Question

我想从视图的输入字段中获取数据并将其存储，以便可以在数据库中创建对象的新实例并将其显示在listView中。到目前为止，我已经设法从输入字段中获取了一个IngredientName。它显示在下面的标签中，因此必须正在发生。但是，当我尝试将其添加到配料实例时，它说的是IngredientName = null。我不知道该怎么办。

    <StackLayout Orientation="Horizontal">
        <Label Text="Your Ingredient is:" />
        <Label Text="{Binding IngredientName}" />
    </StackLayout>

    <Button x:Name="IngrediantsButton"
            Text="Add Ingredient"
            Command="{Binding Path=NewIngredientCommand, Source={StaticResource viewModel}}"/>

    <ListView x:Name="IngredientsListView" ItemsSource="{Binding Ingredients, Source={StaticResource viewModel}}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="{Binding IngredientsName}"/>
                        <Label Text="{Binding Ammount}"/>
                        <Label Text="{Binding Units}"/>
                        <Label Text="{Binding RecipeId}"/>
                    </StackLayout>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

</StackLayout>

ViewModel

  private string _ingredientName { get; set; }
    public string IngredientName
    {
        get
        {
            return _ingredientName;
        }
        set
        {
            if (_ingredientName != value)
            {
                _ingredientName = value;
                OnPropertyChanged("IngredientName");
            }
        }
    }

    public Command NewIngredientCommand
    {
        get
        {
            return new Command(() =>
            {
                Ingredients ingredients = new Ingredients()
                {
                    IngredientsName = IngredientName,
                    Ammount = 0,
                    Units = "g",
                    RecipeId = Recipe1.RecipeID,
                    Recipe = Recipe1
                };

                Ingredients.Add(ingredients);
            });
        }
    }

    protected virtual void OnPropertyChanged(string propertyName)
    {
        var changed = PropertyChanged;
        if (changed != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

Answer 1

 private ICommand _saveIngredientCommand;

    public ICommand SaveIngredientCommand => _saveIngredientCommand ?? (_saveIngredientCommand = new Command(() =>
    {
        Ingredients ingredient = new Ingredients();
        App.RecipeDbcontroller.SaveIngredients(ingredient);

        if (Ingredient.IngredientsName != null && Ingredient.Ammount != 0)
        {
            ingredient.IngredientsName = Ingredient.IngredientsName;
            ingredient.Ammount = Ingredient.Ammount;
            ingredient.Units = Ingredient.Units;
            ingredient.Recipe = Recipe;
            ingredient.RecipeID = Recipe.RecipeID;
            App.RecipeDbcontroller.SaveIngredients(ingredient);
            IngredientsList.Add(ingredient);
            Recipe.Ingredients.Add(ingredient);
            IngredientMessage = "Your ingredient has been added";
        }
        else
        {
            IngredientMessage = "Please add at least one ingredient";
            App.RecipeDbcontroller.DeleteIngredients(ingredient.IngredientsId);
        }

想要向数据库MVVM添加一些内容

1 个答案: