iOS中navigationItem的titleView如何居中

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开发过程中，发现titleview很难居中，通过各种尝试终于找到了解决方法。

首先清楚你个概念：

问题原因：

经过尝试，发现titleview的起点位置和尺寸依赖于leftBarButtonItem和rightBarButtonItem的位置。

解决方案：

设置titleview之前，先初始化leftBarButtonItem和rightBarButtonItem的位置，然后根据leftBarButtonItem和rightBarButtonItem的位置来使titleview居中。

//以下使参考代码。

//必须放在 leftBarButtonItem和rightBarButtonItem初始化之后调用

- (void)setDisplayCustomTitleText:(NSString*)text

{

// Init views with rects with height and y pos

UIView *titleView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];

// Use autoresizing to restrict the bounds to the area that the titleview allows

titleView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin;

titleView.autoresizesSubviews = YES;

titleView.backgroundColor = [UIColorclearColor];

UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];

titleLabel.tag = kUIVIEWCONTROLLER_LABEL_TAG;

titleLabel.backgroundColor = [UIColor clearColor];

titleLabel.font = [UIFont fontWithName:@"Helvetica-Bold" size:16];

titleLabel.textAlignment = UITextAlignmentCenter;

titleLabel.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

titleLabel.textColor = TC_CNavigationTitleColor;

titleLabel.lineBreakMode = UILineBreakModeClip;

titleLabel.textAlignment = UITextAlignmentCenter;

titleLabel.autoresizingMask = titleView.autoresizingMask;

CGRect leftViewbounds = self.navigationItem.leftBarButtonItem.customView.bounds;

CGRect rightViewbounds = self.navigationItem.rightBarButtonItem.customView.bounds;

CGRect frame;

CGFloat maxWidth = leftViewbounds.size.width > rightViewbounds.size.width ? leftViewbounds.size.width : rightViewbounds.size.width;

maxWidth += 15;//leftview 左右都有间隙，左边是5像素，右边是8像素，加2个像素的阀值 5 ＋ 8 ＋ 2

frame = titleLabel.frame;

frame.size.width = 320 - maxWidth * 2;

titleLabel.frame = frame;

frame = titleView.frame;

frame.size.width = 320 - maxWidth * 2;

titleView.frame = frame;

// Set the text

titleLabel.text = text;

// Add as the nav bar's titleview

[titleView addSubview:titleLabel];

self.navigationItem.titleView = titleView;

}

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