【发布时间】：2010-05-22 18:04:49
【问题描述】：
我正在尝试使用 ListBox 播放列表构建一个简单的音乐播放器。将音频文件添加到播放列表时，它首先用文件名填充 ListBox，然后（在单独的线程上）提取 ID3 数据并用正确的艺术家 - 标题信息覆盖文件名（很像 Winamp）。
但是当 ListBox 被更新时，它是不可滚动的，因为它总是在每次覆盖时跳到顶部。
有什么办法防止这种情况发生？
编辑：
代码：
public Form1()
{
//Some initialization code omitted here
BindingList<TAG_INFO> trackList = new BindingList<TAG_INFO>();
// The Playlist
this.playlist = new System.Windows.Forms.ListBox();
this.playlist.Location = new System.Drawing.Point(12, 12);
this.playlist.Name = "playlist";
this.playlist.Size = new System.Drawing.Size(229, 316);
this.playlist.DataSource = trackList;
}
private void playlist_add_Click(object sender, EventArgs e)
{
//Initialize OpenFileDialog
OpenFileDialog opd = new OpenFileDialog();
opd.Filter = "Music (*.WAV; *.MP3; *.FLAC)|*.WAV;*.MP3;*.FLAC|All files (*.*)|*.*";
opd.Title = "Select Music";
opd.Multiselect = true;
//Open OpenFileDialog
if (DialogResult.OK == opd.ShowDialog())
{
//Add opened files to playlist
for (int i = 0; opd.FileNames.Length > i; ++i)
{
if (File.Exists(opd.FileNames[i]))
{
trackList.Add(new TAG_INFO(opd.FileNames[i]));
}
}
//Initialize BackgroundWorker
BackgroundWorker _bw = new BackgroundWorker();
_bw.WorkerReportsProgress = true;
_bw.DoWork += new DoWorkEventHandler(thread_trackparser_DoWork);
_bw.ProgressChanged += new ProgressChangedEventHandler(_bw_ProgressChanged);
//Start ID3 extraction
_bw.RunWorkerAsync();
}
}
void thread_trackparser_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker _bw = sender as BackgroundWorker;
for (int i = 0; i < trackList.Count; ++i)
{
//Pass extracted tag info to _bw_ProgressChanged for thread-safe playlist entry update
_bw.ReportProgress(0,new object[2] {i, BassTags.BASS_TAG_GetFromFile(trackList[i].filename)});
}
}
void _bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
object[] unboxed = e.UserState as object[];
trackList[(int)unboxed[0]] = (unboxed[1] as TAG_INFO);
}
EDIT2：
更简单的测试用例：
尝试向下滚动而不选择项目。变化中的 ListBox 将再次滚动到顶部。
using System;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
public class Form1 : Form
{
private System.ComponentModel.IContainer components = null;
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.listBox1 = new System.Windows.Forms.ListBox();
this.timer1 = new System.Windows.Forms.Timer(this.components);
this.SuspendLayout();
// listBox1
this.listBox1.FormattingEnabled = true;
this.listBox1.Location = new System.Drawing.Point(0, 0);
this.listBox1.Name = "listBox1";
this.listBox1.Size = new System.Drawing.Size(200, 290);
// timer1
this.timer1.Enabled = true;
this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
// Form1
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(200, 290);
this.Controls.Add(this.listBox1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
private System.Windows.Forms.ListBox listBox1;
private System.Windows.Forms.Timer timer1;
public Form1()
{
InitializeComponent();
for (int i = 0; i < 45; i++)
listBox1.Items.Add(i);
}
int tickCounter = -1;
private void timer1_Tick(object sender, EventArgs e)
{
if (++tickCounter > 44) tickCounter = 0;
listBox1.Items[tickCounter] = ((int)listBox1.Items[tickCounter])+1;
}
}
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
【问题讨论】：
-
你能发布一些代码吗？它的更新方式可能与问题有关。
-
添加了用于演示相同问题的更简单的代码。