[英]GUI/progress bar not updating from backgroundworker
I've been trying to get this work, but it just won't update anything on the GUI and my app exists on the error i showed in the code. 我一直在努力完成这项工作,但是它不会在GUI上进行任何更新,并且我的应用程序存在代码中显示的错误。
ListViewItem item;
public void SetStatusStrip()
{
BackgroundWorker bw = new BackgroundWorker();
bw.WorkerReportsProgress = true;
listviewTables.Columns.Add(gDatabase);
bw.DoWork += new DoWorkEventHandler(
delegate(object o, DoWorkEventArgs args)
{
BackgroundWorker b = o as BackgroundWorker;
try
{
MySqlCommand iCommand = new MySqlCommand("SHOW TABLES;", iCon);
iRead = iCommand.ExecuteReader();
int i = 0;
while (iRead.Read())
{
item = new ListViewItem(new[] { iRead.GetString(0) });
bw.ReportProgress(i);
i++;
}
}
catch (MySqlException ex)
{
MessageBox.Show("There was an error getting tables from the database: " + gDatabase + ".\n\nError Dump:\n" + ex, "MySQL Error!");
return;
}
});
bw.ProgressChanged += new ProgressChangedEventHandler(
delegate(object o, ProgressChangedEventArgs args)
{
progressBar1.Value = args.ProgressPercentage;
listviewTables.Items.Add(item); // I get error here: System.ArgumentException
});
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(
delegate(object o, RunWorkerCompletedEventArgs args)
{
progressBar1.Value = 0;
// Finished.
});
bw.RunWorkerAsync();
}
I agree with LarsTech. 我同意LarsTech。
Pass out the ListViewItem in ReportProgress(); 在ReportProgress()中传递ListViewItem;
while (iRead.Read())
{
bw.ReportProgress(i, new ListViewItem(new[] { iRead.GetString(0) }));
i++;
}
Then cast UserState
in ProgressChanged() back to a ListViewItem: 然后将ProgressChanged()中的
UserState
回ListViewItem:
bw.ProgressChanged += new ProgressChangedEventHandler(
delegate(object o, ProgressChangedEventArgs args)
{
progressBar1.Value = args.ProgressPercentage;
listviewTables.Items.Add((ListViewItem)args.UserState);
});
Note that I am NOT using your global var of "item", which is a bad idea to begin with. 请注意,我没有使用全局变量“ item”,这是一个不好的主意。
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