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
首先在.h文件中取一个标签。
这里我取
UILabel * lbl;
然后在。m中viewDidLoad下声明它
lbl = [[UILabel alloc] initWithFrame:CGRectMake(8.0, 0.0,250, 34.0)];
lbl.font=[UIFont systemFontOfSize:14.0];
[lbl setText:@"Write a message..."];
[lbl setBackgroundColor:[UIColor clearColor]];
[lbl setTextColor:[UIColor lightGrayColor]];
[textview addSubview:lbl];
textview是我的textview。
现在声明
-(void)textViewDidChange:(UITextView *)textView {
if (![textView hasText]){
lbl.hidden = NO;
}
else{
lbl.hidden = YES;
}
}
和你的Textview占位符准备好了!
其他回答
我对发布的任何解决方案都不太满意,因为它们有点重。向视图中添加视图并不理想(尤其是在drawRect:)。它们都有漏洞,这也是不可接受的。
这是我的解决方案:SAMTextView
SAMTextView.h
//
// SAMTextView.h
// SAMTextView
//
// Created by Sam Soffes on 8/18/10.
// Copyright 2010-2013 Sam Soffes. All rights reserved.
//
#import <UIKit/UIKit.h>
/**
UITextView subclass that adds placeholder support like UITextField has.
*/
@interface SAMTextView : UITextView
/**
The string that is displayed when there is no other text in the text view.
The default value is `nil`.
*/
@property (nonatomic, strong) NSString *placeholder;
/**
The color of the placeholder.
The default is `[UIColor lightGrayColor]`.
*/
@property (nonatomic, strong) UIColor *placeholderTextColor;
/**
Returns the drawing rectangle for the text views’s placeholder text.
@param bounds The bounding rectangle of the receiver.
@return The computed drawing rectangle for the placeholder text.
*/
- (CGRect)placeholderRectForBounds:(CGRect)bounds;
@end
SAMTextView.m
//
// SAMTextView.m
// SAMTextView
//
// Created by Sam Soffes on 8/18/10.
// Copyright 2010-2013 Sam Soffes. All rights reserved.
//
#import "SAMTextView.h"
@implementation SAMTextView
#pragma mark - Accessors
@synthesize placeholder = _placeholder;
@synthesize placeholderTextColor = _placeholderTextColor;
- (void)setText:(NSString *)string {
[super setText:string];
[self setNeedsDisplay];
}
- (void)insertText:(NSString *)string {
[super insertText:string];
[self setNeedsDisplay];
}
- (void)setAttributedText:(NSAttributedString *)attributedText {
[super setAttributedText:attributedText];
[self setNeedsDisplay];
}
- (void)setPlaceholder:(NSString *)string {
if ([string isEqual:_placeholder]) {
return;
}
_placeholder = string;
[self setNeedsDisplay];
}
- (void)setContentInset:(UIEdgeInsets)contentInset {
[super setContentInset:contentInset];
[self setNeedsDisplay];
}
- (void)setFont:(UIFont *)font {
[super setFont:font];
[self setNeedsDisplay];
}
- (void)setTextAlignment:(NSTextAlignment)textAlignment {
[super setTextAlignment:textAlignment];
[self setNeedsDisplay];
}
#pragma mark - NSObject
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self name:UITextViewTextDidChangeNotification object:self];
}
#pragma mark - UIView
- (id)initWithCoder:(NSCoder *)aDecoder {
if ((self = [super initWithCoder:aDecoder])) {
[self initialize];
}
return self;
}
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
[self initialize];
}
return self;
}
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
if (self.text.length == 0 && self.placeholder) {
rect = [self placeholderRectForBounds:self.bounds];
UIFont *font = self.font ? self.font : self.typingAttributes[NSFontAttributeName];
// Draw the text
[self.placeholderTextColor set];
[self.placeholder drawInRect:rect withFont:font lineBreakMode:NSLineBreakByTruncatingTail alignment:self.textAlignment];
}
}
#pragma mark - Placeholder
- (CGRect)placeholderRectForBounds:(CGRect)bounds {
// Inset the rect
CGRect rect = UIEdgeInsetsInsetRect(bounds, self.contentInset);
if (self.typingAttributes) {
NSParagraphStyle *style = self.typingAttributes[NSParagraphStyleAttributeName];
if (style) {
rect.origin.x += style.headIndent;
rect.origin.y += style.firstLineHeadIndent;
}
}
return rect;
}
#pragma mark - Private
- (void)initialize {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:self];
self.placeholderTextColor = [UIColor colorWithWhite:0.702f alpha:1.0f];
}
- (void)textChanged:(NSNotification *)notification {
[self setNeedsDisplay];
}
@end
它比其他的要简单得多,因为它不使用子视图(或有泄漏)。请随意使用。
更新11/10/11:它现在是文档化的,并支持在接口生成器中使用。
更新11/24/13:指向新的回购。
我做了我自己版本的UITextView的子类。我喜欢Sam Soffes使用通知的想法,但我不喜欢drawRect: overwrite。对我来说太过分了。我认为我做了一个非常干净的实现。
你可以看看我的子类。还包括一个演示项目。
After looking through (and trying out) most of the proposed solutions to this seemingly obvious - but missing - feature of UITextView, the 'best' closest I found was that from BobDickinson. But I didnt like having to resort to a whole new subclass [I prefer drop-in categories for such simple functional additions], nor that it intercepted UITextViewDelegate methods, which is probably going to mess up your existing UITextView handling code. So here's my take on a drop-in category that'll work on any existing UITextView instance...
#import <objc/runtime.h>
// Private subclass needed to override placeholderRectForBounds: to correctly position placeholder
@interface _TextField : UITextField
@property UIEdgeInsets insets;
@end
@implementation _TextField
- (CGRect)placeholderRectForBounds:(CGRect)bounds
{
CGRect rect = [super placeholderRectForBounds:bounds];
return UIEdgeInsetsInsetRect(rect, _insets);
}
@end
@implementation UITextView (Placeholder)
static const void *KEY;
- (void)setPlaceholder:(NSString *)placeholder
{
_TextField *textField = objc_getAssociatedObject(self, &KEY);
if (!textField) {
textField = [_TextField.alloc initWithFrame:self.bounds];
textField.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
textField.userInteractionEnabled = NO;
textField.font = self.font;
textField.contentVerticalAlignment = UIControlContentVerticalAlignmentTop;
textField.insets = UIEdgeInsetsMake(self.textContainerInset.top,
self.textContainerInset.left + self.textContainer.lineFragmentPadding,
self.textContainerInset.bottom,
self.textContainerInset.right);
[self addSubview:textField];
[self sendSubviewToBack:textField];
objc_setAssociatedObject(self, &KEY, textField, OBJC_ASSOCIATION_RETAIN);
[NSNotificationCenter.defaultCenter addObserver:self selector:@selector(updatePlaceholder:) name:UITextViewTextDidChangeNotification object:nil];
}
textField.placeholder = placeholder;
}
- (NSString*)placeholder
{
UITextField *textField = objc_getAssociatedObject(self, &KEY);
return textField.placeholder;
}
- (void)updatePlaceholder:(NSNotification *)notification
{
UITextField *textField = objc_getAssociatedObject(self, &KEY);
textField.font = self.font;
[textField setAlpha:self.text.length? 0 : 1];
}
@end
它使用简单,只是显而易见的
UITextView *myTextView = UITextView.new;
...
myTextView.placeholder = @"enter text here";
它通过添加一个UITextField -在正确的位置-在你的UITextView后面,并利用它的占位符代替(因此你不必担心得到正确的颜色等),然后监听通知,每当你的UITextView被改变显示/隐藏这个UITextField(因此它不会干扰你现有的UITextViewDelegate调用)。这里面没有什么神奇的数字……: -)
objc_setAssociatedObject()/objc_getAssociatedObject()是为了避免必须子类化UITextView。[不幸的是,要正确地定位UITextField,有必要引入一个'private'子类,以覆盖placeholderRectForBounds:]
改编自BobDickinson的斯威夫特回答。
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
另一个解决方案
import UIKit
protocol PlaceholderTextViewDelegate: class {
func placeholderTextViewDidChangeText(_ text: String)
func placeholderTextViewDidEndEditing(_ text: String)
}
final class PlaceholderTextView: UITextView {
weak var notifier: PlaceholderTextViewDelegate?
var ignoreEnterAction: Bool = true
var placeholder: String? {
didSet {
text = placeholder
selectedRange = NSRange(location: 0, length: 0)
}
}
var placeholderColor = UIColor.lightGray {
didSet {
if text == placeholder {
textColor = placeholderColor
}
}
}
var normalTextColor = UIColor.lightGray
var placeholderFont = UIFont.sfProRegular(28)
fileprivate var placeholderLabel: UILabel?
// MARK: - LifeCycle
override var text: String? {
didSet {
if text == placeholder {
textColor = placeholderColor
} else {
textColor = normalTextColor
}
}
}
init() {
super.init(frame: CGRect.zero, textContainer: nil)
awakeFromNib()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func awakeFromNib() {
super.awakeFromNib()
self.delegate = self
}
}
extension PlaceholderTextView: UITextViewDelegate {
// MARK: - UITextViewDelegate
func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
if text == "" && textView.text == placeholder {
return false
}
if let placeholder = placeholder,
textView.text == placeholder,
range.location <= placeholder.count {
textView.text = ""
}
if ignoreEnterAction && text == "\n" {
textView.resignFirstResponder()
return false
}
return true
}
func textViewDidChange(_ textView: UITextView) {
if let placeholder = placeholder {
textView.text = textView.text.replacingOccurrences(of: placeholder, with: "")
}
if let placeholder = placeholder,
text?.isEmpty == true {
text = placeholder
textColor = placeholderColor
selectedRange = NSRange(location: 0, length: 0)
} else {
textColor = normalTextColor
}
notifier?.placeholderTextViewDidChangeText(textView.text)
}
func textViewDidChangeSelection(_ textView: UITextView) {
if let placeholder = placeholder,
text == placeholder {
selectedRange = NSRange(location: 0, length: 0)
}
}
func textViewDidEndEditing(_ textView: UITextView) {
notifier?.placeholderTextViewDidEndEditing(textView.text)
if let placeholder = placeholder,
text?.isEmpty == true {
text = placeholder
textColor = placeholderColor
selectedRange = NSRange(location: 0, length: 0)
} else {
textColor = normalTextColor
}
}
}
结果: