Question

我正在尝试使用代码，在iPad应用上查看我的视图以镜像到外部显示器。在AppDelegate didFinishLaunching中，我有：

 if ([[UIScreen screens] count] > 1)
    {
        UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];
        NSString *availableModeString;

        for (int i = 0; i < secondScreen.availableModes.count; i++)
        {
            availableModeString = [NSString stringWithFormat:@"%f, %f",
                                   ((UIScreenMode *)[secondScreen.availableModes objectAtIndex:i]).size.width,
                                   ((UIScreenMode *)[secondScreen.availableModes objectAtIndex:i]).size.height];

            [[[UIAlertView alloc] initWithTitle:@"Available Mode" message:availableModeString delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil] show];
            availableModeString = nil;
        }

        // undocumented value 3 means no overscan compensation
        secondScreen.overscanCompensation = 3;

        self.secondWindow = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 1280, 720)];
        self.secondWindow.backgroundColor = [UIColor blueColor];
        self.secondWindow.screen = secondScreen;

        ViewController *viewController = [[ViewController alloc] init];
        self.secondWindow.rootViewController = viewController;

        self.secondWindow.hidden = NO;
    }

显示在外部显示器中的所有内容都是代码中设置的蓝色背景颜色。

Answer 1

我可以用我的镜像在我的iPhone 6上镜像：

@interface MirrorViewController ()

@property (nonatomic, retain) UIView *viewToMirror;
@property (nonatomic, retain) UIView *snapshotView;

@end

@implementation MirrorViewController

- (instancetype)initWithViewToMirror:(UIView*)view
{
    self = [super initWithNibName:nil bundle:nil];
    if (self == nil) return nil;
    self.viewToMirror = view;
    return self;
}

- (void)viewDidLoad
{
    CADisplayLink *displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
    [displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}

- (void)update
{
    [self.snapshotView removeFromSuperview];
    self.snapshotView = [self.viewToMirror snapshotViewAfterScreenUpdates:NO];
    [self.view addSubview:self.snapshotView];
}

@end

以下是您在didFinishLaunching代码中使用它的方法：

if ([[UIScreen screens] count] > 1)
{
    UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];

    // [...]

    self.secondWindow = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 1280, 720)];
    self.secondWindow.backgroundColor = [UIColor blueColor];
    self.secondWindow.screen = secondScreen;

    MirrorViewController *mirrorViewController = [[MirrorViewController alloc] initWithViewToMirror:self.window.rootViewController.view];
    self.secondWindow.rootViewController = mirrorViewController;

    self.secondWindow.hidden = NO;
}

我没有在带有外接显示器的iPad上测试它，因为我没有这个装备。

Answer 2

首先检查应用启动时是否存在外部显示器。如果第二个显示器可用，则会为其创建一个窗口。我在我的应用程序中使用了以下代码。

(void)checkForExistingScreenAndInitializeIfPresent
{
    if ([[UIScreen screens] count] > 1)
    {
        // Get the screen object that represents the external display.
        UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];
        // Get the screen's bounds so that you can create a window of the correct size.
        CGRect screenBounds = secondScreen.bounds;

        self.secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];
        self.secondWindow.screen = secondScreen;

        // Set up initial content to display...
        // Show the window.
        self.secondWindow.hidden = NO;
    }
}

通过以下代码注册连接和断开通知。

(void)setUpScreenConnectionNotificationHandlers
{
    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];

    [center addObserver:self selector:@selector(handleScreenDidConnectNotification:)
            name:UIScreenDidConnectNotification object:nil];
    [center addObserver:self selector:@selector(handleScreenDidDisconnectNotification:)
            name:UIScreenDidDisconnectNotification object:nil];
}

处理屏幕连接和断开连接通知

(void)handleScreenDidConnectNotification:(NSNotification*)aNotification
{
    UIScreen *newScreen = [aNotification object];
    CGRect screenBounds = newScreen.bounds;

    if (!self.secondWindow)
    {
        self.secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];
        self.secondWindow.screen = newScreen;

        // Set the initial UI for the window.
    }
}

(void)handleScreenDidDisconnectNotification:(NSNotification*)aNotification
{
    if (self.secondWindow)
    {
        // Hide and then delete the window.
        self.secondWindow.hidden = YES;
        self.secondWindow = nil;

    }

}

如果您没有为显示器创建一个窗口 - 或者如果您创建一个窗口但没有显示它 - 外部显示器上会显示一个黑色字段。

无法保证所有模式都可以在外部显示器中使用，因此您不应该依赖于特定模式的可用性。

在极少数情况下，您可能希望为overscanCompensation属性使用不同的值，但这样做总是会导致您需要做更多的工作。例如，如果使用UIScreenOverscanCompensationInsetBounds，则必须准备好处理非标准显示大小的范围。

Mirror ViewController到外部显示器

2 个答案: