I developed a pretty simple game that uses a custom view for drawing to the screen. On my phone (Android 2.2), I can press the home button on the device and do other tasks. When returning to the game, it is restored to the exact state that it was before. The thing is, I didn't have to override any methods or really do anything for this behavior to occur. However, on Honeycomb, it resets everything like I would expect.
It's very puzzling... I was wondering if there was a way to make Honeycomb behave like 2.2 in this regard. I'm not too familiar with saving view states, but since I have a LOT of variables (hundreds, depending on how custom objects are saved), I imagine it being unpleasant to manually do.
I was able to solve it. Kind of.
Basically, the problem was caused by the way that Android handles the screen being fixed to portrait mode in my activity. In 2.2, Android would open the activity in portrait mode and not restart the activity. However, in Android 3.0, it opens the activity, and THEN rotates the screen, causing it to restart the activity (since that happens when a rotate happens).
To fix this, I added the following to my activity in the manifest:
android:configChanges="keyboardHidden|orientation"
This tells Android that you will handle config changes yourself. In my case, I do nothing, since my application is locked in portrait mode.
The reason the state isn't cleared when the application is paused is because onCreate() doesn't get called. I am aware that Android can kill the application though, which would call onCreate(), so I will still have to handle that situation by saving the Activity variables and recreating the View with them.
Related
I want to test the state of my app when it's left in the backstack for too long.
When I open like 20 apps one after the other my last used app (which is the app I'm testing) eventually terminates and a savedInstanceState occurs. Is there a way to simulate this behaviour for the app I'm testing without having to open another 20 apps in order to burry my app in backstack?
Yes, there's a simple way to do it. Just enable Do not keep activities under Developer options. Your activity will then be immediately destroyed as soon you leave it and onRestoreInstanceState() will be invoked when you return.
Alternatively, you can force a configuration change (like orientation) and that will recreate your activity too. One issue with this approach is that there's a bug with some JellyBean/KitKat versions where the emulators fail to rotate. (This works fine on a device though.)
The workaround is to install the RotateScreenOrientation.apk which can force the emulator to be in portrait or landscape but this quickly becomes tedious if you have the option to Wipe user data on emulator start enabled.
I'm trying to create an app in Android, using Eclipse ADT and I use a HTC phone. Here's the problem: after running the app on the phone from Eclipse, I add elements to my ListView and everything is fine, BUT when I turn the device in landscape mode the hole app seems like it restart, there's no more records inside. It's like new. Any ideas why and how I can solve this problem? Please don't tell me to deactivate the screen rotate option from phone settings.
This is the way android handles orientation changes. It reloads your whole activity. The normal way to handle this situation is to save the state of your activity in onPause() and then retrieve it back in onCreate().
Here is more information on the android activity lifecycle:
http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle
EDIT:
You should implement onPause() anyway, because it will also be called if the phone rings in the middle of running your activity. In this case, when the user comes back from the call your activity will possibly be reloaded from scratch again and the user will lose their state.
There is a similar question here.
Basically you application is restarted. You can either force your application to portrait or follow the steps here to find out how to handle it properly.
I made answer over here about this sort of thing.
Please don't tell me to deactivate the screen rotate option from phone settings.
I'm not sure if you meant the following, but here's a solution:
Add android:configChanges="orientation|screenSize" to your <activity tag, which is in your AndroidManifest.xml, like so:
<activity
android:name="activity_name"
android:label="#string/app_name"
android:configChanges="orientation|screenSize" />
This will prevent the activity from being destroyed when the orientation is changed, like it usually would. There are other ways to fix this as well. Please leave a comment if this is not your desired solution. I can make up another.
I'm first time developer for these types of devices, and UI in general, so I could be missing something basic and obvious.
Everything seems to work fine in the emulator, but I don't know how to simulate turning it.
So I tried running the app on my pandigital (white model - lowest of the low it seems), and each time I turn the Android, it freezes up. At least the UI freezes up, I believe the debug messages are still printing.
This is a home project, I don't have other devices to try it on.
Sorry for being so vague, it's an issue I have been a bit neglecting, trying to work on more interesting issues first, but it's an issue that is bothering me in the back of my mind.
Anyway, I have an Activity that starts up a thread, and creates a class which responds to various events, it implements: MainInterface and SurfaceHolder.Callback. Is there something else I should be handling? possibly?
Is there some specific call I get when the tablet is turned? I'd like to put a debug message in there.
My guess is that you state in your AndroidManifest.xml that this activity will handle rotation events itself (perhaps because you copied it from some project where the activity did do this), and that this statement is a lie, your activity actually makes no attempt to handle rotation.
If this is the case, a sound way to solve your problem is simply to remove the lying android:configChanges from your manifest.
I'm looking to change the screen orientation based on device type. The case is that our development platform is hooked via HMDI to an LCD (and is fixed), and then tested on an actual handset or tablet. I want the development platform to always appear in landscape, and everything else in portrait.
I wrote a little static method that accepts an Activity object and calls it's setScreenOrientation if the device is a certain type. I place the call to this method in the Activitys onCreate, passing itself as the parameter. Alternately, I placed it in the onStart as well. The issue is that it's leading to unpredictable behavior. I suspect the Activity is being restarted by the call to setRequestedOrientation. The API does state that "it is possible for the Activity to be restarted" by calling this method. Sometimes it will change orientation a few times before settling out, sometime it won't, and it always seems to crash the application.
I guess the question becomes: How do I set the orientation for an Activity that hasn't been started yet without using the Manifest?
Any help is appreciated.
Thanks,
Brian
You can't set the orientation dynamically before you actually run.
If you want your orientation to vary, you should use one of the orientation modes: the default one allowing it to vary based on the device preference and how the user rotates the screen, "nosensor" to use the device's preferred orientation without allowing it to changed based on the user rotating the screen, etc.
While testing on Android 1.6 using a G1 I have noticed that when I slide out the keyboard it kills the activity and recreates it even though I have set my activity to only display in portrait mode.
Same happens when I push the keyboard back in.
I get onSaveInstance, onDestroy called, then onCreate, onResume, OnrestoreInstance...
I understand why this is done when the display is being switched to landscape view but why does this happen when I specifically dont want my activity to switch view, its essentially killing and restarting the activity for no reason.
Is it the same on 2.x devices?
Is there something I'm missing to stop it happening?
Can anyone explain if there is any point to it?
This is the recommended behavior in Android. But if you want to stop this you can specify the following property in your Manifest against your Activity
android:configChanges="keyboardHidden|orientation"