在Windows Phone 8.1中的背景任务显示对话框的问题
问题描述:
我有这个代码执行httpwebrequest和响应背景方法,我只想显示对话框的信息,当下载邮编崩溃,我的代码输入在此捕获...在Windows Phone 8.1中的背景任务显示对话框的问题
private void DoSincroFit()
{
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
request.BeginGetResponse(new AsyncCallback(playResponseAsync), request);
}
public async void playResponseAsync(IAsyncResult asyncResult)
{
//Declaration of variables
HttpWebRequest webRequest = (HttpWebRequest)asyncResult.AsyncState;
try
{
string fileName = "sincrofit.rar";
using (HttpWebResponse webResponse = (HttpWebResponse)webRequest.EndGetResponse(asyncResult))
{
byte[] buffer = new byte[1024];
var newZipFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
var newZipFile = await KnownFolders.DocumentsLibrary.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
using (var writeStream = await newZipFile.OpenAsync(FileAccessMode.ReadWrite))
{
using (var outputStream = writeStream.GetOutputStreamAt(0))
{
using (var dataWriter = new DataWriter(outputStream))
{
using (Stream input = webResponse.GetResponseStream())
{
var totalSize = 0;
for (int size = input.Read(buffer, 0, buffer.Length); size > 0; size = input.Read(buffer, 0, buffer.Length))
{
dataWriter.WriteBytes(buffer);
totalSize += size; //get the progress of download
}
await dataWriter.StoreAsync();
await outputStream.FlushAsync();
dataWriter.DetachStream();
}
}
}
}
}
}
catch
{
SMethods.Message_Dialog("Download has stopped!","Error");
}
}
但是,当我的代码执行这种方法,从这个类:
class StandarMethods
{
public async void Message_Dialog(string text, string title)
{
//Declaration of variables
MessageDialog MDialog = new MessageDialog(text, title);
await MDialog.ShowAsync();
}
}
最后我的应用程序崩溃时,尝试执行:
await MDialog.ShowAsync();
这是在后台任务等待...有人可以帮助我吗?有可能使用事件处理程序?为什么?怎么样?提前致谢!
答
解决,我的最终代码是在这里:
private CoreDispatcher dispatcher;
private void DoSincroFit()
{
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
//Add headers to request
request.Headers["Type"] = "sincrofit";
request.Headers["Device"] = "1";
request.Headers["Version"] = "0.000";
request.Headers["Os"] = "WindowsPhone";
dispatcher = CoreWindow.GetForCurrentThread().Dispatcher;
request.BeginGetResponse(new AsyncCallback(playResponseAsync), request);
}
public async void playResponseAsync(IAsyncResult asyncResult)
{
//Declaration of variables
HttpWebRequest webRequest = (HttpWebRequest)asyncResult.AsyncState;
try
{
//For download file with stream
//http://social.msdn.microsoft.com/Forums/windowsapps/en-US/de96a61c-e089-4595-8349-612be5d23ee6/download-file-with-httpwebrequest?forum=winappswithcsharp
string fileName = "sincrofit.rar";
using (HttpWebResponse webResponse = (HttpWebResponse)webRequest.EndGetResponse(asyncResult))
{
byte[] buffer = new byte[1024];
//For acces Local folder of phone device
//http://social.msdn.microsoft.com/Forums/windowsapps/en-US/ec99721c-6565-4ce9-b6cc-218f2265f9c7/what-is-the-uri-of-an-isolatedstorage-file?forum=wpdevelop
var newZipFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
using (var writeStream = await newZipFile.OpenAsync(FileAccessMode.ReadWrite))
{
using (var outputStream = writeStream.GetOutputStreamAt(0))
{
using (var dataWriter = new DataWriter(outputStream))
{
using (Stream input = webResponse.GetResponseStream())
{
var totalSize = 0;
for (int size = input.Read(buffer, 0, buffer.Length); size > 0; size = input.Read(buffer, 0, buffer.Length))
{
dataWriter.WriteBytes(buffer);
totalSize += size; //get the progress of download
dispatcher.RunAsync(CoreDispatcherPriority.Normal, async() =>
{
//Declaration of variables
pBar.Value = sizeFit/totalSize * 100;
});
}
await dataWriter.StoreAsync();
await outputStream.FlushAsync();
dataWriter.DetachStream();
}
}
}
}
}
}
catch
{
dispatcher.RunAsync(CoreDispatcherPriority.Normal, async() =>
{
//Declaration of variables
SMethods.Message_Dialog("Download has stopped!", "Error");
});
}
}
感谢您的时间@loop!
答
Merli你的问题是你正试图从一个背景胎面访问UI线程来显示对话框,用户因此使用调度这个基本的例子是: -
// This is for silverlight part
Deployment.Current.Dispatcher.BeginInvoke(delegate
{
var mbr = MessageBox.Show("Are you sure you want to leave this page?", "Warning",
MessageBoxButton.OKCancel);
if(mbr == MessageBoxResult.OK)
{ OK pressed }
else
{ Cancel pressed }
});
对于WinRT的一部分 -
CoreDispatcher dispatcher = CoreWindow.GetForCurrentThread().Dispatcher;
dispatcher.RunAsync(CoreDispatcherPriority.Normal, async()=>{
// UI code goes here
//Declaration of variables
MessageDialog MDialog = new MessageDialog(text, title);
await MDialog.ShowAsync();
});
答
我的最终代码:
private void DoSincroFit()
{
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
//Add headers to request
request.Headers["Type"] = "sincrofit";
request.Headers["Device"] = "1";
request.Headers["Version"] = "0.000";
request.Headers["Os"] = "WindowsPhone";
request.BeginGetResponse(new AsyncCallback(playResponseAsync), request);
}
public async void playResponseAsync(IAsyncResult asyncResult)
{
//Declaration of variables
HttpWebRequest webRequest = (HttpWebRequest)asyncResult.AsyncState;
try
{
string fileName = "sincrofit.rar";
using (HttpWebResponse webResponse = (HttpWebResponse)webRequest.EndGetResponse(asyncResult))
{
byte[] buffer = new byte[1024];
var newZipFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
using (var writeStream = await newZipFile.OpenAsync(FileAccessMode.ReadWrite))
{
using (var outputStream = writeStream.GetOutputStreamAt(0))
{
using (var dataWriter = new DataWriter(outputStream))
{
using (Stream input = webResponse.GetResponseStream())
{
var totalSize = 0;
for (int size = input.Read(buffer, 0, buffer.Length); size > 0; size = input.Read(buffer, 0, buffer.Length))
{
dataWriter.WriteBytes(buffer);
totalSize += size; //get the progress of download
}
await dataWriter.StoreAsync();
await outputStream.FlushAsync();
dataWriter.DetachStream();
}
}
}
}
}
}
catch
{
dispatcher = CoreWindow.GetForCurrentThread().Dispatcher; //CRASH IN THIS LINE!
dispatcher.RunAsync(CoreDispatcherPriority.Normal, async() =>
{
//Declaration of variables
SMethods.Message_Dialog("Download has stopped!", "Error");
});
}
}
这是我的照片:
谢谢大家!
完美!但是这段代码给了我一个小小的错误...错误:“对象引用没有设置和对象的实例” 这是一个密封的类,没有构造函数methods.Any idea?谢谢大家! – 2014-09-08 07:38:00
在哪一行? – loop 2014-09-08 09:23:02
我更新了ans检查它。 – loop 2014-09-08 09:34:23