初学ios之建立用户文本输入的模态警告框

平时的警告框就是弹出一个警告，没想着可以输入，发现能输入文字并处理也是蛮方便的。

以注册一个用户为例，首先看看头文件需要的东西

@interface ViewController :UIViewController<UIAlertViewDelegate>{
   UITextField *_username;
   UITextField *_password;
    
   UIAlertView *loginAlert;
    UIActivityIndicatorView *indicator;
}
@end

头文件里需要两个输入框，用户名和密码，然后一个警告框，一个模态进度指示器（这个可以不要），UIAlertViewDelegate这个代理让我们处理点击按钮后的事件

实现扩展（参考书上的例子）

@interface UIAlertView (extended)
- (UITextField *) textFieldAtIndex: (int) index;
- (void) addTextFieldWithValue: (NSString *) value label: (NSString *) label;
@end

然后是实现，先在导航控制器上添加注册按钮，嘿嘿，点击它会触发registerUser这个方法。

self.navigationItem.rightBarButtonItem = [[UIBarButtonItemalloc] initWithTitle:@"注册"style:UIBarButtonItemStyleBorderedtarget:selfaction:@selector(registerUser)];

看方法的实现

//注册用户

- (void)registerUser{
    
   if (!loginAlert) {
       loginAlert = [[UIAlertViewalloc]
                     initWithTitle: @"注册"
                     message:@"请输入用户信息"
                     delegate:self
                     cancelButtonTitle:@"Cancel"
                     otherButtonTitles:@"OK",nil];
        [loginAlertaddTextFieldWithValue:@""label:@"用户名"];
        [loginAlertaddTextFieldWithValue:@""label:@"密码"];
        
        // Name field
       UITextField *usernameTxt = [loginAlerttextFieldAtIndex:0];
        usernameTxt.clearButtonMode =UITextFieldViewModeWhileEditing;
        usernameTxt.keyboardType =UIKeyboardTypeAlphabet;
        usernameTxt.keyboardAppearance =UIKeyboardAppearanceAlert;
        usernameTxt.autocapitalizationType =UITextAutocapitalizationTypeWords;
        usernameTxt.autocorrectionType =UITextAutocorrectionTypeNo;
        
       UITextField *passwordTxt = [loginAlerttextFieldAtIndex:1];
        passwordTxt.clearButtonMode =UITextFieldViewModeWhileEditing;
        passwordTxt.keyboardType =UIKeyboardTypeAlphabet;
        passwordTxt.keyboardAppearance =UIKeyboardAppearanceAlert;
        passwordTxt.autocapitalizationType =UITextAutocapitalizationTypeWords;
        passwordTxt.autocorrectionType =UITextAutocorrectionTypeNo;
    }

    [loginAlert show];
}

看看点击后的效果，额，不会旋转，见谅啊

在代理中处理用户交互后的事件。

#pragma mark - UIAlertViewDelegate
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
   //ok
   if (buttonIndex==1) {
        
       NSString *username = [[alertView textFieldAtIndex:0] text];
       NSString *password = [[alertView textFieldAtIndex:1] text];
       if ([self isInvalidInput:username andText:password]) {
            NSMutableString *sql = [NSMutableStringstringWithFormat:@"%@",@"WHERE name = '"];
            [sqlappendFormat:@"%@",username];
            [sql appendFormat:@"' AND password = '"];
            [sqlappendFormat:@"%@' ",password];
            
            //查询数据库中是否已经有这个用户了
           User *u = (User *)[UserfindFirstByCriteria:sql];
           if (u) {
                alertView.message =@"数据库中已有此用户，请重新输入";
                [alertViewtextFieldAtIndex:0].text =@"";
                [alertViewtextFieldAtIndex:1].text =@"";
                [[alertView textFieldAtIndex:0]becomeFirstResponder];
                [indicatorstartAnimating];
                [selfperformSelector:@selector(finishIndicator)withObject:nilafterDelay:1.0f];
            }else{
               User *user = [[Useralloc] init];
                user.name = username;
                user.password = password;
                [usersave];
                
                [indicatorstartAnimating];
                [selfperformSelector:@selector(successRegister)withObject:nilafterDelay:1.0f];
            }
        }
       //cancel
    }elseif(buttonIndex==0){
        //用户注册成功的alert
       if (alertView.tag ==1000) {
            [alertViewrelease];
        }
    }
}

这边顺便提一下模态进度指示器吧，在这里，我的效果是，不管用户输入的正确不正确，警告框都会消失，出现一个模态指示器，大概一秒钟，表示正在处理（我这里实在查询数据库什么的，嘿嘿），处理结束，显示你输入的是否正确，如果输入空值或者已有这个用户了，就显示对应的错误，并且再次显示警告框让你重新输入

看效果，中间那个灰色的菊花

主要是这个方法 [selfperformSelector:@selector(finishIndicator)withObject:nilafterDelay:1.0f];

看成功不成功两个处理

- (void)finishIndicator{
    [indicator stopAnimating];
    [loginAlert show];
}

- (void)successRegister{
    [indicator stopAnimating];
    UIAlertView *sucessAlert = [[UIAlertView alloc]
                                initWithTitle: nil
                                message:@"注册成功，请登录"
                                delegate:self
                                cancelButtonTitle:@"OK"
                                otherButtonTitles:nil, nil];
    sucessAlert.tag = 1000;    
    [sucessAlert show];
}

- (BOOL)isInvalidInput:(NSString *)name andText:(NSString *)pwd{
    if (name == nil || [name isEqualToString:@""]) {
        loginAlert.message = @"名字不能为空，请重新输入";
        [loginAlert textFieldAtIndex:0].text = @"";
        [[loginAlert textFieldAtIndex:0] becomeFirstResponder];
         [indicator startAnimating];
        [self performSelector:@selector(finishIndicator) withObject:nil afterDelay:0.5f];
        return NO;
    }
    if (pwd == nil || [pwd isEqualToString:@""]) {
        loginAlert.message = @"密码不能为空，请重新输入";
        [loginAlert textFieldAtIndex:1].text = @"";
        [[loginAlert textFieldAtIndex:0] resignFirstResponder];
        [[loginAlert textFieldAtIndex:1] becomeFirstResponder];
         [indicator startAnimating];
        [self performSelector:@selector(finishIndicator) withObject:nil afterDelay:0.5f];
        return NO;
    }
    return YES;
}

看看不成功之后出现的提醒输入用户名

差不多就是到这里，中间对于数据库的操作就忽略吧