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
我扩展了KmKndy的答案,这样在用户开始编辑UITextView之前,占位符仍然是可见的,而不仅仅是点击它。这反映了Twitter和Facebook应用程序的功能。我的解决方案不需要你子类和工作,如果用户类型直接或粘贴文本!
- (void)textViewDidChangeSelection:(UITextView *)textView{
if ([textView.text isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]])[textView setSelectedRange:NSMakeRange(0, 0)];
}
- (void)textViewDidBeginEditing:(UITextView *)textView{
[textView setSelectedRange:NSMakeRange(0, 0)];
}
- (void)textViewDidChange:(UITextView *)textView
{
if (textView.text.length != 0 && [[textView.text substringFromIndex:1] isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]]){
textView.text = [textView.text substringToIndex:1];
textView.textColor = [UIColor blackColor]; //optional
}
else if(textView.text.length == 0){
textView.text = @"What's happening?";
textView.textColor = [UIColor lightGrayColor];
[textView setSelectedRange:NSMakeRange(0, 0)];
}
}
- (void)textViewDidEndEditing:(UITextView *)textView
{
if ([textView.text isEqualToString:@""]) {
textView.text = @"What's happening?";
textView.textColor = [UIColor lightGrayColor]; //optional
}
[textView resignFirstResponder];
}
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
if (textView.text.length > 1 && [textView.text isEqualToString:@"What's happening?"]) {
textView.text = @"";
textView.textColor = [UIColor blackColor];
}
return YES;
}
只需要记住在创建时使用准确的文本设置myUITextView即可。
UITextView *myUITextView = [[UITextView alloc] init];
myUITextView.delegate = self;
myUITextView.text = @"What's happening?";
myUITextView.textColor = [UIColor lightGrayColor]; //optional
在包含这些方法之前,让父类成为一个UITextView委托。
@interface MyClass () <UITextViewDelegate>
@end
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。
还有一个简单的答案,使用CATextLayer。
添加CATextLayer到UITextView的层。 使用UITextViewDelegate方法,简单地改变CATextLayer的颜色。
func txtViewPlaceholder() {
let textlayer = CATextLayer()
textlayer.frame = CGRect(x: 5, y: 5, width: 200, height: 18)
textlayer.contentsScale = UIScreen.main.scale
textlayer.fontSize = 12
textlayer.alignmentMode = kCAAlignmentLeft
textlayer.string = "Enter here"
textlayer.isWrapped = true
textlayer.name = "placeholder"
textlayer.backgroundColor = UIColor.white.cgColor
textlayer.foregroundColor = UIColor.black.cgColor
yourTxtVw.layer.insertSublayer(textlayer, at: 0)
}
func removeAddPlaceholder(remove: Bool, textView: UITextView) {
for layers in textView.layer.sublayers! where layers.name == "placeholder" {
if remove {
(layers as! CATextLayer).foregroundColor = UIColor.white.cgColor
} else {
(layers as! CATextLayer).foregroundColor = UIColor.black.cgColor
}
}
}
extension YourViewController : UITextViewDelegate {
func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
removeAddPlaceholder(remove: true, textView: textView)
return true
}
func textViewDidEndEditing(_ textView: UITextView) {
if textView.text.count <= 0 {
removeAddPlaceholder(remove: false, textView: textView)
}
}
}
如果有人需要Swift的解决方案:
添加UITextViewDelegate到类中
var placeHolderText = "Placeholder Text..."
override func viewDidLoad() {
super.viewDidLoad()
textView.delegate = self
}
func textViewShouldBeginEditing(textView: UITextView) -> Bool {
self.textView.textColor = .black
if(self.textView.text == placeHolderText) {
self.textView.text = ""
}
return true
}
func textViewDidEndEditing(textView: UITextView) {
if(textView.text == "") {
self.textView.text = placeHolderText
self.textView.textColor = .lightGray
}
}
override func viewWillAppear(animated: Bool) {
if(currentQuestion.answerDisplayValue == "") {
self.textView.text = placeHolderText
self.textView.textColor = .lightGray
} else {
self.textView.text = "xxx" // load default text / or stored
self.textView.textColor = .black
}
}
好吧,我的阴沟有点不同 我创建了一个小班来为你做这件事。
TextViewShader。m文件
#import "TextViewShader.h"
@implementation TextViewShader
-(id)initWithShadedTextView:(NSString *)text textViewToShade:(UITextView *)textview {
self = [super initWithFrame:textview.frame];
if (self) {
if (shadeLabel==nil)
{
shadeLabel= [[UILabel alloc]initWithFrame:CGRectMake(10, 0, textview.frame.size.width, 30)];
}
shadeLabel.text =text;// @"Enter Your Support Request";
shadeLabel.textColor = [UIColor lightGrayColor];
[textview setDelegate: self];
[textview addSubview:shadeLabel];
}
return self;
}
-(void)textViewDidChange:(UITextView *)textView{
if (textView.text.length==0)
{
shadeLabel.hidden=false;
}
else
{
shadeLabel.hidden=true;
}
}
@end
TextViewShader.h文件
#import <UIKit/UIKit.h>
@interface TextViewShader : UIView<UITextViewDelegate>{
UILabel *shadeLabel;
}
-(id)initWithShadedTextView:(NSString *)text textViewToShade:(UITextView *)textview ;
@end
这是简单的一行代码使用(不要忘记添加#import "TextViewShader.h")
TextViewShader* shader = [[TextViewShader alloc]initWithShadedTextView:@"Enter Your Support Request" textViewToShade: youruitextviewToshade];
玩得开心!
更简单,并且仍然考虑到用户在某些时候输入的一些文本
BOOL placeHolderTextVisible;
在viewDidLoad上,设置它为YES(或DidMoveToSuperview,或awakeFromNib)
然后,在 - (BOOL) textView:(UITextView*)textView shouldBeginEditing
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView;
{
if (placeHolderTextVisible) {
placeHolderTextVisible = NO;
textView.text = @"";
}
return YES;
}