Question

为什么我不能在按钮（或组合框等）事件中将新项目/对象添加到列表中？我的意思是，如果活动不在括号内，活动将看不到我的清单...用红色下划线标出...可以帮我吗？

长话短说：我想通过单击按钮添加一个新对象

 private  int animValue;
    private int strokeWidth = 15;
    private int i = 0;

    public MyCustomView(Context context) :
        base(context)
    {
    }

   public MyCustomView(Context context, IAttributeSet attrs) :
        base(context, attrs)
    {
        animValue = 0;
    }

    public MyCustomView(Context context, IAttributeSet attrs, int defStyle) :
        base(context, attrs, defStyle)
    {
    }

    protected override void OnDraw(Canvas canvas)
    {
        base.OnDraw(canvas);
        Paint paint = new Paint();
        paint.SetStyle(Paint.Style.Stroke);
        paint.StrokeWidth=(strokeWidth);

        RectF rectF = new RectF();
        rectF.Set(strokeWidth, strokeWidth, Width - strokeWidth, Width - strokeWidth);
        paint.Color = (Color.Gray);
        canvas.DrawArc(rectF, 0, 360, false, paint);
        paint.Color=(Color.Blue);
        canvas.DrawArc(rectF, animValue, i++, false, paint);
    }
    public void setValue(int animatedValue)
    {
        animValue = animatedValue;
        Invalidate();
    }
}

Answer 1

我认为您应该全局实例化列表，而不是在Form1_Load事件下。这样，您就可以在整个班级（在这种情况下为窗口）中访问它。

Answer 2

这似乎很好。启动表单时，可能需要将文本框设置为包含有效值。还请确保您在整个form1类中显示该列表。

namespace Samochody
{
    public partial class Form1 : Form
    {

        // make sure your list looks like this, created outside your functions.
        List<Samochod> ListaSamochodow = new List<Samochod>();

        public Form1()
        {
            InitializeComponent();
            label1.Text = "the amount in your list is " + ListaSamochodow.Count.ToString();
            textBox1.Text = "string here";
            textBox2.Text = "string here";
            textBox3.Text = "100";
        }


        private void Form1_Load(object sender, EventArgs e)
        {
            XmlRootAttribute oRootAttr = new XmlRootAttribute();
            XmlSerializer oSerializer = new XmlSerializer(typeof(List<Samochod>), oRootAttr);
            StreamWriter oStreamWriter = null;
            oStreamWriter = new StreamWriter("samochody.xml");
            oSerializer.Serialize(oStreamWriter, ListaSamochodow);
        }


        private void button1_Click_1(object sender, EventArgs e)
        {
            Samochod s = new Samochod(textBox1.Text, textBox2.Text, Convert.ToInt32(textBox3.Text));
            ListaSamochodow.Add(s);
            label1.Text = "the amount in your list is " + ListaSamochodow.Count.ToString();

        }
    }
}

为什么我不能在按钮事件中添加新的List对象

2 个答案: