UITextView垂直居中对齐文本

我想在UItextView垂直居中对齐文本。

我正在使用以下代码

 UITextView *tv = object; CGFloat topCorrect = ([tv bounds].size.height - [tv contentSize].height * [tv zoomScale])/2.0; topCorrect = ( topCorrect < 0.0 ? 0.0 : topCorrect ); tv.contentOffset = (CGPoint){.x = 0, .y = -topCorrect} 

;

不知怎的，这在iOS 5中不起作用，因为返回的contentSize与iOS6中的不同。

任何想法为什么相同textView的contentSize在iOS 5和iOS 6中有所不同？

Answer 1

加载视图时，为UITextView的contentSize键值添加一个观察者： –

 - (void) viewDidLoad { [textField addObserver:self forKeyPath:@"contentSize" options:(NSKeyValueObservingOptionNew) context:NULL]; [super viewDidLoad]; } 

每次contentSize值更改时调整contentOffset： –

  -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { UITextView *tv = object; CGFloat topCorrect = ([tv bounds].size.height - [tv contentSize].height * [tv zoomScale])/2.0; topCorrect = ( topCorrect < 0.0 ? 0.0 : topCorrect ); tv.contentOffset = (CGPoint){.x = 0, .y = -topCorrect}; } 

希望它能帮到你......

你可以从中获取指南

https://github.com/HansPinckaers/GrowingTextView

Answer 2

在iOS7上的observeValueForKeyPath方法上试试这个：

 -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { UITextView *tv = object; CGFloat height = [tv bounds].size.height; CGFloat contentheight; if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"7")) { contentheight = [tv sizeThatFits:CGSizeMake(tv.frame.size.width, FLT_MAX)].height; NSLog(@"iOS7; %f %f", height, contentheight); }else{ contentheight = [tv contentSize].height; NSLog(@"iOS6; %f %f", height, contentheight); } CGFloat topCorrect = height - contentheight; topCorrect = (topCorrect <0.0 ? 0.0 : topCorrect); tv.contentOffset = (CGPoint){.x = 0, .y = -topCorrect}; } 

被定义为：

 #define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v) ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending) 

Answer 3

我修改了Arpit的解决方案，因此它可以适应扩展的textview contentView

 static NSString *const kContentOffsetKeyPath = @"contentOffset"; -(void)viewDidLoad { [self.replyTextView addObserver:self forKeyPath:kContentOffsetKeyPath options:(NSKeyValueObservingOptionNew) context:NULL]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if ([keyPath isEqualToString:kContentOffsetKeyPath]) { // To keep scrolling to bottom while typing and text content view is larger than maximum limit if (textView.contentSize.height > singleLineHeight) { UITextView *textView = object; CGFloat topCorrect = ([textView bounds].size.height - [textView contentSize].height * [textView zoomScale]) / 2.0; CGFloat fineTune = -3.0; topCorrect = (topCorrect < fineTune ? fineTune : topCorrect); // To avoid recursion [textView removeObserver:self forKeyPath:kContentOffsetKeyPath]; textView.contentOffset = (CGPoint){.x = 0, .y = -topCorrect}; // add observer back [textView addObserver:self forKeyPath:kContentOffsetKeyPath options:(NSKeyValueObservingOptionNew) context:NULL]; } } } - (void)dealloc { [self.replyTextView removeObserver:self forKeyPath:kContentOffsetKeyPath]; }