I am trying to build an app where the user can add images from Image Picker, then save it in a Provider as well as in Firebase. For retrieving it should be the other way around: Get it from Firebase and then store it in my Provider.
(ignore the Firebase part, for now I only want to store the images in a Provider, but it should be correctly set up, so I can add the Firebase support later)
The problem is that I am quite new to Flutter and I am not how to start here, because there are so many ways to load images in Flutter. From the ImagePicker I retrieve a File. What is the correct way to store this in a Provider so I can load it in another screen?
I know this is quite a genreal question but I hope some one can shed some light in the dark for me here :D Let me know if you need any more info.
I already setup a ChangeNotifier:
class MemoryImageProvider extends ChangeNotifier {
String path = '';
setImage(String path) {
path = path;
notifyListeners();
}
}
Related
I have looked for many examples of this and I believe they are trying to do something different than what want to do.
I have a set of images stored a folder in my pcl. See Image attached.
PCL Image
Currently I have those images set to embedded resource and they all display in my List View when their name is called. However if an update is made on the server like an image is changed or replaced or added I would like the new image to get saved in the AllImages folder as shown in the image. Is this possible? I've seen a lot of people doing separate dependencies to store the images in the platforms resources/ drawable folder but I don't want I don't want to do that. If i have to change where i am storing my images I can do that as well, but I do need to be able to store the images from the server on my app locally.
I currently have a class dedicated to embedded images, so it would be nice to do it this, but I am not married to the idea.
[ContentProperty("ResourceID")]
public class EmbeddedImage : IMarkupExtension
{
public string ResourceID { get; set; }
public object ProvideValue(IServiceProvider serviceProvider)
{
if (String.IsNullOrWhiteSpace(ResourceID))
return null;
return ImageSource.FromResource(ResourceID);
}
}
I am developing a mobile application using Xamarin.Forms
I had the following Home page contains login info:
How can we have the application to automatically save the user name, so that they do not have to type it in each time (as in a browser)?
You can use Properties dictionary in Xamarin.Forms Application class. And let the Xamarin.Forms framework handle persisting user name between app restarts and pausing/resuming your app.
Save user name by writing it to Properties dictionary
var properties = Xamarin.Forms.App.Current.Properties;
if(!properties.ContainsKey("username")
{
properties.Add("username", username);
}
else
{
properties["username"] = username;
}
Then, when your login screen is about to appear (for example in OnAppearing method) check Properties for user name:
var properties = Xamarin.Forms.App.Current.Properties;
if(properties.ContainsKey("username")
{
var savedUsername = (string)properties["username"];
}
If it's not there, then it means that this is first time when user log in into your application.
A very similar question was posed just a few days ago - my answer on that question also applies to your question: The best way to save Configuration data in Xamarin.Forms based app?
Essentially, you want to store the information using the native settings functionality. I would advise against using Application.Properties for now. It is currently not reliable on Android, and in the past has had other problems. The nuget package referenced in my linked answer is a better approach and will save you some headache in the future.
The right way to be done is through the App settings plugin
https://github.com/jamesmontemagno/Xamarin.Plugins/tree/master/Settings
What i did in my application is.
1) Installed Plugin.Settings from nuget
2)Added to Helpers->Settings.cs (autogenerated file by plugin) the following
public static class Settings
{
private static ISettings AppSettings
{
get { return CrossSettings.Current; }
}
private const string UserNameKey = "username_key";
private static readonly string UserNameDefault = "demo";
public static string UserName
{
get { return AppSettings.GetValueOrDefault<string>(UserNameKey, UserNameDefault); }
set { AppSettings.AddOrUpdateValue<string>(UserNameKey, value); }
}
}
3)In order to keep the username in the Application Context set
Settings.UserName = ViewModel.Username;
4)When you login screen starts
string username = Settings.UserName;
The answer is simple: persistance. Servers do this by setting cookies containing the data (or reference to it) that they want you to see when rendering the form field.
In order to do this in an app (with Xamarin for instance), you need to store the user's data into a file or database somewhere. Since you're using Xamarin you can probably use some sort of ConfigurationManager to keep track of this.
Obviously you could just create a config file in the local storage you have for your app (I don't think you need permissions to create files in that space).
When you have the info stored somewhere, just retrieve it and set the input's value to it.
I have a simple Xamarin Forms app. I've now got a simple POCO object (eg. User instance or an list of the most recent tweets or orders or whatever).
How can I store this object locally to the device? Lets imagine I serialize it as JSON.
Also, how secure is this data? Is it part of Keychains, etc? Auto backed up?
cheers!
You have a couple options.
SQLite. This option is cross-platform and works well if you have a lot of data. You get the added bonus of transaction support and async support as well. EDIT: In the past I suggested using SQLite.Net-PCL. Due to issues involving Android 7.0 support (and an apparent sunsetting of support) I now recommend making use of the project that was originally forked from: sqlite-net
Local storage. There's a great nuget that supports cross-platform storage. For more information see PCLStorage
There's also Application.Current.Properties implemented in Xamarin.Forms that allow simple Key-Value pairs of data.
I think you'll have to investigate and find out which route serves your needs best.
As far as security, that depends on where you put your data on each device. Android stores app data in a secure app folder by default (not all that secure if you're rooted). iOS has several different folders for data storage based on different needs. Read more here: iOS Data Storage
Another option is the Xamarin Forms settings plugin.
E.g. If you need to store a user instance, just serialize it to json when storing and deserialize it when reading.
Uses the native settings management
Android: SharedPreferences
iOS: NSUserDefaults
Windows Phone: IsolatedStorageSettings
Windows RT / UWP: ApplicationDataContainer
public User CurrentUser
{
get
{
User user = null;
var serializedUser = CrossSettings.Current.GetValueOrDefault<string>(UserKey);
if (serializedUser != null)
{
user = JsonConvert.DeserializeObject<User>(serializedUser);
}
return user;
}
set
{
CrossSettings.Current.AddOrUpdateValue(UserKey, JsonConvert.SerializeObject(value));
}
}
EDIT:
There is a new solution for this. Just use Xamarin.Essentials.
Preferences.Set(UserKey, JsonConvert.SerializeObject(value));
var user= JsonConvert.DeserializeObject<User>(Preferences.Get(UserKey, "default_value");
Please use Xamarin.Essentials
The Preferences class helps to store application preferences in a key/value store.
To save a value:
Preferences.Set("my_key", "my_value");
To get a value:
var myValue = Preferences.Get("my_key", "default_value");
If you want to store a simple value, such as a string, follow this Example code.
setting the value of the "totalSeats.Text" to the "SeatNumbers" key from page1
Application.Current.Properties["SeatNumbers"] = totalSeats.Text;
await Application.Current.SavePropertiesAsync();
then, you can simply get the value from any other page (page2)
var value = Application.Current.Properties["SeatNumbers"].ToString();
Additionally, you can set that value to another Label or Entry etc.
SeatNumbersEntry.Text = value;
If it's Key value(one value) data storage, follow below code
Application.Current.Properties["AppNumber"] = "123"
await Application.Current.SavePropertiesAsync();
Getting the same value
var value = Application.Current.Properties["AppNumber"];
I have given task to store the image path in database either xml schema or sqlite database.I am working on Xamarin.Forms PCL project. I am very confused with how to store image path in database.because in android image should be placed in Ressource/drawble,ios image placed in Resources folder. I read this xamarin.forms documentaion. But not getting how to get path and store in database. Please anyone provide any resources or example.
Hope you have gone through this documentation and to distinguish between iOS and Android is also Given here in this documentation .
if (Device.OS == TargetPlatform.iOS) {
// Save in sqlite with iOS path
}if (Device.OS == TargetPlatform.Android) {
// Save in sqlite with Android path
}
Hope it helps.
I have an app that needs to include a links to a second app in the same phone.
If the app is not installed the link should point to the windows store to install it (that part is working fine).
But if the app is already installed the link should go straight to the app and open it. How can I do that?
The app has two versions one form WP7 and other from WP8. if the solution is different for them please point the difference.
Thanks for the help...
I believe a URI Association is what you want. You should be able to create a different association in your WP7 app and in your WP8 app, and handle them accordingly.
A URI association allows your app to automatically launch when another app launches a special URI.
Also note:
If you are interested only in launching your own apps, consider using
APIs from the Windows.Phone.Management.Deployment namespace. You can
use this API to check for other apps that you’ve published, and then
launch them if they’re installed.
You basically just need to update the WMAppManifest.xml file to include the URI Association and then listen for that URI. Example:
<Extensions>
<Protocol Name="contoso" NavUriFragment="encodedLaunchUri=%s" TaskID="_default" />
</Extensions>
Then you can use a custom URI Mapper to handle your association (full example in top link above):
public override Uri MapUri(Uri uri)
{
tempUri = System.Net.HttpUtility.UrlDecode(uri.ToString());
// URI association launch for contoso.
if (tempUri.Contains("contoso:ShowProducts?CategoryID="))
{
// Get the category ID (after "CategoryID=").
int categoryIdIndex = tempUri.IndexOf("CategoryID=") + 11;
string categoryId = tempUri.Substring(categoryIdIndex);
// Map the show products request to ShowProducts.xaml
return new Uri("/ShowProducts.xaml?CategoryID=" + categoryId, UriKind.Relative);
}
// Otherwise perform normal launch.
return uri;
}
Hope this helps!
Is the secondary app one that you have created? If so, do something like this:
IEnumerable<Package> packages = InstallationManager.FindPackagesForCurrentPublisher();
foreach (Package package in packages)
{
if (package.Id.ProductId.ToString().ToLower() == "product id of secondary app")
{
//Launch the app
package.Launch();
}
}
Make sure that your publisher ids match in the WMAppManifest for both apps.
If this secondary app was published by someone else, you'll need to use a custom Uri schema. The app needs to have this feature added by the developer, you can't just launch any app.