以下是addTarget：
import "ViewController.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *nameView;
@property (weak, nonatomic) IBOutlet UITextField *pwdView;
@property (weak, nonatomic) IBOutlet UIButton *loginBtn;
@end
@implementation ViewController
(void)viewDidLoad {
[super viewDidLoad];
[self.nameView addTarget:self action:@selector(textValueChanged) forControlEvents:UIControlEventEditingChanged];
[self.pwdView addTarget:self action:@selector(textValueChanged) forControlEvents:UIControlEventEditingChanged];
}
(void)textValueChanged
{
self.loginBtn.enabled = (self.nameView.text.length != 0 && self.pwdView.text.length != 0);
}
@end
以下是通知：
通知
(void)viewDidLoad {
[super viewDidLoad];
//创建通知
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
//注册通知
[center addObserver:self selector:@selector(textValueChanged:) name:UITextFieldTextDidChangeNotification object:self.nameView];
[center addObserver:self selector:@selector(textValueChanged:) name:UITextFieldTextDidChangeNotification object:self.pwdView];
}
//监听文本框的值的改变
(void)textValueChanged:(NSNotification *)notice
{
self.loginBtn.enabled = (self.nameView.text.length != 0 && self.pwdView.text.length != 0);
}
//移除通知
(void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
以下是KVO：
(void)viewDidLoad {
[super viewDidLoad];
//KVO
[self.nameView addObserver:self forKeyPath:@"text" options:NSKeyValueObservingOptionNew context:nil];
[self.pwdView addObserver:self forKeyPath:@"text" options:NSKeyValueObservingOptionNew context:nil];
}
/**
kvo回调
*/
(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
self.loginBtn.enabled = (self.pwdView.text.length != 0 && self.nameView.text.length != 0);
}
//移除KVO
(void)dealloc
{
[self.nameView removeObserver:self forKeyPath:@"text"];
[self.pwdView removeObserver:self forKeyPath:@"text"];
}
以下是EditingChanged：
/**
监听登录文本框的输入
*/
(IBAction)nameViewChange
{
self.loginBtn.enabled = (self.nameView.text.length != 0 && self.pwdView.text.length != 0);
}
/**
登录密码输入框的输入
*/
(IBAction)pwdViewChange
{
self.loginBtn.enabled = (self.nameView.text.length != 0 && self.pwdView.text.length != 0);
}
这个在连线的时候，选择的是EditingChanged 这个方法
