UITextView+PlaceholderText.h
#import <UIKit/UIKit.h>
#define DEFAULT_PLACEHOLDER_COLOR (UIColor.lightGrayColor)
#define DRAW_DEBUG 0
@interface UITextView (PlaceholderText)
– (void)setPlaceholder:(NSString *)placeholder;
– (NSString *)placeholder;
– (void)setPlaceholderColor:(UIColor *)placeholderColor;
– (UIColor *)placeholderColor;
– (void)setPlaceholderAnimation:(BOOL)placeholderAnimation;
– (BOOL)placeholderAnimation;
@end
UITextView+PlaceholderText.m
#import “UITextView+PlaceholderText.h”
#import <objc/runtime.h>
#import <objc/message.h>
@implementation UITextView (PlaceholderText)
CGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25;
static void * const PLACEHOLDER_KEY = (void*)&PLACEHOLDER_KEY;
static void * const PLACEHOLDER_COLOR_KEY = (void*)&PLACEHOLDER_COLOR_KEY;
static void * const PLACEHOLDER_LABEL_KEY = (void*)&PLACEHOLDER_LABEL_KEY;
static void * const PLACEHOLDER_ANIMATION_KEY = (void*)&PLACEHOLDER_ANIMATION_KEY;
static void
swizzle(Class c, SEL orig, SEL new) {
Method origMethod = class_getInstanceMethod(c, orig);
Method newMethod = class_getInstanceMethod(c, new);
if (class_addMethod(c,
orig,
method_getImplementation(newMethod),
method_getTypeEncoding(newMethod)))
{
class_replaceMethod(c,
new,
method_getImplementation(origMethod),
method_getTypeEncoding(origMethod));
} else {
method_exchangeImplementations(origMethod, newMethod);
}
}
+ (void)initialize {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if ([self isKindOfClass:UITextView.class]) {
swizzle(self, @selector(setText:), @selector(newSetText:));
swizzle(self, @selector(initWithFrame:), @selector(initWithFrameNew:));
}
});
}
– (void)setPlaceholder:(NSString *)placeholder
{
objc_setAssociatedObject(self,
PLACEHOLDER_KEY,
placeholder,
OBJC_ASSOCIATION_COPY_NONATOMIC);
}
– (void)setup {
#if DRAW_DEBUG
self.layer.borderColor = UIColor.blueColor.CGColor;
self.layer.borderWidth = 2;
#endif
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}
– (void)awakeFromNib {
[super awakeFromNib];
[self setup];
}
– (void)textChanged:(NSNotification *)notification
{
if (self.placeholder.length == 0) {
return;
}
if (self.placeholderAnimation) {
[UIView animateWithDuration:UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION
animations:^{
[self viewWithTag:999].alpha = (self.text.length == 0) ? 1 : 0;
}];
} else {
[self viewWithTag:999].alpha = (self.text.length == 0) ? 1 : 0;
}
}
– (id)initWithFrameNew:(CGRect)frame {
if (self = [self initWithFrameNew:frame]) {
[self setup];
}
return self;
}
– (void)newSetText:(NSString *)text {
[self newSetText:text];
[self textChanged:nil];
}
– (NSString *)placeholder
{
return objc_getAssociatedObject(self, PLACEHOLDER_KEY);
}
– (void)setPlaceholderColor:(UIColor *)placeholderColor
{
objc_setAssociatedObject(self,
PLACEHOLDER_COLOR_KEY,
placeholderColor,
OBJC_ASSOCIATION_ASSIGN);
}
– (UIColor *)placeholderColor
{
UIColor *result = objc_getAssociatedObject(self, PLACEHOLDER_KEY);
if (!!result) {
result = DEFAULT_PLACEHOLDER_COLOR;
}
return result;
}
– (UILabel *)newPlaceholderLabel {
UILabel *placeholderLabel = [[UILabel alloc] initWithFrame:self.bounds];
placeholderLabel.lineBreakMode = NSLineBreakByClipping;
placeholderLabel.numberOfLines = 1;
placeholderLabel.font = self.font;
placeholderLabel.adjustsFontSizeToFitWidth = YES;
placeholderLabel.baselineAdjustment = UIBaselineAdjustmentAlignCenters;
placeholderLabel.backgroundColor = UIColor.clearColor;
placeholderLabel.textColor = self.placeholderColor;
#if DRAW_DEBUG
placeholderLabel.layer.borderColor = UIColor.redColor.CGColor;
placeholderLabel.layer.borderWidth = 4;
#endif
placeholderLabel.alpha = 0;
placeholderLabel.tag = 999;
[self addSubview:placeholderLabel];
return placeholderLabel;
}
– (void)setPlaceholderLabel:(UILabel *)placeholderLabel {
objc_setAssociatedObject(self,
PLACEHOLDER_LABEL_KEY,
placeholderLabel,
OBJC_ASSOCIATION_ASSIGN);
}
– (UILabel *)placeholderLabel {
UILabel *placeholderLabel = objc_getAssociatedObject(self, PLACEHOLDER_LABEL_KEY);
if (!placeholderLabel) {
[self setPlaceholderLabel:placeholderLabel = [self newPlaceholderLabel]];
}
return placeholderLabel;
}
– (void)setPlaceholderAnimation:(BOOL)placeholderAnimation {
objc_setAssociatedObject(self,
PLACEHOLDER_ANIMATION_KEY,
[NSNumber numberWithBool:placeholderAnimation],
OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
– (BOOL)placeholderAnimation {
return ((NSNumber *)objc_getAssociatedObject(self, PLACEHOLDER_ANIMATION_KEY)).boolValue;
}
– (void)drawRect:(CGRect)rect
{
if (self.placeholder && self.placeholder.length > 0) {
self.placeholderLabel.text = self.placeholder;
[self sendSubviewToBack:self.placeholderLabel];
if (self.text && self.text.length == 0) {
[self viewWithTag:999].alpha = 1;
}
self.placeholderLabel.textAlignment = self.textAlignment;
}
[super drawRect:rect];
}
@end
iOS Development Objective C 