C# - 从线程更新 windows 窗体元素

Posted 2023-04-13

【中文标题】C# - 从线程更新 windows 窗体元素

【英文标题】：C# - Updating windows forms elements from thread

【发布时间】：2019-06-29 03:41:59

【问题描述】：

我目前正在创建一个程序来将笔记本电脑备份到 U 盘。我创建了一个从中调用方法的类。然后我通过一个单独的线程开始实际的备份。目前，我正在尝试通过此线程更改文本框和进度条。但是，它总是只立即显示第一个更改，而只有在程序运行后才显示其他进度。 我从互联网上尝试了几种解决方案，但到目前为止没有任何效果。也许有人在这里有解决方案。

    backup sales_backup = new backup();

    //Start Backup Button
    private void backup_button_Click(object sender, EventArgs e)
    
        Thread backupprocess = new Thread(new 
        ThreadStart(sales_backup.backup_start));
        backupprocess.Start();
    

    //Backup Function
        public void backup_start()
        
            files_to_copy = 0;
            files_copied = 0;

            var principalForm = System.Windows.Forms.Application.OpenForms.OfType<Form1>().FirstOrDefault();

            if (principalForm.drive_selector.SelectedItem != null)
            
                //Set Parameters
                principalForm.backup_button.Visible = false;
                error_copy = false;
                error_message = "";
                device_removed = false;

                //Fill variables
                string temp = principalForm.drive_selector.SelectedItem.ToString();
                temp = regex_matching_return_match(temp, @"[A-Z,a-z](:\\)");
                backup_device = temp;

                //Set Backup device size
                for (int i = 0; i < backup_devices_list.Count; i++)
                
                    if (backup_devices_list[i].backup_device_name == temp)
                    
                        backup_device_size = backup_devices_list[i].device_size;
                        file_system = backup_devices_list[i].file_system;
                        double temp_free = calculate_GB(backup_devices_list[i].device_free_space.ToString());
                        device_free_space = temp_free;
                        break;
                    
                

                //If no device is initialized
                if (backup_device == null || backup_device_size == 0)
                
                    write_to_textbox(get_create_usb_instance_error(), "red");
                
                else //If select ist successfull
                
                    //Get Backup size
                    get_size();
                    if (backup_size < device_free_space)
                    
                        backup_path_target = backup_device + "\\Backup\\";
                        Directory.CreateDirectory(backup_path_target);

                        //Get file count
                        get_file_count();

                        //Create Copy job
                        for (int i = 0; i < backup_path_source.Length; i++)
                        
                            string backup_path_s = backup_path_source[i] + "\\";
                            string backup_path_t = backup_path_target + backup_path_target_folders[i] + "\\";
                            copy_function(backup_path_s, backup_path_t);
                            int progress = return_progress();
                            TextBox test = principalForm.textBox2;
                            ProgressBar progress_bar = principalForm.progressBar1;
                            //Delegate Textbox
                            if (test.InvokeRequired)
                            
                                test.Invoke(new Action(() => test.Text = "Copying: " + backup_path_t));
                            
                            else
                            
                                test.Text = "Copying: " + backup_path_t;
                            
                            //Delegate Progressbar
                            if (progress_bar.InvokeRequired)
                            
                                test.Invoke(new Action(() => progress_bar.Value = progress));
                            
                            else
                            
                                progress_bar.Value = progress;
                            
                        

【问题讨论】：

您无法从后台线程更新 UI。您也不需要需要Invoke，如果您使用async/await 和Process<T> 类向其他线程报告进度

如果您使用Task.Run 和async/await，则不必使用Invoke().。如果 UI 线程很忙，则调用自身 blocks。您也应该将 UI 与文件处理代码分开 - 当您可以将驱动器等作为方法参数传递时，无需像这样访问主窗体

【参考方案1】：

确保您从正确的线程进行更新。 GUI 只能从它自己的线程更新。更多here。

【参考方案2】：

我无法对此进行测试，但它至少应该可以帮助您到达那里：

private void InvokeIfRequired<C>(C control, Action<C> action) where C : Control

    if (control.InvokeRequired)
    
        control.Invoke((Action)(() => action(control)));
    
    else
    
        action(control);
    


private void backup_button_Click(object sender, EventArgs e)

    var principalForm = System.Windows.Forms.Application.OpenForms.OfType<Form1>().FirstOrDefault();
    if (principalForm.drive_selector.SelectedItem != null)
    
        principalForm.backup_button.Visible = false;

        string temp = principalForm.drive_selector.SelectedItem.ToString();

        TextBox test = principalForm.textBox2;
        ProgressBar progress_bar = principalForm.progressBar1;

        Action<string> updateTest = t => this.InvokeIfRequired<TextBox>(test, c => c.Text = t);
        Action<int> updateProgress = v => this.InvokeIfRequired<ProgressBar>(progress_bar, c => c.Value = v);

        Thread backupprocess = new Thread(new ThreadStart(() => sales_backup.backup_start(temp, updateTest, updateProgress)));
        backupprocess.Start();
    


//Backup Function
public void backup_start(string temp, Action<string> updateTest, Action<int> updateProgress)

    files_to_copy = 0;
    files_copied = 0;

    //Set Parameters

    error_copy = false;
    error_message = "";
    device_removed = false;

    //Fill variables
    temp = regex_matching_return_match(temp, @"[A-Z,a-z](:\\)");
    backup_device = temp;

    //Set Backup device size
    for (int i = 0; i < backup_devices_list.Count; i++)
    
        if (backup_devices_list[i].backup_device_name == temp)
        
            backup_device_size = backup_devices_list[i].device_size;
            file_system = backup_devices_list[i].file_system;
            double temp_free = calculate_GB(backup_devices_list[i].device_free_space.ToString());
            device_free_space = temp_free;
            break;
        
    

    //If no device is initialized
    if (backup_device == null || backup_device_size == 0)
    
        write_to_textbox(get_create_usb_instance_error(), "red");
    
    else //If select ist successfull
    
        //Get Backup size
        get_size();
        if (backup_size < device_free_space)
        
            backup_path_target = backup_device + "\\Backup\\";
            Directory.CreateDirectory(backup_path_target);

            //Get file count
            get_file_count();

            //Create Copy job
            for (int i = 0; i < backup_path_source.Length; i++)
            
                string backup_path_s = backup_path_source[i] + "\\";
                string backup_path_t = backup_path_target + backup_path_target_folders[i] + "\\";
                copy_function(backup_path_s, backup_path_t);
                int progress = return_progress();

                //Delegate Textbox
                updateTest("Copying: " + backup_path_t);

                //Delegate Progressbar
                updateProgress(progress);
            
        
    

【参考方案3】：

您是否尝试过使用progress_bar.Invoke((MethodInvoker)(() => progress_bar.Value = progress));

【讨论】：

这不是答案。它应该被删除。请赚取 50 个代表点来发布 cmets。

更改委托类型不会更改调用的内容。代码可以是progress_bar.Invoke(() => progress_bar.Value = progress);。