I have a problem that the ViewWillAppear method for a UIView does not fire when the application returns from the background. This is a problem, as my main application screen is showing values that are retrieved from the user settings, and if the user has changed these while the application was in the background I need to have the screen refreshed. I have read that one should register for the UIApplicationWillEnterForegroundNotification using NSNotificationCenter.
How do you do this in MonoTouch? Or does anyone know an alternate way of ensuring that the screen is always kept up to date, even when returning from the background?
You could try something along the lines of:
//Register for the notification somewhere in the app
NSNotificationCenter.DefaultCenter.AddObserver(UIApplication.WillEnterForegroundNotification, EnteredForeground);
//snip
void EnteredForeground (NSNotification notification)
{
// do your stuff here
}
Bear in mind you would need to do this for every view controller you'd like to update when enterting from the background!
Related
I am using a plain vanilla UIImagePickerController with my own UIImagePickerControllerDelegate. Doing so the flash mode set by the user gets always lost as I am disposing the whole controller after each capture, so opening the camera again always sets the flash mode "back" to auto (the default value).
I could refactor my camera utility and let it live as long as the app is alive, but the better way seems to be to just get notified when the users changes the flash mode, store that mode and set it before the camera is shown again.
Setting the mode is not the problem, but I don't get notified when it is changed by the user, nor does the property of the UIImagePickerController argument within the FinishedPickingMedia method of the UIImagePickerControllerDelegate contain the latest value set by the user, it's also always "auto".
private class CameraDelegate : UIImagePickerControllerDelegate
{
public override void FinishedPickingMedia(UIImagePickerController picker, NSDictionary info)
{
// Is always UIImagePickerControllerCameraFlashMode.Auto
var foo = picker.CameraFlashMode;
}
}
Any idea how to get that information?
I think you could try using Key-Value Observing to get notified when your property is changed.
You can find a tutorial on how to get KVO working with monotouch here.
And there's always the official Apple Documentation on KVO
I have an activity with a UI with many elements (Radio, EditText, etc.). When I change the text in an EditText I want that UI back at its starting state.
I tried to kill and restart the activity but with poor results. Any ideas?
Thanks
I would try calling setContentView again with a new view or with the xml file you used for rendering your activity in the first place
Once you get the value you need from your editText, you can reset it using
editText.setText("");
You can similarly programatically control other parts of your UI too.
Why not put all of the reset stuff in one function and simply call it when you need to:
public void resetUI()
{
//reset UI programatically
}
You could add a listener to the EditText view and when the text is what you want it to be you can just programmatically empty any TextView's, EditText's, reset any radiobuttons or radio groups to their default values. No need to restart the activity. Just write a helper method that resets your view "manually". Using setContentView() could also work although I haven't tried it and you might have to setup your complete view again with listeners and such.
How do I prevent my GUI from redraw when it comes back from lock screen after receiving a UILocalNotification? In didReceiveLocalNotification I present a modal view, but the old state of my view controllers is shown for a moment before that. How do I prevent this?
Also the order of events I get when I come back on local notification from background is as following:
1. UIApplicationWillEnterForegroundNotification
2. UIApplicationDidBecomeActiveNotification
3. didReceiveLocalNotification
When I come from lock screen:
1. didReceiveLocalNotification
2. UIApplicationDidBecomeActiveNotification
Why is this difference and whether there is something else I'm missing?
Thanks
Here's how it was solved. May be it's not the way, but it worked for me. Since my application is voip/audio, it doesn't come to didFinishLaunchingWithOptions... I found out, that iOS uses a cached image from a previous state for animation when it resumes from background or from sleep mode. So the solution is basically to exchange this cached image with my default.png image. I do it in applicationWillResignActive delegate. There I add a modal view with a Default.png picture and dismiss it in applicationDidBecomeActive. This is really in short. Hopefully it will help somebody else with the same problem.
You can provide a custom image that is displayed when launching/resuming from a local notification. Simply set the alertLaunchImage property on your local notification to the name of the correct image.
From the Docs:
The string is a filename of an image file in the application bundle. This image is a launching image specified for a given notification; when the user taps the action button (for example, “View”) or moves the action slider, the image is used in place of the default launching image. If the value of this property is nil (the default), the system either uses the previous snapshot, uses the image identified by the UILaunchImageFile key in the application’s Info.plist file, or falls back to Default.png.
alertLaunchImage
I have a UITabBarController based iphone application. I added a new tab called Log Out via the Interface Builder.
However I don't need its corresponding view. I want the Log Out tab to redirect to the Login view as soon as it is clicked (of course some session clearing code is executed as well).
The nearest I've got so far is to redirect from the Log Out View using the viewWillAppear. The result is the same but it doesnt look great because it goes into a blank screen for a couple of seconds and then it redirect to the login screen.
Any help would be appreciated.
You can use UITabbarDelegate methods to accomplish this
Use following delegate method to check for logout buttons index and if found then perform your tasks
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController{
if (tabBarController.selectedIndex == 4)
{
// perform logout tasks
}
}
I've made my app play music in the background, I also successfully made it become the media player by calling BeginReceivingRemoteControlEvents. however, the RemoteControlReceived method never gets called. the same logic in Objective C is working fine. Any samples or guidelines appreciated.
You need to ensure it is placed on the First responder view, and if not, the event needs to be passed up along the chain of responders until it reaches your remote events. Try to imagine remote control events the same as keypresses on the keyboard. For example, If the app is focused on a button, and you press some keyboard keys, nothing will happen, as a button isn't listening for key presses.
A similar situation is occurring in your code. Try to create a basic, single viewed project with the BeginReceivingRemoteControlEvents and the method override to receive the event (cant remember what it is, RemoteEventReceived() or something similar.) This should get fired when you press a remote button.
(sorry I cant give sample code, not in front of mac at the minute)
You might want to try using a later mechanism to listen for remote control events. For example, if you want to listen to the headset button:
MPRemoteCommandCenter *commandCenter = [MPRemoteCommandCenter sharedCommandCenter];
[commandCenter.togglePlayPauseCommand addTargetWithHandler:^MPRemoteCommandHandlerStatus(MPRemoteCommandEvent * _Nonnull event) {
NSLog(#"toggle button pressed");
return MPRemoteCommandHandlerStatusSuccess;
}];
or, if you prefer to use a method instead of a block:
[commandCenter.togglePlayPauseCommand addTarget:self action:#selector(toggleButtonAction)];
To stop:
[commandCenter.togglePlayPauseCommand removeTarget:self];
or:
[commandCenter.togglePlayPauseCommand removeTarget:self action:#selector(toggleButtonAction)];
You'll need to add this to the includes area of your file:
#import MediaPlayer;
This works in the background, ONLY if you are an audio app playing in the background (i.e. you have to set that background mode in your app capabilities).