xcode 以编程方式触发 UIAlertController 的 UIAlertAction
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Trigger UIAlertAction of a UIAlertController programmatically
提问by CharlesA
I want to dismiss my UIAlertController with a click on the 'Cancel' button when my app goes in to background.
当我的应用程序进入后台时，我想通过单击“取消”按钮来关闭我的 UIAlertController。
I've set up the background notification with
我已经设置了后台通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(appDidEnterBackground) name:UIApplicationDidEnterBackgroundNotification object:nil];
Then in my appDidEnterBackground function I have:
然后在我的 appDidEnterBackground 函数中，我有：
- (void)appDidEnterBackground {
if (_alertController) {
UIAlertAction *cancelAction = [[_alertController actions] objectAtIndex:0];
//HERE: is there a way to trigger the cancelAction??
[_alertController dismissViewControllerAnimated:NO completion:nil];
}
}
What I'm struggling with is how to trigger the UIAlertAction programmatically. Is this possible?
我正在努力解决的是如何以编程方式触发 UIAlertAction。这可能吗？
采纳答案by CharlesA
I answered this with using the suggestion made by MCKapur.
我使用 MCKapur 提出的建议回答了这个问题。
I already had the UIAlertController in a singleton. What I did was define a variable in my singleton to save the completion action:
我已经在单例中使用了 UIAlertController。我所做的是在我的单例中定义一个变量来保存完成操作：
@property (copy, nonatomic) void (^completion)(BOOL);
Then when I set up the UIAlertController to show it, I also setup the completion code with:
然后当我设置 UIAlertController 来显示它时，我还设置了完成代码：
_completion = ^(BOOL cancelled) {
if (block) {
block (NO, nil);
}
};
Finally, I changed the appDidEnterBackground call to:
最后，我将 appDidEnterBackground 调用更改为：
- (void)appDidEnterBackground {
if (_alertController) {
if (_completion) {
_completion(NO);
_completion = nil;
}
[_alertController dismissViewControllerAnimated:NO completion:nil];
}
}
回答by Tony Langdon
This is old but it is the top result when looking for how to trigger a UIAlertAction programmatically.
这是旧的，但它是寻找如何以编程方式触发 UIAlertAction 时的最佳结果。
Just in case anyone (still doing objC) is prepared to use internal methods - this works with iOS 10 and 11:
以防万一有人（仍在使用 objC）准备使用内部方法 - 这适用于 iOS 10 和 11：
- (void)triggerAction:(UIAlertAction*)action onAlertController:(UIAlertController*)alert {
SEL triggerSelector = NSSelectorFromString(@"_dismissAnimated:triggeringAction:triggeredByPopoverDimmingView:dismissCompletion:");
NSMethodSignature* signature = [[alert class] instanceMethodSignatureForSelector:triggerSelector];
if (!signature) {
// Try pre iOS11 - OK as we're not trying to use the completion block
triggerSelector = NSSelectorFromString(@"_dismissAnimated:triggeringAction:triggeredByPopoverDimmingView:");
signature = [[alert class] instanceMethodSignatureForSelector:triggerSelector];
}
NSAssert(signature != nil, @"Couldn't find trigger method");
NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:signature];
[invocation setTarget:alert];
[invocation setSelector:triggerSelector];
BOOL boolValue = YES; // Animated & dimmingView
[invocation setArgument:&boolValue atIndex:2];
[invocation setArgument:&action atIndex:3];
[invocation setArgument:&boolValue atIndex:4];
// Not setting anything for the dismissCompletion block atIndex:5
[invocation invoke];
}
