iOS控件TextView添加placeholder属性的两种方法

TextView添加placeholder属性的两种方法

1.创建PHATextView类，PHATextView.h中代码如下：

#import <UIKit/UIKit.h>

@interface PHATextView : UITextView {
UIColor *_contentColor;
BOOL _editing;
}

@property(strong, nonatomic) NSString *placeholder;
@property(strong, nonatomic) UIColor *placeholderColor;
@end

2.PHATextView.m中代码如下：

#import "PHATextView.h"

@implementation PHATextView

- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code
_contentColor = [UIColor blackColor];
_editing = NO;
_placeholderColor = [UIColor lightGrayColor];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(startEditing:) name:UITextViewTextDidBeginEditingNotification object:self];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(finishEditing:) name:UITextViewTextDidEndEditingNotification object:self];

}
return self;
}

#pragma mark - super

- (void)setTextColor:(UIColor *)textColor {
[super setTextColor:textColor];
_contentColor = textColor;
}

- (NSString *)text {
if ([super.text isEqualToString:_placeholder] && super.textColor == _placeholderColor) {
return @"";
}
return [super text];
}

- (void)setText:(NSString *)string {
if (string == nil || string.length == 0) {
return;
}
super.textColor = _contentColor;
[super setText:string];
}

#pragma mark - setting

- (void)setPlaceholder:(NSString *)string {
_placeholder = string;
[self finishEditing:nil];
}

#pragma mark - notification

- (void)startEditing:(NSNotification *)notification {
_editing = YES;
if ([super.text isEqualToString:_placeholder] && super.textColor == _placeholderColor) {

super.textColor = _contentColor;
super.text = @"";
}
}

- (void)finishEditing:(NSNotification *)notification {
_editing = NO;
if (super.text.length == 0) {

super.textColor = _placeholderColor;
super.text = _placeholder;
}
}

// 创建EMTextView对象，设置Placeholder，走finishEditing方法，此时super.text.length == 0，

3. 创建PHATextView类对象

#import "ViewController.h"
#import "PHATextView.h"

@interface ViewController ()<UITextViewDelegate>
@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];

// 初始化输入框
PHATextView *textView = [[PHATextView alloc] initWithFrame:CGRectMake(10, 40, 300, 80)];
textView.font = [UIFont systemFontOfSize:14.0];
textView.returnKeyType = UIReturnKeyDone;
textView.placeholder = @"请输入群组简介";
textView.delegate = self;
textView.backgroundColor = [UIColor whiteColor];
textView.layer.borderColor = [[UIColor lightGrayColor] CGColor];
textView.layer.borderWidth = 0.5;
textView.layer.cornerRadius = 3;
[self.view addSubview:textView];
}
@end

1.创建PHBTextView类，PHBTextView.h中代码如下：

#import <UIKit/UIKit.h>

@interface PHBTextView : UITextView

/**
*  提示用户输入的标语
*/
@property (nonatomic, copy) NSString *placeHolder;

/**
*  标语文本的颜色
*/
@property (nonatomic, strong) UIColor *placeHolderColor;

@end

2.PHBTextView.m中代码如下：

#import "PHBTextView.h"

@implementation PHBTextView

#pragma mark - Setters

- (void)setPlaceHolder:(NSString *)placeHolder {

if([placeHolder isEqualToString:_placeHolder]) {
return;
}

NSUInteger maxChars = [PHBTextView maxCharactersPerLine];

if([placeHolder length] > maxChars) {
placeHolder = [placeHolder substringToIndex:maxChars - 8];
placeHolder = [[placeHolder stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] stringByAppendingFormat:@"..."];
}

_placeHolder = placeHolder;
[self setNeedsDis
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play];
}

- (void)setPlaceHolderColor:(UIColor *)placeHolderColor {

if([placeHolderColor isEqual:_placeHolderColor]) {
return;
}
_placeHolderColor = placeHolderColor;

[self setNeedsDisplay];
}

//根据iPhone或者iPad来获取每行字体的高度
+ (NSUInteger)maxCharactersPerLine {
// 判断是不是iPhone设备
return ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPhone) ? 33 : 109;
}

#pragma mark - Text view overrides

- (void)setText:(NSString *)text {
[super setText:text];
[self setNeedsDisplay];
}

- (void)setAttributedText:(NSAttributedString *)attributedText {
[super setAttributedText:attributedText];
[self setNeedsDisplay];
}

- (void)setFont:(UIFont *)font {
[super setFont:font];
[self setNeedsDisplay];
}

- (void)setTextAlignment:(NSTextAlignment)textAlignment {
[super setTextAlignment:textAlignment];
[self setNeedsDisplay];
}

#pragma mark - Notifications

- (void)didReceiveTextDidChangeNotification:(NSNotification *)notification {
[self setNeedsDisplay];
}

#pragma mark - Life cycle

- (void)setup {
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(didReceiveTextDidChangeNotification:)
name:UITextViewTextDidChangeNotification
object:self];

_placeHolderColor = [UIColor lightGrayColor];

self.autoresizingMask = UIViewAutoresizingFlexibleWidth;
self.scrollIndicatorInsets = UIEdgeInsetsMake(10.0f, 0.0f, 10.0f, 8.0f);
self.contentInset = UIEdgeInsetsZero;
self.scrollEnabled = YES;
self.scrollsToTop = NO;   // YES 点击屏幕的Status Bar即可回到顶部
self.userInteractionEnabled = YES;
self.font = [UIFont systemFontOfSize:16.0f];
self.textColor = [UIColor blackColor];
self.backgroundColor = [UIColor whiteColor];
self.keyboardAppearance = UIKeyboardAppearanceDefault;
self.keyboardType = UIKeyboardTypeDefault;
self.returnKeyType = UIReturnKeyDefault;
self.textAlignment = NSTextAlignmentLeft;
}

- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code
[self setup];
}
return self;
}

- (void)dealloc {
_placeHolder = nil;
_placeHolderColor = nil;
[[NSNotificationCenter defaultCenter] removeObserver:self name:UITextViewTextDidChangeNotification object:self];
}

#pragma mark - Drawing

- (void)drawRect:(CGRect)rect {
[super drawRect:rect];

if([self.text length] == 0 && self.placeHolder) {
CGRect placeHolderRect = CGRectMake(10.0f,
7.0f,
rect.size.width,
rect.size.height);
[self.placeHolderColor set];

if (NSFoundationVersionNumber > NSFoundationVersionNumber_iOS_7_0) {
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
paragraphStyle.alignment = self.textAlignment;

[self.placeHolder drawInRect:placeHolderRect
withAttributes:@{ NSFontAttributeName : self.font,
NSForegroundColorAttributeName : self.placeHolderColor,
NSParagraphStyleAttributeName : paragraphStyle }];
}
else {
[self.placeHolder drawInRect:placeHolderRect
withFont:self.font
lineBreakMode:NSLineBreakByTruncatingTail
alignment:self.textAlignment];
}
}
}
@end

3.创建PHBTextView类对象

#import "ViewController.h"
#import "PHBTextView.h"

@interface ViewController ()<UITextViewDelegate>
@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];

// 初始化输入框
PHBTextView *textV = [[PHBTextView  alloc] initWithFrame:CGRectMake(10, 200, 300, 50)];
textV.returnKeyType = UIReturnKeySend;
textV.enablesReturnKeyAutomatically = YES; // UITextView内部判断send按钮是否可以用
textV.placeHolder = @"输入新消息输入新消息输入新消息输入新消息输入新消息";
textV.delegate = self;
textV.backgroundColor = [UIColor clearColor];
textV.layer.borderColor = [UIColor colorWithWhite:0.8f alpha:1.0f].CGColor;
textV.layer.borderWidth = 0.65f;
textV.layer.cornerRadius = 6.0f;
[self.view addSubview:textV];
}
@end