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
- (void)textViewDidChange:(UITextView *)textView
{
placeholderLabel.hidden = YES;
}
在textview上放一个标签。
简单的Swift 3解决方案
添加UITextViewDelegate到类中
设置你的textview .delegate = self
创建placeholderLabel和位置它在你的textview
现在动画placeholderLabel。alpha在textViewDidChange:
func textViewDidChange(_ textView: UITextView) {
let newAlpha: CGFloat = textView.text.isEmpty ? 1 : 0
if placeholderLabel.alpha != newAlpha {
UIView.animate(withDuration: 0.3) {
self.placeholderLabel.alpha = newAlpha
}
}
}
你可能不得不使用placeholderLabel位置来设置它,但这应该不会太难
我找到了自己的解决方案
- (void)textViewDidBeginEditing:(UITextView *)textView
{
if ([textView.text isEqualToString:PLACEHOLDER_TEXT])
{
textView.textColor = [UIColor lightGrayColor];
dispatch_async(dispatch_get_main_queue(), ^
{
textView.selectedRange = NSMakeRange(0, 0);
});
}
else
{
textView.textColor = [UIColor blackColor];
}
[textView becomeFirstResponder];
}
- (void)textViewDidEndEditing:(UITextView *)textView
{
if ([textView.text isEqualToString:@""])
{
textView.text = PLACEHOLDER_TEXT;
textView.textColor = [UIColor lightGrayColor];
}
[textView resignFirstResponder];
}
- (BOOL)textView:(UITextView *)textView
shouldChangeTextInRange:(NSRange)range
replacementText:(NSString *)text
{
if (range.location == 0 && range.length == [[textView text] length] && [text isEqualToString:@""])
{
textView.text = PLACEHOLDER_TEXT;
textView.textColor = [UIColor lightGrayColor];
dispatch_async(dispatch_get_main_queue(), ^
{
textView.selectedRange = NSMakeRange(0, 0);
});
return NO;
}
if ([textView.text isEqualToString:PLACEHOLDER_TEXT])
{
textView.text = @"";
textView.textColor = [UIColor blackColor];
}
return YES;
}
我对bcd的解决方案做了一些小修改,以允许从Xib文件初始化、文本包装和保持背景颜色。希望它能为其他人省去麻烦。
UIPlaceHolderTextView.h:
#import <Foundation/Foundation.h>
IB_DESIGNABLE
@interface UIPlaceHolderTextView : UITextView
@property (nonatomic, retain) IBInspectable NSString *placeholder;
@property (nonatomic, retain) IBInspectable UIColor *placeholderColor;
-(void)textChanged:(NSNotification*)notification;
@end
UIPlaceHolderTextView.m:
#import "UIPlaceHolderTextView.h"
@interface UIPlaceHolderTextView ()
@property (nonatomic, retain) UILabel *placeHolderLabel;
@end
@implementation UIPlaceHolderTextView
CGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25;
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
#if __has_feature(objc_arc)
#else
[_placeHolderLabel release]; _placeHolderLabel = nil;
[_placeholderColor release]; _placeholderColor = nil;
[_placeholder release]; _placeholder = nil;
[super dealloc];
#endif
}
- (void)awakeFromNib
{
[super awakeFromNib];
// Use Interface Builder User Defined Runtime Attributes to set
// placeholder and placeholderColor in Interface Builder.
if (!self.placeholder) {
[self setPlaceholder:@""];
}
if (!self.placeholderColor) {
[self setPlaceholderColor:[UIColor lightGrayColor]];
}
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}
- (id)initWithFrame:(CGRect)frame
{
if( (self = [super initWithFrame:frame]) )
{
[self setPlaceholder:@""];
[self setPlaceholderColor:[UIColor lightGrayColor]];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
- (void)textChanged:(NSNotification *)notification
{
if([[self placeholder] length] == 0)
{
return;
}
[UIView animateWithDuration:UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION animations:^{
if([[self text] length] == 0)
{
[[self viewWithTag:999] setAlpha:1];
}
else
{
[[self viewWithTag:999] setAlpha:0];
}
}];
}
- (void)setText:(NSString *)text {
[super setText:text];
[self textChanged:nil];
}
- (void)drawRect:(CGRect)rect
{
if( [[self placeholder] length] > 0 )
{
if (_placeHolderLabel == nil )
{
_placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
_placeHolderLabel.lineBreakMode = NSLineBreakByWordWrapping;
_placeHolderLabel.numberOfLines = 0;
_placeHolderLabel.font = self.font;
_placeHolderLabel.backgroundColor = [UIColor clearColor];
_placeHolderLabel.textColor = self.placeholderColor;
_placeHolderLabel.alpha = 0;
_placeHolderLabel.tag = 999;
[self addSubview:_placeHolderLabel];
}
_placeHolderLabel.text = self.placeholder;
[_placeHolderLabel sizeToFit];
[self sendSubviewToBack:_placeHolderLabel];
}
if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
{
[[self viewWithTag:999] setAlpha:1];
}
[super drawRect:rect];
}
@end
你也可以创建一个新的类TextViewWithPlaceholder作为UITextView的子类。
(这段代码有点粗糙——但我认为它在正确的轨道上。)
@interface TextViewWithPlaceholder : UITextView
{
NSString *placeholderText; // make a property
UIColor *placeholderColor; // make a property
UIColor *normalTextColor; // cache text color here whenever you switch to the placeholderColor
}
- (void) setTextColor: (UIColor*) color
{
normalTextColor = color;
[super setTextColor: color];
}
- (void) updateForTextChange
{
if ([self.text length] == 0)
{
normalTextColor = self.textColor;
self.textColor = placeholderColor;
self.text = placeholderText;
}
else
{
self.textColor = normalTextColor;
}
}
在委托中,添加以下内容:
- (void)textViewDidChange:(UITextView *)textView
{
if ([textView respondsToSelector: @selector(updateForTextChange)])
{
[textView updateForTextChange];
}
}