BackgroundWorker

Question

带有自定义控件的 WinForms 应用程序 LabelProgressBar，它能够显示进度和一些描述性文本 and/or 完成百分比。这是通过调用 LabelProgressBar.statusInProgress(string message, int percentageCompletion).

完成的

其用法如下：

private void import_begin(System.Object sender, System.ComponentModel.DoWorkEventArgs args)
{
    // first unpack the arguments
    System.Object[] arguments = (System.Object[])args.Argument;
    System.String filename = (System.String)arguments[0];
    System.String why = (System.String)arguments[1];

     // tasks:
     // 1. read excel file and apply changes to model
     // 2. gather changes and format them as XML
     // 3. send request to server
     // 4. commit/rollback changes

      // grab the worker thread so we can report percentage progress
      System.ComponentModel.BackgroundWorker worker = (System.ComponentModel.BackgroundWorker)sender;

     // now do the work
     #region Task1
     Controller.Excel excel = new Controller.Excel(filename);
     try
     {
          // the progress of this needs to be tracked
          overall_result = excel.import_all(out modified_nodes);
     }
     catch (InvalidDataExcetpion invDataEx)
     {
         // deal with it
     }
     #endregion
     worker.ReportProgress(25);

     // complete remaining tasks...
}

工作人员报告其进度的事件处理程序如下：

private void import_progress(object sender, System.ComponentModel.ProgressChangedEventArgs e)
{
    Debug.WriteLine("Import percentage completion: " + e.ProgressPercentage);
    labelProgressBar1.statusInProgress("Import", e.ProgressPercentage);
}

简而言之，import_begin方法被分解成几个"tasks"。这些被分解为 "subtasks"。以import_all方法为例：

public Command_Result import_all(out System.Collections.Generic.List<Model.Data_Node> nodes)
        {
            Command_Result overall_result = Command_Result.OK;
            Command_Result this_result;
            nodes = new System.Collections.Generic.List<Model.Data_Node>(excel.Workbook.Worksheets.Count);
            Model.Data_Node destination;

            // the intent is to report the progress of this particular subtask on the basis of how many worksheets have been processed in this for loop
            foreach (OfficeOpenXml.ExcelWorksheet worksheet in excel.Workbook.Worksheets)
            {
                this_result = import_sheet(worksheet.Name, out destination);
                nodes.Add(destination);
                if (this_result > overall_result)
                {
                    overall_result = this_result;
                }
            }

            return overall_result;
        }

目的是让此 "subtask" 根据循环中已处理的工作表数量报告进度。为此计算百分比是一项微不足道的任务，但我不清楚如何将其报告回 import_begin 方法。当这个"subtask"完成后，总体任务完成度（从import_begin方法的POV）应该是25%。其他任务也类似。如何实现？

Answer 1

import_begin其实不需要获取更新，直接调用子任务即可，而也传递了BackgroundWorker，所以子任务负责直接报告他们的进展。如果 "polluting" 带有 BackgroundWorker 的子任务不可接受，则创建一个委托来调用 BackgroundWorker，这样您的子任务就会调用委托。

private void mainTask(object sender, DoWorkEventArgs e)
{
    var worker = (BackgroundWorker)sender;
    var report = new Action<int>(i => worker.ReportProgress(i)); //the delegate
    smallTask1Clean(report); //this one pass the delegate
    smallTask2(worker); //this one directly call background worker
    worker.ReportProgress(100);
}

void smallTask1Clean(Action<int> a)
{
    for (int i = 0; i < 20; i++)
    {
        Thread.Sleep(500);
        a(i);
    }
}

void smallTask2(BackgroundWorker w)
{
    for (int i = 0; i < 5; i++)
    {
        Thread.Sleep(1000);
        w.ReportProgress(i*80/5+20);
    }
}

您还可以将子任务隔离开来，使其不必知道它们在较大任务中的作用，在这种情况下，委托应采用两个变量，即子任务的当前内部进度和它需要处理的总项目。

private void mainTask(object sender, DoWorkEventArgs e)
{
    var worker = (BackgroundWorker)sender;
    var preTaskProgress = 0;
    var currentTaskTotalPercentage = 0;
    var smarterDelegate = new Action<int, int>((current, total) =>
     {
         worker.ReportProgress(preTaskProgress + (current *currentTaskTotalPercentage/total));
     });

    currentTaskTotalPercentage = 30; //the following task will in total progressed the main task for 30%
    smallTaskClean(smarterDelegate);
    preTaskProgress = currentTaskTotalPercentage; //upate the main the progress before starting the next task
    currentTaskTotalPercentage = 70; //the following task will in total progressed the main task for 70%
    smallTaskClean(smarterDelegate);

    worker.ReportProgress(100);
}

void smallTaskClean(Action<int,int> a)
{
    for (int i = 0; i < 5; i++)
    {
        Thread.Sleep(1500);
        a(i,5);
    }
}

BackgroundWorker - 使用 "sub tasks" 报告进度

BackgroundWorker - reporting progress with "sub tasks"

.net

c#

winforms

progress-bar