/// <summary>
/// Prepares the cancelable media player for playback, asynchronously.
/// </summary>
/// <param name="cancellationToken">The cancellation token to cancel preparing.</param>
/// <seealso cref="CancellationToken"/>
/// <returns>The task that represents the asynchronous prepare operation.</returns>
/// <remarks>To prepare the player, the player must be in the <see cref="PlayerState.Idle"/> state,
/// and a source must be set.
/// The state must be <see cref="PlayerState.Preparing"/> to cancel preparing.
/// When preparing is cancelled, a state will be changed to <see cref="PlayerState.Idle"/> from <see cref="PlayerState.Preparing"/>.</remarks>
/// <exception cref="ObjectDisposedException">The player has already been disposed.</exception>
/// <exception cref="InvalidOperationException">
/// Operation failed; internal error.
/// -or-<br/>
/// The player is not in the valid state.
/// </exception>
/// <seealso cref="PrepareAsync()"/>
/// <seealso cref="Unprepare()"/>
/// <since_tizen> 6 </since_tizen>
public virtual async Task PrepareAsync(CancellationToken cancellationToken)
{
ValidateNotDisposed();
var taskCompletionSource = new TaskCompletionSource <bool>();
if (_source == null)
{
throw new InvalidOperationException("No source is set.");
}
ValidatePlayerState(PlayerState.Idle);
OnPreparing();
SetPreparing();
// register a callback to handle cancellation token anytime it occurs
cancellationToken.Register(() =>
{
ValidatePlayerState(PlayerState.Preparing);
// a user can get the state before finally block is called.
ClearPreparing();
Log.Warn(PlayerLog.Tag, $"preparing will be cancelled.");
NativePlayer.Unprepare(Handle).ThrowIfFailed(this, "Failed to unprepare the player");
taskCompletionSource.TrySetCanceled();
});
_prepareCallback = _ =>
{
Log.Warn(PlayerLog.Tag, $"prepared callback is called.");
taskCompletionSource.TrySetResult(true);
};
try
{
NativePlayer.PrepareAsync(Handle, _prepareCallback, IntPtr.Zero).
ThrowIfFailed(this, "Failed to prepare the player");
await taskCompletionSource.Task.ConfigureAwait(false);
}
finally
{
ClearPreparing();
}
}