ios - 如何在 iOS 中水平居中 UITextView 内容，但不使用对齐中心？

Question

我想实现一些非常具体的东西。很难用语言来描述，所以这里有一些模型。

当前阶段:我有一个 UITextView，它的自动布局约束设置为与父容器一样宽。


我想要实现的目标:我想将 UITextView 中的内容水平居中，以便它们出现在中心但仍然左对齐


大多数解决方案都依赖 TextAlignCenter 选项将文本水平居中，但这不是我想要的，因为它会显示为:


有什么办法可以做到这一点？

我已经尝试过以下方法:

textview.sizeToFit() 似乎调整高度而不是宽度

textview.contentOffset 似乎不起作用

删除自动布局中的约束并使用 Editor > Fix all in scope 似乎适用于 UIButtons 但不适用于 UITextView ..

我想这样做的原因是虽然它在 iPhone 上并不明显，但在 iPad 上，如果文本很短，它们会一直显示在左侧，这与我的应用程序中的其他可交互按钮相距甚远。

Answer 1

看起来你可能正在使用 Swift，但没关系，这是 Objective-C 的代码，只需转换它。

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

然后，将此 TextView 添加到 UIView

[sss addSubview:_descriptionText];

这是 UIView 的代码:

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

向 UIView 添加约束以使 UITextView 居中并在左右两侧将其边界限制为一定的宽度:

[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]];

或为 UITextView 选择一个宽度，像这样使用 CenterX 约束:

[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]];

最后，添加一个 CenterY 约束:

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

最后，将 UIView "sss"约束到它的 super View "self"或者它的 super View 是什么:

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]];

然后，利润!

带有子类 UIView 的格式化代码
ExampleView.m

@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