public DataTemplate CreateQuestionAnswerRadioButtonTemplate(string question, List<string> answers){
DataTemplate template = new DataTemplate(() =>
{
StackLayout parentLayout = new StackLayout()
{
Padding = new Thickness(20, 20, 20, 20),
HeightRequest = 500,
};
ScrollView surveyScrollView = new ScrollView()
{
Orientation = ScrollOrientation.Vertical,
};
StackLayout questionLayout = new StackLayout()
{
Padding = new Thickness(5, 5, 5, 5),
HeightRequest = 500,
};
Label questLabel = new Label();
questLabel.Text = question;
questLabel.TextColor = Color.FromHex("#EF4D80");
questLabel.FontAttributes = FontAttributes.Bold;
questLabel.FontSize = 18;
BindableRadioGroup radioGroup = new BindableRadioGroup(false);
radioGroup.ItemsSource = answers;
questionLayout.Children.Add(questLabel);
questionLayout.Children.Add(radioGroup);
surveyScrollView.Content = questionLayout;
parentLayout.Children.Add(surveyScrollView);
return parentLayout;
});
return template;
}
Adding these Data Templates to a List.
new CarouselView
{
Margin = new Thickness(0, 20, 0, 0),
ItemsSource = dataTemplates,
ItemTemplate = dataTemplates[0],
};
Now when I swipe the Carousel, How do I load dataTemplates[1 or 2 or 3] ??
I have a Next Button in which in am setting the item source of the Carousel View to dataTemplates[1] but the template does not get updated
Pls Suggest the right approach ?
dataTemplates = new List<DataTemplate>();
dataTemplates.Add(CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_1, SurveyQuestion_1_Answers));
dataTemplates.Add(CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_3, SurveyQuestion_3_Answers));
dataTemplates.Add(CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_4, SurveyQuestion_4_Answers));
dataTemplates.Add(CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_5, SurveyQuestion_5_Answers));
You need a DataTemplateSelector for your CarouselView.
in your code behind of the page:
new CarouselView
{
Margin = new Thickness(0, 20, 0, 0),
ItemsSource = dataTemplates,
ItemTemplate = new SurveyDataTemplateSelector()
};
SurveyDataTemplateSelector
DataTemplate survey1Template;
DataTemplate survey3Template;
DataTemplate survey4Template;
DataTemplate survey5Template;
public SurveyDataTemplateSelector()
{
survey1Template = CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_1, SurveyQuestion_1_Answers);
survey3Template = CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_3, SurveyQuestion_3_Answers);
survey4Template = CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_4, SurveyQuestion_4_Answers);
survey5Template = CreateQuestionAnswerRadioButtonTemplate(Constants.SurveyQuestion_5, SurveyQuestion_5_Answers);
}
protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
{
// Here you define which DataTemplate is selected, for example:
if (item == null)
{
return null;
}
SurveyAnswers answers = item as SurveyAnswers;
if (answers.question == 1)
{
return survey1Template;
}
else if (answers.question == 3)
{
return survey3Template;
}
else if (answers.question == 4)
{
return survey4Template;
}
else if (answers.question == 5)
{
return survey5Template;
}
return null;
}
Check this link for a good documentation by Xamarin: https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/templates/data-templates/selector/
Related
I have used Segmented Control in my application. I don't know how to add two content pages to Segment control like a tabbed page. I have attached the sample file. Please give any suggestion Link for Sample Application
Sample Code:
public partial class SamplePage : ContentPage
{
SegmentedControl segControl;
SegmentedControlOption optionOne;
SegmentedControlOption optionTwo;
public SamplePage()
{
segControl = new SegmentedControl();
optionOne = new SegmentedControlOption();
optionTwo = new SegmentedControlOption();
optionOne.Text = "One";
optionTwo.Text = "Two";
segControl.Children.Add(optionOne);
segControl.Children.Add(optionTwo);
var stack = new StackLayout()
{
VerticalOptions = LayoutOptions.StartAndExpand,
HorizontalOptions = LayoutOptions.CenterAndExpand,
Children = { segControl }
};
this.Content = stack;
}
}
ScreenShot Attached
Just some suggestions and explanations.
We can't put a ContentPage inside another ContentPage
It's better to use ContentView instead of ContentPage
Grid is more recommended in this scenario , since it fills with the whole Screen.
Use ValueChanged event to change the view dynamically.
Code :
Page
public partial class SegmentedAppPage : ContentPage
{
SegmentedControl segControl;
SegmentedControlOption scOptionOne;
SegmentedControlOption scOptionTwo;
Grid grid;
View1 view1 = new View1();
View2 view2 = new View2();
public SegmentedAppPage()
{
InitializeComponent();
segControl = new SegmentedControl();
segControl.SelectedValue = "One";
scOptionOne = new SegmentedControlOption();
scOptionTwo = new SegmentedControlOption();
scOptionOne.Text = "One";
scOptionTwo.Text = "Two";
segControl.Children.Add(scOptionOne);
segControl.Children.Add(scOptionTwo);
grid = new Grid();
grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(1, GridUnitType.Auto) });
grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(1, GridUnitType.Star) });
grid.Children.Add(segControl, 0, 0);
grid.Children.Add(view1, 0, 1);
this.Content = grid;
segControl.ValueChanged += SegControl_ValueChanged;
}
private void SegControl_ValueChanged(object sender, EventArgs e)
{
SegmentedControl control = sender as SegmentedControl;
if(control.SelectedValue is "One")
{
grid.Children.Remove(view2);
grid.Children.Add(view1,0,1); //This line
}
else if (control.SelectedValue is "Two")
{
grid.Children.Remove(view1);
grid.Children.Add(view2, 0, 1); //This line
}
this.Content = grid;
}
}
ContentView
public class View1 : ContentView
{
public View1()
{
Content = new StackLayout
{
BackgroundColor = Color.Green,
Children = {
new Label { Text = "View1" }
}
};
}
}
To set default value on segmentedControl , modify code in SegmentedControlRenderers
protected override void OnElementChanged(ElementChangedEventArgs<SegmentedControl> e)
{
base.OnElementChanged(e);
var segmentedControl = new UISegmentedControl();
for (var i = 0; i < e.NewElement.Children.Count; i++)
{
segmentedControl.InsertSegment(e.NewElement.Children[i].Text, i, false);
}
segmentedControl.ValueChanged += (sender, eventArgs) => {
e.NewElement.SelectedValue = segmentedControl.TitleAt(segmentedControl.SelectedSegment);
};
segmentedControl.SelectedSegment = 0; // add this line
SetNativeControl(segmentedControl);
}
Test
I'm setting the ItemSource of a listview and trying to create multiple Labels within the listview DataTemplate based on the children of a property of that particular item (the items are gigs, and they have a list of band members and im trying to list the band members).
I'm not sure how to get the properties of the current item that's having it's template created, can someone help?
ListView listView = new ListView {
ItemsSource = viewModel.gigs,
ItemTemplate = new DataTemplate (() => {
var grid = new Grid();
grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(1, GridUnitType.Star)});
for(int x = 0;x<=viewModel.bandMembers.Count;x++) {
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star)});
}
var venueName = new Label { Text = "Top Left" };
venueName.SetBinding (Label.TextProperty, "Venue");
grid.Children.Add(venueName, 0, 0);
for(int x = 0;x<THISITEM.bandMembers.Count;x++) {
grid.Children.Add(new Label() {Text="Test"},x,0);
}
return new ViewCell { View = grid };
});
// Build the page.
this.Content = new StackLayout {
Children = {
header,
listView
}
};
You can override OnBindingContextChnaged function in ViewCell and get the ItemData from BindingContext
I am using FlowListView To set gallery view in my xamarin forms application, with following code..
public class Page1 : ContentPage
{
public Page1()
{
ObservableCollection<ItemModel> List = new ObservableCollection<ItemModel>();
string[] images = {
"https://farm9.staticflickr.com/8625/15806486058_7005d77438.jpg",
"https://farm5.staticflickr.com/4011/4308181244_5ac3f8239b.jpg",
"https://farm8.staticflickr.com/7423/8729135907_79599de8d8.jpg",
"https://farm3.staticflickr.com/2475/4058009019_ecf305f546.jpg",
"https://farm6.staticflickr.com/5117/14045101350_113edbe20b.jpg",
"https://farm2.staticflickr.com/1227/1116750115_b66dc3830e.jpg",
"https://farm8.staticflickr.com/7351/16355627795_204bf423e9.jpg",
"https://farm1.staticflickr.com/44/117598011_250aa8ffb1.jpg",
"https://farm8.staticflickr.com/7524/15620725287_3357e9db03.jpg",
"https://farm9.staticflickr.com/8351/8299022203_de0cb894b0.jpg",
};
int number = 0;
for (int n = 0; n < 20; n++)
{
for (int i = 0; i < images.Length; i++)
{
number++;
var item = new ItemModel()
{
ImageUrl = images[i],
FileName = string.Format("image_{0}.jpg", number),
};
List.Add(item);
}
}
FlowListView listView = new FlowListView()
{
FlowColumnTemplate = new DataTemplate(typeof(ListCell)),
SeparatorVisibility = SeparatorVisibility.None,
HasUnevenRows = true,
FlowColumnMinWidth = 110,
FlowItemsSource = List,
};
listView.FlowItemTapped += (s, e) =>
{
var item = (ItemModel)e.Item;
if (item != null)
{
App.Current.MainPage.DisplayAlert("Alert", "Tapped {0} =" + item.FileName, "Cancel");
}
};
Content = new StackLayout
{
Children = {
listView
}
};
}
}
public class ItemModel
{
public string ImageUrl { get; set; }
public string FileName { get; set; }
}
public class ListCell : View
{
public ListCell()
{
CachedImage IconImage = new CachedImage
{
HeightRequest = 100,
Aspect = Aspect.Fill,
DownsampleHeight = 100,
DownsampleUseDipUnits = false,
LoadingPlaceholder = "image_loading.png",
ErrorPlaceholder = "image_error.png"
};
IconImage.SetBinding(CachedImage.SourceProperty, "ImageUrl");
Label NameLabel = new Label
{
Opacity = 0.5,
HorizontalOptions = LayoutOptions.Fill,
HorizontalTextAlignment = TextAlignment.Center,
VerticalOptions = LayoutOptions.End,
};
NameLabel.SetBinding(Label.TextProperty, "FileName");
Grid grd = new Grid
{
Padding = 3,
ColumnDefinitions = {
new ColumnDefinition { Width = new GridLength (1, GridUnitType.Star) },
},
RowDefinitions = {
new RowDefinition { Height=GridLength.Star},
},
};
grd.Children.Add(IconImage,0,0);
grd.Children.Add(NameLabel, 0, 1);
}
}
i added all the dependency of FlowListView, FFImage etc,
This above code just showing blank screen, Not displaying any data...
You're ListCell has nothing to show.
Append the existing lines to set the content to the grid in your custom ViewCell.
grd.Children.Add(IconImage,0,0);
grd.Children.Add(NameLabel, 0, 1);
Content = grd; <--- add this line
Also have you done the following as per advice from the author? i.e. You've added the nuget library to the platforms in addition to the PCL and added the corresponding initialisation code for the library?
You must add this line to your platform specific project (AppDelegate.cs, MainActivity.cs, etc) before you use FFImageLoading:
CachedImageRenderer.Init();
This is what I got in my IOS:
[Register("AppDelegate")]
public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
global::Xamarin.Forms.Forms.Init();
FFImageLoading.Forms.Touch.CachedImageRenderer.Init(); <---- this line
LoadApplication(new App());
return base.FinishedLaunching(app, options);
}
}
I have an app with a Xamarin forms listview that's fed by an ObservableCollection to list user games I fetch from my server. The first time I load it up it works just fine. If I modify that existing ObservableCollection in any way my app crashes with a NullException. I've narrowed it down to my custom ViewCell (GameCell) and I've posted that below. If I comment one line out toward the bottom:
this.SetBinding(IsEnabledProperty, "Enabled");
Then it no longer crashes updating the ObservableCollection, but then I no longer get the functionality to have some cells enabled and some cells disabled. I'm guessing it's trying to set the isEnabled property to a cell that no longer exists because it's been removed on my reload. Any ideas how do this with out crashing? BTW, this works fine on Android, just not on iOS
using System;
using Xamarin.Forms;
using FFImageLoading.Forms;
namespace Upwords
{
public class GameCell : ViewCell
{
public GameCell ()
{
var icon = new CachedImage () {
Aspect = Aspect.AspectFit,
HorizontalOptions = LayoutOptions.Fill,
VerticalOptions = LayoutOptions.Fill,
BackgroundColor = AppStyle.IconColor,
IsVisible = false,
};
icon.SetBinding (CachedImage.SourceProperty, "Icon");
icon.SetBinding (CachedImage.LoadingPlaceholderProperty, "IconPlaceholder");
icon.SetBinding (CachedImage.ErrorPlaceholderProperty, "IconPlaceholder");
icon.SetBinding (CachedImage.WidthRequestProperty, "Height");
icon.SetBinding (CachedImage.HeightRequestProperty, "Height");
icon.Success += (object sender, CachedImageEvents.SuccessEventArgs e) => {
icon.FadeAnimationEnabled = false;
if(icon.Source.GetType() == typeof(Xamarin.Forms.UriImageSource)) {
icon.BackgroundColor = Color.Transparent;
}
};
icon.PropertyChanged += (object sender, System.ComponentModel.PropertyChangedEventArgs e) => {
if(icon.Source != null)
icon.IsVisible = true;
else
icon.IsVisible = false;
};
var nameLabel = new Label () {
FontFamily = "Helvetica",
FontAttributes = FontAttributes.Bold,
FontSize = Device.GetNamedSize (NamedSize.Medium, typeof(Label)),
TextColor = Color.Black,
};
nameLabel.SetBinding (Label.TextProperty, "Name");
//Hide label if it's blank
nameLabel.PropertyChanged += (object sender, System.ComponentModel.PropertyChangedEventArgs e) => {
if(nameLabel.Text == "")
nameLabel.IsVisible = false;
else
nameLabel.IsVisible = true;
};
var detailsLabel = new Label () {
FontFamily = "Helvetica",
FontSize = Device.GetNamedSize (NamedSize.Small, typeof(Label)),
FontAttributes = FontAttributes.Bold,
TextColor = Color.FromHex ("#666"),
IsVisible = false,
};
detailsLabel.SetBinding (Label.TextProperty, "Details");
//Hide label if it's blank
detailsLabel.PropertyChanged += (object sender, System.ComponentModel.PropertyChangedEventArgs e) => {
if(string.IsNullOrEmpty( detailsLabel.Text ) )
detailsLabel.IsVisible = false;
else
detailsLabel.IsVisible = true;
};
var textLayout = new StackLayout {
Padding = new Thickness (5, 0, 0, 0),
Spacing = 0,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.CenterAndExpand,
Children = { nameLabel, detailsLabel}
};
var optionSwitch = new Switch() {
HorizontalOptions = LayoutOptions.End,
VerticalOptions = LayoutOptions.Center,
IsVisible = false,
};
optionSwitch.SetBinding (Switch.IsVisibleProperty, "IsSwitch");
var statusLayout = new StackLayout {
Padding = new Thickness (10, 10, 10, 10),
Orientation = StackOrientation.Horizontal,
HorizontalOptions = LayoutOptions.FillAndExpand,
Children = { icon, textLayout, optionSwitch}
};
statusLayout.SetBinding (StackLayout.HeightRequestProperty, "Height");
var separatorBox = new BoxView {
HeightRequest = 1,
HorizontalOptions = LayoutOptions.FillAndExpand,
BackgroundColor = Color.FromRgb(.75,.75,.75),
};
separatorBox.SetBinding (BoxView.HeightRequestProperty, "SeparatorHeight");
var separatorBoxLayout = new StackLayout {
Padding = new Thickness (50, 0, 0, 0),
HorizontalOptions = LayoutOptions.FillAndExpand,
Children = { separatorBox }
};
var cellLayout = new StackLayout {
Spacing = 0,
Padding = new Thickness (0, 0, 0, 0),
Orientation = StackOrientation.Vertical,
HorizontalOptions = LayoutOptions.FillAndExpand,
BackgroundColor = Color.White,
Opacity = 1.0,
Children = { statusLayout, separatorBoxLayout }
};
cellLayout.SetBinding (StackLayout.OpacityProperty, "Opacity");
var headerFrame = new ListViewLabel () {
};
headerFrame.SetBinding (ListViewLabel.IsVisibleProperty, "IsLabel");
headerFrame.SetBinding (ListViewLabel.TextProperty, "Name");
headerFrame.SetBinding (ListViewLabel.HeightRequestProperty, "Height");
headerFrame.PropertyChanged += (object sender, System.ComponentModel.PropertyChangedEventArgs e) => {
if(headerFrame.IsVisible)
cellLayout.IsVisible = false;
else
cellLayout.IsVisible = true;
};
var paddedLayout = new StackLayout {
Spacing = 0,
Orientation = StackOrientation.Horizontal,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.FillAndExpand,
Children = { headerFrame, cellLayout }
};
this.SetBinding(IsEnabledProperty, "Enabled");
this.View = paddedLayout;
}
}
public class GameCellData
{
public string Icon { get; set; }
public string IconPlaceholder { get; set; }
public string Name { get; set; }
public string Details { get; set; }
public int Height { get; set; }
public int SeparatorHeight { get; set; }
public bool Enabled { get; set; }
public double Opacity { get; set; }
public bool IsLabel { get; set; }
public bool IsSwitch { get; set; }
}
}
Turns out updating to latest packages fixed the crash.
So I have a horizontal scrollview that I'm trying to dynamically populate when the user takes a certain action. The items I am throwing into the view each contain 4 labels that are using custom fonts. When I try to add about 10 of these items it lags for about 1.5 seconds on android and 1 second on IOS. If I take the custom font out then its about 1 second on each platform. If I take out 3 of the labels and only display one then its almost instantaneous. Is there any known reason for the lag? And is there any way around it so I can still use a custom font without a huge lag?
Here's a quick sample I made that pretty much does what I'm doing in my app. However, my app has more stuff so the lag isn't quite as bad here but it is still very noticeable
public class App : Application
{
public int count;
public ScrollView scroll, scroll2, scroll3;
public App ()
{
count = 1;
scroll = new ScrollView {
VerticalOptions = LayoutOptions.Center,
Orientation = ScrollOrientation.Horizontal
};
scroll2 = new ScrollView {
VerticalOptions = LayoutOptions.Center,
Orientation = ScrollOrientation.Horizontal
};
Button button = new Button(){
Text = "click",
};
button.Clicked += (sender, e) => AddStuff();
Button button2 = new Button(){
Text = "click",
};
button2.Clicked += (sender, e) => AddStuff2();
MainPage = new ContentPage {
BackgroundColor = Color.White,
Content = new StackLayout{
Children={
button,
scroll,
button2,
scroll2
}
}
};
}
//this one is instantaneous
public void AddStuff()
{
StackLayout stack = new StackLayout () {
Orientation = StackOrientation.Horizontal,
HorizontalOptions = LayoutOptions.FillAndExpand,
HeightRequest = 200,
};
for (int i = 0; i < 11; i++)
stack.Children.Add (
new StackLayout(){
Children = {
new Label (){TextColor = Color.Blue, Text = "Size: ", WidthRequest = 100 },
}
}
);
scroll.Content = stack;
count++;
}
//this one takes forever
public void AddStuff2()
{
StackLayout stack = new StackLayout () {
Orientation = StackOrientation.Horizontal,
HorizontalOptions = LayoutOptions.FillAndExpand,
HeightRequest = 200,
};
for (int i = 0; i < 11; i++)
stack.Children.Add (
new StackLayout(){
Children = {
new Label (){TextColor = Color.Blue, Text = "Size: ", WidthRequest = 100 },
new Label (){TextColor = Color.Blue, Text ="" + count*i, WidthRequest = 100 },
new Label (){TextColor = Color.Blue, Text = "Size: ", WidthRequest = 100 },
new Label (){TextColor = Color.Blue, Text ="" + count*i, WidthRequest = 100 }
}
}
);
scroll2.Content = stack;
count++;
}
}
and the custom font label for droid
[assembly: ExportRenderer (typeof (Label), typeof (CustomFontLabel_Droid))]
namespace df.Droid
{
public class CustomFontLabel_Droid:LabelRenderer
{
protected override void OnElementChanged (ElementChangedEventArgs<Xamarin.Forms.Label> e) {
base.OnElementChanged (e);
var label = (TextView)Control;
Typeface font = Typeface.CreateFromAsset (Forms.Context.Assets, "SourceSansPro-Semibold.otf");
label.Typeface = font;
}
}
}
Just incase anyone else is having a similar problem, if you make a static typeface property in the android MainActivity instead of calling createFromAsset inside the Label.OnElementChanged function every time then it gets rid of the extra lag on android.
CustomFontLabel_Droid.cs
[assembly: ExportRenderer (typeof (Label), typeof (CustomFontLabel_Droid))]
namespace df.Droid
{
public class CustomFontLabel_Droid:LabelRenderer
{
protected override void OnElementChanged (ElementChangedEventArgs<Xamarin.Forms.Label> e) {
base.OnElementChanged (e);
var label = (TextView)Control;
// this guy slows things down-> Typeface font = Typeface.CreateFromAsset (Forms.Context.Assets, "SourceSansPro-Semibold.otf");
label.Typeface = MainActivity.semiBoldFont;
}
}
}
MainActivity.cs
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsApplicationActivity
{
public static Typeface semiBoldFont = null;
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
global::Xamarin.Forms.Forms.Init (this, bundle);
LoadApplication (new App ());
semiBoldFont = Typeface.CreateFromAsset (Forms.Context.Assets, "SourceSansPro-Semibold.otf");
}
}