_tabViews objectAtIndex:i-1] frame].size.width;

            TTTab *tab = [_tabViews objectAtIndex:i];
            [tab setLeft:(start + margin)];
        }
    } else {
        // do the normal, scrollbar logic
        _scrollView.contentOffset = contentOffset;
    }
    return size;
}
@end

Answer 2

coneybeare，感谢您解决这个问题，但您的解决方案并没有按预期工作。它改变了栏上标签的位置，但间距不正确。这似乎对我更有效：

#import "TTTabStrip+Justify.h"
#import <Three20UI/UIViewAdditions.h>

// Width returned by [super layoutTabs] is always 10 px more than sum of tab widths
static CGFloat const kContentWidthPadding = 10;
// Adds fixed margin to left of 1st tab, right of last tab
static CGFloat const kHorizontalMargin = 5;

@implementation TTTabStrip (JustifyCategory)

- (CGSize)layoutTabs {
    CGSize size = [(TTTabStrip*)super layoutTabs];

    CGPoint contentOffset = _scrollView.contentOffset;
    _scrollView.frame = self.bounds;
    _scrollView.contentSize = CGSizeMake(size.width, self.height);

    CGFloat contentWidth = size.width - kContentWidthPadding + 2 * kHorizontalMargin;
    if (contentWidth < _scrollView.size.width) {
        // do the justify logic

        // see how many items there are
        int count = [_tabViews count];

        // calculate remaining white space
        float whitespace = _scrollView.size.width - contentWidth;

        // calculate necessary spacing between tabs
        float spacing = whitespace / (count + 1);       

        // apply the spacing
        for (int i = 0; i < count; i++) {
            CGFloat lastTabRight = kHorizontalMargin;

            if (i > 0) {
                TTTab *lastTab = [_tabViews objectAtIndex:i-1];
                lastTabRight = [lastTab right];
            }

            TTTab *tab = [_tabViews objectAtIndex:i];
            [tab setLeft:(lastTabRight + spacing)];
        }

    } else {
        // do the normal, scrollbar logic
        _scrollView.contentOffset = contentOffset;
    }
    return size;
}

@end

Morgz，我也遇到了几个编译器错误。我需要导入 UIViewAdditions.h 并告诉它 super 是一个 TTTabStrip。