117 lines
4.7 KiB
VB.net
117 lines
4.7 KiB
VB.net
Public Class MyImage
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Inherits Image
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#Region "辅助属性注册"
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''' <summary>
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''' 网络图片的缓存有效期。
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''' 在这个时间后，才会重新尝试下载图片。
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''' </summary>
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Public FileCacheExpiredTime As New TimeSpan(7, 0, 0, 0) '7 天
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''' <summary>
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''' 是否允许将网络图片存储到本地用作缓存。
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''' </summary>
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Public Property EnableCache As Boolean
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Get
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Return _EnableCache
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End Get
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Set(value As Boolean)
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_EnableCache = value
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End Set
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End Property
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Private _EnableCache As Boolean = True
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'将 Source 属性映射到 XAML
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Public Shared Shadows ReadOnly SourceProperty As DependencyProperty = DependencyProperty.Register(
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"Source", GetType(String), GetType(MyImage), New PropertyMetadata(New PropertyChangedCallback(
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Sub(sender, e) If sender IsNot Nothing Then CType(sender, MyImage).Source = e.NewValue.ToString())))
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#End Region
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Private _Source As String = ""
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''' <summary>
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''' 与 Image 的 Source 类似。
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''' 若输入以 http 开头的字符串，则会尝试下载图片然后显示，图片会保存为本地缓存。
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''' 支持 WebP 格式的图片。
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''' </summary>
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Public Shadows Property Source As String '覆写 Image 的 Source 属性
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Get
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Return _Source
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End Get
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Set(value As String)
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If value = "" Then value = Nothing
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If _Source = value Then Exit Property
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_Source = value
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Dim TempPath As String = $"{PathTemp}MyImage\{GetHash(value)}.png"
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Try
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'空
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If value Is Nothing Then
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MyBase.Source = Nothing
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Exit Property
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End If
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'本地图片
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If Not value.StartsWithF("http") Then
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MyBase.Source = New MyBitmap(value)
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Exit Property
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End If
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'从缓存加载网络图片
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If EnableCache AndAlso File.Exists(TempPath) Then
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MyBase.Source = New MyBitmap(TempPath)
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If (Date.Now - File.GetCreationTime(TempPath)) < FileCacheExpiredTime Then
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Exit Property '无需刷新缓存
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Else
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File.Delete(TempPath) '需要刷新缓存
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End If
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Else
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MyBase.Source = Nothing '清空显示
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End If
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'下载网络图片
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RunInNewThread(
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Sub()
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Dim Url As String = value '重新捕获变量，以检测在下载过程中 Source 被修改的情况
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Dim Retried As Boolean = False
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RetryStart:
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Dim TempDownloadingPath As String = TempPath & RandomInteger(0, 10000000)
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Try
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Log("[MyImage] 正在下载图片：" & Url)
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NetDownload(Url, TempDownloadingPath, True)
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If Url <> Source Then
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'若 Source 在下载时被修改，则不显示
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File.Delete(TempDownloadingPath)
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ElseIf EnableCache Then
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'保存缓存并显示
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Rename(TempDownloadingPath, TempPath)
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RunInUi(Sub() MyBase.Source = New MyBitmap(TempPath))
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Else
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'直接显示
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RunInUiWait(Sub() MyBase.Source = New MyBitmap(TempDownloadingPath))
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File.Delete(TempDownloadingPath)
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End If
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Catch ex As Exception
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Try
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File.Delete(TempDownloadingPath)
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Catch
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End Try
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If Not Retried Then
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Log(ex, $"下载图片可重试地失败（{Url}）", LogLevel.Developer)
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Retried = True
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Thread.Sleep(1000)
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GoTo RetryStart
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Else
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Log(ex, $"下载图片失败（{Url}）", LogLevel.Hint)
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End If
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End Try
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End Sub, "MyImage PicLoader " & GetUuid() & "#", ThreadPriority.BelowNormal)
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Catch ex As Exception
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Log(ex, $"加载图片失败（{value}）", LogLevel.Hint)
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Try
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File.Delete(TempPath) '删除缓存，以免缓存出现问题导致一直加载失败
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Catch
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End Try
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End Try
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End Set
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End Property
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End Class
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