Textview中心文本对齐IOS 7答案

【问题标题】：Textview Center Text Alignment IOS 7Textview中心文本对齐IOS 7
【发布时间】：2013-10-13 16:37:57
【问题描述】：

-(void)observeValueForKeyPath:(NSString *)keyPath   ofObject:(id)object   change:(NSDictionary *)change   context:(void *)context 
{
    NSLog(@"Hello");
    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};
}

我在 Viewdidload 中这样称呼它

[myTextView1 addObserver:self forKeyPath:@"contentSize" options:(NSKeyValueObservingOptionNew) context:NULL];

【问题讨论】：

这是垂直对齐吗？你有什么理由在 UILabel 上使用 UITextView 吗？标签将免费为您执行此操作。
stackoverflow.com/questions/17024375/…

标签： iphone ios objective-c

【解决方案1】：

textView.textAlignment = NSTextAlignmentCenter;

【讨论】：

【解决方案2】：

在 iOS7 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};
}

待定义：

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

【讨论】：

这很好用，除非内容适合一行。然后它与底部对齐。如果添加 `CGFloat topCorrect = (height - contentheight * [tv zoomScale])/2.0;`，就完美了。

【解决方案3】：

对于快速：

        itemTextView.addObserver(self, forKeyPath:"contentSize", options: NSKeyValueObservingOptions.New, context: nil)

和

    override func observeValueForKeyPath(keyPath: String!, ofObject object: AnyObject!, change: [NSObject : AnyObject]!, context: UnsafeMutablePointer<Void>) {
    var tv : UITextView = object as UITextView;
    var height = tv.bounds.size.height;
    var contentheight = tv.sizeThatFits(CGSizeMake(tv.frame.size.width,1000)).height


    var topCorrect : CGFloat = height - contentheight;
    if(topCorrect < 0) {
        topCorrect = 0
    }
    tv.contentOffset = CGPointMake(0, -topCorrect/2)

}

【讨论】：