iOS 13 - 带占位符的 UITextField 应用崩溃

Question

在 iOS 13 中，访问 UITextField _placeholderLabel.textColor 标签键时发生崩溃。

用于应用占位符文本颜色的键。

[textfield setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];

"NSGenericException" - reason: "Access to UITextField's _placeholderLabel ivar is prohibited. This is an application bug"

Answer 1

您可以使用运行时来完成：

在placeholder setting底部添加如下代码

Ivar ivar =  class_getInstanceVariable([UITextField class], "_placeholderLabel");
UILabel *placeholderLabel = object_getIvar(textField, ivar);
placeholderLabel.textColor = [UIColor whiteColor];

在Xcode11 beta2，这段代码可以用，但我不知道GM版或正式版。

完整代码：

Objective-C版本


#import "ViewController.h"
#import <objc/runtime.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor grayColor];
    self.title = @"UITextField Demo";

    UITextField *textField = [UITextField new];
    textField.frame = CGRectMake(0, 100, 300, 50);
    textField.placeholder = @"UITextField Demo";
    [self.view addSubview:textField];

    Ivar ivar =  class_getInstanceVariable([UITextField class], "_placeholderLabel");
    UILabel *placeholderLabel = object_getIvar(textField, ivar);

    placeholderLabel.textColor = [UIColor whiteColor];
}

@end

Swift版本：

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        let textField = UITextField()
        textField.frame = CGRect(x: 0, y: 100, width: 300, height: 50)
        textField.placeholder = "UITextField Demo"
        view.addSubview(textField)

        let iVar = class_getInstanceVariable(UITextField.self, "_placeholderLabel")!
        let placeholderLabel = object_getIvar(textField, iVar) as! UILabel
        placeholderLabel.textColor = .red
    }
}

2019/09/25更新

以上实现可以解决问题，但不提倡

使用私有 api 的应用程序将来可能会损坏。

请使用新的 api :

var attributedPlaceholder: NSAttributedString? { get set }

讨论

This property is nil by default. If set, the placeholder string is drawn using system-defined color and the remaining style information (except the text color) of the attributed string. Assigning a new value to this property also replaces the value of the placeholder property with the same string data, albeit without any formatting information. Assigning a new value to this property does not affect any other style-related properties of the text field.

完整代码：

let textField = UITextField()
textField.frame = CGRect(x: 0, y: 100, width: 300, height: 50)
let placeholderString = NSAttributedString.init(string: "UITextField Demo", attributes: [NSAttributedString.Key.foregroundColor : UIColor.red])
textField.attributedPlaceholder = placeholderString
view.addSubview(textField)

Answer 2

您可以使用 attributedPlaceholder 方法设置 UITextField 占位符文本颜色、字体，如下所示：

NSString *text = [textField text];
textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:text attributes:@{NSForegroundColorAttributeName: [UIColor redColor], NSFontAttributeName: [UIFont fontWithName:@"HelveticaNeue-Medium" size:14.0f]}];

Answer 3

我是这样做的:

对象

NSMutableAttributedString *placeholderAttributedString = [[NSMutableAttributedString alloc] initWithAttributedString:searchField.attributedPlaceholder];
[placeholderAttributedString addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0, [placeholderAttributedString length])];
searchField.attributedPlaceholder = placeholderAttributedString;

Swift 5

var placeholderAttributedString = NSMutableAttributedString(attributedString: searchField.attributedPlaceholder)
    placeholderAttributedString.addAttribute(.foregroundColor, value: UIColor.red, range: NSRange(location: 0, length: placeholderAttributedString.length))
    searchField.attributedPlaceholder = placeholderAttributedString

有点长，但我暂时没有更好的。

Answer 4

- Swift 版本

将以下代码添加到占位符设置的底部：

    let iVar = class_getInstanceVariable(UITextField.self, "_placeholderLabel")!
    let placeholderLabel = object_getIvar(textField, iVar) as! UILabel

    placeholderLabel.textColor = .white

例如：

override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = .gray

    let textField = UITextField()
    textField.frame = CGRect(x: 0, y: 100, width: 300, height: 50)
    textField.placeholder = "UITextField Demo"
    view.addSubview(textField)
    let iVar = class_getInstanceVariable(UITextField.self, "_placeholderLabel")!
    let placeholderLabel = object_getIvar(textField, iVar) as! UILabel

    placeholderLabel.textColor = .white
}

Answer 5

"Erase all contents and settings"

这对我有用。

Answer 6

Swift 5

这是属性的正确 Swift 替换。请注意，如果您还更改了文本字段的其他属性的对齐方式，那么您也需要将这些属性设置为占位符的属性文本。通常只改变颜色和字体：

/// Set placeholder text color
/// - Parameter color: the color
func setPlaceholderColor(_ color: UIColor) {
    // Color
    var attributes: [NSAttributedString.Key: Any] = [.foregroundColor: color]
    var range = NSRange(location: 0, length: 1)

    // Font
    if let text = attributedText, text.length > 0, let attrs = attributedText?.attributes(at: 0, effectiveRange: &range), let font = attrs[.font] {
        attributes[.font] = font
    }
    else if let font = font {
        attributes[.font] = font
    }
    self.attributedPlaceholder = NSAttributedString(string: self.placeholder ?? "", attributes: attributes)
}

Answer 7

如果您使用的是 UITextView+Placeholder.h class 请更改以下方法如果问题仍然存在请清理并构建

Objective C

+(UIColor *)defaultPlaceholderColor {

    static UIColor *color = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        UITextField *textField = [[UITextField alloc] init];
        textField.placeholder = @" ";
        //        color = [textField valueForKeyPath:@"_placeholderLabel.textColor"];
        Ivar ivar =  class_getInstanceVariable([UITextField class], "_placeholderLabel");
        UILabel *placeholderLabel = object_getIvar(textField, ivar);
        color =  placeholderLabel.textColor;

    });
    return color;

}

Answer 8

用于 UISEARCHBAR 占位符颜色

Xcode 11.1

从iOS13开始SDK提供UISearchBar.searchTextField所以我们可以使用 public API 而不是私有 API。在 UISearchBar 的子类中，我使用此代码更改占位符颜色

UITextField *textField = [self findSubviewOfClass:[UITextField class]];
textField.textColor = [UIColor whiteColor];
//textField.font = [UIFont fontWithName:@"HelveticaNeue-Regular" size:14.0f];

if (@available(iOS 13.0, *)) {
    self.searchTextField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:self.placeholder attributes:@{NSForegroundColorAttributeName: [UIColor colorWithRed:0.8 green:0.82 blue:0.81 alpha:1]}];

}else {
    [textField setValue:[UIColor colorWithRed:0.8 green:0.82 blue:0.81 alpha:1] forKeyPath:@"_placeholderLabel.textColor"];

}

Answer 9

对于IOS13，您可以通过一行代码设置UITextField占位符颜色。

Objective C

[textField setAttributedPlaceholder:[[NSAttributedString alloc] initWithString:@"PlaceHolder Text" attributes:@{NSForegroundColorAttributeName:[UIColor whiteColor]}]];

在Swift 5

txtTitle.attributedPlaceholder = NSAttributedString(string:"PlaceHolder Text", attributes: [NSAttributedString.Key.foregroundColor: UIColor.white])

Answer 10

我认为这是 XCode 方面的错误，希望他们会在下一个版本中修复此错误。您可以通过擦除模拟器设备上的所有内容和设置来快速解决此问题。

Answer 11

我删除了 "User Defined Runtime Attributes" 部分中的变量“_placeholderLabel”

Answer 12

删除下划线“_”并试试这个。

[textfield setValue:[UIColor whiteColor] forKeyPath:@"placeholderLabel.textColor"];

它应该适用于所有版本！

Answer 13

是的，这个问题与 Xcode 版本有关。我有 Xcode 11.2.1，我面临着同样的问题。

_placeholderLabel.textColor

如果您从情节提要中将它用作运行时变量并遇到问题，那么只需删除“_”

那样

删除“_”运行时变量后开始工作

Answer 14

只需将 _placeholderLabel 替换为 placeholderLabel

Answer 15

从“_placeholderLabel.textColor”中删除“_”，尝试使用“placeholderLabel.textColor”。

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