I have a WinForms application that gets Car data from a Sqlite database file which is generated by a CSV file from a WebService, and the related Parts for each Car. When instanced, the Car class populates all properties from the database and gets a lot of data from a WebService that takes about 30 seconds to finish so I just call an async Task after populating the database properties and let it run asyncronously. After the web service returns all data and all work is done, the instance is saved in a List that works like an internal cache.
All works well until the user makes an operation on a Part which requires the property ParentCar to be returned while the WebService method is still running, causing a new Car to be instantiated and re polling the web service as many times the property is requested while the Car doesn't exist on the cache list. This stops as soon as the first instance finishes processing but all changes will be overwritten every time the next instances finish.
I'm struggling to find a way to ensure that a Car is only instanced one time without blocking the UI during the application life time, any ideas?
This is the code that I currently have:
public class Car
{
private List<Part> _parts = new List<Part>();
public string Id { get; private set; }
public int DbIndex
{
get { return DbClass.GetCarIndexById(Id); }
}
public ReadOnlyCollection<Part> Parts { get => _parts.AsReadOnly(); }
public Car(System.Data.SQLite.SQLiteDataReader sQLiteDataReader)
{
// Code to Load all properties from sQLiteDataReader
Task.Run(() => LongRuningWebServiceTask());
}
private async Task LongRuningWebServiceTask
{
// Long running code that will populate even more properties
SaveToInternalDb();
}
private void SaveToInternalDb()
{
if (DbIndex > -1)
DbClass.UpdateCarData(this);
else
DbClass.AddCar(this);
}
public void RelateParts(IEnumerable<Part> parts)
{
_parts.AddRange(parts);
}
~Car()
{
SaveToInternalDb();
}
}
public class Part
{
public string ParentCarId { get; private set; }
public Car ParentCar
{
get
{
Task getCar = DbClass.GetCarById(ParentCarId);
getCar.Wait();
return getCar.Result;
}
}
}
public static class DbClass
{
private static SQLiteConnection sqlConn;
private readonly string sqlFile = "pathToDbFile";
private static List<Car> CarCache = new List<Car>();
public static async Task<Car> GetCarById(string> carId, bool ignoreCache = false)
{
Car foundCar = null;
if (!ignoreCache)
foundCar = CarCache.Find(s => s.Id == carId);
if (foundCar == null)
{
try
{
string sql = string.Format("SELECT * FROM all_Cars WHERE Car = '{0}';", carId);
using (SQLiteCommand command = new SQLiteCommand(sql, sqlConn))
{
using (SQLiteDataReader reader = (SQLiteDataReader)await command.ExecuteReaderAsync())
{
while (await reader.ReadAsync())
foundCar = new Car(reader));
}
}
}
catch (Exception e)
{
string m = e.Message;
}
if (foundCar != null)
{
var partsList = await GetPartsByCarId(carId);
if (partsList.Count > 0)
Car.RelateParts(partsList);
if (!ignoreCache)
{
if (foundCar.DbIndex == -1)
CarCache.Add(foundCar);
}
}
}
return foundCar;
}
public static async Task<List<Part>> GetPartsByCarId(string carId)
{
List<Part> foundParts = new List<Part>();
int index = GeCarIndexById(carId);
Car foundCar = index > -1 ? CarCache[index] : null;
if (foundCar != null)
foundParts = await GetPartsByCarId(carId);
return foundParts;
}
public static void InitiateSqlConnection()
{
if (sqlConn == null)
{
sqlConn = new SQLiteConnection("Data Source=" + sqlFile.FullName + ";Version=3;");
try
{
sqlConn.Open();
}
catch (Exception e)
{
var m = e.Message;
}
}
else
{
if(sqlConn.State == System.Data.ConnectionState.Broken || sqlConn.State == System.Data.ConnectionState.Closed)
sqlConn.Open();
}
}
public static int GetCarIndexById(string carId)
{
int index = -1;
for(int c = 0; c < CarCache.Count;c++)
{
if(CarCache[c].Id == carId)
{
index = c;
break;
}
}
return index;
}
public static void AddCar(Car car)
{
CarCache.Add(car);
}
public static void UpdateCarData(Car car)
{
if(car != null)
{
int index = car.DbIndex;
if(index > -1)
CarCache[index] = car;
}
}
}
Related
I am using #aspnet/signalr to connect to a hub and from the hub i am calling the method to return me some data.
When i first initialize the server the connection is established normally, but if i refresh the window 3 or 4 times the client stop sending connection request to the server.
I tried logging the HubConnection, the connectionState at first is equal to 1 but after the problem accrues the connectionState is alwase equal 0
Here is how i am building the hubConnection:
buildConnection() {
this.hubConnection = new HubConnectionBuilder()
.withUrl(this.tradesService.getStockQuotationsHubUrl())
.build();
this.hubConnection.serverTimeoutInMilliseconds = 1000 * 10;
this.hubConnection.onclose(() => setTimeout(() => this.startSignalRConnection(), 2000));}
Here is how i am starting the hubConnection:
startConnection() {
this.hubConnection
.start()
.then(() => {
this.hubConnection.on('updateMethod', (data: any) => {
this.store.push([
{ type: 'update', key: data.stockID, data },
]);
});
this.dataSource = new DataSource({
store: this.store,
reshapeOnPush: true,
});
});}
Note: I am listing to 5 hubs at once in my page but the only one having problems is this one.
[Update]
The problem is from the server because when i restart the server the connection is reestablished between the client and the server, but if the client refresh or quit the page for multiple times the hub does not even try to connect to the client
public class StockQuotationsHub : Microsoft.AspNetCore.SignalR.Hub
{
private string SectorID { get; set; }
private int TradingSession { get; set; }
private int MarketID { get; set; }
public static StockQuotationExt stockQuotationExt { get; set; }
private readonly StockQuotationTicker _stockTicker;
public StockQuotationsHub(StockQuotationTicker stockTicker){
_stockTicker = stockTicker;
}
public override Task OnConnectedAsync(){
return base.OnConnectedAsync();
}
public IEnumerable<StockQuotation> GetAllStockQuotations(string[] stockID, string sectorID, int tradingSession, int marketType){
return _stockTicker.
GetAllStocks(Context.ConnectionId, stockID, sectorID, tradingSession, marketType);
}
public override async Task OnDisconnectedAsync(Exception exception){
await base.OnDisconnectedAsync(exception);
}
and here is my stock ticker class:
public IEnumerable<StockQuotation> GetAllStocks(string connectionId, string[] stockID, string sectorID, int tradingSession, int marketType)
{
_stocks = new List<StockQuotation>();
_stocks = Task.Run(async () => await GetStockQuotationModelAsync("", 0, 1, 0)).Result.ToList();
this.MaxTimeStamp = _stocks.Max(s => s.TStamp);
this.SectorID = sectorID;
this.TradingSession = tradingSession;
this.MarketID = marketType;
AddToGroups(connectionId, stockID);
if (_timer==null)
_timer = new Timer(UpdateStockPrices, null, _updateInterval, _updateInterval);
if (stockID.Length == 0)
{
return _stocks;
}
else
{
var stocksList = new List<StockQuotation>();
foreach (var stock in stockID)
{
stocksList.AddRange(_stocks.Where(s => s.StockID == stock).ToList());
}
return stocksList;
}
}
private void AddToGroups(string connectionId, string[] stockID)
{
if (_stocks.Count > 0)
{
if (stockID.Length == 0)
{
Hub.Groups.AddToGroupAsync(connectionId, "ALL");
}
else
{
foreach (var stock in stockID)
{
Hub.Groups.AddToGroupAsync(connectionId, stock);
var s = _stocks.FirstOrDefault(s => s.StockID == stock);
if(s != null)
{
s.Snapshots = new List<double>(GetStockQuotationSnapshots(stock));
}
}
}
}
}
private void AddToGroups(string connectionId, string[] stockID)
{
if (_stocks.Count > 0)
{
if (stockID.Length == 0)
{
Hub.Groups.AddToGroupAsync(connectionId, "ALL");
}
else
{
foreach (var stock in stockID)
{
Hub.Groups.AddToGroupAsync(connectionId, stock);
var s = _stocks.FirstOrDefault(s => s.StockID == stock);
if(s != null)
{
s.Snapshots = new List<double>(GetStockQuotationSnapshots(stock));
}
}
}
}
}
I really appreciated the help.
Eventually the problem was that the project type was MVC, so I changed it to be webApi
and everything worked successfully
Even if you fix it I would like to recommend you to add the following code in order to know exactly the root cause of disconnection.
First of all enable the extended debug info in the service configuration:
services.AddSignalR(o =>
{
o.EnableDetailedErrors = true;
});
Furthermore, you need to attach to the event Closed in HubConnection like that:
hubConnection.Closed += (exception) =>
{
if (exception == null)
{
Console.WriteLine("Connection closed without error.");
}
else
{
Console.WriteLine($"Connection closed due to an error: {exception}");
}
return null;
};
I'm building an app which will scrape some data from a website and shows a notification when some criteria are met.
Everything works well without problems when the app is open (because the WebView is being rendered) but when I close the app the WebView is disabled so I cannot use it to scrape data anymore.
The scraping code is inside a class called from a ForegroundService.
I've already looked on the internet but I'm unable to find a solution or a substitute to WebView, do you have any ideas?
I'm sorry if this question looks stupid to you, I've started to develop for mobile just one week ago
Below the JDMonitoring class which is called from the AlarmTask class
using System;
using System.Collections.Generic;
using System.Net;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace CGSJDSportsNotification {
public class JDMonitoring {
class Ticket {
string owner;
string title;
string store;
string lastUpdated;
string link;
public string ID { get; set; }
public string Owner {
get {
return owner == null ? "Nobody" : owner;
} set {
owner = value.Remove(0, value.IndexOf('(') + 1).Replace(")", "");
}
}
public string Title {
get {
return title;
} set {
if (value.StartsWith("(P"))
title = value.Remove(0, value.IndexOf(')') + 2);
}
}
public string Status { get; set; }
public string Store {
get {
return store;
} set {
store = value.Replace(#"\u003C", "").Replace(">", "");
}
}
public string LastUpdated {
get {
return lastUpdated;
} set {
string v;
int time = Convert.ToInt32(System.Text.RegularExpressions.Regex.Replace(value, #"[^\d]+", ""));
// Convert to minutes
if (value.Contains("hours"))
time *= 60;
v = time.ToString();
if (value.Contains("seconds"))
v = v.Insert(v.Length, " sec. ago");
else
v = v.Insert(v.Length, " min. ago");
lastUpdated = v;
}
}
public string Link {
get {
return link;
} set {
link = "https://support.jdplc.com/" + value;
}
}
}
public JDMonitoring() {
WB.Source = JDQueueMainUrl;
WB.Navigated += new EventHandler<WebNavigatedEventArgs>(OnNavigate);
}
IForegroundService FgService { get { return DependencyService.Get<IForegroundService>(); } }
WebView WB { get; } = MainPage.UI.MonitoringWebView;
string JDQueueMainUrl { get; } = "https://support.jdplc.com/rt4/Search/Results.html?Format=%27%3Cb%3E%3Ca%20href%3D%22__WebPath__%2FTicket%2FDisplay.html%3Fid%3D__id__%22%3E__id__%3C%2Fa%3E%3C%2Fb%3E%2FTITLE%3A%23%27%2C%0A%27%3Cb%3E%3Ca%20href%3D%22__WebPath__%2FTicket%2FDisplay.html%3Fid%3D__id__%22%3E__Subject__%3C%2Fa%3E%3C%2Fb%3E%2FTITLE%3ASubject%27%2C%0AStatus%2C%0AQueueName%2C%0AOwner%2C%0APriority%2C%0A%27__NEWLINE__%27%2C%0A%27__NBSP__%27%2C%0A%27%3Csmall%3E__Requestors__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__CreatedRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__ToldRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__LastUpdatedRelative__%3C%2Fsmall%3E%27%2C%0A%27%3Csmall%3E__TimeLeft__%3C%2Fsmall%3E%27&Order=DESC%7CASC%7CASC%7CASC&OrderBy=LastUpdated%7C%7C%7C&Query=Queue%20%3D%20%27Service%20Desk%20-%20CGS%27%20AND%20(%20%20Status%20%3D%20%27new%27%20OR%20Status%20%3D%20%27open%27%20OR%20Status%20%3D%20%27stalled%27%20OR%20Status%20%3D%20%27deferred%27%20OR%20Status%20%3D%20%27open%20-%20awaiting%20requestor%27%20OR%20Status%20%3D%20%27open%20-%20awaiting%20third%20party%27%20)&RowsPerPage=0&SavedChartSearchId=new&SavedSearchId=new";
bool MonitoringIsInProgress { get; set; } = false;
public bool IsConnectionAvailable {
get {
try {
using (new WebClient().OpenRead("http://google.com/generate_204"))
return true;
} catch {
return false;
}
}
}
async Task<bool> IsOnLoginPage() {
if (await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('left')[0].innerText") != null)
return true;
return false;
}
async Task<bool> Login() {
await WB.EvaluateJavaScriptAsync($"document.getElementsByName('user')[0].value = '{UserSettings.SecureEntries.Get("rtUser")}'");
await WB.EvaluateJavaScriptAsync($"document.getElementsByName('pass')[0].value = '{UserSettings.SecureEntries.Get("rtPass")}'");
await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('button')[0].click()");
await Task.Delay(1000);
// Checks for wrong credentials error
if (await WB.EvaluateJavaScriptAsync("document.getElementsByClassName('action-results')[0].innerText") == null)
return true;
return false;
}
async Task<List<Ticket>> GetTickets() {
List<Ticket> tkts = new List<Ticket>();
// Queue tkts index (multiple of 2)
int index = 2;
// Iterates all the queue
while (await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].innerText") != null) {
Ticket tkt = new Ticket();
tkt.LastUpdated = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index + 1}].getElementsByTagName('td')[4].innerText");
// Gets only the tkts which are not older than the value selected by the user
if (Convert.ToInt32(System.Text.RegularExpressions.Regex.Replace(tkt.LastUpdated, #"[^\d]+", "")) > Convert.ToInt32(UserSettings.Entries.Get("searchTimeframe")))
break;
tkt.ID = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[0].innerText");
tkt.Owner = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[4].innerText");
tkt.Title = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[1].innerText");
tkt.Status = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[2].innerText");
tkt.Store = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index + 1}].getElementsByTagName('td')[1].innerText");
tkt.Link = await WB.EvaluateJavaScriptAsync($"document.getElementsByClassName('ticket-list collection-as-table')[0].getElementsByTagName('tbody')[0].getElementsByTagName('tr')[{index}].getElementsByTagName('td')[1].getElementsByTagName('a')[0].getAttribute('href')");
tkts.Add(tkt);
index += 2;
}
return tkts;
}
//async Task<string> QueueGetTkt
async void OnNavigate(object sender, WebNavigatedEventArgs args) {
if (MonitoringIsInProgress)
return;
if (IsConnectionAvailable) {
if (await IsOnLoginPage()) {
if (await Login() == false) {
// If the log-in failed we can't proceed
MonitoringIsInProgress = false;
FgService.NotificationNewTicket("Log-in failed!", "Please check your credentials");
// Used to avoid an infinite loop of OnNavigate method calls
WB.Source = "about:blank";
return;
}
}
// Main core of the monitoring
List<Ticket> tkts = await GetTickets();
if (tkts.Count > 0) {
foreach(Ticket t in tkts) {
// Looks only after the tkts with the country selected by the user (and if it was selected by the user, also for the tkts without a visible country)
// Firstly we look in the title
if (t.Title.Contains(MainPage.UI.CountryPicker.SelectedItem.ToString())) {
FgService.NotificationNewTicket($"[{t.ID}] {t.LastUpdated}",
$"{t.Title}\r\n\r\n" +
$"Status: {t.Status}\r\n" +
$"Owner: {t.Owner}\r\n" +
$"Last updated: {t.LastUpdated}");
break;
}
}
}
}
MonitoringIsInProgress = false;
}
}
}
AlarmTask class
using Android.App;
using Android.Content;
using Android.Support.V4.App;
namespace CGSJDSportsNotification.Droid {
[BroadcastReceiver(Enabled = true, Exported = true, DirectBootAware = true)]
[IntentFilter(new string[] { Intent.ActionBootCompleted, Intent.ActionLockedBootCompleted, "android.intent.action.QUICKBOOT_POWERON", "com.htc.intent.action.QUICKBOOT_POWERON" }, Priority = (int)IntentFilterPriority.HighPriority)]
public class AlarmTask : BroadcastReceiver {
IAlarm _MainActivity { get { return Xamarin.Forms.DependencyService.Get<IAlarm>(); } }
public override void OnReceive(Context context, Intent intent) {
if (intent.Action != null) {
if (intent.Action.Equals(Intent.ActionBootCompleted)) {
// Starts the app after reboot
var serviceIntent = new Intent(context, typeof(MainActivity));
serviceIntent.AddFlags(ActivityFlags.NewTask);
context.StartActivity(serviceIntent);
Intent main = new Intent(Intent.ActionMain);
main.AddCategory(Intent.CategoryHome);
context.StartActivity(main);
// Does not work, app crashes on boot received
/*if (UserSettings.Entries.Exists("monitoringIsRunning")) {
if ((bool)UserSettings.Entries.Get("monitoringIsRunning"))
FgService.Start();
}*/
}
} else
// Checks for new tkts on a new thread
new JDMonitoring();
// Restarts the alarm
_MainActivity.AlarmStart();
}
// Called from JDMonitoring class
public static void NotificationNewTicket(string title, string message, bool icoUnknownCountry = false) {
new AlarmTask().NotificationShow(title, message, icoUnknownCountry);
}
void NotificationShow(string title, string message, bool icoUnknownCountry) {
int countryFlag = Resource.Drawable.newTktUnknownCountry;
if (icoUnknownCountry == false) {
switch (MainPage.UI.CountryPicker.SelectedItem.ToString()) {
case "Italy":
countryFlag = Resource.Drawable.newTktItaly;
break;
case "Spain":
countryFlag = Resource.Drawable.newTktSpain;
break;
case "Germany":
countryFlag = Resource.Drawable.newTktGermany;
break;
case "Portugal":
countryFlag = Resource.Drawable.newTktPortugal;
break;
}
}
var _intent = new Intent(Application.Context, typeof(MainActivity));
_intent.AddFlags(ActivityFlags.ClearTop);
_intent.PutExtra("jdqueue_notification", "extra");
var pendingIntent = PendingIntent.GetActivity(Application.Context, 0, _intent, PendingIntentFlags.OneShot);
NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(Application.Context, "newTktNotification_channel")
.SetVisibility((int)NotificationVisibility.Public)
.SetPriority((int)NotificationPriority.High)
.SetDefaults((int)NotificationDefaults.Sound | (int)NotificationDefaults.Vibrate | (int)NotificationDefaults.Lights)
.SetSmallIcon(Resource.Drawable.newTktNotification)
.SetLargeIcon(Android.Graphics.BitmapFactory.DecodeResource(Application.Context.Resources, countryFlag))
.SetSubText("Click to check the queue")
.SetStyle(new NotificationCompat.BigTextStyle()
.SetBigContentTitle("New ticket available!")
.BigText(message))
.SetContentText(title)
.SetAutoCancel(true)
.SetContentIntent(pendingIntent);
NotificationManagerCompat.From(Application.Context).Notify(0, notificationBuilder.Build());
}
}
}
And the ForegroundService class which is responsible to trigger for the first time the alarm
using Android.App;
using Android.Content;
using Android.OS;
namespace CGSJDSportsNotification.Droid {
[Service]
class ForegroundService : Service {
IAlarm _MainActivity { get { return Xamarin.Forms.DependencyService.Get<IAlarm>(); } }
public override IBinder OnBind(Intent intent) { return null; }
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId) {
// Starts the Foreground Service and the notification channel
StartForeground(9869, new ForegroundServiceNotification().ReturnNotif());
Android.Widget.Toast.MakeText(Application.Context, "JD Queue - Monitoring started!", Android.Widget.ToastLength.Long).Show();
_MainActivity.AlarmStart();
return StartCommandResult.Sticky;
}
public override void OnDestroy() {
Android.Widget.Toast.MakeText(Application.Context, "JD Queue - Monitoring stopped!", Android.Widget.ToastLength.Long).Show();
_MainActivity.AlarmStop();
UserSettings.Entries.AddOrEdit("monitoringIsRunning", false);
UserSettings.Entries.AddOrEdit("monitoringStopPending", false, false);
base.OnDestroy();
}
public override bool StopService(Intent name) {
return base.StopService(name);
}
}
}
Thank you!
[BETTER-FINAL-SOLUTION]
After several hours I've discovered Android WebView which does exactly what I need (I'm developing this app only for Android)
I've written this Browser helper class
class Browser {
public Android.Webkit.WebView WB;
static string JSResult;
public class CustomWebViewClient : WebViewClient {
public event EventHandler<bool> OnPageLoaded;
public override void OnPageFinished(Android.Webkit.WebView view, string url) {
OnPageLoaded?.Invoke(this, true);
}
}
public Browser(CustomWebViewClient wc, string url = "") {
WB = new Android.Webkit.WebView(Android.App.Application.Context);
WB.Settings.JavaScriptEnabled = true;
WB.SetWebViewClient(wc);
WB.LoadUrl(url);
}
public string EvalJS(string js) {
JSInterface jsi = new JSInterface();
WB.EvaluateJavascript($"javascript:(function() {{ return {js}; }})()", jsi);
return JSResult;
}
class JSInterface : Java.Lang.Object, IValueCallback {
public void OnReceiveValue(Java.Lang.Object value) {
JSResult = value.ToString();
}
}
}
[EDIT]
Improved the JS returning function with async callbacks (so the JS return value will be always delivered).
Credits to ChristineZuckerman
class Browser {
public Android.Webkit.WebView WB;
public class CustomWebViewClient : WebViewClient {
public event EventHandler<bool> OnPageLoaded;
public override void OnPageFinished(Android.Webkit.WebView view, string url) {
OnPageLoaded?.Invoke(this, true);
}
}
public Browser(CustomWebViewClient wc, string url = "") {
WB = new Android.Webkit.WebView(Android.App.Application.Context);
WB.ClearCache(true);
WB.Settings.JavaScriptEnabled = true;
WB.Settings.CacheMode = CacheModes.NoCache;
WB.Settings.DomStorageEnabled = true;
WB.Settings.SetAppCacheEnabled(false);
WB.Settings.UserAgentString = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10";
WB.LoadUrl(url);
WB.SetWebViewClient(wc);
}
public async Task<string> EvalJS(string js, bool returnNullObjectWhenNull = true) {
string JSResult = "";
ManualResetEvent reset = new ManualResetEvent(false);
Device.BeginInvokeOnMainThread(() => {
WB?.EvaluateJavascript($"javascript:(function() {{ return {js}; }})()", new JSInterface((r) => {
JSResult = r;
reset.Set();
}));
});
await Task.Run(() => { reset.WaitOne(); });
return JSResult == "null" ? returnNullObjectWhenNull ? null : "null" : JSResult;
}
class JSInterface : Java.Lang.Object, IValueCallback {
private Action<string> _callback;
public JSInterface(Action<string> callback) {
_callback = callback;
}
public void OnReceiveValue(Java.Lang.Object value) {
string v = value.ToString();
if (v.StartsWith('"') && v.EndsWith('"'))
v = v.Remove(0, 1).Remove(v.Length - 2, 1);
_callback?.Invoke(v);
}
}
}
Example:
Browser.CustomWebViewClient wc = new Browser.CustomWebViewClient();
wc.OnPageLoaded += BrowserOnPageLoad;
Browser browser = new Browser(wc, "https://www.google.com/");
void BrowserOnPageLoad(object sender, bool e) {
string test = browser.EvalJS("document.getElementsByClassName('Q8LRLc')[0].innerText");
// 'test' will contain the value returned from the JS script
// You can acces the real WebView object by using
// browser.WB
}
// OR WITH THE NEW RETURNING FUNCTION
async void BrowserOnPageLoad(object sender, bool e) {
string test = await browser.EvalJS("document.getElementsByClassName('Q8LRLc')[0].innerText");
// 'test' will contain the value returned from the JS script
// You can acces the real WebView object by using
// browser.WB
}
[FINAL-SOLUTION]
Finally I've found an easy and efficient alternative to WebView.
Now I'm using SimpleBroswer and works great!
[SEMI-SOLUTION]
Alright, I've written a workaround but I don't really like this idea, so please, if you know a better method let me know.
Below my workaround:
In my ForegroundServiceHelper interface I've added a method to check if the MainActivity (where the WebView it's rendered) is visible or not, if isn't visible the MainActivity will be shown and immediately will be hidden back.
And the app will be removed from the last used applications
Method inside my ForegroundServiceHelper Interface
public void InitBackgroundWebView() {
if ((bool)SharedSettings.Entries.Get("MainPage.IsVisible") == false) {
// Shows the activity
Intent serviceIntent = new Intent(context, typeof(MainActivity));
serviceIntent.AddFlags(ActivityFlags.NewTask);
context.StartActivity(serviceIntent);
// And immediately hides it back
Intent main = new Intent(Intent.ActionMain);
main.AddFlags(ActivityFlags.NewTask);
main.AddCategory(Intent.CategoryHome);
context.StartActivity(main);
// Removes from the last app used
ActivityManager am = (new ContextWrapper(Android.App.Application.Context)).GetSystemService(Context.ActivityService).JavaCast<ActivityManager>();
if (am != null) {
System.Collections.Generic.IList<ActivityManager.AppTask> tasks = am.AppTasks;
if (tasks != null && tasks.Count > 0) {
tasks[0].SetExcludeFromRecents(true);
}
}
}
}
The SharedSettings class is an helper class wrapped around the App.Current.Properties Dictionary
And in the OnAppearing and OnDisappearing callbacks I set the shared values to true/false
[EDIT]
This workaround works only if the user is on the homepage, so I need to find an another solution...
I'm implementing the MailChimp.NET wrapper in both synchronous and asynchronous ways and calls are going through without a problem, BUT results tend to get lost in the synchronous methods. In other words, if I send 100 members to be added (by batches of 10 due to the simultaneous connections limit of the MailChimp API), all 100 will indeed be visible in my MC audience but I'll loose from 5 to 25% of the results on code side. Here's the concerned bit of my implementation :
public class MailChimpClient : IDisposable
{
private MailChimpManager _mcm;
private string _apiKey;
private bool _isDisposed;
private ConcurrentQueue<MailChimpMember> _updatedMembersQueue;
private ConcurrentQueue<MailChimpBaseException> _exceptionsQueue;
private const int BatchSize = 10;
private const int TaskDelay = 100;
private ConcurrentQueue<MailChimpMember> UpdatedMembersQueue
{
get { return _updatedMembersQueue = _updatedMembersQueue ?? new ConcurrentQueue<MailChimpMember>(); }
set { _updatedMembersQueue = value; }
}
private ConcurrentQueue<MailChimpBaseException> ExceptionsQueue
{
get { return _exceptionsQueue = _exceptionsQueue ?? new ConcurrentQueue<MailChimpBaseException>(); }
set { _exceptionsQueue = value; }
}
public MailChimpClient(string apiKey)
{
_apiKey = apiKey;
_mcm = new MailChimpManager(apiKey);
}
private async Task AddOrUpdateMember(MailChimpMember member, string listId)
{
try
{
var model = member.ToApiMember();
model = await _mcm.Members.AddOrUpdateAsync(listId, model);
UpdatedMembersQueue.Enqueue(new MailChimpMember(model));
await Task.Delay(TaskDelay);
}
catch (Exception ex)
{
var mccex = new MailChimpClientException($"Error adding/updating member \"{(member != null ? member.MailAddress.ToString() : "NULL")}\" to list with ID \"{listId}\".", ex);
ExceptionsQueue.Enqueue(mccex);
}
}
private MailChimpClientResult AddOrUpdateMemberRange(IEnumerable<MailChimpMember> members, string listId)
{
var batches = members.GetBatches(BatchSize);
var result = new MailChimpClientResult();
var i = 0;
foreach (var batch in batches)
{
AddOrUpdateMemberBatch(batch, listId);
i++;
FlushQueues(ref result);
}
return result;
}
private void AddOrUpdateMemberBatch(MailChimpMember[] batch, string listId)
{
Task.WaitAll(batch.Select(async b => await AddOrUpdateMember(b, listId)).ToArray(), -1);
}
private void FlushQueues(ref MailChimpClientResult result)
{
result.UpdatedMembers.FlushQueue(UpdatedMembersQueue);
result.Exceptions.FlushQueue(ExceptionsQueue);
}
public MailChimpClientResult AddOrUpdate(MailChimpMember member, string listId)
{
return AddOrUpdateMemberRange(new MailChimpMember[] { member }, listId);
}
public MailChimpClientResult AddOrUpdate(IEnumerable<MailChimpMember> members, string listId)
{
return AddOrUpdateMemberRange(members, listId);
}
}
public static class CollectionExtensions
{
public static T[][] GetBatches<T>(this IEnumerable<T> items, int batchSize)
{
var result = new List<T[]>();
var batch = new List<T>();
foreach (var t in items)
{
if (batch.Count == batchSize)
{
result.Add(batch.ToArray());
batch.Clear();
}
batch.Add(t);
}
result.Add(batch.ToArray());
batch.Clear();
return result.ToArray();
}
public static void FlushQueue<T>(this IList<T> list, ConcurrentQueue<T> queue)
{
T item;
while (queue.TryDequeue(out item))
list.Add(item);
}
}
MailChimpMember being a public copy of the MailChimp.NET Member. The problem seems to happen in the batch processing method, the Task.WaitAll(...) instruction firing its completion event before all calls are complete, therefore not all results are queued. I tried delaying the execution of each individual treatment with Task.Delay() but with little to no result.
Does anyone have an idea what is failing in my implementation ?
I have an application which caches some data at startup. There are several things to put in a cache, but they are very similar. I created classes like this, the only difference in them is the type of the item to be added to the dictionary (in this example the Setting class), and the _sqlNotifyCommand.CommandText.
public class SettingsCache : ILoggerClass
{
private Dictionary<int, Dictionary<int, Setting>> _cachedItems;
private string _entityConnectionString;
private SQLNotifier _sqlNotifier;
private SqlCommand _sqlNotifyCommand = new SqlCommand();
private bool _dataLoaded = false;
private void AddItem(Setting item)
{
if (!_cachedItems.ContainsKey(item.PartnerId))
{
_cachedItems.Add(item.PartnerId, new Dictionary<int, Setting>());
}
if (_cachedItems[item.PartnerId].ContainsKey(item.Id))
{
_cachedItems[item.PartnerId].Remove(item.Id);
}
_cachedItems[item.PartnerId].Add(item.Id, item);
}
public Setting GetSetting(int partnerId, int id)
{
if (_cachedItems.ContainsKey(partnerId))
{
if (_cachedItems[partnerId].ContainsKey(id))
{
return _cachedItems[partnerId][id];
}
return null;
}
return null;
}
public SettingsCache(string connectionString)
{
_entityConnectionString = connectionString;
_cachedItems = new Dictionary<int, Dictionary<int, Setting>>();
LoadData();
try
{
using (var db = new partnerEntity(connectionString))
{
string adoSqlConnectionString = ((EntityConnection) db.Connection).StoreConnection.ConnectionString;
_sqlNotifier = new SQLNotifier(adoSqlConnectionString);
_sqlNotifier.NewMessage += _sqlNotifier_NewMessage;
_sqlNotifyCommand.CommandType = CommandType.Text;
_sqlNotifyCommand.CommandText = "SELECT setting_id, setting_value, partner_id FROM dbo.setting";
_sqlNotifyCommand.Notification = null;
_sqlNotifier.RegisterDependency(_sqlNotifyCommand);
}
}
catch (Exception exception)
{
this.Log(this, LogLevel.Error, 0, exception);
}
}
private void _sqlNotifier_NewMessage(object sender, SqlNotificationEventArgs e)
{
if (e.Info == SqlNotificationInfo.Insert || e.Info == SqlNotificationInfo.Update)
{
this.Log(this, LogLevel.Info, 0, string.Format("Database changed, reloading settings data..."));
LoadData();
}
_sqlNotifier.RegisterDependency(_sqlNotifyCommand);
}
private void LoadData()
{
_dataLoaded = false;
try
{
using (var db = new partnerEntity(_entityConnectionString))
{
var dbData = db.setting.ToList();
foreach (var cItem in dbData)
{
AddItem(new Setting
{
PartnerId = cItem.partner_id,
Id = cItem.setting_id,
Value = cItem.setting_value
});
}
}
_dataLoaded = true;
}
catch (Exception exception)
{
this.Log(this, LogLevel.Error, 0, exception);
}
if (!_dataLoaded)
{
Task.Delay(TimeSpan.FromSeconds(10)).ContinueWith(_ => { LoadData(); });
}
}
}
Is there a more generic way to do this? The last thing which was needed in the classes this part:
if (!_dataLoaded)
{
Task.Delay(TimeSpan.FromSeconds(10)).ContinueWith(_ => { LoadData(); });
}
And I had to modify every Caching class. I needed to declare the variable, add it to the try-catch block, and after the block insert the same line in 6 classes. This code seems very boilerplate to me, I can't believe there is no simpler solution. I tried to make an Interface with AddItem, LoadData, OnLoadDataFailed methods, but in the AddItem method I need to specify the item, I'm stuck.
Here is the basic structure of what (I think) you want to accomplish using Generics.
First, declare a common interface for cached items so that the AddItem method still works:
public interface ICacheItem
{
int Id { get; set; }
int PartnerId { get; set; }
}
Now you can create the SettingsCache<T> that holds the items:
public class SettingsCache<T> : ILogger where T : ICacheItem
{
private Dictionary<int, Dictionary<int, T>> _cachedItems;
//...
public SettingsCache(string connectionString, string commandText)
{
//...
}
private void AddItem(T item)
{
if (!_cachedItems.ContainsKey(item.PartnerId))
{
_cachedItems.Add(item.PartnerId, new Dictionary<int, T>());
}
if (_cachedItems[item.PartnerId].ContainsKey(item.Id))
{
_cachedItems[item.PartnerId].Remove(item.Id);
}
_cachedItems[item.PartnerId].Add(item.Id, item);
}
}
I left out most of the implementation to focus on your two biggest concerns, the command text and the AddItem method. The generic has a constraint so that it can only accept items that are of ICacheItem, so you can use any properties that ICacheItem defines.
To use a cache, simply create one with the specific type (assuming Setting implements ICacheItem):
var settingsCache = new SettingsCache<Setting>("connection string", "command string");
This is a basically a class library project which is somehow exposed as a WCF service. The code below is a part of the Data Access Layer. 'db' is an object of a DataContext class. To save a file, we do the following-
public static Guid SaveFile(FileDetails fileDetails)
{
System.Nullable<Guid> id = null;
SystemDataContext.UsingWrite(db =>
{
db.SaveFileData(fileDetails.RunId, fileDetails.FileData, fileDetails.FileExtension, ref id);
});
return id ?? Guid.Empty;
}
Then, the below would execute-
public static void UsingWrite(Action<SoftCashCreditDBDataContext> action)
{
using (var context = new SystemDataContext())
{
try
{
action(context.Write);
}
catch (Exception ex)
{
DataAccessExceptionHandler.HandleExcetion(ex, Config.DataLayerPolicy);
}
}
}
public SystemDataContext()
{
if (_stack == null)
{
_stack = new Stack<SystemDataContext>();
this.Depth = 1;
this.Read = new SoftCashCreditDBDataContext(Config.ReadDatabaseConnection);
this.Write = new SoftCashCreditDBDataContext(Config.WriteDatabaseConnection);
}
else
{
var parent = _stack.Peek();
/// Increment level of node.
this.Depth = parent.Depth + 1;
/// Copy data context from the parent
this.Read = parent.Read;
this.Write = parent.Write;
}
_stack.Push(this);
}
public int Depth { get; private set; }
public bool IsRoot { get { return this.Depth == 1; } }
[ThreadStatic]
private static Stack<SystemDataContext> _stack = null;
public SoftCashCreditDBDataContext Read { get; private set; }
public SoftCashCreditDBDataContext Write { get; private set; }
#region IDisposable Members
public void Dispose()
{
var context = _stack.Pop();
if (context.IsRoot == true)
{
context.Read.Dispose();
context.Write.Dispose();
_stack = null;
}
}
#endregion
}
They have implemented LINQ to SQL here, and created a DBContext class. The 'SaveFileData()' method is actually part of that class, where it just calls an SP inside to save the file.
What I did not follow-
What exactly does the call to UsingWrite() do here? What is passed to the 'Action action' parameter, and what is it doing?
I understand your confusion. They use 2 delegates.
This is passed to the action parameter:
db =>
{
db.SaveFileData(fileDetails.RunId, fileDetails.FileData, fileDetails.FileExtension, ref id);
}
So when UsingWrite is called, the SoftCashCreditDBDataContext delegate which was set in the Write delegate will call SaveFileData.
A simplified example to help you understand Action:
public void Main()
{
Test(x => Debug.Write(x));
}
private void Test(Action<string> testAction)
{
testAction("Bla");
}
This function will call Debug.Write with the argument x, which is a string that is passed to the test action function.