单击另一个用户控件上的按钮后动态加载用户控件 [英] Dynamically loading UserControl after clicking button on another UserControl

问题描述

我在表单上显示 UserControl 时遇到问题.

I have a problem with displaying UserControl on my Form.

简而言之程序:

1. 在 Form1 中，我有一个按钮.单击此按钮后，在面板(容器)中动态加载了我的第一个 UserControl (new.cs).
2. 在该面板上，我有另一个按钮，可通向另一个 UserControl (choice.cs)，我想在 Form1 的同一个面板(容器)中显示它.

第一点效果很好，但第二点有问题.我想我必须纠正choice_button_Click 函数.有什么简单的方法吗?

The first point works good, but I have a problem with second one. I think I have to correct choice_button_Click function. Is there an easy way to do it?

这是我的代码:

Form1.cs:

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void new_button_Click(object sender, EventArgs e)
        {
            if (!container.Controls.Contains(@new.Instance))
            {
                container.Controls.Add(@new.Instance);
                @new.Instance.Dock = DockStyle.Fill;
                @new.Instance.BringToFront();
            }
            else
            {
                @new.Instance.BringToFront();
            }
        }

        public Panel getContainer()
        {
            return container;
        }
    }
}

new.cs:

namespace WindowsFormsApp1
{
    public partial class @new : UserControl
    {
        private static @new _instance;
        public static @new Instance
        {
            get
            {
                if (_instance == null)
                    _instance = new @new();
                return _instance;
            }
        }

        public @new()
        {
            InitializeComponent();
        }

        private void choice_button_Click(object sender, EventArgs e)
        {
            using (Form1 main = new Form1())
            {
                if (!main.getContainer().Controls.Contains(choice.Instance))
                {
                    main.getContainer().Controls.Add(choice.Instance);
                    choice.Instance.Dock = DockStyle.Fill;
                    choice.Instance.BringToFront();
                }
                else
                {
                    choice.Instance.BringToFront();
                }
            }    
        }
    }
}

choice.cs:

namespace WindowsFormsApp1
{
    public partial class choice : UserControl
    {
        private static choice _instance;
        public static choice Instance
        {
            get
            {
                if (_instance == null)
                    _instance = new choice();
                return _instance;
            }
        }

        public choice()
        {
            InitializeComponent();
        }
    }
}

推荐答案

您的功能问题是您没有将 choice.Instance 放在 Form1 的实例中.相反，您正在创建一个新表单，将其放置在那里，然后丢弃该表单.

Your functional problem is that you aren't placing choice.Instance inside your instance of your Form1. You are creating a new form instead, placing it there, then discarding that form.

但是，您的设计也存在问题，您违反了原则，其中 UserControl 不应直接访问和修改其父表单.您最好向 @new 添加一个事件，从按钮单击引发该事件，然后在表单实例中处理该事件.

However, you also have an issue in your design, where you are violating the principal wherein a UserControl shouldn't be directly accessing and modifying its parent form. You would be better off adding an event to @new, raising that event from the button click, then handling that event in your form instance.

例如:

new.cs:

namespace WindowsFormsApp1
{
    public partial class @new : UserControl
    {
        private static @new _instance;
        public static @new Instance
        {
            get
            {
                if (_instance == null)
                    _instance = new @new();
                return _instance;
            }
        }

        public event EventHandler StepCompleted;

        public @new()
        {
            InitializeComponent();
        }

        private void choice_button_Click(object sender, EventArgs e)
        {
            StepCompleted?.Invoke(this, EventArgs.Empty);
        }
    }
}

和 Form1.cs:

And Form1.cs:

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void new_button_Click(object sender, EventArgs e)
        {
            if (!container.Controls.Contains(@new.Instance))
            {
                container.Controls.Add(@new.Instance);
                @new.Instance.Dock = DockStyle.Fill;
                @new.Instance.BringToFront();
            }
            else
            {
                @new.Instance.BringToFront();
            }
        }

        private void new_StepCompleted(object sender, EventArgs e)
        {
            if (!container.Controls.Contains(choice.Instance))
            {
                container.Controls.Add(choice.Instance);
                choice.Instance.Dock = DockStyle.Fill;
                choice.Instance.BringToFront();
            }
            else
            {
                choice.Instance.BringToFront();
            }
        }
    }
}

现在您显然要处理同一个表单实例，因为它本身就是处理事件的对象.此外，@new 不需要进行任何笨拙的查找来找到正确的 Form1 实例并修改表单.

Now you're obviously going to be working on the same form instance, since it itself is the one handling the event. Also, @new doesn't need to do any awkward lookup to find the proper Form1 instance and modify the form.

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