I'm developing a scientific app in Android Studio. It works smoothy.
The set of source code files is not small, but, as I don't have practically user interface, there is only one activity and there is no intent.
All initialization code is inside OnCreate. Most of times, my app preserves all data, when he gets out of the foreground.
However, maybe (I cannot find a pattern of this event) he loses all data and restart (shows a white screen for 2 / 3 seconds), even if the cell phone don't enter in lock screen and there are just 2 apps running.
There are situations that I comute for another app (like WhatsApp) and resumes for my app, and my data was gone. The app restart again.
There is no error message, no logcat. Nothing.
Mostly, when I lock the screen and enter again, all my app data is there.
PS: My orientation is locked.
PS 2: I've read all related question and there is no hint for me. Based in one answer, I've tried to put in onCreate the following code.
if (!isTaskRoot() {
&& getIntent().hasCategory(Intent.CATEGORY_LAUNCHER)
&& getIntent().getAction() != null
&& getIntent().getAction().equals(Intent.ACTION_MAIN)) {
finish();
return;
}
No changes for me.
Update:
I've stumbled in solution. it can be read in my own answer. it's related to undesired back button effect for one-activity-app (read here and here ).
For me, as my application has only one activity, back needs to be like a home button: exit the app but preserve all activity data. My app has a real exit button, where the user shows that really wants to do this.
It's my first app that I developing in mobile world and, for extension, Android world
Some problems seems to me like that it is only possible find the solution if one has a hint about its solution. it's a contradiction. One doesn't know but has to know to solve that don't know!
And, in this situation, it's not the case. No hints. Just question marks.
Before, I had not noticed any pattern. People sometimes act so automatically ... However, suddenly the penny dropped.
I've stumbled in solution. Fortunately!
Not in a million years could I suppose that if someone has an activity and presses Back button, (right button in the bottom), you practically quit the application, even if it remains as a running app for the left button in the bottom (app switcher button)
When I've noticed it, I start to research with another focus. And I've discovered two sources: Disable back button in android and Android - Simulate Home click
So the solution is simply to make the Back button act like the Home button (middle button in the bottom). Return to the home screen without losing application data.
And this is done simply by putting in the onCreate, for my only activity, the following code.
override fun onBackPressed() {
val i = Intent(Intent.ACTION_MAIN)
i.addCategory(Intent.CATEGORY_HOME)
startActivity(i)
}
Related
Before people say this is a duplicate of "check if android is on first run", this question is to check if the activity itself (not the app in whole) is open for the first time.
I have different activities that run Material Tap Target Prompt, so a few pop-ups that explain the buttons and functions.
But I only want it to run for first time users.
Now I tried the following:
if (prefs.getBoolean("firstRun", true)) {
prefs.edit().putBoolean("firstRun",false).apply();
........Do the pop ups
}
But this will set it for the whole app and so when the user gets to the next screen it won't run because the boolean is set to false.
So I am trying to find a way to check if the activity itself is opened for the first time but I can't seem to find anything that would solve this issue.
I thought about using a variable then setting it to 1. But if the users restarts the app, it crashes etc then that var will be reset.
May other option is to create a row in a DB and then check if that is set to 1 or whatever depending on the activity.
But maybe there is an easier way?
Thank you
Why don't you just create preference keys for each Activity. Sample code added below:
if (prefs.getBoolean(MainActivity.class.getCanonicalName(), true)) {
prefs.edit().putBoolean(MainActivity.class.getCanonicalName(),false).apply();
........Do the pop-ups
}
I've spent a few hours looking for this. My test device is a nexus 6, though it has been tried on android 4.4 and 5.0+ as well.
Basically I want to catch a user's click of the onBackPress, but I want to do this outside of the activity. Say I've got an object that is initialized and while its running, It is to handle onBackPress, until the its killed.
I've looked into setting an onKeyListener to the contentView but that does not work at all (I figured as much, but its worth a shot).
Any idea how to do this (again, outside the scope of overriding in the activity)?
I cannot imagine something like that being possible since it would be a rather large security risk if a regular application could just catch user input outside of its scope.
The only hardware button I know of that you can detect being pressed even when your activity is not running in the foreground is the camera button, since pressing that generates an Intent. http://developer.android.com/reference/android/content/Intent.html#ACTION_CAMERA_BUTTON
I'm currently following some video tutorials on Android development, and it's gone fine up until the 8th tutorial, we make a splash screen, and after 2 seconds it's supposed to go to the main application. The problem is, after 2 seconds, the screen goes black and the app crashes.
Logcat Output
I followed the tutorial exactly as he did it, the only difference with mine is that I'm developing for 4.2 instead of 2.2.
I'm also using my Galaxy Note 2 instead of an emulator to test.
I did it all as he did, and pressed play, the app opened on my device and the splash screen was there for 2 seconds (i set it to 2000) and then the spinner (which I added) freezes. The screen goes black, and then it crashes and says "Unfortunately, The Basic Series has stopped."
I've tried both sleep(2000) and Thread.sleep(2000).
Code for the AndroidManifest.xml and the main.java are here
If anyone is curious, this is the video I was following.
avoid splash screens except if u really need them to do some preparation operations..
avoid Thread sleep otherwise you will face ANR crashes (use post runnable with delay instead)
avoid reading this hint: What is your activity class name? Menu, menu, MENU or uNeM?
not so good tutorial IMHO
not honorable mention: if u really want to do it in this (btw not recommended way) check video at 8:48 and try to add catch clause and log exception.
If you need to do some initializations , use AsyncTask , or a thread that upon completion will use Activity.runOnUiThread (so that it won't crash when doing UI operations).
If you need to just show the splash screen and close it after some time , use Handler.postDelayed .
In all possible solutions , don't forget to cancel them upon onPause/onDestroy (depending on what you do/need) , so that if the user has left the app (exited or left it in the background) , it won't open up with the new activity when he resumes it (or worse , show it while it has gone to the background) .
Hi and thanks in advance for your time and attention.
I actually have 2 questions i'm not too sure about building an android app. Pretty basic stuff I believe:
1) My app is fully on Horizontal mode, like AngryBirds for example. When it starts the user figures out he should hold the phone like that, if he isn't already. And that is setup in the manifest for all the activities and works fine. but is there a way to prevent the physical device tilting to call onCreate again? can i override it's method or whatever? the reason i'm asking, is because i have a few ButtonViews that after you click on them, change their picture. i am using onRetainNonConfigurationInstance() to save the array of those ImageButtons, and i even mark the ones changed with the ImageButton setTag() and getTag() methods, so when onCreate is called because of the device tilt it gets the saved array from getLastNonConfigurationInstance() , but i've been trying to make it work for quite some time now and I just can't get it right. After the device tilt (I'm actually using the emulator so it's Ctrl+F11 but i believe it will happen with a device as well) all of the ImageButtons loose their pictures.. Long story short - are there better ways of doing this that you can recommend or is preventing the tilt from doing anything is possible or better?
2) What is the best way to know how many seconds the user has been on a screen? I tried to use two longs that i get via SystemClock.currentThreadTimeMillis() as follows: get the starting time onCreate, and the ending time on the method i call to move to the second intent just before i startActivity. but I think because they are called from different threads, the endingpoint - startingpoint is not correct. What is the way to insure both of the methods of SystemClock.currentThreadTimeMillis() are called from the same thread, the main thread of the activity that i'm stopwatching? Is there a better way to go around this?
Thanks again.
You are doing the right to handle orientation change. Please refer to this link http://developer.android.com/guide/topics/resources/runtime-changes.html . This will help you to get it working.
Good way would be to count the time between onResume and onPause. OnCreate is not called all the time if you are resuming activity.
1) You can try adding the property android:configChanges="orientation" to your activity in the manifest file. It worked for me when my dynamic Action Bar tabs got messed up upon rotation of the screen.
You need specify orientation in android manifest for each of your activities, it will not call onCreate then. android:screenOrientation look at http://developer.android.com/guide/topics/manifest/activity-element.html
User see and interact with your activity starting since onResume and ends on onPause. Other time it does not guarantee that user actually see and can click on something in the activity. System.getCurrentMillis() is good enough.
I have a small Android application with a TabScreen as my main screen. I have a small problem where my application currently loses focus on the last Activity the user was on.
This is the scenario:
User launches application
Application shows login screen
User enters login details and goes to tab screen
User leaves application via home key
User presses application icon to return to app and the login screen displays again
I want the application to return to the last known displayed Activity in this case.
What I do at the minute is launch the login screen as the Main/Launcher Actvitiy, then when correct credentials are entered launch the tab screen activity and finish the Login activity.
Is there a launch mode or something I should be using to achieve this?
EDIT: More info
The Tab screen is launched simply like this:
Intent intentTabActivity = new Intent(getApplicationContext(), TabScreenActivity.class);
startActivity(intentTabActivity);
Leaving the application through the home button.
I intend to persist the login state and bypass the login but on smaller applications I have created the application returns to the last displayed activity automatically and does not return to the initial Launcher screen every time and I was wondering why this is not the same behavior in this application.
Also as per my other question HERE the behavior seems to be different for debug and signed releases.
This has always been tested on real devices.
This is the correct behavior. Essentially what happens is as soon as the activity goes in the background it is on the mercy of Android DVM. If DVM feels it needs space it will essentially go ahead and kill your application. So once you try to start the application from the icon it actually restarts it from scratch.
However to solve your problem, you should have a checkbox like "Automatically login" or "Remember password" on the login screen and when the user checks it everytime the app opens it should automatically log you in and take to the next screen. This behavior needs to be implemented by you using some sort of persistent storage.
Might be because you are using your onPause() so that your tabs does some action when the tab is passed.
So eventually when the home key is pressed onPause() will be called which might lead you to this problem. Maybe you will have to check your onPause() for this case.
on home button only onStop is called, are you doing finish of activity on onStop? If not it preserves what was the activity which is top of the stack.