c# - 如果进行了更改，如何在退出时显示消息框？

Question

如果用户对图片框中的图像进行了更改，例如使用旋转 R、旋转 L 按钮，然后用户单击退出按钮，我希望它显示一个消息框，上面写着“您想将更改保存到以下物品？” 我似乎做不到，这就是我所拥有的。

Answer 1

您需要设置一个标志来确定是否单击了按钮。然后检查该标志Exit_Click：

private void Exit_Click(object sender, EventArgs e)
{
    if (_rotrButtonClicked &&
        MessageBox.Show("Would you like to save this file?",
            "Media Player",
            MessageBoxButtons.YesNo) == DialogResult.Yes)
    {
        // save the changes
    }
}

您可以将标志声明为private表单上的字段：

private bool _rotrButtonClicked;

然后在RotRButton_Click集合中：

_rotrButtonClicked = true;

Answer 2

您应该将逻辑封装到一个可以为您跟踪更改状态的类中。例如

public class ImageMutator
{
    private bool HasChanged { get; set; }   
    private PictureBox myPictureBox {get;set}
    public ImageMutator(PictureBox pictureBox)//Most abstract type that has functionality
    {
       myPictureBox = pictureBox;
    }
    public void RotateRight()
    {
        HasChanged = true;
        //manipulate myPictureBox
    }

    public void RotateLeft()
    {
        HasChanged = true;
        //manipulate myPictureBox
    }

    //other methods

    public void ConfirmChange()
    {
        if (HasChanged)
        {
            var save = (MessageBox.Show("Would you like to save this file?", "Media Player", MessageBoxButtons.YesNo) == DialogResult.Yes);
            if (save)
            {
                //Save
            }

        }
    }
}

然后您可以将此类添加为表单的成员并在退出时确认：

public partial class Form1 : Form
{
    private ImageMutator mutator ;/private member "has-a" relationship

    public Form1()
    {
        InitializeComponent();
        mutator = new ImageMutator(pictureBox);//whatever image type is
    }

    private void Exit_Click(object sender, EventArgs e)
    {
        mutator.ConfirmChange();//Only saves if mutation occurred         
    }
}

Answer 3

当用户单击旋转按钮时，您必须跟踪更改。在退出按钮中，您只需检查变量的值以了解是否有更改：

private bool hasChanges = false;

private void RotRButton_Click(object sender, EventArgs e) {
    hasChanges = true;
}

private void Exit_Click(object sender, EventArgs e)
{
    if (hasChanges)
    {
        if (MessageBox("Would you like to save this file?", "Media Player", MessageBoxButtons.YesNo) == DialogResult.Yes) {
           //Do something
        }

    }
}