c# - 鼠标光标位置变化

Question

嗨，我有一个 Windows 窗体应用程序，我想移动鼠标然后拖放将起作用，但我尝试使用 mousemove 鼠标事件来执行此操作，但似乎拖放非常敏感。所以我要问的是是否有可能检测鼠标光标是否距离当前光标至少移动一定距离，然后执行拖放代码。

Answer 1

我了解您只有在鼠标移动了一定距离时才想执行拖放代码。如果是这样：

一旦用户执行了初始操作（鼠标按下要拖动的项目？），您就可以挂钩鼠标移动事件。然后比较鼠标移动事件上的鼠标坐标，一旦坐标差高于您设置的任意值，就会触发“拖放代码”。

private int difference = 10;
private int xPosition;
private int yPosition;

private void item_MouseDown(object sender, MouseEventArgs e) 
{
    this.MouseMove += new MouseEventHandler(Form_MouseMove);
    xPosition = e.X;
    yPosition = e.Y;
}

private void Form_MouseMove(object sender, MouseEventArgs e) 
{
    if (e.X < xPosition - difference
        || e.X > xPosition + difference
        || e.Y < yPosition - difference
        || e.Y > yPosition + difference) 
    {
        //Execute "dragdrop" code
        this.MouseMove -= Form_MouseMove;
    }
}

这将在光标移出虚拟 10x10 正方形时执行拖放操作。

Answer 2

我真的不明白你的问题和你想要达到的效果。顺便说一句，如果我的解释是正确的，那么只有当“拖动距离”大于某个量时，您才会尝试做某事。

下面的这段代码不使用拖放事件，而是使用 mouseup、mousedown 和 mousemove 事件。

它会在按下左键时跟踪鼠标移动的距离。当距离大于固定量时，它会改变鼠标光标（在拖动动作期间）

当释放鼠标按钮时，如果经过的距离大于最小偏移量，我们将执行我们的假放下动作。

创建一个新的 windows 窗体项目并将 Form1 自动生成的类替换为下面的类

希望这可以帮助。

public partial class Form1 : Form
{
    private bool isDragging;            //We use this to keep track that we are FakeDragging
    private Point startPosition;        //The start position of our "Fake" dragging action
    private double dragDistance = 0;    //The distance(absolute) from the drag action starting point    
    private const int MINIMUM_DRAG_DISTANCE = 100;  //minimum FakeDrag distance.

    private Label label1 = new Label();


    public Form1()
    {
        #region Support form generation code
            InitializeComponent();
            this.label1 = new System.Windows.Forms.Label();
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(54, 242);
            this.label1.Name = "Distance:";
            this.label1.Size = new System.Drawing.Size(35, 13);

            this.Controls.Add(label1);

            this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseUp);
            this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown);
            this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseMove);
        #endregion
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        //if the mouse button is pressed then 
        //there's the chanche a dragAction
        //is being performed and we take note
        //of the position of the click
        //(we will use this later on the mouseMove event
        //to calculate the distance mouse has traveled
        if (e.Button.Equals(MouseButtons.Left))
            startPosition = e.Location;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        ///at the mouse up event we can execute code that does something
        if (isDragging && dragDistance > MINIMUM_DRAG_DISTANCE)
        {
            MessageBox.Show("we have fakedragged!\nDo something useful here");
            //Do your Drag & Drop code here.
        }

        ///but WE MUST signal our system that the Fake Drag has ended
        ///and reset our support variables.
        this.Cursor = Cursors.Default;
        isDragging = false;
        dragDistance = 0;
    }


    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        ///when the mouse moves we control if the mouse button is still pressed.
        ///if it is so, we surely are FakeDragging and we set our boolean to true
        ///(it will be useful in the mouseUP event).
        ///Then we calculate the absolute distance the mouse has traveld since the
        ///user has pressed the left mouseButton.


        Point currentPosition = e.Location;
        if (e.Button.Equals(MouseButtons.Left))
        {
            isDragging = true;
            dragDistance =
                Math.Abs(
                    Math.Sqrt(
                        (
                            Math.Pow(
                                (currentPosition.X - startPosition.X), 2)
                        +
                            Math.Pow(
                                (currentPosition.Y - startPosition.Y), 2)
                        )));
        }

        //we set the label text displaying the distance we just calculated
        label1.Text = 
            String.Format(
                "Distance: {0}", 
                dragDistance.ToString());

        Application.DoEvents();


        ///At last, if the distance il greater than our offset, we change the 
        ///mouse cursor(this is not required in a real case scenario)
        if (dragDistance > MINIMUM_DRAG_DISTANCE)
            this.Cursor = Cursors.Hand;
        else
            this.Cursor = Cursors.Default;

    }
}