Beispiel #1
0
        public PhotoListViewModel(IRouter router = null, IPhotosService service = null)
            : base(router)
        {
            Service = service ?? Locator.Current.GetService <IPhotosService>();
            var canLoad = Resumed.FirstAsync().Select(r => r?.LoadedPhotos == null);

            LoadPhotos = ReactiveCommand.CreateAsyncTask(canLoad, async o => await Service.GetPhotosAsync());
            var canLoadData = this.WhenAnyValue(vm => vm.LoadedPhotos)
                              .Select(p => p != null);

            LoadPhotoData = ReactiveCommand.CreateAsyncTask(canLoadData, async o => await LoadPhotoDataImpl());
            Share         = ReactiveCommand.CreateAsyncTask(async o => await ShareImpl());
            ShowPhoto     = ReactiveCommand.CreateAsyncTask(async p => await ShowPhotoImpl((int)p));
            loadedPhotos  = Resumed.Select(state => state?.LoadedPhotos).Merge(LoadPhotos)
                            .ObserveOn(RxApp.MainThreadScheduler)
                            .ToProperty(this, vm => vm.LoadedPhotos, new Photo[0]);
            loadedPhotoBytes = LoadPhotoData
                               .ObserveOn(RxApp.MainThreadScheduler)
                               .ToProperty(this, vm => vm.LoadedPhotoData);
            isLoading = LoadPhotos.IsExecuting.CombineLatest(LoadPhotoData.IsExecuting, (l, ld) => l || ld)
                        .DistinctUntilChanged()
                        .ObserveOn(RxApp.MainThreadScheduler)
                        .ToProperty(this, vm => vm.IsLoading);

            this.WhenAnyValue(vm => vm.LoadedPhotos)
            .InvokeCommand(this, vm => vm.LoadPhotoData);
        }