Warning: file_get_contents(/data/phpspider/zhask/data//catemap/9/ios/108.json): failed to open stream: No such file or directory in /data/phpspider/zhask/libs/function.php on line 167

Warning: Invalid argument supplied for foreach() in /data/phpspider/zhask/libs/tag.function.php on line 1116

Notice: Undefined index: in /data/phpspider/zhask/libs/function.php on line 180

Warning: array_chunk() expects parameter 1 to be array, null given in /data/phpspider/zhask/libs/function.php on line 181
Ios 如何在后台使用应用程序清除所有子视图_Ios_View_Background Process - Fatal编程技术网

Ios 如何在后台使用应用程序清除所有子视图

Ios 如何在后台使用应用程序清除所有子视图,ios,view,background-process,Ios,View,Background Process,我使用下面的代码,我从斯坦福大学的一个讲座中借用了这个代码,把一个子视图(一个数字)放上去,然后“旋转”这个视图。除了当应用程序在屏幕上显示一个数字时进入后台外,一切正常。当它回来时,号码被冻结了。我想当它进入背景时,我需要清除所有的子视图,但我不知道该怎么做。有什么建议吗? 这是我从斯坦福讲座中“借用”的代码 - (void)drain { for (UIView *view in self.firstView.subviews) { CGAffineTransform

我使用下面的代码,我从斯坦福大学的一个讲座中借用了这个代码,把一个子视图(一个数字)放上去,然后“旋转”这个视图。除了当应用程序在屏幕上显示一个数字时进入后台外,一切正常。当它回来时,号码被冻结了。我想当它进入背景时,我需要清除所有的子视图,但我不知道该怎么做。有什么建议吗? 这是我从斯坦福讲座中“借用”的代码

- (void)drain
{
    for (UIView *view in self.firstView.subviews) {
        CGAffineTransform transform = view.transform;
        if (CGAffineTransformIsIdentity(transform)) {
            UIViewAnimationOptions options = UIViewAnimationOptionCurveLinear;
            [UIView animateWithDuration:DRAIN_DURATION/3 delay:0 options:options animations:^{
                view.transform = CGAffineTransformRotate(CGAffineTransformScale(transform, 0.7, 0.7), 2*M_PI/3);
            } completion:^(BOOL finished) {
                if (finished) {
                    [UIView animateWithDuration:DRAIN_DURATION/3 delay:0 options:options animations:^{
                        view.transform = CGAffineTransformRotate(CGAffineTransformScale(transform, 0.4, 0.4), -2*M_PI/3);
                    } completion:^(BOOL finished) {
                        if (finished) {
                            [UIView animateWithDuration:DRAIN_DURATION/3 delay:0 options:options animations:^{
                                view.transform = CGAffineTransformScale(transform, 0.1, 0.1);
                            } completion:^(BOOL finished) {
                                if (finished) [view removeFromSuperview];
                            }];
                        }
                    }];
                }
            }];
        }
    }
}

您需要在app delegate的did enter background方法-applicationidentinterbackground中执行这段代码:

if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)]) { //Check if your iOS version supports multitasking I.E iOS 4
    if ([[UIDevice currentDevice] isMultitaskingSupported]) { //Check if device supports mulitasking
        UIApplication *application = [UIApplication sharedApplication]; //Get the shared application instance
        __block UIBackgroundTaskIdentifier background_task; //Create a task object
        background_task = [application beginBackgroundTaskWithExpirationHandler: ^ {

        [application endBackgroundTask: background_task]; //Tell the system that we are done with the tasks
            background_task = UIBackgroundTaskInvalid; //Set the task to be invalid
            //System will be shutting down the app at any point in time now
        }];
        //Background tasks require you to use asyncrous tasks
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            //Perform your tasks that your application requires


 // Call your drain method here or raise a notification if this drain is not in the app delegate

            NSLog(@"\n\nRunning in the background!\n\n");
            [application endBackgroundTask: background_task]; //End the task so the system knows that you are done with what you need to perform
            background_task = UIBackgroundTaskInvalid; //Invalidate the background_task
        });
    }
}

希望这能有所帮助。

我来看看。谢谢。