我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
当前回答
你可以在textview上设置一个标签。
MyUITextView.h
@interface MyUITextView : UITextView {
UILabel* _placeholderLabel;
}
@property(nonatomic, assign)NSString *placeholder;
MyUITextView.m
@implementation MyUITextView
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
// Create placeholder
viewFrame = CGRectMake(0, 0, frame.size.width, 15);
_placeholderLabel = [[UILabel alloc] initWithFrame:viewFrame];
_placeholderLabel.textColor = [UIColor lightGrayColor];
[self addSubview:_placeholderLabel];
// Add text changed notification
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
- (void)setPlaceholder:(NSString *)placeholder {
_placeholderLabel.text = placeholder;
}
- (NSString*)placeholder {
return _placeholderLabel.text;
}
#pragma mark UITextViewTextDidChangeNotification
- (void)textChanged:(NSNotification *)notification {
_placeholderLabel.hidden = ([self.text lenght] == 0);
}
@end
其他回答
嗨,你可以使用IQTextView可用的IQKeyboard管理器,这是简单的使用和集成只是设置类你的textview到IQTextView,你可以使用它的属性设置占位符标签与你想要的颜色。 您可以从IQKeyboardManager下载该库
或者你也可以从cocoapods上安装。
我修改了Sam Soffes的实现以适应iOS7:
- (void)drawRect:(CGRect)rect
{
[super drawRect:rect];
if (_shouldDrawPlaceholder)
{
UIEdgeInsets insets = self.textContainerInset;
CGRect placeholderRect = CGRectMake(
insets.left + self.textContainer.lineFragmentPadding,
insets.top,
self.frame.size.width - insets.left - insets.right,
self.frame.size.height - insets.top - insets.bottom);
[_placeholderText drawWithRect:placeholderRect
options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingTruncatesLastVisibleLine
attributes:self.placeholderAttributes
context:nil];
}
}
- (NSDictionary *)placeholderAttributes
{
if (_placeholderAttributes == nil)
{
_placeholderAttributes = @
{
NSFontAttributeName : self.font,
NSForegroundColorAttributeName : self.placeholderColor
};
}
return _placeholderAttributes;
}
记住在可能改变字体和其他可能影响它们的东西的方法中设置_placeholderattributes = nil。如果没有问题的话,您可能还想跳过属性字典的“惰性”创建。
编辑:
如果你想让占位符在自动布局动画之后看起来更好,记得在setBounds的重写版本中调用setNeedsDisplay。
简单地创建UITextView的@IBDesignable子类:
@IBDesignable class AttributedTextView: UITextView {
private let placeholderLabel = UILabel()
@IBInspectable var placeholder: String = "" {
didSet {
setupPlaceholderLabelIfNeeded()
textViewDidChange()
}
}
override var text: String! {
didSet {
textViewDidChange()
}
}
//MARK: - Initialization
override func awakeFromNib() {
super.awakeFromNib()
setupPlaceholderLabelIfNeeded()
NotificationCenter.default.addObserver(self, selector: #selector(textViewDidChange), name: .UITextViewTextDidChange, object: nil)
}
//MARK: - Deinitialization
deinit {
NotificationCenter.default.removeObserver(self)
}
//MARK: - Internal
func textViewDidChange() {
placeholderLabel.isHidden = !text.isEmpty
layoutIfNeeded()
}
//MARK: - Private
private func setupPlaceholderLabelIfNeeded() {
placeholderLabel.removeFromSuperview()
placeholderLabel.frame = CGRect(x: 0, y: 8, width: frame.size.width, height: 0)
placeholderLabel.textColor = UIColor.lightGray
placeholderLabel.text = placeholder
placeholderLabel.sizeToFit()
insertSubview(placeholderLabel, at: 0)
}
}
然后在标识检查器中设置占位符:
一个更简单的方法是创建一个次要的UITextView,它具有与原始文本视图相同的所有属性,除了不同的textColor,并带有约束以确保它们保持对齐。然后当任何字符进入主文本视图时,隐藏克隆文本视图,否则显示带有一些文本的克隆文本视图。
这可以通过几种方式实现,但相对简单的方法是子类化UITextView并将所有这些逻辑保留在子类中。
所以,子类UITextView并允许它惰性地创建它的占位符视图
接口文件:
@interface FOOTextView : UITextView <UITextViewDelegate>
@property (nonatomic, copy) NSString *placeholderText;
- (void)checkPlaceholder;
@end
实现文件:
#import "FOOTextView.h"
@interface FOOTextView ()
@property (nonatomic, strong) UITextView *placeholderTextView;
@end
@implementation FOOTextView
- (void)checkPlaceholder {
// Hide the placeholder text view if we've got any text
self.placeholderTextView.hidden = (self.text.length > 0 || self.attributedText.length > 0);
}
- (void)setPlaceholderText:(NSString *)placeholderText {
_placeholderText = [placeholderText copy];
// Setup the placeholder text view if we haven't already
[self setupPlaceholderTextView];
// Apply the placeholder text to the placeholder text view
self.placeholderTextView.text = placeholderText;
}
- (void)setupPlaceholderTextView {
if (!self.placeholderTextView) {
// Setup the place holder text view, duplicating our visual setup
self.placeholderTextView = [[UITextView alloc] initWithFrame:CGRectZero];
self.placeholderTextView.translatesAutoresizingMaskIntoConstraints = NO;
self.placeholderTextView.textColor = self.placeholderTextColor ? self.placeholderTextColor : [UIColor colorWithRed:199.f/255.f green:199.f/255.f blue:205.f/255.f alpha:1.f];
self.placeholderTextView.userInteractionEnabled = NO;
self.placeholderTextView.font = self.font;
self.placeholderTextView.textAlignment = self.textAlignment;
self.placeholderTextView.backgroundColor = self.backgroundColor;
self.placeholderTextView.editable = NO;
// Our background color must be clear for the placeholder text view to show through
self.backgroundColor = [UIColor clearColor];
// Insert the placeholder text view into our superview, below ourself so it shows through
[self.superview insertSubview:self.placeholderTextView belowSubview:self];
// Setup constraints to ensure the placeholder text view stays aligned with us
NSLayoutConstraint *constraintCenterX = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.f constant:0.f];
NSLayoutConstraint *constraintCenterY = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterY multiplier:1.f constant:0.f];
NSLayoutConstraint *constraintWidth = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeWidth multiplier:1.f constant:0.f];
NSLayoutConstraint *constraintHeight = [NSLayoutConstraint constraintWithItem:self.placeholderTextView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeHeight multiplier:1.f constant:0.f];
NSArray *constraints = @[constraintCenterX, constraintCenterY, constraintWidth, constraintHeight];
[self.superview addConstraints:constraints];
}
}
- (void)setPlaceholderTextColor:(UIColor *)placeholderTextColor {
_placeholderTextColor = placeholderTextColor;
self.placeholderTextView.textColor = _placeholderTextColor;
}
- (void)setBackgroundColor:(UIColor *)backgroundColor {
// We don't want a background color ourselves, instead we want our placeholder text view to have the desired background color
[self.placeholderTextView setBackgroundColor:backgroundColor];
}
- (void)removeFromSuperview {
// Ensure we also remove our placeholder text view
[self.placeholderTextView removeFromSuperview];
self.placeholderTextView = nil;
[super removeFromSuperview];
}
#pragma mark - Text View Delegation
- (void)textViewDidChange:(UITextView *)textView {
[self checkPlaceholder];
}
@end
使用上面的类,如果你设置了一个FOOTextView的委托实例到它自己,一切都将开箱工作:
FOOTextView *myTextView = ...
myTextView.placeholderText = @"What's on your mind?";
myTextView.placeholderTextColor = [UIColor lightGrayColor];
myTextView.delegate = myTextView;
如果你想另一个对象接管作为委托,那么你只需要在textViewDidChange: delegate方法中调用文本视图的checkPlaceholder方法,例如;
FOOTextView *myTextView = ...
myTextView.placeholderText = @"What's on your mind?";
myTextView.placeholderTextColor = [UIColor lightGrayColor];
myTextView.delegate = self;
self.myTextView = myTextView;
- (void)textViewDidChange:(UITextView *)textView {
// Call the checkPlaceholder method to update the visuals
[self.myTextView checkPlaceholder];
}
我已经创建了一个快速3版本的最高排名的答案
你只需要做UITextView的子类化。
import UIKit
class UIPlaceHolderTextView: UITextView {
//MARK: - Properties
@IBInspectable var placeholder: String?
@IBInspectable var placeholderColor: UIColor?
var placeholderLabel: UILabel?
//MARK: - Initializers
override func awakeFromNib() {
super.awakeFromNib()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
// Use Interface Builder User Defined Runtime Attributes to set
// placeholder and placeholderColor in Interface Builder.
if self.placeholder == nil {
self.placeholder = ""
}
if self.placeholderColor == nil {
self.placeholderColor = UIColor.black
}
NotificationCenter.default.addObserver(self, selector: #selector(textChanged(_:)), name: NSNotification.Name.UITextViewTextDidChange, object: nil)
}
func textChanged(_ notification: Notification) -> Void {
if self.placeholder?.count == 0 {
return
}
UIView.animate(withDuration: 0.25) {
if self.text.count == 0 {
self.viewWithTag(999)?.alpha = 1
}
else {
self.viewWithTag(999)?.alpha = 0
}
}
}
// Only override draw() if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
override func draw(_ rect: CGRect) {
super.draw(rect)
if (self.placeholder?.count ?? 0) > 0 {
if placeholderLabel == nil {
placeholderLabel = UILabel.init()
placeholderLabel?.lineBreakMode = .byWordWrapping
placeholderLabel?.numberOfLines = 0
placeholderLabel?.font = self.font
placeholderLabel?.backgroundColor = self.backgroundColor
placeholderLabel?.textColor = self.placeholderColor
placeholderLabel?.alpha = 0
placeholderLabel?.tag = 999
self.addSubview(placeholderLabel!)
placeholderLabel?.translatesAutoresizingMaskIntoConstraints = false
placeholderLabel?.topAnchor.constraint(equalTo: self.topAnchor, constant: 7).isActive = true
placeholderLabel?.leftAnchor.constraint(equalTo: self.leftAnchor, constant: 4).isActive = true
placeholderLabel?.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
placeholderLabel?.rightAnchor.constraint(equalTo: self.rightAnchor).isActive = true
}
placeholderLabel?.text = self.placeholder
placeholderLabel?.sizeToFit()
self.sendSubview(toBack: self.placeholderLabel!)
}
if self.text.count == 0 && (self.placeholder?.count ?? 0) > 0 {
self.viewWithTag(999)?.alpha = 1
}
}
}