//將要開始編輯的時候
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField; // return NO to disallow editing.
//已經(jīng)開始編輯的時候
- (void)textFieldDidBeginEditing:(UITextField *)textField; // became first responder
//將要結(jié)束編輯的時候
- (BOOL)textFieldShouldEndEditing:(UITextField *)textField;
//已經(jīng)結(jié)束編輯的時候
- (void)textFieldDidEndEditing:(UITextField *)textField; // may be called if forced even if shouldEndEditing returns NO (e.g. view removed from window) or endEditing:YES called
//這里的textField.text是獲取的是上一次編輯的內(nèi)容
//string可以獲取本次輸入的內(nèi)容(只能檢測英文和數(shù)字)（可以用來控制輸入）
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string; // return NO to not change text
//將要開始清除
- (BOOL)textFieldShouldClear:(UITextField *)textField;
//將要開始返回
- (BOOL)textFieldShouldReturn:(UITextField *)textField;
