监听UITextField获得\失去焦点

在UITextField的代理方法里做相关处理即可：

// 获得焦点- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{    _descLabel.text = @"获得焦点";    return YES;}// 失去焦点- (void)textFieldDidEndEditing:(UITextField *)textField{    _descLabel.text = @"失去焦点";}