Question

我刚刚开始使用C＃，作为一个项目，我决定尝试制作一个图像转换器，但我似乎无法在button1上下文中获取变量“open”，我不是在寻找关于我的代码有多糟糕的评论，我刚刚开始..我只想完成它并添加它，我将在以后改进代码，谢谢。那么如何让它可以访问呢？

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;

namespace WindowsFormsApplication9
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    public void button2_Click(object sender, EventArgs e)
    {
        OpenFileDialog open = new OpenFileDialog();
        // image filters
        open.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp";
        if (open.ShowDialog() == DialogResult.OK)
        {
            // image in picture box
           pictureBox1.Image = new Bitmap(open.FileName);
           pictureBox1.SizeMode = PictureBoxSizeMode.AutoSize;
            // image file path
           string path = Directory.GetCurrentDirectory();
           textBox1.Text = Path.GetDirectoryName(open.FileName);
        }

       }


    public void Form1_Load(object sender, EventArgs e)
    {
        this.AutoSize = true;
        this.AutoSizeMode = AutoSizeMode.GrowAndShrink;

        flowLayoutPanel1 = new FlowLayoutPanel();
        flowLayoutPanel1.AutoSize = true;
        flowLayoutPanel1.AutoSizeMode = AutoSizeMode.GrowAndShrink;
        this.Controls.Add(flowLayoutPanel1);
    }

    public void button1_Click(object sender, EventArgs e)
    {
        int selectedIndex = comboBox1.SelectedIndex;
        Object selectedItem = comboBox1.SelectedItem;

        if ((string)comboBox1.SelectedItem == "*.jpg")
        {
           pictureBox1.Image.Save(@"" + textBox1.Text + open.FileName + "", System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}
}

Answer 1

您可以将变量移出方法并进入类，使其成为类的实例字段。然后任何方法都能看到它。但是，这种方法存在一些问题：

OpenFileDialog与任何模态对话框一样，在完成后应予以处理。在实例字段中存储引用会延长其生命周期，直到您下次创建新表单或表单关闭时为止，以先到者为准。
你真正需要的只是文件名，而不是OpenFileDialog所带来的所有其他数据和资源，所以它很浪费。
从用户体验的角度来看，最好让用户有机会保存到不同的文件。您最好向用户提供SaveFileDialog，并使用当前选定的文件名进行初始化。

坚持使用您当前的UI设计，以下是正确的方法：

private string fileName;

public void button2_Click(object sender, EventArgs e)
{
    using (OpenFileDialog open = new OpenFileDialog())
    {
        // image filters
        open.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp";
        if (open.ShowDialog() == DialogResult.OK)
        {
            // image in picture box
           filename = open.FileName;
           pictureBox1.Image = new Bitmap(open.FileName);
           pictureBox1.SizeMode = PictureBoxSizeMode.AutoSize;
           // image file path
           string path = Directory.GetCurrentDirectory();
           textBox1.Text = Path.GetDirectoryName(open.FileName);
        }
    }
}

public void button1_Click(object sender, EventArgs e)
{
    if (string.IsNullOrEmpty(fileName))
    {
        return;
    }

    int selectedIndex = comboBox1.SelectedIndex;
    Object selectedItem = comboBox1.SelectedItem;

    if ((string)comboBox1.SelectedItem == "*.jpg")
    {
       pictureBox1.Image.Save(@"" + textBox1.Text + fileName + "", System.Drawing.Imaging.ImageFormat.Jpeg);
    }
}

请注意使用using确保OpenFileDialog实例在不再需要时正确处置。

Answer 2

C＃没有全局变量，但您可以为此设置解决方法，

public class GlobalObjects
{
    private static OpenFileDialog ofd;

    public static OpenFileDialog OpenFileDlg
    {
        get
        {
            if (ofd == null)
                ofd = new OpenFileDialog();
            return ofd;
        }
    }

}

并称之为，

var fileDlg = GlobalObjects.OpenFileDlg;

如何使OpenFileDialog变量全局？

2 个答案: