I am using Silverlight 4 to access the web cam. Everything works ok when I start the web cam on a button click event, I get the prompt for permission. I would like the web cam to start when User Control loads, but for some reason when I run the same code on the Loaded event, I don't get a prompt when executing the following code:'
CaptureDeviceConfiguration.RequestDeviceAccess()
Does anyone have a work around for this?
I found a workaround to the problem. I am automatically clicking the button that starts the webcam streaming on the Loaded event of the control.
ButtonAutomationPeer peer = new ButtonAutomationPeer(btnStartWebcam);
IInvokeProvider invokeProv =
peer.GetPattern(PatternInterface.Invoke)
as IInvokeProvider;
invokeProv.Invoke();
This does the job for me because I don't mind having a button on the UI. But I guess you can create a dummy one and hide it if it's necessary.
The security around accessing local devices is very tight. Starting the capture must be preceded by a user action.
Instead of starting the capture from the loaded event, you'll have to move it to a Click event.
Code behind:
public void StartCam()
{
VideoCaptureDevice dev = CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();
if(CaptureDeviceConfiguration.RequestDeviceAccess() &&
CaptureDeviceConfiguration.AllowedDeviceAccess)
{
CaptureSource capture = new CaptureSource();
capture.VideoCaptureDevice = dev;
VideoBrush videoBrush = new VideoBrush();
videoBrush.SetSource(capture);
capture.Start();
WebCamRectangle.Fill = videoBrush;
}
}
private void button1_Click(object sender, RoutedEventArgs e)
{
StartCam();
}
Xaml:
<Grid x:Name="LayoutRoot" Background="White">
<Grid.RowDefinitions>
<RowDefinition Height="49*" />
<RowDefinition Height="251*" />
</Grid.RowDefinitions>
<Rectangle Name="WebCamRectangle"
Stroke="Black" StrokeThickness="1" Grid.Row="1" />
<Button Content="Start" Height="25" HorizontalAlignment="Left"
Margin="12,12,0,0" Name="button1" VerticalAlignment="Top"
Width="135" Click="button1_Click" />
</Grid>
Related
How to force the layout measurements update?
I have simplified layout I am problem with; when you click the button first time you get one measurement and on the second click different one.
private void Window_Loaded(object sender, RoutedEventArgs e)
{
var w = mywindow.ActualWidth;
gridx.Width = w;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
btn3.Width = 100;
var w = mywindow.ActualWidth;
gridx.Width = w - btn3.Width;
InvalidateArrange();
InvalidateMeasure();
MessageBox.Show(btn1.ActualWidth.ToString());
}
Window
<Window x:Class="resizet.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded" Name="mywindow">
<DockPanel HorizontalAlignment="Stretch" LastChildFill="False">
<Grid HorizontalAlignment="Stretch" DockPanel.Dock="Left" Name="gridx">
<Button HorizontalAlignment="Stretch" Content="btn in grid" Click="Button_Click" />
</Grid>
<Button Name="btn2" Content="btn2" Width="0" DockPanel.Dock="Right" HorizontalAlignment="Left"></Button>
</DockPanel>
</Window>
This fixes the problem:
btn3.Width = 100;
btn3.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
var w = mywindow.ActualWidth;
gridx.Width = w - btn3.Width;
with additional
private static Action EmptyDelegate = delegate() { };
Changing the Width property must invalidate the layout on its own, you don't need to call InvalidateXXX() yourself.
The catch is that the layout is not updated immediately, but on the next iteration of the message loop. So the ActualWidth will not be changed immediately.
If you want the Grid to resize automatically when the button width is increasing, why not use the layout management and put the both into different columns of an outer Grid?
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid x:Name="gridx"
Grid.Column="0">
<Button HorizontalAlignment="Stretch"
Click="Button_Click"/>
</Grid>
<Button x:Name="btn2"
Content="btn2"
Width="0"
Grid.Column="1"/>
</Grid>
And in code-behind
private void Button_Click(object sender, RoutedEventArgs e)
{
btn2.Width = 100;
}
In a strict sense, #Daniel has provided some code that fixes the problem posed by the question. But the result is rather bad, putting layouting code into an event handler. The grid and the button might look good after the button got pressed, but once the user makes the window size bigger, the grid will not grow and will not use the available size. The user would have to press the button again to make the grid grow. That's most likely not how things should be and that's why #Vlad's answer is better.
WPF uses just one thread to process events and layouting, but they get executed in different phases. If width gets changed, the MeasureDirty flag of the control gets set, then the processing of the event continues immediately. Once this event and all other events needing processing are completed, only then starts WPF with the layouting (i.e. measure, arrange, render). Here is an overview how that works:
For a detailed description what happens in every step, see my article on CodeProject Deep Dive into WPF Layouting and Rendering
btn3.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
This statement halts the execution of the button event handler and forces a whole layouting / render phase to run, only then continues with the event handler code to change the width of the grid, which will force another layouting / render cycle to run.
Recommendations:
Do not set Height and Width in event handlers, unless you want them to be fixed and not to change, even the available space changes.
Use WPF controls like Grid, etc. to make best use of the available space
If you cannot find a WPF control like Grid which matches your layouting needs, write your own Control and put all the layouting code into MeasureOverride() and ArrangeOverride().
I have a WPF window that basically has this occupying its entire space:
<WindowsFormsHost Grid.RowSpan="2" Name="wfh" VerticalAlignment="Stretch" Width="Auto" Height="Auto" Cursor="IBeam" ForceCursor="True" SnapsToDevicePixels="True" >
<ax:AxViewerActiveX x:Name="_axViewer" AutoSize="True" Cursor="Cross" Margin="0,0,0,0" Padding="0,0,0,0" UseWaitCursor="True">
</ax:AxViewerActiveX>
</WindowsFormsHost>
The first time I do ShowDialog() of this window, the window appears blank:
The second time it appears as it should:
Please, can someone help to make the rendering of the window correctly the first time?
Constructor of this window class:
this.InitializeComponent();
_axViewer.BeginInit();
_axViewer.EndInit();
Focus();
_axViewer.Focus();
When calling it is simple as:
w3d.WindowState = WindowState.Maximized;
w3d.ShowDialog();
Try putting the initialization for the ActiveX control in the .Loaded() method?
this.InitializeComponent();
Loaded += delegate {
_axViewer.BeginInit();
_axViewer.EndInit();
Focus();
_axViewer.Focus();
};
My application page contains a WebBrowser. I want to add a GestureListener in order to handle the Flick event. But when Flick on the WebBrowser region, it doesn't work. I have tried many ways to let it work, but I failed. I have also tried to use Manipulation instead, but to no effect.
Could someone tell me how to do or whether there is another solution instead?
Following code is the working solution for the Flick or Hold event on the WebBrowser control.
Try the same, it may help you.
Assuming xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit" being present in the phone:PhoneApplicationPage tag.
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0" Grid.RowSpan="2">
<phone:WebBrowser x:Name="myWebBrowser" Visibility="Visible" IsScriptEnabled="True" IsHitTestVisible="True" Margin="-12,6,0,6" />
<toolkit:GestureService.GestureListener>
<toolkit:GestureListener Flick="GestureListener_Flick" Hold="GestureListener_Hold"></toolkit:GestureListener>
</toolkit:GestureService.GestureListener>
</Grid>
And xaml.cs has functions as follows.
private void GestureListener_Flick(object sender, FlickGestureEventArgs e)
{
MessageBox.Show("Flick");
}
private void GestureListener_Hold(object sender, Microsoft.Phone.Controls.GestureEventArgs e)
{
MessageBox.Show("Hold");
}
i want to do a screen capture of a running silverlight 3 application, from within the app, and then i want to present this to the user as a thumbnail, say in an Image control.
am i dreaming?
For a simple page:
<Grid x:Name="LayoutRoot" Background="White">
<StackPanel>
<Ellipse Fill="Red" Width="100" Height="100"></Ellipse>
<Button x:Name="btnCapture" Click="btnCapture_Click" Width="30" Height="25"></Button>
<Image x:Name="imgThumbnail" Width="50" Height="50"></Image>
</StackPanel>
</Grid>
with the event handler:
private void btnCapture_Click(object sender, RoutedEventArgs e)
{
WriteableBitmap bmp = new WriteableBitmap(LayoutRoot, null);
this.imgThumbnail.Source = bmp;
}
You are dreaming if you want to do a true screen capture (outside the plugin).
The WriteableBitmap answer is correct if you just want to capture a partial or complete visual tree rendering of the Silverlight app only.
I'm trying to implement a piece of functionality that will let the user to drag files into an application to be opened in the FlowDocumentReader.
My problem is that is though I have AllowDrop=true on the FlowDocumentReader, the cursor does not change to the "drop here" icon but changes instead to "drop is not allowed" icon.
This happens only to the FlowDocumentReader, all other parts og the UI (window itself, other controls) work as expected. The FlowDocumentReader actually receives the events, and it is possible to handle the drop, but the user does not have a visual indication that he can release the mouse here.
I also cannot hide the "drop is not allowed" cursor by setting Cursor=Cursors.None
Need to handle DragOver event in FlowDocument to allow dropping here.
xaml:
<!--
<FlowDocumentReader x:Name="fdr" Background="White">
<FlowDocument x:Name="doc" AllowDrop="True" DragEnter="doc_DragOver" Drop="doc_Drop" Background="White"/>
</FlowDocumentReader>
-->
<FlowDocumentReader x:Name="fdr" Background="White">
<FlowDocument x:Name="doc" AllowDrop="True" DragOver="doc_DragOver" Drop="doc_Drop" Background="White"/>
</FlowDocumentReader>
code behind:
private void doc_DragOver(object sender, DragEventArgs e)
{
e.Effects = DragDropEffects.All;
e.Handled = true;
}
private void doc_Drop(object sender, DragEventArgs e)
{
}
I couldn't find any direct way to solve this, so here is what I have ended up with:
I placed a grid on top of the FlowDocumentReader. This grid has a sold color, opacity of 0 (transparent) and Visibility=Collapsed. The purpose of this grid is to serve as a drop target.
When FlowDocument within the FlowDocumentReader received the DragEnter event, I switch the grid's visibility to Visible. The grid starts receiving drag events and the cursor stays in the "drop here" form.
When grid receives Drop or DragLeave events, its visibility is turned back to Collapsed to allow the FlowDocument receive mouse events
<FlowDocumentReader x:Name="fdr" Grid.Row="1" Background="White">
<FlowDocument x:Name="doc" DragEnter="doc_DragEnter" Background="White"/>
</FlowDocumentReader>
<Grid x:Name="dtg" Grid.Row="1" Background="White" Opacity="0"
Drop="dtg_Drop" DragLeave="dtg_DragLeave" Visibility="Collapsed"/>