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
TextView占位符
import UIKit
@IBDesignable
open class KMPlaceholderTextView: UITextView {
private struct Constants {
static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
public let placeholderLabel: UILabel = UILabel()
private var placeholderLabelConstraints = [NSLayoutConstraint]()
@IBInspectable open var placeholder: String = "" {
didSet {
placeholderLabel.text = placeholder
}
}
@IBInspectable open var placeholderColor: UIColor = KMPlaceholderTextView.Constants.defaultiOSPlaceholderColor {
didSet {
placeholderLabel.textColor = placeholderColor
}
}
override open var font: UIFont! {
didSet {
if placeholderFont == nil {
placeholderLabel.font = font
}
}
}
open var placeholderFont: UIFont? {
didSet {
let font = (placeholderFont != nil) ? placeholderFont : self.font
placeholderLabel.font = font
}
}
override open var textAlignment: NSTextAlignment {
didSet {
placeholderLabel.textAlignment = textAlignment
}
}
override open var text: String! {
didSet {
textDidChange()
}
}
override open var attributedText: NSAttributedString! {
didSet {
textDidChange()
}
}
override open var textContainerInset: UIEdgeInsets {
didSet {
updateConstraintsForPlaceholderLabel()
}
}
override public init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
commonInit()
}
required public init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
private func commonInit() {
#if swift(>=4.2)
let notificationName = UITextView.textDidChangeNotification
#else
let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
#endif
NotificationCenter.default.addObserver(self,
selector: #selector(textDidChange),
name: notificationName,
object: nil)
placeholderLabel.font = font
placeholderLabel.textColor = placeholderColor
placeholderLabel.textAlignment = textAlignment
placeholderLabel.text = placeholder
placeholderLabel.numberOfLines = 0
placeholderLabel.backgroundColor = UIColor.clear
placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
addSubview(placeholderLabel)
updateConstraintsForPlaceholderLabel()
}
private func updateConstraintsForPlaceholderLabel() {
var newConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints += NSLayoutConstraint.constraints(withVisualFormat: "V:|-(\(textContainerInset.top))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints.append(NSLayoutConstraint(
item: placeholderLabel,
attribute: .width,
relatedBy: .equal,
toItem: self,
attribute: .width,
multiplier: 1.0,
constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
))
removeConstraints(placeholderLabelConstraints)
addConstraints(newConstraints)
placeholderLabelConstraints = newConstraints
}
@objc private func textDidChange() {
placeholderLabel.isHidden = !text.isEmpty
self.layoutIfNeeded()
}
open override func layoutSubviews() {
super.layoutSubviews()
placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}
deinit {
#if swift(>=4.2)
let notificationName = UITextView.textDidChangeNotification
#else
let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
#endif
NotificationCenter.default.removeObserver(self,
name: notificationName,
object: nil)
}
}
使用
其他回答
让我们简单点
创建一个UILabel并把它放在你的文本视图上(给文本作为占位符-设置颜色为灰色-你可以在你的xib中做这一切) 现在在头文件中声明UILabel和textviewDelegate 现在你可以简单地隐藏标签,当你点击textview
完整代码如下
头
@interface ViewController :UIViewController<UITextViewDelegate>{
}
@property (nonatomic,strong) IBOutlet UILabel *PlceHolder_label;
@property (nonatomic,strong) IBOutlet UITextView *TextView;
@end
实现
@implementation UploadFoodImageViewController
@synthesize PlceHolder_label,TextView;
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView{
if([textView isEqual:TextView]){
[PlceHolder_label setHidden:YES];
[self.tabScrlVw setContentOffset:CGPointMake(0,150) animated:YES];
}
return YES;
}
@end
别忘了连接textView和UILabel文件所有者从xib
TextView占位符
import UIKit
@IBDesignable
open class KMPlaceholderTextView: UITextView {
private struct Constants {
static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
public let placeholderLabel: UILabel = UILabel()
private var placeholderLabelConstraints = [NSLayoutConstraint]()
@IBInspectable open var placeholder: String = "" {
didSet {
placeholderLabel.text = placeholder
}
}
@IBInspectable open var placeholderColor: UIColor = KMPlaceholderTextView.Constants.defaultiOSPlaceholderColor {
didSet {
placeholderLabel.textColor = placeholderColor
}
}
override open var font: UIFont! {
didSet {
if placeholderFont == nil {
placeholderLabel.font = font
}
}
}
open var placeholderFont: UIFont? {
didSet {
let font = (placeholderFont != nil) ? placeholderFont : self.font
placeholderLabel.font = font
}
}
override open var textAlignment: NSTextAlignment {
didSet {
placeholderLabel.textAlignment = textAlignment
}
}
override open var text: String! {
didSet {
textDidChange()
}
}
override open var attributedText: NSAttributedString! {
didSet {
textDidChange()
}
}
override open var textContainerInset: UIEdgeInsets {
didSet {
updateConstraintsForPlaceholderLabel()
}
}
override public init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
commonInit()
}
required public init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
private func commonInit() {
#if swift(>=4.2)
let notificationName = UITextView.textDidChangeNotification
#else
let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
#endif
NotificationCenter.default.addObserver(self,
selector: #selector(textDidChange),
name: notificationName,
object: nil)
placeholderLabel.font = font
placeholderLabel.textColor = placeholderColor
placeholderLabel.textAlignment = textAlignment
placeholderLabel.text = placeholder
placeholderLabel.numberOfLines = 0
placeholderLabel.backgroundColor = UIColor.clear
placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
addSubview(placeholderLabel)
updateConstraintsForPlaceholderLabel()
}
private func updateConstraintsForPlaceholderLabel() {
var newConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints += NSLayoutConstraint.constraints(withVisualFormat: "V:|-(\(textContainerInset.top))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints.append(NSLayoutConstraint(
item: placeholderLabel,
attribute: .width,
relatedBy: .equal,
toItem: self,
attribute: .width,
multiplier: 1.0,
constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
))
removeConstraints(placeholderLabelConstraints)
addConstraints(newConstraints)
placeholderLabelConstraints = newConstraints
}
@objc private func textDidChange() {
placeholderLabel.isHidden = !text.isEmpty
self.layoutIfNeeded()
}
open override func layoutSubviews() {
super.layoutSubviews()
placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}
deinit {
#if swift(>=4.2)
let notificationName = UITextView.textDidChangeNotification
#else
let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
#endif
NotificationCenter.default.removeObserver(self,
name: notificationName,
object: nil)
}
}
使用
这里还有另一种方法,它复制了UITextField占位符的轻微缩进:
将UITextField拖到UITextView的右边,这样它们的左上角就对齐了。将占位符文本添加到文本字段。
在viewDidLoad中添加:
[tView setDelegate:self];
tView.contentInset = UIEdgeInsetsMake(-8,-8,0,0);
tView.backgroundColor = [UIColor clearColor];
然后添加:
- (void)textViewDidChange:(UITextView *)textView {
if (textView.text.length == 0) {
textView.backgroundColor = [UIColor clearColor];
} else {
textView.backgroundColor = [UIColor whiteColor];
}
}
这里有一个更简单的解决方案,它的行为完全像UITextField的占位符,但不需要绘制自定义视图,或辞职第一响应器。
- (void) textViewDidChange:(UITextView *)textView{
if (textView.text.length == 0){
textView.textColor = [UIColor lightGrayColor];
textView.text = placeholderText;
[textView setSelectedRange:NSMakeRange(0, 0)];
isPlaceholder = YES;
} else if (isPlaceholder && ![textView.text isEqualToString:placeholderText]) {
textView.text = [textView.text substringToIndex:1];
textView.textColor = [UIColor blackColor];
isPlaceholder = NO;
}
}
(else if语句中的第二个检查是针对没有输入任何内容且用户按下退格键的情况)
只需要将你的类设置为UITextViewDelegate。在viewDidLoad中,你应该这样初始化
- (void) viewDidLoad{
// initialize placeholder text
placeholderText = @"some placeholder";
isPlaceholder = YES;
self.someTextView.text = placeholderText;
self.someTextView.textColor = [UIColor lightGrayColor];
[self.someTextView setSelectedRange:NSMakeRange(0, 0)];
// assign UITextViewDelegate
self.someTextView.delegate = self;
}
你能做的是在文本属性中设置文本视图的初始值,并将textColor更改为[UIColor grayColor]或类似的东西。然后,每当文本视图变为可编辑时,清除文本并显示游标,如果文本字段再次为空,则将占位符文本放回。根据需要将颜色更改为[UIColor blackColor]。
它与UITextField中的占位符功能不完全相同,但很接近。