I am trying to implement a simple notifier that will broadcast a message when the network connectivity changes in an app.
The problem I am having is that although the class returns the correct connection status when my code asks for it, the .SetNotification method of my networkreachability object does not get fired when the connection status changes.
Here is my connection status checking code, if anyone could help highlight what I have done wrong it would be much appreciated, thank you.
public event EventHandler ReachabilityChanged;
public NetworkStatus Status ()
{
if(_defaultRouteReachability == null)
{
_defaultRouteReachability = new NetworkReachability(new IPAddress(0));
}
_defaultRouteReachability.SetNotification(OnChange);
_defaultRouteReachability.Schedule(CFRunLoop.Current, CFRunLoop.ModeDefault);
_defaultRouteReachability.TryGetFlags (out _flags);
return ParseFlags ();
}
NetworkStatus ParseFlags ()
{
if (_flags == 0)
return NetworkStatus.NotReachable;
if (_flags.HasFlag(NetworkReachabilityFlags.ConnectionRequired) ||
_flags.HasFlag(NetworkReachabilityFlags.InterventionRequired) ||
_flags.HasFlag(NetworkReachabilityFlags.ConnectionOnDemand))
{
return NetworkStatus.NotReachable;
}
if (_flags.HasFlag (NetworkReachabilityFlags.TransientConnection) ||
_flags.HasFlag (NetworkReachabilityFlags.IsWWAN))
{
return NetworkStatus.ReachableViaCarrierDataNetwork;
}
return NetworkStatus.ReachableViaWiFiNetwork;
}
void OnChange(NetworkReachabilityFlags flags)
{
var h = ReachabilityChanged;
if (h != null)
h(null, EventArgs.Empty);
}
I can't say what's wrong with your approach, but I've done that a few days ago, so here's my working example:
https://thomasbandt.com/how-to-check-network-reachability-with-xamarinios-on-ios-8
You should try using ready Connectivity Plugin available in xamarin, really handy to use.
It is a Simple cross platform plugin to check connection status of mobile device, gather connection type, bandwidths, and more.
Related
I'm trying to request a permission at runtime for my app. I use a service provider to talk between the portable class and Android.
I start by calling this code on button press in the PCL:
using (new Busy(this))
{
var locationHelper = scope.Resolve<ILocationHelper>();
locationHelper.GetLocation(this);
}
This calls my Android level service:
public class AndroidLocationHelper : ILocationHelper, ILocationListener
{
readonly string[] PermissionsLocation =
{
Manifest.Permission.AccessCoarseLocation
};
const int RequestLocationId = 0;
public void GetLocation(SearchViewModel viewModel)
{
try
{
const string permission = Manifest.Permission.AccessCoarseLocation;
if (((int)Build.VERSION.SdkInt < 23) || (CheckSelfPermission(permission) == Permission.Granted))
{
}
else
RequestPermissions(PermissionsLocation, RequestLocationId);
}
catch (Exception ex)
{
Debug.WriteLine("Error while getting Location service");
Debug.WriteLine(ex.Message);
Messaging.AlertUser("There was an error with determining your location");
}
}
However, I get two errors on CheckSelfPermission and RequestPermissions. These two methods are only available to activities. The code works fine in MainActivity; however, I want to ask for permissions when the user hits a button, not in OnCreate or OnResume, etc.
Thanks for any help.
In your Android project, You can use this and use the Dependency Service to call it in Xamarin.Forms PCL project later:
var thisActivity = Forms.Context as Activity;
ActivityCompat.RequestPermissions(thisActivity, new string[] {
Manifest.Permission.AccessFineLocation }, 1);
ActivityCompat.RequestPermissions(thisActivity,
new String[] { Manifest.Permission.AccessFineLocation },
1);
You can try with ContextCompat.CheckSelfPermission, passing the application context, like this:
ContextCompat.CheckSelfPermission(Android.App.Application.Context, permission)
Update
In case of ActivityCompat.RequestPermissions, which requires an activity reference, you can keep track of the current activity. There is a very handy lib for that, called "CurrentActivityPlugin". You can find at https://github.com/jamesmontemagno/CurrentActivityPlugin
Rafael came up with a solution but I found another option that is a lot less effort just using MessagingCenter. In the MainActivity's OnCreate add a receiver that runs all the location code, that way you have access to all of the activities methods (and there are a bunch of tutorials on doing location services in MainActivity). Then add the Send inside of your service (the class).
To expound Rafael Steil's answer, I tried the suggested CurrentActivityPlugin and it worked on me. In my case I am trying to execute a voice call which needs CALL_PHONE permission. Here is the code snippet in your case: I used the ContextCompat & ActivityCompat so that I don't need to check the VERSION.SdkInt
using Plugin.CurrentActivity;
public void GetLocation(SearchViewModel viewModel){
var context = CrossCurrentActivity.Current.AppContext;
var activity = CrossCurrentActivity.Current.Activity;
int YOUR_ASSIGNED_REQUEST_CODE = 9;
if (ContextCompat.CheckSelfPermission(context, Manifest.Permission.AccessCoarseLocation) == (int)Android.Content.PM.Permission.Granted)
{
//Permission is granted, execute stuff
}
else
{
ActivityCompat.RequestPermissions(activity, new string[] { Manifest.Permission.AccessCoarseLocation }, YOUR_ASSIGNED_REQUEST_CODE);
}
}
It's dead simple
public bool CheckPermission()
{
const string permission = Manifest.Permission.ReceiveSms;
return ContextCompat.CheckSelfPermission(Forms.Context, permission) == (int) Permission.Granted;
}
I have an application which when starting requests a qr code from the user, and according to the qr scanned, a different fragment is loaded in the activity
I am using ZXing mobile scanner to do this
unfortunatelly the scanner returns a reply way before it shuts down and returns to the calling activity
this means that when I call the transaction code to replace the current fragment with the new one, the activity is not yet in the foreground so nothing happens
To solve this I created a ManualResetEvent (I'm using Xamarin, but I will use a Semaphore when I have to convert this to Android Studio) that I set before starting the scan , and then reset in the OnResume part of the activity
this seems to solve the problem, but it feels like there is a much better solution
Is there something I am missing?
thanks in advance for any help you can provide
Edit: the code I am currently using
public class MyActivity : Activity {
ManualResetEvent _has_resumed = new ManualResetEvent(false);
.....
protected override void OnResume() {
base.OnResume();
_has_resumed.Set();
}
......
void scan_qr(Action<string> finished_callback) {
#region initialize the scanner
MobileBarcodeScanner scanner = new MobileBarcodeScanner();
MobileBarcodeScanningOptions options = new MobileBarcodeScanningOptions();
options.UseNativeScanning = true; //use native scan
options.AutoRotate = false;//do not rotate the screen
options.PossibleFormats = new List<BarcodeFormat> { BarcodeFormat.QR_CODE }; // only allow qr_codes;
#endregion
#region perform the actual scan, when it finishes return to the main thread and execute the callback
_has_resumed.Reset();
scanner.Scan(this, options) //do scan
.ContinueWith(result => {
_has_resumed.WaitOne();
return result.Result;
})//wait until the activity has resumed
.ContinueWith((task_result) => { //then return the result
Result result = task_result.Result;
if (result == null) {
show_toast( Resource.String.questions_select_error_no_qr_scanned );
} else {
finished_callback(result.Text);
}
}, System.Threading.Tasks.TaskScheduler.FromCurrentSynchronizationContext());
#endregion
}
}
I'm using Xcode 7 and Swift 2 but my question isn't necessarily code specific, I'll gladly take help of any variety.
In my app I have a list of favorites. Due to API TOS I can't store any data, so I just keep a stub I can use to lookup when the user opens the app. I also have to look up each favorite one by one as there is no batch method. Right now I have something like this:
self.api.loadFavorite(id, completion: { (event, errorMessage) -> Void in
if errorMessage == "" {
if let rc = self.refreshControl {
dispatch_async(dispatch_get_main_queue()) { () -> Void in
rc.endRefreshing()
}
}
dispatch_async(dispatch_get_main_queue()) { () -> Void in
self.viewData.append(event)
self.viewData.sortInPlace({ $0.eventDate.compare($1.eventDate) == NSComparisonResult.OrderedDescending })
self.tableView.reloadData()
}
} else {
// some more error handling here
}
})
in api.loadFavorite I'm making a typical urlSession.dataTaskWithURL which is itself asynchronous.
You can see what happens here is that the results are loaded in one by one and after each one the view refreshes. This does work but its not optimal, for long lists you get a noticeable "flickering" as the view sorts and refreshes.
I want to be able to get all the results then just refresh once. I tried putting a dispatch group around the api.loadFavorites but the async calls in dataTaskWith URL don't seem to be bound by that group. I also tried putting the dispatch group around just the dataTaskWithURL but didn't have any better luck. The dispatch_group_notify always fires before all the data tasks are done.
Am I going at this all wrong? (probably) I considered switching to synchronous calls in the background thread since the api only allows one connection per client anyway but that just feels like the wrong approach.
I'd love to know how to get async calls that make other async calls grouped up so that I can get a single notification to update my UI.
For the record I've read about every dispatch group thread I could find here and I haven't been able to make any of them work. Most examples on the web are very simple, a series of print's in a dispatch group with a sleep to prove the case.
Thanks in advance.
If you want to invoke your method loadFavorite asynchronously in a loop for all favorite ids - which executes them in parallel - you can achieve this with a new method as shown below:
func loadFavorites(ids:[Int], completion: ([Event], ErrorType?) -> ()) {
var count = ids.count
var events = [Event]()
if count == 0 {
dispatch_async(dispatch_get_global_queue(0, 0)) {
completion(events, nil)
}
return
}
let sync_queue = dispatch_queue_create("sync_queue", dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, 0))
for i in ids {
self.api.loadFavorite(i) { (event, message) in
dispatch_async(sync_queue) {
if message == "" {
events.append(event)
if --count == 0 {
dispatch_async(dispatch_get_global_queue(0, 0)) {
completion(events, nil)
}
}
}
else {
// handle error
}
}
}
}
}
Note:
- Use a sync queue in order to synchronise access to shared array
events and the counter!
- Use a global dispatch queue where you invoke the completion handler!
Then call it like below:
self.loadFavorites(favourites) { (events, error) in
if (error == nil) {
events.sortInPlace({ $0.eventDate.compare($1.eventDate) == NSComparisonResult.OrderedDescending })
dispatch_async(dispatch_get_main_queue()) { () -> Void in
self.viewData = events
self.tableView.reloadData()
}
}
if let rc = self.refreshControl {
dispatch_async(dispatch_get_main_queue()) { () -> Void in
rc.endRefreshing()
}
}
Note also, that you need a different approach when you want to ensure that your calls to loadFavorite should be sequential.
If you need to support cancellation (well, who does not require this?), you might try to cancel the NSURLSession's tasks. However, in this case I would recommend to utilise a third party library which already supports cancellation of network tasks.
Alternatively, and in order to greatly simplify your asynchronous problems like those, build your network task and any other asynchronous task around a general utility class, frequently called Future or Promise. A future represents an eventual result, and is quite light wight. They are also "composable", that is you can define "continuations" which get invoked when the future completes, which in turn returns yet another future where you can add more continuations, and so force. See wiki Futures and Promises.
There are a couple of implementations in Swift and Objective-C. Ideally, these should also support cancellation. Unfortunately, I don't know any Swift library implementing Futures or Promises which support cancellation at this time - except my own library, which is not yet Open Source.
Another library which helps to solve common and also very complex asynchronous patterns is ReactiveCocoa, though it has a very steep learning curve and adds quite a lot of code to your project.
This is what finally worked for me. Easy once I figured it out. My problem was trying to take ObjC examples and rework them for swift.
func migrateFavorites(completion:(error: Bool) -> Void) {
let migrationGroup = dispatch_group_create()
let queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
// A lot of other code in there, fetching some core data etc
dispatch_group_enter(migrationGroup)
self.api.loadFavorite(id, completion: { (event, errorMessage) -> Void in
if errorMessage == "" {
if let rc = self.refreshControl {
dispatch_async(dispatch_get_main_queue()) { () -> Void in
rc.endRefreshing()
}
}
dispatch_async(dispatch_get_main_queue()) { () -> Void in
self.viewData.append(event)
self.viewData.sortInPlace({ $0.eventDate.compare($1.eventDate) == NSComparisonResult.OrderedDescending })
self.tableView.reloadData()
}
} else {
// some more error handling here
}
dispatch_group_leave(migrationGroup)
})
dispatch_group_notify(migrationGroup, queue) { () -> Void in
NSLog("Migration Queue Complete")
dispatch_async(dispatch_get_main_queue()) { () -> Void in
completion(error: migrationError)
}
}
}
The key was:
ENTER the group just before the async call
LEAVE the group as the last line in the completion handler
As I mentioned all this is wrapped up in a function so I put the function's completion handler inside the dispatch_group_notify. So I call this function and the completion handler only gets invoked when all the async tasks are complete. Back on my main thread I check for the error and refresh the ui.
Hopefully this helps someone with the same problem.
I want to close my app if network not available.
I check network in App.cs:
private void Application_Launching(object sender, LaunchingEventArgs e)
{
if (!NetworkInterface.GetIsNetworkAvailable())
{
//close my app
}
else
{
//continue to work
}
}
Is there a better way to do it?
Thanks in advance.
just add reference to Microsoft.Xna.Framework.Game i'm sure you can achieve exit with this code and it will be ok. if you wanna show message box you have to do it in main page
what i would do:
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (!NetworkInterface.GetIsNetworkAvailable())
{
MessageBoxResult m = MessageBox.Show(Sorry, no internet connection is available.do you want to exit the application , "Oops...", MessageBoxButton.OKCancel);
if (m == MessageBoxResult.OK)
{
var g = new Microsoft.Xna.Framework.Game();
g.Exit();
}
}
}
you should provide a "gentle" way for closing
5.1.2 - App closure
The app must handle exceptions raised by the any of the managed or native System API
and not close unexpectedly. During the certification process, the app is monitored
for unexpected closure. An app that closes unexpectedly fails certification. The app
must continue to run and remain responsive to user input after the exception is
handled.
for more information visit this link
Application.Current.Terminate();
For internet checking i wrote the below lines of code.
bool isAvailable = NetworkInterface.GetIsNetworkAvailable();
if (isAvailable == true)
{
}
the above line always returning true if net is not available also.please tell me how to check the internet connection?
Check NetworkInterfaceType. If Internet is available then It
should be other than None
return (Microsoft.Phone.Net.NetworkInformation.NetworkInterface.NetworkInterfaceType
!= Microsoft.Phone.Net.NetworkInformation.NetworkInterfaceType.None);
Reference Answer By vjsrinath: https://stackoverflow.com/questions/8341169/how-to-check-internetconnection-in-wp7
Hope this helps.
You can also try,
bool isAvailable = Microsoft.Phone.Net.NetworkInformation.DeviceNetworkInformation.IsNetworkAvailable;
Always check this in a thread, it takes some time
internal static bool IsNetworkAvailable()
{
bool _bhasNetworkConnection = false;
try
{
_bhasNetworkConnection = (NetworkInterface.NetworkInterfaceType != NetworkInterfaceType.None);
}
catch
{
_bhasNetworkConnection = false;
}
return _bhasNetworkConnection;
}
Checking NetworkInterface.NetworkInterfaceType in the UI thread is "dangerous" as it is a blocking call! It is possible that this call takes up to 20 seconds...
Use the following method to have a non-blocking call:
public static void IsConnected(Action<bool> completed)
{
ThreadPool.QueueUserWorkItem(o =>
{
var type = NetworkInterface.NetworkInterfaceType;
completed(type != NetworkInterfaceType.None);
});
}
See https://xp-dev.com/svn/mytoolkit/MyToolkit.Wp8/Networking/NetworkState.cs (From my project page)
If you would like to change the UI in the completed action you have to run the logic in the UI thread. E.g.:
NetworkState.IsConnected(connected => {
if (connected)
{
Deployment.Current.Dispatcher.BeginInvoke(delegate {
// TODO add your UI logic
});
}
});
If you need a lot of connection checks, check out the NetworkStateTracker, which is my project:
https://xp-dev.com/svn/mytoolkit/MyToolkit.Wp8/Networking/NetworkStateTracker.cs