iOS：是否可以捕獲閃屏的圖像？

Question

我試圖捕捉和使用下面的代碼保存裏面application:didFinishLaunchingWithOptions:閃屏的圖像：

UIWindow *w = [[[UIApplication sharedApplication] windows] firstObject]; 

UIGraphicsBeginImageContext(w.bounds.size); 
[w.layer renderInContext:UIGraphicsGetCurrentContext()]; 
UIImage *img = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

NSString *applicationDocumentsDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
time_t unixTime = (time_t) [[NSDate date] timeIntervalSince1970]; 
NSString *storePath = [NSString stringWithFormat:@"%@/%ld.png", applicationDocumentsDir, unixTime]; 
[UIImagePNGRepresentation(img) writeToFile:storePath atomically:YES]; 

然而不幸的是，圖像保存爲透明圖像。這可能是因爲我的對象不是正確的。任何人都可以指導我成功嗎？

Answer 1

爲什麼不在設置LaucnhScreen.storyboard文件視圖控制器的Storyboard ID之後嘗試下面的代碼。

UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"LaunchScreen" 
                  bundle: nil]; 

    UIViewController *controller = (UIViewController*)[mainStoryboard 
                 instantiateViewControllerWithIdentifier: @"Launch"]; 
    UIGraphicsBeginImageContext(w.bounds.size); 
    [controller.view.layer renderInContext:UIGraphicsGetCurrentContext()]; 
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    NSString *applicationDocumentsDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
    time_t unixTime = (time_t) [[NSDate date] timeIntervalSince1970]; 
    NSString *storePath = [NSString stringWithFormat:@"%@/%ld.png", applicationDocumentsDir, unixTime]; 
    [UIImagePNGRepresentation(img) writeToFile:storePath atomically:YES]; 

Answer 2

關於answer 的UIApplicationDelegate通常有「主窗口」的引用：

[[[UIApplication sharedApplication] delegate] window];