占位符文字的颜色

#define Placeholder @"placeholderLabel.textColor"
[self setValue:[UIColor grayColor] forKeyPath:Placeholder];

添加监听方法

[self addTarget:self action:@selector(editingDidBegin) forControlEvents:UIControlEventEditingDidBegin];
[self addTarget:self action:@selector(editingDidEnd) forControlEvents:UIControlEventEditingDidEnd];


代理也有相应的方法 可以在类里找到


还有通知的方法
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(editingDidBegin) name:UITextFieldTextDidBeginEditingNotification object:textField];// 参数

 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(editingDidEnd) name:UITextFieldTextDidEndEditingNotification object:textField]; //  参数


// 实现的方法

- (void)editingDidBegin{
    [self setValue:[UIColor whiteColor] forKeyPath:Placeholder];
}

- (void)editingDidEnd{
    [self setValue:[UIColor grayColor] forKeyPath:Placeholder];
}

通过下面放大也可以监听

- (BOOL)becomeFirstResponder{
    [self setValue:[UIColor whiteColor] forKeyPath:Placeholder];
    return [super becomeFirstResponder];
}

- (BOOL)resignFirstResponder{
    [self setValue:[UIColor grayColor] forKeyPath:Placeholder];
    return [super resignFirstResponder];
}