对象未显示在画布上（WPF 应用程序）

Question

在这个应用程序中，我有一个带有名为 Spawn 的方法的汽车类（它应该在我在 XAML 文件中定义的 Canvas 上绘制对象）。我在 MainWindow 中调用方法，但是当我运行我的程序时，没有汽车被绘制到画布上。

这里是 Spawn 方法：

        public void Spawn(Canvas cvs)
        {
            cvs = new Canvas();
            cvs.Children.Clear();

            carBody.Width = 70;
            carBody.Height = 120;
            carBody.Background = new SolidColorBrush(Color);

            Canvas.SetLeft(carBody, SpawnLocation.X);
            Canvas.SetTop(carBody, SpawnLocation.Y);

            Rectangle[] tires = new Rectangle[4];
            Rectangle[] windows = new Rectangle[2];
            Label lblBrand = new Label();

            RotateTransform rotation = new RotateTransform();

            // Reifen
            tires[0] = new Rectangle()
            {
                Fill = Brushes.Black,
                Width = 20,
                Height = 30
            };

            Canvas.SetLeft(tires[0], -9);
            Canvas.SetTop(tires[0], 18);

            tires[1] = new Rectangle()
            {
                Fill = Brushes.Black,
                Width = 20,
                Height = 30
            };

            Canvas.SetLeft(tires[1], 61);
            Canvas.SetTop(tires[1], 18);

            tires[2] = new Rectangle()
            {
                Fill = Brushes.Black,
                Width = 20,
                Height = 30
            };

            Canvas.SetLeft(tires[2], -9);
            Canvas.SetTop(tires[2], 80);

            tires[3] = new Rectangle()
            {
                Fill = Brushes.Black,
                Width = 20,
                Height = 30
            };

            Canvas.SetLeft(tires[3], 61);
            Canvas.SetTop(tires[3], 80);

            // Fenster
            windows[0] = new Rectangle() // Front
            {
                Fill = Brushes.White,
                Width = 50,
                Height = 40
            };

            Canvas.SetLeft(windows[0], 0);
            Canvas.SetTop(windows[0], 0);

            windows[1] = new Rectangle() // rear
            {
                Fill = Brushes.White,
                Width = 50,
                Height = 50
            };

            Canvas.SetLeft(windows[1], 0);
            Canvas.SetTop(windows[1], 0);

            // Label Automarke
            lblBrand.Width = 40;
            lblBrand.Height = 23;
            lblBrand.Content = Brand;

            // Add2Canvas
            for (int i = 0; i < tires.Length; i++)
                carBody.Children.Add(tires[i]);
            for (int i = 0; i < windows.Length; i++)
                carBody.Children.Add(windows[i]);
            carBody.Children.Add(lblBrand);

            if (Direction == "nord")
            {
                rotation.Angle = 0;
                rotation.CenterX = SpawnLocation.X;
                rotation.CenterY = SpawnLocation.Y;

                carBody.RenderTransform = rotation;
            }
            else if (Direction == "süd")
            {
                rotation.Angle = 180;
                rotation.CenterX = SpawnLocation.X;
                rotation.CenterY = SpawnLocation.Y;

                carBody.RenderTransform = rotation;
            }
            else if (Direction == "west")
            {
                rotation.Angle = 90;
                rotation.CenterX = SpawnLocation.X;
                rotation.CenterY = SpawnLocation.Y;

                carBody.RenderTransform = rotation;
            }
            else if (Direction == "ost")
            {
                rotation.Angle = 270;
                rotation.CenterX = SpawnLocation.X;
                rotation.CenterY = SpawnLocation.Y;

                carBody.RenderTransform = rotation;
            }

            cvs.Children.Add(carBody);
        }

调用方法MainWindow：

        Car car1;
        public MainWindow()
        {
            InitializeComponent();
            car1 = new Car("Audi", Colors.Red);
            car1.Direction = "west";
            car1.SpawnLocation = new Point(550, 340);
            car1.Spawn(gameScreen);
        }

提前致谢！

Answer 1

修好了！我初始化了 Spawn 方法的参数，在我删除它后它现在可以工作了。

我的方法首先看起来像这样：

        public void Spawn(Canvas cvs)
        {
            cvs = new Canvas();
            cvs.Children.Clear();

            carBody.Width = 70;
     

我初始化了 Argument，但由于我不想创建新的 Canvas，因此我删除了方法的前两行。

        public void Spawn(Canvas cvs)
        {

            carBody.Width = 70;
            carBody.Height = 120;
            carBody.Background = new SolidColorBrush(Color);

现在它工作正常。