为什么是多个项目不工作的列表框
本文关键字：工作 列表 项目 为什么 | 更新日期: 2023-09-27 18:03:23
我创建了一个媒体播放器播放列表。
遵循我的代码:
Xaml:<MediaElement x:Name="mePlayer" Margin="64,0,90,61" ></MediaElement>
<ListBox x:Name="listbox4" Background="Salmon" BorderBrush="Black" BorderThickness="3" Drop="listbox4_Drop" >
</ListBox>
<Button x:Name="load" Content="Load" HorizontalAlignment="Left" VerticalAlignment="Top" Width="76" Click="load_Click" Margin="184,285,0,0"/>
Xaml.cs :
private Dictionary<string, string> fileDictionary = new Dictionary<string, string>();
private void load_Click(object sender, RoutedEventArgs e)
{
Microsoft.Win32.OpenFileDialog ofd = new Microsoft.Win32.OpenFileDialog();
ofd.DefaultExt = ".mp3";
ofd.Filter = "All|*.*";
ofd.Multiselect = true;
Nullable<bool> result = ofd.ShowDialog();
if (result == true)
{
for (int i = 0; i < ofd.FileNames.Length; i++)
{
var filePath = ofd.FileNames[i];
var fileName = System.IO.Path.GetFileName(filePath);
fileDictionary.Add(fileName, filePath);
listbox4.Items.Add(fileName);
listbox4.SelectedItem = fileName;
}
}
}
private void listbox4_Drop(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
foreach (string droppedFilePath in droppedFilePaths)
{
for (int i = 0; i < droppedFilePaths.Length; i++)
{
var filePath = droppedFilePaths[i];
var fileName = System.IO.Path.GetFileName(filePath);
fileDictionary.Add(fileName, filePath);
listbox4.Items.Add(fileName);
listbox4.SelectedItem = fileName;
}
}
}
}
它是工作的单一文件，但当我删除多个文件，然后它不会添加到列表框。
加载多个文件，但不删除多个文件。
我如何在列表框上放置多个文件?
由于我无法复制您列出的问题，因此我目前无法在这方面帮助您。不过，我可以在我认为合适的地方帮助你。
你当前的Drop方法有一个额外的循环，可以将你添加到列表框中的项数乘以。
当前方法:
private void listbox4_Drop(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
foreach (string droppedFilePath in droppedFilePaths)
{
//if you keep this loop, you will all the dropped files for each dropped file
//therefore, if I dropped 3 files, I'd get 9 entries in the listbox
//if I dropped 4 files, I'd get 16 entries and so on...
for (int i = 0; i < droppedFilePaths.Length; i++)//this has to go
{//this has to go
var filePath = droppedFilePaths[i];//this needs to be a different variable since "i" will no longer exist
var fileName = System.IO.Path.GetFileName(filePath);
//fileDictionary.Add(fileName, filePath);
listbox4.Items.Add(fileName);
listbox4.SelectedItem = fileName;
}//this has to go
}
}
}
重构(使用ForEach)
private void blaze_125_listbox4_Drop(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
foreach (string droppedFilePath in droppedFilePaths)
{
var filePath = droppedFilePath;
var fileName = System.IO.Path.GetFileName(filePath);
//fileDictionary.Add(fileName, filePath);
listbox4.Items.Add(fileName);
listbox4.SelectedItem = fileName;
}
}
}
这也可以(使用ForLoop)
private void blaze_125_listbox4_Drop_anotherSpin(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
for (int i = 0; i < droppedFilePaths.Length; i++)
{
var filePath = droppedFilePaths[i];
var fileName = System.IO.Path.GetFileName(filePath);
//fileDictionary.Add(fileName, filePath);
listbox4.Items.Add(fileName);
listbox4.SelectedItem = fileName;
}
}
}
苗条
private void blaze_125_listbox4_Drop_Slimmer(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
foreach (string droppedFilePath in droppedFilePaths)
{
listbox4.Items.Add(System.IO.Path.GetFileName(droppedFilePath));
}
}
}
使用字典存储项，并更新列表
Dictionary<string, string> fileDictionary = new Dictionary<string, string>();
private void blaze_125_listbox4_Drop_Slimmer(object sender, DragEventArgs e)
{
if (e.Data.GetDataPresent(DataFormats.FileDrop))
{
string[] droppedFilePaths =
e.Data.GetData(DataFormats.FileDrop, true) as string[];
foreach (string droppedFilePath in droppedFilePaths)
{
//listbox4.Items.Add(System.IO.Path.GetFileName(droppedFilePath));//don't need this anymore
//Check if the file is already in the dictionary.
//Check by looking up the key, and by looking up the value too.
if (fileDictionary.ContainsKey(System.IO.Path.GetFileName(droppedFilePath)) || fileDictionary.ContainsValue(droppedFilePath))
{
//no need to add this file, it's already in the dictionary
//if you try to add a file with a KEY identical to a KEY that already exists in the dictionary,
//it will throw an exception
//A dictionary can contain the same value multiple times, but it can not contain the same key more than once.
}
else
{
//the file is not listed in the dictionary, so lets add it
fileDictionary.Add(System.IO.Path.GetFileName(droppedFilePath), droppedFilePath);
}
}
}
//Now lets call the method in charge of updating the listbox
UpdateTheListbox(fileDictionary, listbox4);
}
private void UpdateTheListbox(Dictionary<string, string> incomingDictionary, ListBox listboxToModify)
{
listboxToModify.Items.Clear();//clear all the items in the list
foreach (KeyValuePair<string, string> item in incomingDictionary)
{
listboxToModify.Items.Add(item.Key);
}
//this method should probably be optimized because if your listBox already contains a large number of items
//it may be quicker to only add the missing items, instead of reverting back to an empty list, and adding all the items to it again.
//Though I'll leave this up to you to implement. We'll be here to answer questions if you have a hard time doing it.
}
更新了在存在选定项时维护选定项的方法
private void UpdateTheListboxMaintainExistingSelection(Dictionary<string, string> incomingDictionary, ListBox listboxToModify)
{
var preSelectedItem = listboxToModify.SelectedItem;//store the current selection
listboxToModify.Items.Clear();//clear all the items in the list
foreach (KeyValuePair<string, string> item in incomingDictionary)
{
listboxToModify.Items.Add(item.Key);
}
//this method should probably be optimized because if your listBox already contains a large number of items
//it may be quicker to only add the missing items, instead of reverting back to an empty list, and adding all the items to it again.
//Though I'll leave this up to you to implement. We'll be here to answer questions if you have a hard time doing it.
//Maintain the selected item if there was one
if (preSelectedItem != null)
{
listboxToModify.SelectedItem = preSelectedItem;
}
}
保持选中项，如果没有选中项，则选择最后一项
private void UpdateTheListboxMaintainExistingOrSelectLastAdded(Dictionary<string, string> incomingDictionary, ListBox listboxToModify)
{
var preSelectedItem = listboxToModify.SelectedItem;//store the current selection
listboxToModify.Items.Clear();//clear all the items in the list
foreach (KeyValuePair<string, string> item in incomingDictionary)
{
listboxToModify.Items.Add(item.Key);
}
//this method should probably be optimized because if your listBox already contains a large number of items
//it may be quicker to only add the missing items, instead of reverting back to an empty list, and adding all the items to it again.
//Though I'll leave this up to you to implement. We'll be here to answer questions if you have a hard time doing it.
if (preSelectedItem != null)
{
//Maintain the selected item if there was one
listboxToModify.SelectedItem = preSelectedItem;
}
else
{
//select the last item in the listbox if nothing was pre-selected
listboxToModify.SelectedItem = listboxToModify.Items[listboxToModify.Items.Count - 1];
}
}