使用 NSNotificationCenter 捕获按键事件
这个解决方案 接收 iPhone 键盘事件
提供了一种使用通知中心捕获按键事件的方法。
[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(keyPressed:) name: UITextFieldTextDidChangeNotification object: nil];
[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(keyPressed:) name: UITextViewTextDidChangeNotification object: nil];
........
-(void) keyPressed: (NSNotification*) notification
{
NSLog([[notification object]text]);
}
它工作正常，但是对于从键盘上按下的每个键， keyPressed 函数都会被调用 3 次。
这是正常现象还是我做错了什么？
特奥
this solution
Receive iPhone keyboard events
offers a way to capture the keypress event using notification center.
[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(keyPressed:) name: UITextFieldTextDidChangeNotification object: nil];
[[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(keyPressed:) name: UITextViewTextDidChangeNotification object: nil];
........
-(void) keyPressed: (NSNotification*) notification
{
NSLog([[notification object]text]);
}
It works ok, but for every key that is been pressed from the keyboard the keyPressed function gets called 3 times.
Is this normal or am i doing something wrong?
Teo
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评论（1）
每次按下按键时，通知只应出现一次。至少这是我在测试时得到的。我唯一能想到的是您调用了
addObserver:selector:name:object:三次。也许您在多个视图控制器中执行此操作，但忘记调用
removeObserver:name:object:？或者您在一个被多次调用的函数中调用
addObserver:selector:name:object:？viewDidLoad通常是放置此类代码的好地方。The notification should only appear once per key pressed. At least that is what I get when testing. The only thing I can think of is that you are calling
addObserver:selector:name:object:three times.Perhaps you are doing it in several view controllers and forget to call
removeObserver:name:object:?Or you are calling
addObserver:selector:name:object:in a function that gets called several times?viewDidLoadis normally a good place to put code like this.