在“秒表+”上线之后很多人都建议支持自定义背景，这个确实有点儿难度，最后终于在小梦的帮助下完成了。以下介绍如何从图片库读取图片并保存到本地，并在程序启动时自动加载背景。
首先在你的页面的类下添加一个变量
FileOpenPickerContinuationEventArgs _filePickerEventArgs = null;
然后再写这个么个函数
public FileOpenPickerContinuationEventArgs FilePickerEvent
{
get { return _filePickerEventArgs; }
set
{
_filePickerEventArgs = value;
ContinueFileOpenPicker(_filePickerEventArgs);
}
}
这个复制粘贴就好
然后在这里用户点了某个按钮想要更换背景图片
处理如下
private void changeback(object sender, RoutedEventArgs e)
{
FileOpenPicker openPicker = new FileOpenPicker();
openPicker.ViewMode = PickerViewMode.Thumbnail;
openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
openPicker.FileTypeFilter.Add(“.jpg”);
openPicker.FileTypeFilter.Add(“.jpeg”);
openPicker.FileTypeFilter.Add(“.png”);
openPicker.PickSingleFileAndContinue();
}
用户打了√之后程序将会执行到app.xaml.cs里，在这里添加这样一个函数，如果有，就改装吧
protected override void OnActivated(IActivatedEventArgs args)
{
if (args is FileOpenPickerContinuationEventArgs)
{
Frame rootFrame = Window.Current.Content as Frame;
if (!rootFrame.Navigate(typeof(normal )))//这个normal是你刚才点按钮的页面的类名
throw new Exception(“Failed to create target page”);
var p = rootFrame.Content as normal ;
p.FilePickerEvent = (FileOpenPickerContinuationEventArgs)args;
}
Window.Current.Activate();
}
回到刚才的页面之后，程序将会执行到这里 这个函数也可以复制粘贴，只是这里有些内容你可能需要读懂才能用。
public async void ContinueFileOpenPicker(FileOpenPickerContinuationEventArgs args)
{
if ( args.Files != null && args.Files.Count > 0)
{
StorageFile file = args.Files[0];
IRandomAccessStream fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read);
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.SetSource(fileStream);
ImageBrush newback = new ImageBrush();
newback.ImageSource = bitmapImage;
页背景[3] = newback;
pageback = 页背景[3];
applycolor();
WriteFile(“changedbacksetting”, ”yes”);
StorageFolder applicationFolder = ApplicationData.Current.LocalFolder;
StorageFile storageFile = await applicationFolder.CreateFileAsync(@”userback.jpg”, CreationCollisionOption.ReplaceExisting);
IRandomAccessStream outStream = await storageFile.OpenAsync(FileAccessMode.ReadWrite);
outStream.Size = 0;
IRandomAccessStream inStream = fileStream;//供移植用
BitmapDecoder decoder = await BitmapDecoder.CreateAsync(inStream);
PixelDataProvider provider = await decoder.GetPixelDataAsync();
byte[] data = provider.DetachPixelData();
var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, outStream);
encoder.SetPixelData(decoder.BitmapPixelFormat, decoder.BitmapAlphaMode, decoder.PixelWidth, decoder.PixelHeight, decoder.DpiX, decoder.DpiY, data);
try
{
await encoder.FlushAsync();
}
catch (Exception err)
{
Debug.WriteLine(err.ToString());
}
finally
{
inStream.Dispose();
outStream.Dispose();
}
}
}
在刚才的函数中我们把目标图像设置成了背景图片，并将它保存到了本地，下面就是如何在程序启动的时候调取本地图像
public async void ReadImg()
{
try
{
string fileName = @”userback.jpg”;
StorageFolder applicationFolder = ApplicationData.Current.LocalFolder;
StorageFile storageFile = await applicationFolder.GetFileAsync(fileName);
IRandomAccessStream accessStream = await storageFile.OpenReadAsync();
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.SetSource(accessStream);
ImageBrush back = new ImageBrush();
back.ImageSource = bitmapImage;
normal.userback = back;
accessStream.Dispose();
}
catch (Exception ex)
{
string x = ex.ToString();
}
}
这个函数一定得在页面类的构造函数中调用，不然时间来不及。这么写一般还是来得及的，反正我写的应用还没在这方面出过问题，放心的用吧。
最后附送几个uri的操作吧，很实用的。
await Windows.System.Launcher.LaunchUriAsync(new Uri(“ms-windows-store:navigate?appid=” + ”f561757a-e831-4e06-95e9-458501e4d160″));//让用户访问某一个特定应用的页面，引导下载
await Windows.System.Launcher.LaunchUriAsync(new Uri(“ms-windows-store:reviewapp?appid=” + Windows.ApplicationModel.Store.CurrentApp.AppId));//让用户评价本应用
await Windows.System.Launcher.LaunchUriAsync(new Uri(“mailto:[imwangxiaoxin@live.com]“));给你发邮件反馈
这些都是异步的操作，别忘了给本函数加上async标记