iOS 关于UIAlertController、UIAlertView弹窗问题

关于UIAlertController弹窗问题

目标：同时弹出2个以上的弹窗

问题：在弹出一个alertController的时候，第二个alertController是无法弹出的

UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"提示" message:@"弹窗1" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
    }];
    UIAlertAction *skipAction = [UIAlertAction actionWithTitle:@"ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    }];
    [alertController addAction:cancelAction];
    [alertController addAction:skipAction];
    [self presentViewController:alertController animated:YES completion:nil];
    
    UIAlertController *alertController2 = [UIAlertController alertControllerWithTitle:@"提示" message:@"弹窗2" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *cancelAction2 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
    }];
    UIAlertAction *skipAction2 = [UIAlertAction actionWithTitle:@"ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    }];
    [alertController2 addAction:cancelAction2];
    [alertController2 addAction:skipAction2];
    [self presentViewController:alertController2 animated:YES completion:nil];

报错：

xcode给出的理由是：试图呈现已经呈现在self上的alert2

原因分析：

扩展

使用present，弹出普通的控制器

UIViewController *ctrl1 = [UIViewController new];
ctrl1.view.backgroundColor = [UIColor redColor];
[self presentViewController:ctrl1 animated:YES completion:nil];

UIViewController *ctrl2 = [UIViewController new];
ctrl2.view.backgroundColor = [UIColor yellowColor];
[self presentViewController:ctrl2 animated:YES completion:nil];
    
NSLog(@"self->%p",self);
NSLog(@"111->%p",ctrl1);
NSLog(@"222->%p",ctrl2);

结果：系统依旧不能present弹出两个视图，想弹出第二个视图的话，需要将self换成ctrl1；由于UIAlertController是继承自UIViewController的，UIViewController既然不能present弹出两个视图控制器，UIAlertController自然也不行

view is not in the window hierarchy!：视图不在窗口层次结构中

关于UIAlertView弹窗问题

目标：弹出两个提示窗体

UIAlertView *alertView1 = [[UIAlertView alloc] initWithTitle:@"提示" message:@"弹窗1" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
UIAlertView *alertView2 = [[UIAlertView alloc] initWithTitle:@"提示" message:@"弹窗2" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
[alertView1 show];
[alertView2 show];

测试结果：是可以弹出两个视图的，会展现最新弹窗，点击消失后，继续弹出之前的弹窗
似乎使用UIAlertView就可以满足弹出两个窗体的需求，但是新的问题随之而来

新问题的产生

在弹出UIAlertView窗体时，如果接下来使用到了[UIApplication sharedApplication].keyWindow.rootViewController来获取控制器等相关操作时，会出现闪退问题

原因：使用UIAlertView的show时，系统使用了一个新的Window来展现UIAlertView，所以当show弹窗时，keyWindow已经被替换

验证：我们来输出keyWindow的内存地址

// 弹窗之前window的内存地址
UIWindow *delegateWindow = [UIApplication sharedApplication].delegate.window;
UIWindow *keyWindow_pre = [UIApplication sharedApplication].keyWindow;
NSLog(@"delegateWindow->%p",delegateWindow);
NSLog(@"keyWindow_pre->%p",keyWindow_pre);
    
UIAlertView *alertView1 = [[UIAlertView alloc] initWithTitle:@"提示" message:@"弹窗1" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
UIAlertView *alertView2 = [[UIAlertView alloc] initWithTitle:@"提示" message:@"弹窗2" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil];
[alertView1 show];
[alertView2 show];
// 弹窗之后window的内存地址
UIWindow *delegateWindow_now = [UIApplication sharedApplication].delegate.window;
UIWindow *keyWindow_now = [UIApplication sharedApplication].keyWindow;
NSLog(@"delegateWindow_now->%p",delegateWindow_now);
NSLog(@"keyWindow_now->%p",keyWindow_now);

结果：

上图可知：

结论：

扩展：验证UIAlertController的keyWindow

验证：将弹窗换成UIAlertController，其他不变

// 弹窗之前window的内存地址
UIWindow *delegateWindow = [UIApplication sharedApplication].delegate.window;
UIWindow *keyWindow_pre = [UIApplication sharedApplication].keyWindow;
NSLog(@"delegateWindow->%p",delegateWindow);
NSLog(@"keyWindow_pre->%p",keyWindow_pre);
    
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"提示" message:@"弹窗1" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
    }];
UIAlertAction *skipAction = [UIAlertAction actionWithTitle:@"ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    }];
[alertController addAction:cancelAction];
[alertController addAction:skipAction];
[self presentViewController:alertController animated:YES completion:nil];
    
UIAlertController *alertController2 = [UIAlertController alertControllerWithTitle:@"提示" message:@"弹窗2" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAction2 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
    }];
UIAlertAction *skipAction2 = [UIAlertAction actionWithTitle:@"ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    }];
[alertController2 addAction:cancelAction2];
[alertController2 addAction:skipAction2];
[self presentViewController:alertController2 animated:YES completion:nil];
// 弹窗之后window的内存地址
UIWindow *delegateWindow_now = [UIApplication sharedApplication].delegate.window;
UIWindow *keyWindow_now = [UIApplication sharedApplication].keyWindow;
NSLog(@"delegateWindow_now->%p",delegateWindow_now);
NSLog(@"keyWindow_now->%p",keyWindow_now);

结果：

结论：

综上所述：