UIAlertController中block使用出现的问题

iOS开发

自iOS 8.0 以及以后的版本，API推荐使用UIAlertCtroller.

一段代码

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id sendAlert(id object){
     NSString *text=[NSString stringWithFormat:@"%@",object];
     NSString *button=[NSBundle localizedString:@"ZHIDAOLE"];
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=nil;
        [alert addButton:button withBlock:nil];
        [alert show];
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        UIAlertAction *action = [UIAlertAction actionWithTitle:button style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            [alert dismissViewControllerAnimated:YES completion:nil];
        }];
        [alert addAction:action];
        UIViewController *root = [UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        return alert;
    }
    return nil;
}
id sendAlertBlock(id object,dispatch_block_t block){
    NSString *text=[NSString stringWithFormat:@"%@",object];
    NSString *button=[NSBundle localizedString:@"ZHIDAOLE"];
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=nil;
        [alert addButton:button withBlock:block];
        [alert show];
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        
        UIAlertAction *action=[UIAlertAction actionWithTitle:button style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            [alert dismissViewControllerAnimated:YES completion:^{}];
            if (block) {
                 block();
            }
        }];
        [alert addAction:action];
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        return alert;
    }
    return nil;
}

id sendToast(id object){
    return sendToastWithTimeout(object, 2);
}
id sendToastWithTimeout(id object,NSTimeInterval timeout){
    NSString *text=[NSString stringWithFormat:@"%@",object];
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=nil;
        [alert show];
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(timeout * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [alert dismissWithClickedButtonIndex:-1 animated:YES];
        });
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(timeout * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [alert dismissViewControllerAnimated:YES completion:^{}];
        });
        return alert;
    }
    return nil;
}

id sendConfirm(id object,dispatch_block_t block){
    dispatch_block_t non=^{};
    return sendConfirm2(object, block, non);
}
id sendConfirm2(id object,dispatch_block_t yesblock,dispatch_block_t noblock){
    NSString *text=[NSString stringWithFormat:@"%@",object];
    NSString *confirm=[NSBundle localizedString:@"QUEDING"];
    NSString *cancel=[NSBundle localizedString:@"QUXIAO"];
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=nil;
        [alert addButton:confirm withBlock:yesblock];
        [alert addButton:cancel withBlock:noblock];
        [alert show];
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        
        UIAlertAction *actionConfirm=[UIAlertAction actionWithTitle:confirm style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            if (yesblock) {
                yesblock();
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                [alert dismissViewControllerAnimated:YES completion:^{}];
            });
        }];
        [alert addAction:actionConfirm];
        
        UIAlertAction *actionConcel=[UIAlertAction actionWithTitle:cancel style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            if (noblock) {
                noblock();
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                [alert dismissViewControllerAnimated:YES completion:^{}];
            });
        }];
        [alert addAction:actionConcel];
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        return alert;
    }
    return nil;
}

id sendTask(id object,dispatch_block_t block){
    NSString *text=[NSBundle localizedString:@"QINGSHAOHOU"];
    if (object) {
        text=[NSString stringWithFormat:@"%@",object];
    }
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=nil;
        [alert show];
        static dispatch_queue_t queue;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            queue=dispatch_queue_pool("serial.alert", NULL);
        });
        [[UIApplication sharedApplication] setNetworkActivity:YES];
        dispatch_async(queue, ^{
            if (block) {
                block();
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                [[UIApplication sharedApplication] setNetworkActivity:NO];
                [alert dismissWithClickedButtonIndex:-1 animated:YES];
            });
        });
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        static dispatch_queue_t queue;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            queue=dispatch_queue_pool("serial.alert", NULL);
        });
        [[UIApplication sharedApplication] setNetworkActivity:YES];
        dispatch_async(queue, ^{
            if (block) {
                block();
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                [alert dismissViewControllerAnimated:YES completion:^{}];
                [[UIApplication sharedApplication] setNetworkActivity:NO];
            });
        });
        return alert;
    }
    return nil;
}
id sendTaskWithCallback(id object,UIAlertViewBlock block){
    NSString *text=[NSBundle localizedString:@"QINGSHAOHOU"];
    if (object) {
        text=[NSString stringWithFormat:@"%@",object];
    }
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        if (!block) {
            block=^(UIAlertView *alertView){};
        }
        
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.message=@"-";
        [alert show];
        static dispatch_queue_t queue;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            queue=dispatch_queue_pool("serial.alert", NULL);
        });
        dispatch_async(queue, ^{
            dispatch_async(dispatch_get_main_queue(), ^{
                [[UIApplication sharedApplication] setNetworkActivity:YES];
            });
            block(alert);
            dispatch_async(dispatch_get_main_queue(), ^{
                [[UIApplication sharedApplication] setNetworkActivity:NO];
                [alert dismissWithClickedButtonIndex:-1 animated:YES];
            });
        });
        return alert;
    }else{
        if (!block) {
            block=^(UIAlertController *alertView){};
        }
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=@"-";
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        static dispatch_queue_t queue;
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            queue=dispatch_queue_pool("serial.alert", NULL);
        });
        dispatch_async(queue, ^{
            dispatch_async(dispatch_get_main_queue(), ^{
                [[UIApplication sharedApplication] setNetworkActivity:YES];
            });
            block(alert);
            dispatch_async(dispatch_get_main_queue(), ^{
                [[UIApplication sharedApplication] setNetworkActivity:NO];
                [alert dismissViewControllerAnimated:YES completion:nil];
            });
        });
        return alert;
    }
    return nil;
}
id sendLongTaskWithCallback(id object,UIAlertViewBlock block){
    if (!block) {
        if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
            block=^(UIAlertView *alertView){};
        }else{
            block=^(UIAlertController *alertView){};
        }
    }
    UIAlertViewBlock newblock=^(id alertView) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication] setIdleTimerDisabled:YES];
        });
        block(alertView);
        dispatch_async(dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication] setIdleTimerDisabled:NO];
        });
    };
    return sendTaskWithCallback(object, newblock);
}

id sendInputAlert(id object,UIAlertViewStyle style,UIAlertViewBlock block){
    NSString *text=[NSString stringWithFormat:@"%@",object];
    NSString *confirm=[NSBundle localizedString:@"QUEDING"];
    NSString *cancel=[NSBundle localizedString:@"QUXIAO"];
    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"8.0")){
        UIAlertDialog *alert=[[UIAlertDialog alloc] init];
        alert.title=text;
        alert.alertViewStyle=style;
        [alert addButton:confirm withAlertBlock:block];
        [alert addButton:cancel withBlock:nil];
        [alert show];
        return alert;
    }else{
        UIAlertController *alert=[UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleAlert];
        alert.title=text;
        alert.message=nil;
        
        switch (style) {
            case UIAlertViewStyleSecureTextInput:
                {
                    [alert addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
                        textField.secureTextEntry = YES;
                        textField.borderStyle = UITextBorderStyleLine;
                    }];
                }
                break;
             
            case UIAlertViewStylePlainTextInput:
                {
                    [alert addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
                        textField.borderStyle = UITextBorderStyleLine;
                    }];
                }
                break;
            
            case UIAlertViewStyleLoginAndPasswordInput:
                {
                    [alert addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
                        textField.secureTextEntry = YES;
                        textField.borderStyle = UITextBorderStyleLine;
                    }];
                    [alert addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
                        textField.borderStyle = UITextBorderStyleLine;
                    }];
                }
                break;
                
            default:
                break;
        }
        
        UIAlertAction *actionConfirm=[UIAlertAction actionWithTitle:confirm style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            if (block) {
                block(alert);
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                [alert dismissViewControllerAnimated:YES completion:^{}];
            });
        }];
        [alert addAction:actionConfirm];
        
        UIAlertAction *actionConcel=[UIAlertAction actionWithTitle:cancel style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            [alert dismissViewControllerAnimated:YES completion:^{}];

        }];
        [alert addAction:actionConcel];
        UIViewController *root=[UIApplication sharedApplication]. keyWindow.rootViewController;
        [root presentViewController:alert animated:YES completion:^{}];
        return alert;
    }
    return nil;
}

Analysis

分析如下：

  1. iOS 8.0以及以后的版本，API内推荐使用UIalertController；
  2. 但是8.0以前的版本，会经常出现键盘跳来跳去的问题；
  3. 为了兼容两个版本，写出来上述代码。

但是：

1.设置弹出消息时，按照上面的代码来写的，有一个问题，当在一个sendAlert里面弹出一个新的alert时，原来的alert是被present出来的，没有消失掉，又要弹出新的alert，app终端就会提示已经有一个模态推出的视图；为了让它可以被推出；

2.我又在present的时候做了判断，判断当前的window的rootWindow，是否有presentedViewController并且这个Controller的状态是否是isBeDismissed，有值且没有被dismiss，那有就先dismiss掉，之后再调用presented方法；但问题还在，有时会出现还没有dismiss掉，present的动作就又发起了；

3.又重新找了一个方法，依然判断是否存在presentedViewController并且这个Controller的状态是否是isBeDismissed，有值且没有被dismiss，那有就先dismiss掉，在dismiss的结束block里面去present新的alert，没有的就直接present出来，这样，这个问题就避免了。

然并卵

领导说,这样做其实很费力的，感觉会遗留很多问题出来（我是有点儿说不清楚，至少window这个角色我就觉得有些问题），所以没有做。

我觉得，后续可以看三方的比较好的alert的处理方案，借鉴代码也是可以的，只要逻辑相通，代码的修改量不大，都是可以接受的。

总结

突然就对UIWindow这个东西感兴趣，想要做出一个类似于UIAlertView的东西，来兼容两个版本，可我发现，UIWindow在makeKeysAndVisible这个方法上，必须要有rootViewController使我非常不明白，后续弄清楚了，再继续补充说明吧。