I have created a list of stores added it to a picker but from the views it is not loading. It is showing a picker with no items.
ViewModel code as follows
public List<string> Stores = new List<string>
{
"store 1",
"store 2",
"store 3"
};
private int _selectedStoreIndex = -1;
public int SelectedStoreIndex
{
get { return _selectedStoreIndex; }
set
{
if (_selectedStoreIndex != value)
{
_selectedStoreIndex = value;
UpdateStoreSelection();
OnPropertyChanged();
}
}
}
Xaml file
<Picker ItemsSource="{Binding Stores}" SelectedIndex="{Binding SelectedStoreIndex}"/>
When a cold start is made OnStart method in App.xaml.cs is called. You can then use Secure Storage / Preference to save a key in local storage in each platform and then just use DateTime.Now to just calculate the difference. And when the app is destroyed and restarted , OnStart will be called again and just reset the key.
You just need get the start time of the process,and the current time.
var startime = Process.GetCurrentProcess().StartTime;
var currenttime = DateTime.Now;
var runningtime = (nowtime - startime).TotalSeconds;
I have fixed the issue with Updating the Data from ViewModel
Related
in my xamarin project, picker binding, the SelectedItem is not working. When I have the ItemSource set to a List, the SelectedItem works, but when I change the ItemSource to an ObservableCollection, the SelectedItem always returns null. Can someone see what I am doing wrong?
on loading the view, the pickers are populated through databinding. then on a button event I try and grab the SelectedItem.... which is when it is coming back as null.
xaml
<Picker x:Name="PickerMarket2" Title="Market2" ClassId="PickerMarket2"
ItemsSource="{Binding TestList2}"
ItemDisplayBinding="{Binding ShortDesc}"
SelectedItem="{Binding SelectedMarket}"
Grid.Row="0" Grid.Column="1" >
</Picker>
view model
class VamiMarketViewModel: INotifyPropertyChanged
{
private List<string> _testList;
public List<string> TestList
{
get { return _testList; }
set
{
{
_testList = value;
NotifyPropertyChanged();
}
}
}
private ObservableCollection<Performance> _testList2;
public ObservableCollection<Performance> TestList2
{
get { return _testList2; }
set
{
{
_testList2 = value;
NotifyPropertyChanged();
}
}
}
private string _selectedMarket;
public string SelectedMarket
{
get { return _selectedMarket; }
set
{
{
_selectedMarket = value;
NotifyPropertyChanged();
}
}
}
I just explained the same in your other question here.
To what I see from your code, the SelectedItem seems to be the problem.
Since your Picker's ItemsSource(TestList property) is of type List<Performance>, the SelectedItem property bound to the Picker must be of type Performance. But, in your case, you have kept it as string instead of Performance.
The ItemDisplayBinding must be the name of any property inside your Performance object which in your case is fine since you have a string property called ShortDesc inside your Performance class.
That's the problem I see in your code. Change the type of the property ShortDesc like below and assign any one of the items in your collection TestList to it. Your code will start working fine.
private Performance _shortDesc;
public Performance ShortDesc
{
get { return _shortDesc; }
set
{
{
_shortDesc = value;
NotifyPropertyChanged();
}
}
}
Refer to the documentation here which explains a clear example for Binding objects to Picker.
I hope that helps.
While I'm using frame in Mainwindow , initially i hide an item in Mainwindows.
When i pressed a button in frame Page1 , I want to make item in mainwindow as visible.But i can't do it.I tried to updatelayout() , refresh() functions but anything is changed.Anyone has a knowledge about this??
This code is in MainWindow
private void Window_Loaded(object sender, RoutedEventArgs e)
{
müsteributton.IsEnabled = false;
string yer = "Pages/kullanicigiris.xaml";
frame1.Source = new Uri(yer, UriKind.Relative);
frame1.Margin = new Thickness(-175, 0, 0, 0);
}
This code is in kullanicigiris page
private void Dispatcher_Tick(object sender, EventArgs e)
{
i++;
if (i == 2)
{
dispatcher.Stop();
frm1 = new MainWindow();
frm1.frame1 = null;
DependencyObject currParent = VisualTreeHelper.GetParent(this);
while (currParent != null && frm1.frame1 == null)
{
frm1.frame1 = currParent as Frame;
currParent = VisualTreeHelper.GetParent(currParent);
}
// Change the page of the frame.
if (frm1.frame1 != null)
{
frm1.frame1.Source = new Uri("Window1.xaml", UriKind.Relative);
frm1.müsteributton.IsEnabled = true;
}
}
}
Thanks.
You can define a DependencyProperty in the MainWindows.
<TextBlock x:Name="textBlock" Height="399" TextWrapping="Wrap" Text="Show/ Hide" VerticalAlignment="Top" Visibility="{Binding SetVisibility, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
public static readonly DependencyProperty SetVisibilityProperty =
DependencyProperty.Register("SetVisibility", typeof(Visibility), typeof(Mainfreampage), new
PropertyMetadata(Visibility.Visible, null));
public Visibility SetVisibility
{
get { return (Visibility)GetValue(SetVisibilityProperty); }
set { SetValue(SetVisibilityProperty, value); }
}
In your page click event, you can use the following code find the MainWindows and change the DependencyProperty value.
var mw = Application.Current.Windows
.Cast<Mainfreampage>()
.FirstOrDefault(window => window is Mainfreampage) as Mainfreampage;
mw.SetVisibility = Visibility.Hidden;
Your bug is here:
frm1 = new MainWindow();
You are creating a brand new window, and then making your changes in that window.
But: that's not the window the user's looking at!
Taking the approach you've embarked on, your frame code needs to keep track of the Window object it's actually being hosted in, and then use that reference for dealing with the update.
That said, that entire approach is flawed. The navigation should be modeled in a view model data structure, activated via an ICommand object, and optionally via timer (as you seem to be doing here). Frame source and button state can be manipulated through bindings to properties in your view model data structure.
But, at the end of the day, the code you've got should work fine, once you start using the correct Window object.
Am trying to load ItemSource of a picker when the picker is focused.
But the data is not loaded on 1st focus.
here is the code sample
List<object> itmSrc;
Picker picker = new Picker();
itmSrc = Controls[i].ItemSource;
picker.Focused += BindItemSourceOnFocus;
public void BindItemSourceOnFocus(object sender, FocusEventArgs e)
{
var p = e.VisualElement as Picker;
p.ItemsSource = itmSrc;
}
If any other different approach is possible, let me know.
You can do it adding items on an async method, or another thread. Load the data on view focus is just transferring the issue to another place, and it gives a bad user experience at all.
If you run a code block inside a Task.Run(), for example, this code will be executed on another thread, and the interface should not hang on data loading.
Something like this:
public class MyPage : ContentPage
{
List<object> itmSrc;
Picker picker;
public MyPage()
{
// Your stuff goes here
itmSrc = new List<object>();
picker = new Picker();
StackLayout content = new StackLayout();
content.Crindren.Add(picker);
this.Content = content;
Task.Run(() => LoadData());
}
private void LoadData()
{
// Get your data from anywhere and put it on the itemSrc from here.
// Then...
picker.ItemsSource = itmSrc;
}
}
I hope it helps.
Solved: The answer was to update all of the nuget packages and target a newer version of Android. Now images loads as expected. I'm not happy with this as I was using exactly the code that Xamarin provided and targeting newer versions has deprecated some of the items the code relys on. Initial version was Xamarin.Forms v23 and I updated to V25
I have a brand new Xamarin forms project with a simple view in which I'm trying to display an image. I've tried several ways of getting an image to display and I am not having any luck at all.
I'm using <image> and I have also tried FFImageLoader control as well.
<StackLayout Orientation="Vertical">
<ff:CachedImage Source="https://static.pexels.com/photos/104827/cat-pet-animal-domestic-104827.jpeg" WidthRequest="100" HeightRequest="100" />
<Button x:Name="btn" Text="Image" Clicked="Button_Clicked" />
<Frame OutlineColor="Red">
<Image x:Name="StupidImage" Source="{Binding Thumbnail}" Aspect="Fill" HeightRequest="100" WidthRequest="100" />
</Frame>
</StackLayout>
This is the current view. I've also set the Source directly to a value with no result.
I'm able to get a stream for the image. I'm able to read all of the bytes from the stream. I built a debug visualizer to display the bytes as an image. Getting the image from a source is not a problem. Getting the image control(s) to display the image is a problem.
I tried binding with a view model. When that failed, I tried that directly setting the source
StupidImage.Source = ImageSource.FromStream(() => result.Stream);
I also made a copy of the bytes and tried
StupidImage.Source = ImageSource.FromStream(() => new MemoryStream(imageBytes));
I've tried ImageSource.FromFile() and .FromUri. I tried adding an image to the project as a resource. Each try was the same, the resource was read and the bytes were available, but the image control just doesn't display it.
I thought maybe it was a size problem, so I set the size of the control. Nothing. I thought maybe it was a resolution problem, so I used a smaller image. I tried several different images of varying quality.
Then I gave up on the image control and I got the FFImageLoading nuget package and gave it a direct url to an image. Same example that FFImageLoading examples used. Still no image.
I tried the emulator and I tried 2 different physical devices. Same result.
I also tried setting an image on a button using btn.Image = "whatever.jpg" with the same result.
This is the result every time. I'm lost. How do I get images to display?
EDIT:
I did get this to work, but only on the emulator
<Image x:Name="StupidImage" Source="https://static.pexels.com/photos/104827/cat-pet-animal-domestic-104827.jpeg" />
and same for
StupidImage.Source = ImageSource.FromUri(new Uri("https://static.pexels.com/photos/104827/cat-pet-animal-domestic-104827.jpeg"));
EDIT 2 - Clarification
My goal is to allow the user to select a photo from the device and then display a preview of it.
If you want to use images in you app you can load them into your Shared Project, like
Make sure you change the Build Action to Embedded resource
Then in your code
image.Source = ImageSource.FromResource("App5.Images.useravatar.png");
Note the Resource name.
And XAML
<ContentPage.Content>
<StackLayout>
<Image x:Name="image" WidthRequest="50"/>
</StackLayout>
</ContentPage.Content>
Just a few things you can take off the list:
[x] Adding a image from Visual studio :
Right click on the correct folder
select Add >> New File ...
NB: you have to add it with visual studio and not just throw it in the folder. Visual studio needs to know about it
[x] When Adding the image is it in the correct place :
For android: it has to be in
ProjectName.Driod.Resources.drawable folder
For ios: it has to be in
ProjectName.iOS.Resources folder
[x] Naming Convention
Its always best to use .png , all lowercase , no spaces or special char on both android and ios
with ios you normally get 3 images of the same image with the following namting convention
theman.png
theman#2x.png
theman#3x.png
They are all the same image just different sizes
[x] Showing it in xaml :
<StackLayout>
<Image Source="thedog.png" HeightRequest="100" WidthRequest="100" />
</StackLayout>
In your example you used a frame , how about a stacklayout ? a frame has more requirements.
for MVVM you can change Source with the following , dont forget that twoway :)
Source="{Binding Thumbnail, Mode=TwoWay}"
NB This is VERY basic explanations
You can try implementing the CrossMedia Plugin.
Then in your button clicked code section, put the following:
Button_Clicked.Clicked += async (sender, args) =>
{
if ( !CrossMedia.Current.IsPickPhotoSupported )
{
DisplayAlert("Error message here", "More message", "OK");
return;
}
var file = await Plugin.Media.CrossMedia.Current.PickPhotoAsync(new Plugin.Media.Abstractions.PickMediaOptions
{
PhotoSize = Plugin.Media.Abstractions.PhotoSize.Medium
});
if (file == null)
return;
image.Source = ImageSource.FromStream(() =>
{
var stream = file.GetStream();
file.Dispose();
return stream;
});
};
Once the button is clicked, the gallery/directory will be displayed. You can choose the photo you want. Once you hit OK the image will be displayed in the Image control/tag. I'm not sure if this is the solution you are looking for. Hopes it gets you on the right direction.
This may or may not help I'll add some code, one of the surprising things about Xamarin forms and Android and using a memory stream.. is that the device density multiplier is still applied even if you aren't using a resource(If I am remembering correctly) so I would imagine if you are looking at the ADB interface you will see memory issues which is why you cant display an image... I solved this previously via sampling
The way I solved it was creating a new Image subclass -ResourceImage,
public class ResourceImage :Image
{
public enum SourceTypes{
Database,
File,
Function,
}
private bool _LoadAct = false;
public bool LoadAct { get{
return _LoadAct;
}
set{ _LoadAct = value; OnPropertyChanged ("LoadAct");
}
}
public Func<Stream> Func{ get; set; }
public SourceTypes SourceType{ get; set;}
public string ResName{ get; set;}
public ResourceImage ()
{
}
public ResourceImage (string name)
{
ResName = name;
}
public ResourceImage(Func<Stream> func){
SourceType = SourceTypes.Function;
Func = func;
}
}
then in the Android Renderer : I did the following
public class ResourceImageRenderer : ImageRenderer
{
protected override void OnElementChanged (ElementChangedEventArgs<Image> e)
{
base.OnElementChanged (e);
if (e.OldElement == null)
{
var el = (ResourceImage)Element;
if (el.SourceType == ResourceImage.SourceTypes.Database) {
//Ignore for now
} else if (el.SourceType == ResourceImage.SourceTypes.File) {
using (global::Android.Graphics.BitmapFactory.Options options = new global::Android.Graphics.BitmapFactory.Options ()) {
options.InJustDecodeBounds = false;
options.InSampleSize = 1;//calculateInSampleSize (options, outS.X / 4, outS.Y / 4);
var gd = Context.Resources.GetIdentifier (el.ResName.Split (new char[]{ '.' }) [0], "drawable", Context.PackageName);
using (global::Android.Graphics.Rect rt = new global::Android.Graphics.Rect (0, 0, 0, 0)) {
var bitmap = global::Android.Graphics.BitmapFactory.DecodeResource (Context.Resources, gd, options);//DecodeStream (ms, rt, options);
bitmap.Density = global::Android.Graphics.Bitmap.DensityNone;
Control.SetImageDrawable (new global::Android.Graphics.Drawables.BitmapDrawable (bitmap));
}
}
} else if (el.SourceType == ResourceImage.SourceTypes.Function) {
new Task (() => {
var ms = el.Func();
if(ms == null)return;
global::Android.Graphics.BitmapFactory.Options options = new global::Android.Graphics.BitmapFactory.Options ();
options.InJustDecodeBounds = false;
options.InSampleSize = 2;//calculateInSampleSize (options, outS.X / 4, outS.Y / 4);
ms.Position = 0;
Device.BeginInvokeOnMainThread(()=>{
using (global::Android.Graphics.Rect rt = new global::Android.Graphics.Rect (0, 0, 0, 0)) {
try{
var bitmap = global::Android.Graphics.BitmapFactory.DecodeStream (ms, rt, options);
bitmap.Density = global::Android.Graphics.Bitmap.DensityNone;
Control.SetImageDrawable (new global::Android.Graphics.Drawables.BitmapDrawable (bitmap));
}catch(Exception eee){
}
}
});
}).Start();
}
}
}
Looking back at the code(haven't touched it in years.) there are plenty of places for improvement, I had to add the sampling to solve the same issue , users were selecting images to display in a messaging app and it worked perfectly on iOS just never displayed on Android
This is how I allow a user to select an image and then display it on a page.
I call my image service Select Image method passing in a callback method
await _imageService.SelectImage(ImageSelected);
This is my SelectImage method. There is some permission checking at the start. It uses the Media Plugin to display the gallery and allow the user to select an image.
public async Task SelectImage(Action<MediaFile> imageAction)
{
var allowed = await _permissionService.CheckOrRequestStoragePermission();
if (!allowed) return;
if (!_media.IsPickPhotoSupported)
{
throw new GalleryUnavailableException("Gallery unavailable");
}
var file = await _media.PickPhotoAsync(new PickMediaOptions
{
PhotoSize = PhotoSize.Small,
CompressionQuality = 92
});
imageAction(file);
}
It returns a MediaFile
Here is the Image Selected callback method
private void ImageSelected(MediaFile image)
{
if (image == null)
{
return;
}
ChosenImage = new IncidentImage
{
ImageBytes = image.ToByteArray()
};
}
ChosenImage is a Property in my view model
public IncidentImage ChosenImage {get; set;}
I use PropertyChanged.Fody to trigger property changed notifications but you can also use INotifyPropertyChanged.
And IncidentImage is a class I use to both store and display images
public class IncidentImage
{
[PrimaryKey, AutoIncrement]
public int Id { get; set; }
public int IncidentDetailsId { get; set; }
public byte[] ImageBytes { get; set; }
[Ignore]
public ImageSource ImageSource
{
get
{
ImageSource retval = null;
try
{
if (ImageBytes != null)
{
retval = ImageSource.FromStream(() => new MemoryStream(ImageBytes));
}
}
catch (Exception e)
{
Debug.WriteLine(e);
}
return retval;
}
}
}
And here is the XAML
<Image Source="{Binding ChosenImage.ImageSource}"
Aspect="AspectFit"/>
I have an issue with an Mvvmcross / Xamarin application in droid part.
I have made a "MvxSpinner menu" wich is bind on a list of couple
ViewModel.cs
private List<CoupleIntString> _actions = new List<CoupleIntString>() {
new CoupleIntString(0,"Actions"),
new CoupleIntString(1, "Mail"),
new CoupleIntString(2,"Imprimer"),
new CoupleIntString(3, "Totaux"),
new CoupleIntString(4, "Fiche client")
};
public List<CoupleIntString> Actions {
get { return _actions; }
set {
_actions = value;
RaisePropertyChanged(() => Actions);
}
}
droid.axml
<MvxSpinner
android:id="#+id/action_spinner"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="wrap_content"
local:MvxItemTemplate="#layout/item_spinner"
local:MvxDropDownItemTemplate="#layout/item_spinnerdropdown"
local:MvxBind="ItemsSource Actions;SelectedItem ActionSelected" />
When I select one item, I set the SelectedAction of my FirstViewModel and show the viewmodel I want to load.
public CoupleIntString ActionSelected {
set {
int xx = value.intPart;
switch (xx) {
case 1: //mail
GoToMailCommand.Execute();
break;
case 2: //impression
GoToImpressionCommand.Execute();
break;
case 3: //totaux
GoToTotauxCommand.Execute();
break;
case 4: //impression
GoToDetailsClientCommand.Execute();
break;
default:
break;
}
}
But, when i come back on the FirstViewModel, it automatically re-set the SelectedAction and go back to the second Viewmodel.
I have tried to set my SelectedAction to none in Init, ReloadState, Start, InitFromBundle and ReloadFromBundle but after all these calls, there is another one with the value I selected before and I don't know where it comes from.
I would propose to add a SelectedItem listener and set SelectedItem to 0.
var spinner = FindViewById<MvxSpinner>(Resource.Id.action_spinner);
spinner.ItemSelected += Spinner_ItemSelected;
MvvmCross has a SelectedItem target binding for MvxSpinner, you are almost right with your code. However, you need to use a command instead of a property for the SelectedItem binding to work:
private MvxCommand<CoupleIntString> _itemSelected;
public ICommand ItemSelected =>
_itemSelected = _itemSelected ??
(_itemSelected = new MvxCommand<CoupleIntString>(DoItemSelected));
private void DoItemSelected(CoupleIntString item)
{
ActionSelected = item;
}
Then make your binding look like:
local:MvxBind="ItemsSource Actions; SelectedItem ItemSelected"