如何在iOS中將UITextView內容水平居中，但不使用居中對齊？

Question

我想達到一些非常具體的東西。這很難用文字描述，所以這裏有一些模型。

當前階段：我有一個UITextView，其自動佈局約束設置爲與父容器一樣寬。

我想達到的目標：我想水平居中的內容在UITextView中，使他們出現在中心，但仍然左對齊

大多數解決方案依靠TextAlignCenter選項居中文本水平，但這不是我想要的東西，因爲它會出現這樣，而不是：

任何方式來實現這一目標？

我已經試過以下：

1. textview.sizeToFit（）似乎調整高度而不是寬度
2. textview.contentOffset似乎並沒有工作
3. 去除自動版式的約束並使用編輯器>修復所有範圍似乎在UIButtons工作，但不是UITextView的..

我想這樣做的原因是，雖然它不是在iPhone noticable，在iPad上，如果文本AR簡而言之，它們會一直顯示在左邊，這與我的其他應用程序中的其他可交互按鈕非常相似。

Answer 1

它看起來像你可能使用Swift，但沒關係，這是Objective-C的代碼，只是將其轉換。

UITextView * _descriptionText = [UITextView new]; 
[_descriptionText setDelegate:self]; 
[_descriptionText setBackgroundColor:[UIColor whiteColor]; 
[_descriptionText setTranslatesAutoresizingMaskIntoConstraints:false]; 
[_descriptionText setTextColor:[UIColor lightGrayColor]]; 
[_descriptionText setTextAlignment:NSTextAlignmentLeft]; 

那麼，這個TextView的添加到一個UIView

[sss addSubview:_descriptionText]; 

下面是UIView的代碼：

UIView * sss = [UIView new]; 
[sss setTranslatesAutoresizingMaskIntoConstraints:FALSE]; 
[self addSubview:sss]; 

添加約束UIView的居中的UITextView並限制它的邊界在左右兩側有一定的寬度：

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeHeight multiplier:1.0f constant:SOME_HEIGHT_NUMBER_YOU_CHOOSE]]; 

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeHeight multiplier:1.0f constant:SOME_RIGHT_MARGIN_NUMBER_YOU_CHOOSE]]; 

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeLeft multiplier:1.0f constant:SOME_LEFT_MARGIN_NUMBER_YOU_CHOOSE]]; 

或選擇的UITextView的這樣一個的centerX約束寬度：

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:SOME_WIDTH_NUMBER_YOU_CHOOSE]]; 

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0]]; 

最後，添加CenterY約束：

[sss addConstraint:[NSLayoutConstraint constraintWithItem:descriptionText attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeCenterY multiplier:1.0f constant:0]]; 

最後，約束UIView的 「SSS」，以它的超級查看「自我」或任何它的超級看法是：

NSDictionary * views = NSDictionaryOfVariableBindings(sss); 
NSDictionary * metrics = @{@"bh" : @30, @"bsh" : @40, ... etc, etc,}; 

[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[sss]|" options:0 metrics:metrics views:views]]; 
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-bh-[sss]" options:0 metrics:metrics views:views]]; 

然後，利潤！

具有子類UIView的格式化代碼 ExampleView。米

@implementation ExampleView 

- (id)initWithFrame:(CGRect)frame 
{ 
    self = [super initWithFrame:frame]; 
    if (self) 
    { 
     UIView * sss = [UIView new]; 
     [sss setTranslatesAutoresizingMaskIntoConstraints:false]; 
     [self addSubview:sss]; 

     UITextView * _descriptionText = [UITextView new]; 
     [_descriptionText setBackgroundColor:[UIColor whiteColor]]; 
     [_descriptionText setTranslatesAutoresizingMaskIntoConstraints:false]; 
     [_descriptionText setTextColor:[UIColor lightGrayColor]]; 
     [_descriptionText setTextAlignment:NSTextAlignmentLeft]; 
     [sss addSubview:_descriptionText]; 

     //do these three constraints 
     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeHeight multiplier:1.0f constant:SOME_HEIGHT_NUMBER_YOU_CHOOSE]]; 

     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeRight multiplier:1.0f constant:SOME_RIGHT_MARGIN_NUMBER_YOU_CHOOSE]]; 

     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeLeft multiplier:1.0f constant:SOME_LEFT_MARGIN_NUMBER_YOU_CHOOSE]]; 

     //or do these three constraints, but don't do all 6 constraints between these three and the three above 

     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:SOME_WIDTH_NUMBER_YOU_CHOOSE]]; 

     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0]]; 

     [sss addConstraint:[NSLayoutConstraint constraintWithItem:_descriptionText attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:sss attribute:NSLayoutAttributeCenterY multiplier:1.0f constant:0]]; 

     NSDictionary * views = NSDictionaryOfVariableBindings(sss); 
     NSDictionary * metrics = @{@"bh" : @30, @"bsh" : @40}; 

     [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[sss]|" options:0 metrics:metrics views:views]]; 
     [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-bh-[sss]" options:0 metrics:metrics views:views]]; 
// this: V:|-bh-[sss] SHOULD WORK, BUT IT MIGHT REQUIRE YOU TO DO THIS: V:|-bh-[sss(HEIGHT_OF_THE_TEXT_VIEW_THAT_YOU_CHOOSE)] 
    } 
    return self; 
} 
@end 

ExampleView.h

#import <UIKit/UIKit.h> 
@interface NSHMessagesView : UIView 

@end 

Answer 2

我想你也可以繼承的UITextView或設置contentInset。因爲它是子類scrollView，所以我猜設置contentInset可以achevie的目標。