Free text annotations in Xamarin Pdf Viewer (SfPdfViewer)
4 Jan 202313 minutes to read
Xamarin PDF Viewer allows you to include free text annotations in a PDF document and provides options to modify or remove the existing ones.
Adding free text annotations using toolbar
Enabling free text annotation mode
Set the AnnotationMode
property of the PDF viewer to FreeText
. After setting the annotation mode, the zooming, panning, and scrolling will be disabled. Tap anywhere on the displayed PDF page, a popup will appear. Type the text in the popup and click "Ok" to add text to the page. Once the free text annotation is added, the zooming, panning, and scrolling will be enabled again.
<syncfusion:SfPdfViewer x:Name="pdfViewer"/>
<Button x:Name="freeTextAnnotationButton" Command="{Binding AnnotationModeCommand, Source={x:Reference Name=pdfViewer}}" CommandParameter="FreeText" />
SfPdfViewer pdfViewer = new SfPdfViewer();
pdfViewer.AnnotationMode = AnnotationMode.FreeText;
Disabling free text annotation mode
Setting the annotation mode to None
disables the free text mode.
<syncfusion:SfPdfViewer x:Name="pdfViewer"/>
<Button x:Name="resetAnnotationButton" Command="{Binding AnnotationModeCommand, Source={x:Reference Name=pdfViewer}}" CommandParameter="None" />
pdfViewer.AnnotationMode = AnnotationMode.None;
Detecting the inclusion of free text annotations
The event FreeTextAnnotationAdded
will be raised when a free text annotation is added to the PDF.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationAdded="PdfViewer_FreeTextAnnotationAdded"/>
pdfViewer.FreeTextAnnotationAdded += PdfViewer_FreeTextAnnotationAdded;
Adding free text annotations programmatically
By AddAnnotation
method , You can add the free text annotations programmatically. The created free text annotation object passed as a parameter. The FreeTextAnnotation
instance acquires the text, page number and bounds as the parameters.
The following code sample illustrates the same.
string text = "Syncfusion";
//Creates the free text annotation
FreeTextAnnotation freeTextAnnotation = new FreeTextAnnotation(text, 1, new Rectangle(100, 100, 100, 50));
//Add the free text annotation to the specified page
pdfViewer.AddAnnotation(freeTextAnnotation);
Detecting tap on free text annotations
Tapping a free text annotation selects it or deselects if it is already selected. The event FreeTextAnnotationTapped
is raised when a free text is tapped.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationTapped="PdfViewer_FreeTextAnnotationTapped"/>
pdfViewer.FreeTextAnnotationTapped += PdfViewer_FreeTextAnnotationTapped;
Selecting free text annotations
You can select a free text annotation by tapping on it. When a free text is selected, the FreeTextAnnotationSelected
event will be raised. The properties of the selected free text can be retrieved using the args
parameter of the event handler.
private void PdfViewer_FreeTextAnnotationSelected(object sender, FreeTextAnnotationSelectedEventArgs args)
{
//Get the bounds
Rectangle bounds = args.Bounds;
//Get the page number on which the deselected free text is
int pageNumber = args.PageNumber;
//Get the text of the free text annotation
string text = args.Text;
//Get the text color
Color textColor = args.TextColor;
//Get the text size
float textSize = args.TextSize;
}
Selecting free text annotation programmatically
By SelectAnnotation
method, You can select the free text annotation programmatically. The specified free text annotation object passed as a parameter.
The following code sample illustrates the same.
//Selects the specified free text annotation
pdfViewer.SelectAnnotation(freetextAnnotation);
NOTE
Once
SelectAnnotation
method is called and as long as the annotation stays selected, theSelectedAnnotation
property will return the same instance as the parameter of this method.
Deselecting free text annotations
You can deselect a selected free text annotation by tapping on it or somewhere on the PDF page. Deselection can be detected using the FreeTextAnnotationDeselected
event.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationDeselected="PdfViewer_FreeTextAnnotationDeselected"/>
pdfViewer.FreeTextAnnotationDeselected += PdfViewer_FreeTextAnnotationDeselected;
Deselecting free text annotation programmatically?
By DeselectAnnotation
method, You can deselect the free text annotation. The specified free text annotation object passed as a parameter.
The following code sample illustrates the same.
//Deselects the specified free text annotation
pdfViewer.DeselectAnnotation(freetextAnnotation);
NOTE
There is no effect in calling
DeselectAnnotation
method, if the given annotation is not selected. Once this method is called, theSelectedAnnotation
property will return null until any other annotation gets selected.
Customizing the appearance of free text annotations
You can customize the default text color and text size of free text annotations to be added. This will not affect the already added free text annotations. The appearance of a selected free text can also be modified.
Setting the default text color
You can set the default text color of the free text annotations by using the SfPdfViewer.AnnotationSettings.FreeTextAnnotationSettings.TextColor
property. Refer to the following code.
pdfViewer.AnnotationSettings.FreeTextAnnotationSettings.TextColor = Color.Red;
Setting the default text size
You can set the default text size of the free text annotations by using the SfPdfViewer.AnnotationSettings.FreeTextAnnotationSettings.TextSize
property. Refer to the following code example.
pdfViewer.AnnotationSettings.FreeTextAnnotationSettings.TextSize = 4;
Setting the default background-color
You can set the background color for the free text annotations using the SfPdfViewer.AnnotationSettings.FreeText.FillColor
property. The default value is set to Color.Transparent
.
//Setting the background color of the free text annotation
pdfViewerControl.AnnotationSettings.FreeText.FillColor = Color.LightBlue;
Setting the default minimum size
By the SfPdfViewer.AnnotationSettings.FreeText.MinimumSize
property, You can set the minimum size to which the free text annotations could be resized.
Refer the following code example:
//Sets the minimum size for the free text annotations
pdfViewerControl.AnnotationSettings.FreeText.MinimumSize = new Size(10, 10);
Changing the properties of a selected free text
You can change the properties of the selected annotation by casting the sender
parameter of the FreeTextAnnotationSelected
event handler to FreeTextAnnotation and modify its properties. The following code shows how to change the properties.
Button changeFreeTextPropertiesButton = new Button();
changeFreeTextPropertiesButton.Clicked += changeFreeTextPropertiesButton_Clicked;
FreeTextAnnotation selectedFreeTextAnnotation;
private void PdfViewer_FreeTextAnnotationSelected(object sender, FreeTextAnnotationSelectedEventArgs args)
{
//Cast the sender object to FreeTextAnnotation
selectedFreeTextAnnotation = sender as FreeTextAnnotation;
}
private void changeFreeTextPropertiesButton_Clicked(object sender, EventArgs e)
{
//Change the color of the text
selectedFreeTextAnnotation.Settings.TextColor = Color.Blue;
//Change the size of the text
selectedFreeTextAnnotation.Settings.TextSize = 7;
}
Moving or resizing free text annotations
To move or resize the annotation, it should be selected. After the selector appears, tapping and dragging anywhere inside the selector will move the annotation. Tapping on the bubbles around the selector and dragging will resize the annotation.
Detecting the move or resize of a free text annotation
The event FreeTextAnnotationMovedOrResized
will be raised when you move or resize the free text annotation.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationMovedOrResized="PdfViewer_FreeTextAnnotationMovedOrResized"/>
pdfViewer.FreeTextAnnotationMovedOrResized += PdfViewer_FreeTextAnnotationMovedOrResized;
The properties of the moved or resized free text can be obtained from the args
parameter of the event handler.
private void PdfViewer_FreeTextAnnotationMovedOrResized(object sender, FreeTextAnnotationMovedOrResizedEventArgs args)
{
//Retrieve the old bounds of the annotation
Rectangle oldBounds = args.OldBounds;
//Retrieve the new bounds of the annotation
Rectangle newBounds = args.NewBounds;
//Retrieve the page number in which the free text is
int pageNumber = args.PageNumber;
}
Deleting free text annotations
PDF viewer can remove a selected annotation or all annotations in the PDF document.
Removing a selected free text annotation
The following code snippet illustrates removing a selected free text from the PDF document.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationSelected="PdfViewer_FreeTextAnnotationSelected"/>
<Button x:Name="deleteFreeTextAnnotationButton" Grid.Row="1" Clicked="deleteFreeTextAnnotationButton_Clicked" />
FreeTextAnnotation selectedFreeTextAnnotation;
private void PdfViewer_FreeTextAnnotationSelected(object sender, FreeTextAnnotationSelectedEventArgs args)
{
//Cast the sender object to free text annotation.
selectedFreeTextAnnotation = sender as FreeTextAnnotation;
}
private void deleteFreeTextAnnotationButton_Clicked(object sender, EventArgs e)
{
//Delete the selected free text annotation
pdfViewer.RemoveAnnotation(selectedFreeTextAnnotation);
}
Removing all annotations
The ClearAllAnnotations
method can be used to delete all annotations irrespective of their types from the PDF.
<syncfusion:SfPdfViewer x:Name="pdfViewer" />
<Button x:Name="deleteAllAnnotationsButton" Command="{Binding ClearAllAnnotationsCommand, Source={x:Reference Name=pdfViewer}} />
private void DeleteAllAnnotationsButton_Clicked(object sender, EventArgs e)
{
pdfViewer.ClearAllAnnotations();
}
Detecting the removal of a free text
The event FreeTextAnnotationRemoved
will be raised when a free text annotation is removed from the PDF.
<syncfusion:SfPdfViewer x:Name="pdfViewer" FreeTextAnnotationRemoved="PdfViewer_FreeTextAnnotationRemoved"/>
pdfViewer.FreeTextAnnotationRemoved += PdfViewer_FreeTextAnnotationRemoved;
The properties of the removed free text can be obtained from the args
parameter of the event handler.
private void PdfViewer_FreeTextAnnotationRemoved(object sender, FreeTextAnnotationRemovedEventArgs args)
{
//Get the bounds
Rectangle bounds = args.Bounds;
//Get the page number on which the deselected free text is
int pageNumber = args.PageNumber;
//Get the text of the free text annotation
string text = args.Text;
//Get the text color
Color textColor = args.TextColor;
//Get the text size
float textSize = args.TextSize;
}
How to lock or unlock the free text annotations?
To lock or unlock all the free text annotation, set the IsLocked
API to true
or false
respectively, and the following sample explains the same. But other annotation types can be moved, resized, removed or their attributes can be changed.
//Disable the free text annotation interaction such as move, resize, remove, and attributes changes.
pdfViewerControl.AnnotationSettings.FreeText.IsLocked = true;
Interactions with free text annotation types such as move, resize, remove or attribute changes will be allowed only if the SfPdfViewer.AnnotationSettings.IsLocked
API is set to false
. The following code prevents the unlocking of the free text annotations, although the IsLocked
property of the free text annotation is set to false
.
//Disable the free text annotation interaction, though its 'IsLocked' property is set to ‘false’ .
pdfViewerControl.AnnotationSettings.IsLocked = true;
pdfViewerControl.AnnotationSettings.FreeText.IsLocked = false;
How to enable or disable the free text annotation selection?
To enable or disable the free text annotation selection, set the Constraints
API to AnnotationConstraints.Selectable
or ~AnnotationConstraints.Selectable
respectively, and the following sample explains the same. But other annotation types can be selected, moved, resized, removed or their attributes can be changed.
//Disable the selection of free text annotations.
pdfViewerControl.AnnotationSettings.FreeText.Constraints = ~AnnotationConstraints.Selectable;
Free text annotation selection will be allowed only if the SfPdfViewer.AnnotationSettings.Constraints
API is set to AnnotationConstraints.Selectable
. The following code prevents the free text annotations selection, even though the Constraints
property of the free text annotation is set to AnnotationConstraints.Selectable
.
//Disable the free text annotation selection, though its 'Constraints' property is set to ‘AnnotationConstraints.Selectable’
pdfViewerControl.AnnotationSettings.Constraints= ~AnnotationConstraints.Selectable;
pdfViewerControl.AnnotationSettings.FreeText.Constraints = AnnotationConstraints.Selectable;
How to get and set the name of the free text annotations?
The PDF Viewer allows the users to get and set the name of free text annotations through the Name API.
The following code sample explains modifying the name of the free text annotation in the FreeTextAnnotationAdded event.
private void PdfViewerControl_ FreeTextAnnotationAdded (object sender, FreeTextAnnotationAddedEventArgs args)
{
//Sets the name for the annotation.
(sender as FreeTextAnnotation).Name = "FreeText1";
}
NOTE
For illustration purposes, we have only provided the sample for modifying the name of the free text annotation in the FreeTextAnnotationAdded event. But this can be done in all other events as well.
NOTE
You can also explore our Xamarin.Forms PDF Viewer example to knows the functionalities of each feature.