我知道这里有很多用于 UITextView 占位符的链接，我尝试了一个对我有用的链接，但我没有用。即使我开始在 textView 中输入，它们的占位符文本也会一直存在。有人知道为什么吗？我在下面粘贴了我的代码。
AddExerciseViewController.m
#import "AddExerciseViewController.h"
@implementation AddExerciseViewController
@synthesize nameTextField = _nameTextField;
@synthesize descriptionTextView = _descriptionTextView;
@synthesize placeholderLabel = _placeholderLabel;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void)viewDidLoad
{
_descriptionTextView.layer.borderWidth = 3.0f;
_descriptionTextView.layer.borderColor = [[UIColor grayColor ] CGColor];
_descriptionTextView.layer.cornerRadius = 5;
_descriptionTextView.clipsToBounds = YES;
_placeholderLabel = [[UILabel alloc] initWithFrame:CGRectMake(10.0, 0.0, _descriptionTextView.frame.size.width - 20.0, 34.0)];
[_placeholderLabel setText: @"FooBar"];
// placeholderLabel is instance variable retained by view controller
[_placeholderLabel setBackgroundColor:[UIColor clearColor]];
[_placeholderLabel setTextColor:[UIColor lightGrayColor]];
[_descriptionTextView addSubview:_placeholderLabel];
[super viewDidLoad];
}
- (void) textViewDidChange:(UITextView *)theTextView
{
if(![_descriptionTextView hasText]) {
[_descriptionTextView addSubview:_placeholderLabel];
[UIView animateWithDuration:0.15 animations:^{
_descriptionTextView.alpha = 1.0;
}];
} else if ([[_descriptionTextView subviews] containsObject:_placeholderLabel]) {
[UIView animateWithDuration:0.15 animations:^{
_placeholderLabel.alpha = 0.0;
} completion:^(BOOL finished) {
[_placeholderLabel removeFromSuperview];
}];
}
}
- (void)textViewDidEndEditing:(UITextView *)theTextView
{
if (![_descriptionTextView hasText]) {
[_descriptionTextView addSubview:_placeholderLabel];
[UIView animateWithDuration:0.15 animations:^{
_placeholderLabel.alpha = 1.0;
}];
}
}
- (void)viewDidUnload
{
[self setDescriptionTextView:nil];
[self setNameTextField:nil];
[super viewDidUnload];
}
@结尾