Ios UITextView垂直居中对齐文本

我想在

UItextView

中将文本垂直居中对齐

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}

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}

)

这在iOS 5中不起作用，因为返回的contentSize与我在iOS 6中得到的不同

---

知道为什么同一文本视图的

contentSize

在iOS 5和iOS 6中不同吗？

加载视图时，为UITextView的contentSize键值添加观察者：-

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

每次更改contentSize值时调整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};
}

-（void）observeValueForKeyPath:（NSString*）对象的键路径：（id）对象更改：（NSDictionary*）更改上下文：（void*）上下文{
UITextView*tv=对象；
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}；
}

希望它能帮助你

你可以从我这儿领路

---

在iOS7上的observeValueForKeyPath方法上尝试以下操作：

-(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};
}

---

我已经修改了Arpit的解决方案，使其能够适应扩展的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];
    }

静态NSString*const kContentOffsetKeyPath=@“contentOffset”；
-（无效）viewDidLoad{
[self.replyTextView addObserver:self
forKeyPath:kContentOffsetKeyPath
选项：（NSKeyValueObservingOptionNew）
上下文：NULL]；
}
-（void）observeValueForKeyPath:（NSString*）对象的键路径：（id）对象更改：（NSDictionary*）更改上下文：（void*）上下文{
if（[keyPath isEqualToString:kContentOffsetKeyPath]）{
//在键入和文本内容视图大于最大限制时保持滚动到底部
如果（textView.contentSize.height>singleLineHeight）{
UITextView*textView=对象；
CGFloat topCorrect=（[textView bounds].size.height-[textView contentSize].height*[textView zoomScale]）/2.0；
CGFloat fineTune=-3.0；
topCorrect=（topCorrect

这不会使文本始终垂直居中，因为如果调整UITextView的大小（例如，当键盘出现时），则UITextView中的内容将恢复为顶部对齐。这是一段非常棒的代码，除了作为键路径观察者的价值之外。谢谢。我在

UITableView

中使用此代码时发生崩溃。在ios8上运行良好，但在完成对齐后还需要删除观察者。将此行添加为

observeValueForKeyPath

方法的最后一行：

[tv removeObserver:self forKeyPath:@“contentSize”]可能重复的
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];
    }