我正在构建一个应用程序，该应用程序将从网站上抓取一些数据，并在满足某些条件时显示通知。
在打开应用程序（因为正在渲染WebView）时，一切工作正常，没有问题，但是当我关闭应用程序时，WebView被禁用，因此我无法再使用它来抓取数据。
抓取代码位于从ForegroundService调用的类中。
我已经看过Internet，但是找不到WebView的解决方案或替代品，您有什么想法吗？
很抱歉，如果您觉得这个问题很愚蠢，就在一周前，我才开始开发移动版
在 JDMonitoring 类之下，该类从 AlarmTask 类
中调用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 类
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());
}
}
}
以及负责首次触发警报的 ForegroundService 类
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);
}
}
}
谢谢！
答案 0 :(得分：0)
[更好的最终解决方案]
几个小时后，我发现了 Android WebView ，它确实满足了我的需求（我正在开发此应用仅适用于Android）
我已经编写了此浏览器帮助程序类
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();
}
}
}
[编辑]
改进了异步回调的JS返回功能（因此JS返回值将总是 传递）。
归功于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);
}
}
}
示例：
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
}
[最终解决方案]
最后，我找到了一种简单有效的WebView替代方法。
现在我正在使用SimpleBroswer，效果很好！
[SEMI-SOLUTION]
好的，我已经写了一个解决方法，但是我不太喜欢这个主意，所以，如果您知道更好的方法，请告诉我。
以下解决方法：
在我的 ForegroundServiceHelper 界面中，我添加了一种方法来检查 MainActivity （呈现WebView的位置）是否可见，如果看不到MainActivity，则会立即显示它，并立即将其隐藏起来。
该应用将从最近使用的应用中删除
我的 ForegroundServiceHelper 界面中的方法
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);
}
}
}
}
SharedSettings 类是围绕 App.Current.Properties 字典
在 OnAppearing 和 OnDisappearing 回调中，我将共享值设置为true / false
[编辑]
仅当用户位于主页上时，此解决方法才有效，因此我需要找到其他解决方案...