I have a NSURL class member wich can point to a local file, to a URL or to an Asset. I've found out that I have to use the Asset Library to load an Asset instead of:
[NSData dataWithContentsOfURL:nsurl];
So my Question is: How can I check if my NSURL object points to an Asset?
I've tried the search, but I've only how to check if it's a local file :(
PS: My App has to be iOS4 compatible
Assuming the URL is well-formed, it is an Assets Library URL iff [[url scheme] isEqualToString:#"assets-library"].
Related
This is strange, but basically I download and save a video locally, and the store the url path to provide to an AVPlayer to play.
This works fine the first time I do it. I download a file, and then I can play it to my hearts content as many times UNTIL I exit the app. When I launch the app a second time, I now get a black screen when I try to play the same exact video using the same exact path.
Because I am using the Simulator I can verify that the videos and pictures indeed very much still exist in the same folder I saved them to, and I can still play them if I click on them from the Finder.
Maybe it's a caching issue? If it matters, I've saved them straight to the Library directory as I test this.
Relevant Code:
NSString *outputFile = [NSString stringWithFormat:#"video_%#.mp4", guid];
NSString *outputDirectory = [NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *tempPath = [outputDirectory stringByAppendingPathComponent:outputFile];
NSURL *fileURL = [NSURL fileURLWithPath:tempPath];
// save the video to the URL
Then I "persist" it using an NSString [fileURL path] (The way I've built this out, assume the solution requires an NSString to NSURL conversion).
Later I create an AVPlayerItem:
NSURL *url = [NSURL fileURLWithPath:persistedObject.contentURL];
NSLog(#"url: %#", url); // prints a valid location**
AVPlayerItem *item = [AVPlayerItem playerItemWithURL:url];
** for example this is a sample url location
url: file:///Users/gabriel/Library/Developer/CoreSimulator/Devices/CE1FC933-808C-4003-9BE4-DEC59B787FF7/data/Containers/Data/Application/FAD072B4-B5B0-4487-8A76-57B047324A00/Library/picture_D8DEAFA5-0843-4AA3-BB32-C61E32D13579.mp4
It's been suggested I use URLForDirectory:inDomain:appropriateForURL:create:error: and URLByAppendingPathComponent: instead, which I will look into. But still confused as to why it would play when I first download it, but not after app exits when it's the same exact file.
You've made a classic mistake. You are persisting the full path. But the full path changes. Never persist a full path. Only persist the part of the path relative to the value obtained from NSSearchPathForDirectoriesInDomains.
Given what you are doing, you should only persist the base filename (outputFile). Then when the app starts, you rebuild the full path again like you did originally but use the persisted filename to append it to the dynamically obtained path to the application support folder.
I get asset URL by calling [asset valueForProperty:ALAssetPropertyAssetURL] sometimes it returns nil or may be asset is nil (I've seen it in the crash logs).
I've read in the documentation:
ALAssetPropertyAssetURL
The key to retrieve a URL identifier for the asset.
The corresponding value is an NSURL object.
This URL is used by the library-change notifications to identify assets and asset groups. Only the ALAssetRepresentation and ALAssetsGroup classes support this property.
I think it is mean, that I can't get ALAssetPropertyAssetURL property from ALAsset, but it works any time when I run it.
Questions:
How I can get Asset url to use it in [PHAsset fetchAssetsWithALAssetURLs: ....]?
UPD
I don't understand this: "How to get URL if only the ALAssetRepresentation and ALAssetsGroup classes support this property?"
We could use something like this with ALAsset object
[[asset defaultRepresentation] url]
I have found that so far the path sent to application:openURL:sourceApplication:annotation: is:
file://localhost/private/var/mobile/Applications/<GUID>/Documents/Inbox/file
To check that the filesystem operations that I am about to perform are indeed likely to succeed (and that the url given to me is not a location outside the sandbox), it looks like I have to do this:
NSString* hdurl = [[#"file://localhost/private" stringByAppendingString:NSHomeDirectory()] stringByAppendingString: #"/"];
NSString* path = url.absoluteString;
if ([path hasPrefix:hdurl]) {
// now ready to e.g. call fopen on: [path substringFromIndex:#"file://localhost".length]
Now, I seem to vaguely recall (and this is probably wrong) that in the past I have seen the file:/// style URL being used. That would clearly cause this code to fail.
How am I to know that it will always give me a file://localhost URL prefix?
Apple's documentation on URLs is strangely missing a section on file URLs.
An NSURL that points to a file on the local file system is called a "file URL". To convert the NSURL to an NSString representing the file's path you use:
NSString *filePath = [url path];
To check to see if an NSURL represents a file URL, use:
BOOL isFileURL = [url isFileURL];
Keep in mind that if your app is passed a file URL, you will always have access to the file. There is no need to check if it starts with any prefix. Why would iOS pass you a file that you don't have access to?
In my code I have to use URLWithString to play streaming(HLS) video and fileURLWithPath to play local video.
What is the difference between these two methods?
How should I use single method to play both videos.
Also I need to show last frame as still image when HSL video ends. Its now showing blank screen when it ends. How should i achieve this?
+URLWithString: produces an NSURL that represents the string as given. So the string might be #"http://www.google.com" and the URL represents http://www.google.com.
+fileURLWithPath: takes a path, not a URL, and produces an NSURL that represents the path using a file:// URL. So if you give it /foo/bar/baz the URL would represent file:///foo/bar/baz.
You can of course construct a file URL string manually and pass it to +URLWithString:, but +fileURLWithPath: is simpler to use when you already have a path, as you don't have to deal with escaping the string and coercing it to a URL format.
Similar thing happened in my app which use AVAudioPlayer. I tried with [NSURL URLWithString:path] and found out it fails to open certain mp3 files. I looked into error by a line like [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL URLWithString:path] fileTypeHint:AVFileTypeMPEGLayer3 error:&error], but the error was simply nil
However it was resolved by replacing the url with [NSURL fileURLWithPath:path].
In both case, the path path NSString * #"/var/mobile/Containers/Data/Application/4D96D4AE-2ED4-40B0-85D2-230E1AFA90E7/Documents/01-AudioTrack 01.mp3" 0x1457a8f0 Still I don't know the reason but now I should be careful using [NSURL URLWithString:].
PS. In NSURL Reference document, Apple said as below:
IMPORTANT
To create NSURL objects for file system paths, use fileURLWithPath:isDirectory: instead.
which clearly indicates [NSURL fileURLWithPath:] should be used for open file, though [NSURL URLWithString] also works for some cases.
Is there a way to turn the asset url returned by the following call to the physical path on the device?
NSURL *assetUrl = [_selectedAsset defaultRepresentation] url];
There is no way. (And even if you had the path to file, your app could not read the file because of sandboxing.)
The only way to get the raw data of an asset is getBytes:fromOffset:length:error: in ALAssetRepresentation.