I'm trying to display James Montemagno's Media Picker immediately when a user navigates to one of my tabbed pages. I found a function called OnAppearing() that I tried overriding to create this result. Although it technically shows the camera immediately when I switch tabs, after I close out of the media picker I get an error saying "only one operation can be active at a time".
Here is how I'm trying to implement this feature:
protected override async void OnAppearing()
{
TakePhotoButton_Clicked();
}
async void TakePhotoButton_Clicked()
{
//Allows users to take pictures in the app
if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
{
DisplayAlert("No Camera", "Camera is not available.", "OK");
return;
}
var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions
{
//Sets the properties of the photo file
SaveToAlbum = true,
PhotoSize = PhotoSize.MaxWidthHeight,
DefaultCamera = CameraDevice.Rear
});
if (file == null)
return;
}
I'm pretty new to all of this and I feel as if I'm making a technical error. I read this post https://damian.fyi/2016/07/06/only-one-operation-can-be-active-at-at-time/ about someone getting the same error. They claimed, "I finally realized that after taking the photo it was re-displaying the form, causing the appearing event to be fired again, and thus causing a new photo to be taken while the old one was being taken. Hence the crash."
However, I'm not catching how my code is causing this. Any guidance would be appreciated.
use a bool variable to check if you have already taken a picture
bool first = true;
protected override async void OnAppearing()
{
if (first) TakePhotoButton_Clicked();
}
async void TakePhotoButton_Clicked()
{
first = false;
...
}
Related
We are trying to use the plugin "Xam.Plugin.Geolocator" in our Xamarin Forms project. The project is currently IOS only.
Our app returns a list of business based on the device users current location. We hit an API to return our JSON formatted list data and the API is functioning correctly.
We would like the list to update whenever the user pulls down, changes tab and when the page initially loads but currently this is only working once or twice in around 100 attempts. I've not found a pattern yet to why it's failing, or indeed when it works.
We set App Properties when the page loads, the tab is selected and the user refreshes like this -
public async void GetLocation()
{
try
{
locator = CrossGeolocator.Current;
if (locator.IsGeolocationAvailable && locator.IsGeolocationEnabled)
{
var position = await locator.GetPositionAsync();
App.Current.Properties["Longitude"] = position.Longitude.ToString();
App.Current.Properties["Latitude"] = position.Latitude.ToString();
}
else
{
await DisplayAlert("Location Error", "Unable to retrieve location at this time", "Cancel");
}
}catch(Exception e)
{
await DisplayAlert("Location Error", "Unable to retrieve location at this time","Cancel");
}
}
We call the above method in the three areas
1) when the page is loaded
public NearbyPage()
{
InitializeComponent();
GetLocation();
SetNearbyBusinesses();
NearbyBusinesses = new List<NearbyBusiness>();
SetViewData();
SetViewVisibility();
}
2) when the tab is clicked
protected override void OnAppearing()
{
base.OnAppearing();
GetLocation();
SetNearbyBusinesses();
NearbyLocationsView.ItemsSource = NearbyBusinesses;
NoLocationsView.ItemsSource = UserMessages;
SetViewVisibility();
}
3) when the user pulls down to refresh
public void RefreshData()
{
if (!CrossConnectivity.Current.IsConnected)
{
NoInternetMessage.IsVisible = true;
return;
}
GetLocation();
NoInternetMessage.IsVisible = false;
SetNearbyBusinesses();
NearbyLocationsView.ItemsSource = NearbyBusinesses;
NoLocationsView.ItemsSource = UserMessages;
SetViewVisibility();
_analyticsService.RecordEvent("Refresh Event: Refresh nearby businesses", AnalyticsEventCategory.UserAction);
}
Can anyone shed some light on what we're doing wrong or have experience with this plugin that can help us resolve this issue?
Thank you
EDIT
By "work", i mean that we'd like it to hit our API with the users current location data and return new results from the API every time the user pulls down to refresh, the page is loaded initially or when they press on a specific tab. Currently it works occasionally, very occasionally.
We can't debug with a phone connected to a macbook, as since we installed the geolocator plugin the app always crashes when connected. The app seems to work ok when deployed to a device, apart from the location stuff. We're currently deploying to test devices via Microsofts Mobile Centre.
Ok, so with the debugger always crashing and being unable to see any stack trace etc we took a few shots in the dark.
We've managed to get this working by adding async to our method signatures down through our code stack. This has resolved the issue and the geo location and refresh is working perfectly.
For example when we changed the above method 3. to refresh the data, it worked perfectly.
public async Task RefreshData()
{
if (!CrossConnectivity.Current.IsConnected)
{
NoInternetMessage.IsVisible = true;
return;
}
GetLocation();
NoInternetMessage.IsVisible = false;
SetNearbyBusinesses();
NearbyLocationsView.ItemsSource = NearbyBusinesses;
NoLocationsView.ItemsSource = UserMessages;
SetViewVisibility();
_analyticsService.RecordEvent("Refresh Event: Refresh nearby businesses", AnalyticsEventCategory.UserAction);
}
We refactored more of that code but adding async was what got it working.
I hope this helps someone else save some time.
We have an image with a gesture recognizer, which calls the CrossShare.Current.Share method. On Android this works fine but on iOS it does not. No error is thrown and there doesn't seem to be any issues, but the share sheet does not appear and from the user's point of view nothing happens when you click the button.
Have I missed some permissions or something somewhere?
This is my method;
async void On_Share(object sender, EventArgs e)
{
if (CrossConnectivity.Current.IsConnected)
{
var message = "Check out this";
var title = "Share this";
await CrossShare.Current.Share(new ShareMessage { Text = message, Title = title}, new ShareOptions { ExcludedUIActivityTypes = new[] { ShareUIActivityType.PostToFacebook } });
}
else
{
NoInternetLabel.IsVisible = true;
}
}
It doesn't throw any errors and I can step through the method fine - it definitely hits the Share line. This problem is only showing on iOS, Android has no issues.
EDIT: Seems to be working fine (we've tried doing it natively as well - without plugin) but now I'm getting Warning: Attempt to present on whose view is not in the window hierarchy!
I recently received a support ticket that some of our web app's functionality is crashing safari on the iPad. This functionality had no problems prior to the latest iOS 7.0.6 update. We have a few GWT ValueListBoxes that change the DOM when their values are changed. Prior to making the changes, we present the user with a Window.confirm() message to inform them of the effects the changes will have and ask whether or not they would still like to proceed. Since the update, the confirm choices do nothing and Safari crashes. This is only happening on the iPad. The functionality works fine on the desktop browsers (IE, Chrome, Firefox, Safari and the Chrome mobile emulator), but crashes safari on the iPad. Is anyone else having this issue?
Here's a screenshot of the crash:
And here's a sample of the code:
this._view.isPrimaryFoodGen().addValueChangeHandler(new ValueChangeHandler<Boolean>()
{
#Override
public void onValueChange(final ValueChangeEvent<Boolean> event)
{
#SuppressWarnings("unchecked")
ValueListBoxWithOldValue<Boolean> vlb = (ValueListBoxWithOldValue<Boolean>)event.getSource();
if (confirmQuestionChange() ){
changeGroupAndQuestions(CONSTANTS.PRIMARY_FOOD, event.getValue());
}
else {
vlb.setValue(vlb.getOldValue());
}
}
});
public boolean confirmQuestionChange()
{
if (!this._view.isImageCriteriaQuestionsVisible())
{ //questions aren't currently visible
return true;
}
boolean confirmed = Window.confirm("Changing this response will delete image data already collected. Do you wish to proceed?");
return confirmed;
}
Any help on a solution for preventing the crash on the iPad would be greatly appreciated. I have tried focusing on another element prior to calling Window.confirm() in hopes that the overlay and the ValueListBox choices would be removed to stop any JS conflicts, but it hasn't worked.
Am I at the mercy of Apple until the next update fixes this?
Or is there a viable solution?
OK, so it turns out that since I couldn't find a fix to continue using Window.confirm(), I had to implement a solution by changing the onValueChange() and confirmQuestionChange() methods to use a manually created DialogBox instead of Window.confirm(). It isn't the optimal solution, but Safari does not crash on the iPad anymore and users can get their work done. Here are the code changes:
this._view.isPrimaryFoodGen().addValueChangeHandler(new ValueChangeHandler<Boolean>()
{
#Override
public void onValueChange(final ValueChangeEvent<Boolean> event)
{
confirmQuestionChange(CONSTANTS.PRIMARY_FOOD, event);
}
});
public void confirmQuestionChange(final String question, ValueChangeEvent<Boolean> event)
{
final ValueListBoxWithOldValue<Boolean> vlb = (ValueListBoxWithOldValue<Boolean>)event.getSource();
if (!this._view.isImageCriteriaQuestionsVisible()) //questions aren't currently visible, can change them no problem
{
changeGroupAndQuestions(question, vlb.getValue());
}
else{
//the following fix was put in place for issues with Safari on the iPad OPS-76
final DialogBox dialogBox = new DialogBox();
dialogBox.setHTML("<center>Changing this response will delete<br />image data already collected.<br />Do you wish to proceed?</center>");
dialogBox.setAnimationEnabled(true);
Button yesButton = new Button("YES");
Button noButton = new Button("NO");
HorizontalPanel dialogHPanel = new HorizontalPanel();
dialogHPanel.setWidth("100%");
dialogHPanel.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_CENTER);
dialogHPanel.add(noButton);
dialogHPanel.add(yesButton);
noButton.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
vlb.setValue(vlb.getOldValue());
dialogBox.hide();
}
});
yesButton.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
changeGroupAndQuestions(question, vlb.getValue());
dialogBox.hide();
}
});
// Set the contents of the Widget
dialogBox.setWidget(dialogHPanel);
dialogBox.setPopupPosition(180, 425);
dialogBox.show();
}
}
Here's a screenshot:
As you can see, the ValueListBox options close before the DialogBox appears and the screen no longer locks.
Inside my application, I'm displaying a website using BrowserField. And when each link inside the site is selected, I need to show loading screen so that the user won't feel blank.
I was able to add the loading screen inside this method
public void documentCreated(BrowserField browserField,
ScriptEngine scriptEngine, Document document)
But the problem is only when connection is established, this method will be called and so there will be a delay before the loading screen is displayed.
So I tried implementing the ProtocolController and adding the loading screen inside this method
public void handleNavigationRequest(BrowserFieldRequest request)
But still, the loading screen is displayed after a small delay (same as when it was under documentCreated method)
This is my code snippet
public void handleNavigationRequest(BrowserFieldRequest request)
throws Exception {
if (!NetworkUtil.isNetworkAvailable()) {
Dialog.inform(Strings.NETWORK_ERROR);
} else {
UiApplication.getUiApplication().invokeAndWait(new Runnable() {
public void run() {
BaseScreen.showLoadingProgress(Strings.LOADING);
}
});
InputConnection ic = handleResourceRequest(request);
browserField.displayContent(ic, request.getURL());
}
}
I tried this outside the thread as well....Still the same is happening. For testing, I added a dialog inside this method and it was coming on the same time I'm clicking any link inside the site. Only this loading screen takes time to load.
Is there any way to make this happen ?
Also, the browser field is taking a bit longer to load the website compared to the native browser.
Am I missing something here ! Please help
I have tried the documentUnloading method as you suggested. But it is not getting triggered. Given below is the code snippet, could you please check what I'm doing wrong here...!!
protected void onUiEngineAttached(boolean attached) {
if (attached) {
BaseScreen.showLoadingProgress(Strings.LOADING);
}
super.onUiEngineAttached(attached);
}
try {
listener = new BrowserFieldListener() {
// Page starts loading...
public void documentCreated(BrowserField browserField,
ScriptEngine scriptEngine, Document document)
{
// show the loading screen
//showLoadingProgress(Strings.LOADING);
}
public void documentError(BrowserField browserField,
Document document) {
hideLoadingProgress();
Dialog.inform(Strings.NETWORK_ERROR);
}
public void documentAborted(BrowserField browserField,
Document document) {
hideLoadingProgress();
Dialog.inform(Strings.NETWORK_ERROR);
}
public void documentUnloading(BrowserField browserField,
Document document) {
BaseScreen.showLoadingProgress(Strings.LOADING);
}
// Page loaded
public void documentLoaded(BrowserField browserField,
Document document) {
// the document has loaded, hide loading popup ...
BaseScreen.hideLoadingProgress();
}
};
} catch (Exception ex) {
Dialog.inform(Strings.NETWORK_ERROR);
}
browserField.addListener(listener);
// add the browser field to a ui manager or screen
add(browserField);
// request the content
browserField.requestContent(URL);
I do this using the BrowserFieldListener (see BrowserFieldListener.html). It is slightly counter intuitive, but I display the loading screen in documentUnloading(), and remove it in documentLoaded(). When I first populate the BrowserField I also push the loading screen, and when the screen with the BrowserField is closed, I make sure the loading screen is popped too. So not a pretty solution, but it works for me.
And yes, in general, the BrowserField is slower than the Browser. I have not found a way round it. However one significant aspect is caching. Look for information on creating your own cache for the BrowserField - there is Thread on here and a KB article on the BB Web site. Sorry can't find them atm, will update when I do.
Update
As found by the OP, the caching article is here.
Further Update
Just to clarify two things:
You must associate the Listener with the BrowserField, using the addListener method.
Assuming you do the usual requestContent() for the initial load of your BrowserField, you will need to push the loading screen yourself because the first method in listener that will be invoked (assuming it has worked of course), will be documentLoaded().
A sample demonstrating how to use the Listener is included here:
listener sample
Hello I am trying to create a please wait screen.This screen will appear when my program requests data from web service and will hide when the process is finished.Also I want to add a time out if request process lasts longer than 90 seconds.
can anyone help or show me a guiding example about that matter.
public static void showBusyDialog() {
try
{
if (busyDialog == null) {
busyDialog = new Dialog("Please Wait", null, null, 0, Bitmap.getPredefinedBitmap(Bitmap.HOURGLASS));
busyDialog.setEscapeEnabled(false);
}
synchronized (Application.getEventLock()) {
busyDialog.show();
}
}
catch(Exception e)
{
}
}
and my hiding code is
public static void hideBusyDialog() {
try
{
if (busyDialog == null) {
// busyDialog = new Dialog("Please wait...", null, null, 0, Bitmap.getPredefinedBitmap(Bitmap.HOURGLASS));
busyDialog.setEscapeEnabled(false);
}
synchronized (Application.getEventLock()) {
busyDialog.close();
}
}catch(Exception e)
{
}
}
Many BlackBerry® smartphone applications need to wait for some network activity (or another blocking operation, which must process in the background), while still holding up the User Interface (UI) and displaying a progress indicator.
You can follow through this links
Links
Sample "Please Wait" screen - part 1
Sample "Please Wait" screen - part 2
Sample "Please Wait" screen - part 4
you can download simple examples for Please wait screen
PleaseWait1.zip 25 KB
PleaseWait2.zip 25 KB
PleaseWait3.zip 25 KB
Note :in case above Links not working then just follow following contents
There seem to be two common issues when programming this:
1) As applications are not allowed to block the Event Thread, how do they get the UI processing to wait?
2)How can the background Thread update the UI?
This article is intended to help with these issues and provide a fully functioning "Please Wait" sample Popup Screen. However, as there is quite a lot to explain, in this first article, we will just create a popup screen that will show itself, hold up the UI, and then remove itself once the background processing has finished. This does not give us any progress indication, nor does it let the user cancel the wait. These points will be covered in a followup article. But the code supplied with this article will be useful anyway, especially when the duration of the background processing is not known and the user may not cancel the processing.
First, we start with the background processing we need to run. While this could be anything, typically this will be network processing, like the following:
httpConn = (HttpConnection)Connector.open(_url + ";deviceside=true");
responseCode = httpConn.getResponseCode();
responseMessage = "Response Code: " + Integer.toString(responseCode);
To initiate this network processing, we have a MainScreen that contains
1) A BasicEditField that allows the entry of a URL
2) A RichTextField that should display the response code (or error message). Here are the important parts of that screen:
BasicEditField _requestedURLField = new BasicEditField("http://", "www.blackberry.com", 255, BasicEditField.FILTER_URL);
RichTextField _responseField = new RichTextField("<response code>", RichTextField.NON_FOCUSABLE);
We would like the MainScreen to be updated with the result. As noted above, background processing can't directly update the UI; UI updating code must be on the Event Thread. There are several ways to get a background process onto the Event Thread, see the related article for more. In this case, we will use the following code:
// Make things final so we can use them in the inner class
final String textString = responseMessage;
final RichTextField rtf = _resultField;
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
rtf.setText(textString);
}
});
Now we must define the PleaseWaitPopupScreen to be displayed while waiting.
To give the user something to look at while they are waiting, we have an animated .gif, which is diplayed using the code in the AnimatedGIFField (see related link). And, so the user knows what they are waiting for, the PleaseWaitPopupScreen is supplied with a String to display, as the following constructor shows:
private PleaseWaitPopupScreen(String text) {
super(new VerticalFieldManager(VerticalFieldManager.VERTICAL_SCROLL | VerticalFieldManager.VERTICAL_SCROLLBAR));
GIFEncodedImage ourAnimation = (GIFEncodedImage) GIFEncodedImage.getEncodedImageResource("cycle.agif");
_ourAnimation = new AnimatedGIFField(ourAnimation, Field.FIELD_HCENTER);
this.add(_ourAnimation);
_ourLabelField = new LabelField(text, Field.FIELD_HCENTER);
this.add(_ourLabelField);
}
PleaseWaitPopupScreen provides a method – showScreenAndWait(..) – which will create and display the Popup screen, run the Background processing, and then dismiss the Popup screen.
The final piece of the puzzle involves supplying showScreenAndWait(..) with the processing to run.
Java has the concept of a Runnable, which is an Object that contains a public void run() method that should be executed. In this case, we have the Connection code and screen update code, given above, that should be executed. So, this code is packaged up into a new Runnable Object, which is supplied to showScreenAndWait(..). And here is that method. Note how a new Thread is created and run.
public static void showScreenAndWait(final Runnable runThis, String text) {
final PleaseWaitPopupScreen thisScreen = new PleaseWaitPopupScreen(text);
Thread threadToRun = new Thread() {
public void run() {
// First, display this screen
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
UiApplication.getUiApplication().pushScreen(thisScreen);
}
});
// Now run the code that must be executed in the Background
try {
runThis.run();
} catch (Throwable t) {
t.printStackTrace();
throw new RuntimeException("Exception detected while waiting: " + t.toString());
}
// Now dismiss this screen
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
UiApplication.getUiApplication().popScreen(thisScreen);
}
});
}
};
threadToRun.start();
}
And this is the key part of the PleaseWaitPopupScreen. Note how this code will create and display a Popup screen to the user, including an animated icon, while it is running the background processing. Input from the user is blocked by the Popup screen until the processing completes. The originating screen is updated as a result of the background processing.
Download the associated .zip archive, which contains the source included in this article.
In the next article, we will extend this code to be able to handle:
a) Status updates from the Background Thread
b) "Time to go" indication
c) Being cancelled by the BlackBerry smartphone user
Just put timer after you show busy dialog.
showBusyDialog();
Timer timer = new Timer();
TimerTask task = new TimerTask() {
public void run() {
hideBusyDialog();
}
};
timer.schedule(task, 9000);
this is for time out. If the process finishes less than 90 seconds you should call
timer.cancel();
timer = null;
task = null;