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
我创建了一个实例变量来检查是否显示占位符:
BOOL showPlaceHolder;
UITextView * textView; // and also the textView
在viewDidLoad上设置:
[self setPlaceHolder];
下面是它的作用:
- (void)setPlaceholder
{
textView.text = NSLocalizedString(@"Type your question here", @"placeholder");
textView.textColor = [UIColor lightGrayColor];
self.showPlaceHolder = YES; //we save the state so it won't disappear in case you want to re-edit it
}
我还创建了一个按钮来退出键盘。您不必这样做,但这里很酷的事情是,如果没有输入任何内容,占位符将再次显示
- (void)textViewDidBeginEditing:(UITextView *)txtView
{
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:self action:@selector(resignKeyboard)];
if (self.showPlaceHolder == YES)
{
textView.textColor = [UIColor blackColor];
textView.text = @"";
self.showPlaceHolder = NO;
}
}
- (void)resignKeyboard
{
[textView resignFirstResponder];
//here if you created a button like I did to resign the keyboard, you should hide it
if (textView.text.length == 0) {
[self setPlaceholder];
}
}
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。
下面是swift 3.1的代码
原始代码由杰森乔治在第一个答案。
不要忘记设置你的自定义类的TextView在接口生成器UIPlaceHolderTextView,然后设置占位符和占位符属性。
import UIKit
@IBDesignable
class UIPlaceHolderTextView: UITextView {
@IBInspectable var placeholder: String = ""
@IBInspectable var placeholderColor: UIColor = UIColor.lightGray
private let uiPlaceholderTextChangedAnimationDuration: Double = 0.05
private let defaultTagValue = 999
private var placeHolderLabel: UILabel?
override func awakeFromNib() {
super.awakeFromNib()
NotificationCenter.default.addObserver(
self,
selector: #selector(textChanged),
name: NSNotification.Name.UITextViewTextDidChange,
object: nil
)
}
override init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
NotificationCenter.default.addObserver(
self,
selector: #selector(textChanged),
name: NSNotification.Name.UITextViewTextDidChange,
object: nil
)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
NotificationCenter.default.addObserver(
self,
selector: #selector(textChanged),
name: NSNotification.Name.UITextViewTextDidChange,
object: nil
)
}
deinit {
NotificationCenter.default.removeObserver(
self,
name: NSNotification.Name.UITextViewTextDidChange,
object: nil
)
}
@objc private func textChanged() {
guard !placeholder.isEmpty else {
return
}
UIView.animate(withDuration: uiPlaceholderTextChangedAnimationDuration) {
if self.text.isEmpty {
self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(1.0)
}
else {
self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(0.0)
}
}
}
override var text: String! {
didSet{
super.text = text
textChanged()
}
}
override func draw(_ rect: CGRect) {
if !placeholder.isEmpty {
if placeHolderLabel == nil {
placeHolderLabel = UILabel.init(frame: CGRect(x: 0, y: 8, width: bounds.size.width - 16, height: 0))
placeHolderLabel!.lineBreakMode = .byWordWrapping
placeHolderLabel!.numberOfLines = 0
placeHolderLabel!.font = font
placeHolderLabel!.backgroundColor = UIColor.clear
placeHolderLabel!.textColor = placeholderColor
placeHolderLabel!.alpha = 0
placeHolderLabel!.tag = defaultTagValue
self.addSubview(placeHolderLabel!)
}
placeHolderLabel!.text = placeholder
placeHolderLabel!.sizeToFit()
self.sendSubview(toBack: placeHolderLabel!)
if text.isEmpty && !placeholder.isEmpty {
viewWithTag(defaultTagValue)?.alpha = 1.0
}
}
super.draw(rect)
}
}
你可以在UITextView上设置标签
[UITextView addSubView:lblPlaceHoldaer];
并隐藏在TextViewdidChange方法上。
这是一个简单易行的方法。
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];
}
}
这里有一个简单而聪明的方法来获得完美的行为。
让我们借用UITextField中的占位符。
Set up a textField and set its text transparent. self.placeholderTextField = [[UITextField alloc] init]; /* adjust the frame to fit it in the first line of your textView */ self.placeholderTextField.frame = CGRectMake(0.0, 0.0, yourTextView.width, 30.0); self.placeholderTextField.textColor = [UIColor clearColor]; self.placeholderTextField.userInteractionEnabled = NO; self.placeholderTextField.font = yourTextView.font; self.placeholderTextField.placeholder = @"sample placeholder"; [yourTextView addSubview:self.placeholderTextField]; Set textView's delegate and synchronize the textField and textView. yourTextView.delegate = self; then - (void)textViewDidChange:(UITextView *)textView { self.placeholderTextField.text = textView.text; } That's all.