Question

I need to use the loadedTimeRanges property of the AVPlayerItem class to know which part of the file has been downloaded. Unfortunately, this property don’t seems to be available in MonoTouch.

In MonoTouch Rosetta Stone reference, the method is present but commented:

Selector: loadedTimeRanges
Property: // NSArray loadedTimeRanges { get; }

Somebody know if the method will be added in the future?

In the mean time, I tried to map the objective-c selector according to xamarin doc

I defined the missing selector:

[System.Runtime.InteropServices.DllImport(MonoTouch.Constants.ObjectiveCLibrary, EntryPoint="objc_msgSend")]
    static extern NSArray nsarray_objc_msgSend (
    IntPtr target, IntPtr selector);

And after, called the method like that:

/* Call loadedTimeRanges selector on AVPlayerItem */
AVPlayerItem target = m_playerItem;
MonoTouch.ObjCRuntime.Selector selector = new MonoTouch.ObjCRuntime.Selector ("loadedTimeRanges");
NSArray loadedTimeRanges = nsarray_objc_msgSend(target.Handle, selector.Handle);


/* Convert the returned value as CMTimeRange */
IntPtr intPtr = loadedTimeRanges.ValueAt(0);
System.Runtime.InteropServices.GCHandle handle = System.Runtime.InteropServices.GCHandle.FromIntPtr(intPtr);
NSValue v = (NSValue)handle.Target;
MonoTouch.CoreMedia.CMTimeRange timeRange = v.CMTimeRangeValue;

But, I get the following error when calling my selector:

Unhandled Exception: System.Runtime.InteropServices.MarshalDirectiveException: Type MonoTouch.Foundation.NSObject which is passed to unmanaged code must have a StructLayout attribute.

Someone know whart I am missing? Thanks in advance!

Answer 1

You can’t return NSArray from the DllImport, you need to declare IntPtr as the return type. In any case you don’t have to add the DllImport yourself, it’s already there ready to use:

IntPtr ptr = MonoTouch.ObjCRuntime.Messaging.IntPtr_objc_msgSend (target.Handle, selector.Handle);
NSArray loadedTimesRange = new NSArray (ptr);

In this case this is even better:

NSValue [] values = NSArray.ArrayFromHandle<NSValue> (ptr);

A single value would be:

CMTime timestamp = values [0].CMTimeValue;