Understanding iOS Device Orientation Notifications

Introduction

When developing iOS applications, understanding how the device’s orientation changes can be crucial for delivering a seamless user experience. The UIDeviceOrientationDidChangeNotification notification is sent to the application when the device’s orientation changes, but what happens when an MPMoviePlayer is playing? In this article, we will explore how to receive notifications on iPhone device orientation while an MPMoviePlayer is visible.

Background

iOS applications can be affected by the device’s orientation in various ways. The UIDeviceOrientationDidChangeNotification notification is sent to the application whenever the device’s orientation changes. However, this notification may not always be reliable, especially when other system activities are taking place, such as playing a movie.

MPMoviePlayerController is an iOS component that allows you to play video content within your app. When a MPMoviePlayer is visible, it takes control of the screen and prevents any other windows from being visible. This can make it challenging for our application to receive notifications about device orientation changes.

How Notifications Work in iOS

To understand how notifications work on iOS, let’s take a closer look at the UIDeviceOrientationDidChangeNotification notification.

// Import the necessary framework
#import <Foundation/Foundation.h>

// Define the notification name
#define UIDeviceOrientationDidChangeNotification @"UIDeviceOrientationDidChangeNotification"

// Register for the notification in the application delegate
- (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken {
    // ...

    // Register for notifications
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleOrientationChange:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

In this example, we are registering our application delegate to receive the UIDeviceOrientationDidChangeNotification notification. When this notification is sent, it will be handled by the handleOrientationChange: method.

The Problem with MPMoviePlayer

However, when a MPMoviePlayer is visible, the system may not send the UIDeviceOrientationDidChangeNotification notification in a timely manner or at all. This can happen due to the way the player takes control of the screen and prevents other windows from being visible.

To demonstrate this issue, let’s take a look at an example code snippet that simulates playing a movie:

// Create an MPMoviePlayerController instance
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL URLWithString:@"http://example.com/movie.mp4"]];

// Add the player to a view controller
[self.view addSubview:player.view];

// Play the movie
[player prepareToPlay];
[player play];

In this example, we create an MPMoviePlayerController instance and add it to our view controller. We then play the movie using the prepareToPlay and play methods.

Solution

So, how can we receive notifications about device orientation changes while a MPMoviePlayer is playing? The solution lies in understanding the way the system handles notifications when other system activities are taking place.

When a MPMoviePlayer is visible, it takes control of the screen and prevents any other windows from being visible. This means that our application delegate will not be notified about device orientation changes while the player is active.

To overcome this issue, we can use a combination of techniques:

1. Check for notifications manually: Instead of relying on the system to send us notifications, we can check for them manually in our view controller.
2. Use the viewDidLayoutSubviews method: The viewDidLayoutSubviews method is called after the layout of our view has been updated. This method provides a good opportunity for us to update our notification observer.
3. Handle orientation changes before showing the player: We can handle device orientation changes before we show the MPMoviePlayer instance.

Let’s take a closer look at these techniques:

Check for Notifications Manually

// Create an MPMoviePlayerController instance
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL URLWithString:@"http://example.com/movie.mp4"]];

// Add the player to a view controller
[self.view addSubview:player.view];

// Play the movie
[player prepareToPlay];
[player play];

// Check for notifications manually
- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    // Register for notifications
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleOrientationChange:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

In this example, we are checking for the UIDeviceOrientationDidChangeNotification notification in our viewDidLayoutSubviews method. This ensures that we receive notifications about device orientation changes while the movie is playing.

Use the viewDidLayoutSubviews Method

// Create an MPMoviePlayerController instance
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL URLWithString:@"http://example.com/movie.mp4"]];

// Add the player to a view controller
[self.view addSubview:player.view];

// Play the movie
[player prepareToPlay];
[player play];

// Use the viewDidLayoutSubviews method
- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];

    // Check for notifications manually in this method
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleOrientationChange:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

In this example, we are using the viewDidLayoutSubviews method to register our notification observer.

Handle Orientation Changes Before Showing the Player

// Create an MPMoviePlayerController instance
MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL URLWithString:@"http://example.com/movie.mp4"]];

// Add the player to a view controller
[self.view addSubview:player.view];

// Play the movie
[player prepareToPlay];
[player play];

// Handle orientation changes before showing the player
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    // Check for notifications manually in this method
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleOrientationChange:) name:UIDeviceOrientationDidChangeNotification object:nil];
}

In this example, we are handling device orientation changes before we show the MPMoviePlayer instance.

Conclusion

Receiving notifications about device orientation changes on an iPhone can be challenging when an MPMoviePlayer is playing. However, by using a combination of techniques such as checking for notifications manually, using the viewDidLayoutSubviews method, and handling orientation changes before showing the player, we can ensure that our application receives these important updates.

We hope this article has provided you with the knowledge and tools necessary to overcome any challenges related to device orientation notifications on an iPhone.

Last modified on 2023-08-26