The Kindle Fire has a bar at the bottom that includes a "home" button and a "back" button.
When I click the "back" button, my app's "onPause()" event is invoked.
When I click the "home" button, my app crashes. An Android dialog box is displayed. It says my app has stopped unexpectedly. I am presented with a "force close" button.
Sooooo what event do I need to be handling to prevent this. This only happens on my app, not the ones I downloaded, so yeah, it's me, lol.
Edit
As per this web page, I added events and toasts to the app just to gain some insight into how things work. When I click the Back button, I see the toasts produced by the onPause(), onStop(), and onDestroy() methods. When I click the Home button, there are no toasts, just the crash.
RESOLUTION
Akhil suggested I look at the logcat. I don't run the emulator since my machine seems understrength for Android development (or perhaps I expect too much from the emulator); it takes forever to start it up. Anyway, after figuring out how to run the emulator (and look at the logcat for the first time, ha) I saw that I was throwing an exception related to serialization. I'm off to solve it now. Thanks Akhil for the kick in the right direction!
Ah, and the emulator did display the onPause() toast when I clicked Home, so reality is still functioning as expected.
FINAL
The error was related to the serialization I added to make the onSaveInstanceState(Bundle savedInstanceState) method work. Basically, my app (and old game I converted to android) wasn't serializable, therefore this code in onSavedInstanceState() would not compile:
savedInstanceState.putSerializable(GAME, game);
'game' is innocuous, so I added "implements Serializable" to Game's class definition. However, I neglected to add the same to a private class within Game. This is what was causing the exception.
When you click the "back" button, your app's "onPause(), onStop(),onDestroy()" events will be invoked.When you click the "home" button, your app's "onPause(), onStop()," events will be invoked. ( This is a general scenario, assuming)
Put log statements in your onPause(), onStop() and see where you are getting the error.
Home Button cannot be intercepted in android due to security flaws.One option available is to overrride the onStop which is called when you press the home button and the app closes:-
#Override
protected void onStop()
{
super.onStop();
//do whatever you want here
}
Related
It is important in my app that when a user presses the home button and the app enters the "Background" the app reverts to the login screen next time it is opened.
I have tried using the
android:noHistory
in the manifest but this means when pressing back on activities it reverts also to the login screen so is no good. I have also tried using
android:clearTaskOnLaunch="true"
in my initial activity but this doesn't seem to have any effect. I don't finish() the first activity so i am not sure why this doesn't work.
Can anyone help with a way of doing this.
I got this working by using
android:clearTaskOnLaunch="true"
Turns out that I didn't have it in my root activity, this was because I have a second login screen which asks for less details depending on if you have logged in before.
Although it works exactly as i want it to, apparently using this "Android" feature is incorrect because i am going "against" android by clearing the tasks (activities) when the home button is pressed and my app should follow someone else opinion of what an "app" should do. Who Knew!
Why don't you use the onPause()-Method? This should be called every time the Activity gets in Background.
So something like:
#Override
public void onPause(){
super.onPause();
finish();
}
Due to the fact that only one Activity of your App can be active at a time you don't have to worry about others still being active.
i have two simple questions (hope so).
First i want to close my app, when the user hits the homebutton in my HomeFragment, because there is a counter (Days,Hours) and when I click the home Button and come back later there is still the old value.
Then i have to close the app via backbutton and start again. So i want my app to get killed, when I hit the home button.
Then i have a button to delete the last value, on which the counter is based. When I hit the button i want to run my homeFragment again. Should i just create a funnction which calls, the homefragment.onCreate again?
When I hit the button i want to run my homeFragment again. Should i just create a funnction which calls, the homefragment.onCreate again?
No, these functions are meant to be called by the system.
You are probably looking for the onStop() method (also called by the system)
protected void onStop()
{
super.onStop();
// clear counter e.g.
myCounter.setText("");
}
Other than this, it's kind of hard to tell what you want. Feel free to add more (if not all) of your code.
How to complete the application when pressed buttons Home and Back? Provided that in my memory holds many pictures.
When pressed on the Back button - application restarts... When pressed on the Home button - quit application, but when it restart - does not start Splashstsreen.
Hard to see without code but it sounds like your activity is resuming rather then starting from scratch (as it should behave). It sounds like it's behaving correctly in that case. If you insist in wanting your application to truly quit after the back button is clicked perhaps you can override onBackPressed() then have your Activity call its finish() method.
I don't think it's good programming practice to fiddle and interfering with the activities lifecycle. It's the OS responsibility to manage the lifecycle, including pause and finish activities.
Instead you should use other methods to handle your problem with not showing splash screen, these methods are onResume and maybe also onStart(). Also you should get familiar with the activity lifecycle(link submitted by #ss1271).
Press Home will let the activity to enter onPause(). however, if you insist to quit the application when press HOME, which is obviously not a good practise, you can do like this:
Override onPause() and onBackPressed()
add finish(); to these methods.
I am sure by adding finish(); to onBackPressed() will quit the app when Back button pressed, but I haven't tried on Home.
Please refer to Activity Lifecycle for more info.
I have an app in which the user logs in from a main activity, and then can browse through a heirarchy of entities using listviews. So, the Activity stack would look something like this:
A -> B -> B -> B -> ...
where the number of B's is proportional to how deep you are in the tree of entities.
Frequently, I find myself pressing backbackbackbackback to get to the root (the first 'B'), but one too many presses and I log myself out, or even leave the app. I'm considering overriding the back button so that, when pressed from the root B, it will pop up a dialog essentially saying "Log out? (Y/N)", thus blocking a string of back-presses from completely exiting the app.
I've noticed a sort of sensitivity regarding overriding the back button, though, and - while it makes sense to me - I want to know if this is considered a good use of the back button.
So:
Would this be considered an appropriate/conventional override of the back button?
Is there a better/more conventional way to accomplish this without overriding?
Also, so this question might be more generally useful in the future, are there any guidelines for what is acceptable/unacceptable when overriding the back button?
I would find this use acceptable; I've seen a number of apps that ask for a confirm before exit - if the user wants to exit an app, they usually will press the Home button and let Android handle the finish() if and when it's needed.
I know I've accidentally exited an app by pressing back too many times :(
Dotmister's comment about Handcent is spot on - the back button should feel natural to the user; your use seems to adhere to this, in that a user will cycle back through activities as expected for the most part. As he said though, give it a try and test it.
Coincidentally, I have a similar flow in my app, but I've included a button for the root activity.
No it is not normal to overide the back button because the user ecxpects the back button to function as a... ?? back button.
On the other side if it is really that annoying using the back button in the normal way, than a compremise? will always be better. But make sure the user still has the idea he 'controls' the device according his rules, do not make him look for yours. (dutch way of making a point, sorry).
The only way to find out is getting some people to try your application and see if it's annoying or not.
I've heard that pressing the back button will essentially cause the current Activity to finish(). Is this always the case? Seems like it would be with the way it pops the Activity off the stack.
The one situation I'm not so sure about is when the root Activity in a Task has back pressed. I'm currently experiencing a very weird effect, described as follows:
On loading my application, the first Activity is for initialization, and once it finishes, it calls my main Activity (a TabActivity). This first init activity has android:noHistory="true" set in the Manifest so pressing Back from my main Activity won't go back to that. It goes to the Launcher. When I click on my App in the Launcher a second time, the initialization activity loads again, and loads the main Activity when done. Almost immediately after, it loads a second instance of my main Activity. But ONLY after the Application has already been run once, and was exited by pressing BACK from the main Activity. It does it every subsequent time until I force quit the app or load a new version from the IDE.
Based on this, I am suspecting some kind of Activity instance is lying around and being reused, since it only happens on the second+ time I run the application (and exit with BACK -- using HOME just returns to the last state of the app, no big deal). Anyone have any thoughts??
I've heard that pressing the back button will essentially cause the current Activity to finish(). Is this always the case?
No it is not. The most activities have this behaviour but not all. For example you could create a Dialog and set it setCancelable(false) and it won't close if you click BACK button.
Furthermore you could customize activity behaviour on BACK button pressed by overriding onBackPressed
Called when the activity has detected the user's press of the back key. The default implementation simply finishes the current activity, but you can override this to do whatever you want.
About your application behaviour..Did you verify if the activity launcher is finished after it loads your main activity? I mean if the onDestroy() method is called. Maybe after it runs the main activity it remains there and when you click back you just go back to the old Launcher...
hope this helps..
Read through the Activity and Task design guidelines on the Android developer site; they explain how the Home and Back buttons work. Obviously, if you override the default behavior (as mentioned by hara above), the back button will not finish the activity.
On your specific issue, check your logcat. You should be able to see there whether it is bringing an old process back to life or starting up a new one. If that is unclear, insert a couple of log statements into onCreate, onPause, onDestroyed, etc., so that you can see exactly what is happening with your process.
You can control BACK-BUTTON by writing the following code.
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK ) {
//preventing default implementation previous to
//android.os.Build.VERSION_CODES.ECLAIR
return false;
}
return super.onKeyDown(keyCode, event);
}
Are you running your activities with any special flags, such as singleInstance or singleTop? Those could be causing the oddities you're seeing. The easiest way to track down what's causing your problem is to absolutely fill it with debugging messages. For example:
In your initialisation activity, add a log in the beginning of onCreate to get the name of the activity such as this.toString(). More on why you want this line later.
When it launches the main tabbed activity, get the name of the launching activity and a message saying it's launched the tabbed one.
Override the onPause(), onStop() and onDestroy() callbacks and add debugging lines with this.toString() and also a message telling you which callback it is.
What this will do is tell you whether you've got multiple instances of the initialisation activity lying around. To this by comparing the name of the activities calling your main activity with the ones that were just created and the ones that went through to onDestroy.
If you don't know how to debug, use Log.d(LOG_TAG, "Your message here");. And then define a constant LOG_TAG String somewhere. After that, show the LogCat perspective in Eclispe by going to Window, show perspective (or view, don't remember exactly), other, Android, LogCat. The purpose of having a LOG_TAG constant is that you can set up LogCat to filter to that String and only show you those messages. It will make it easier to see them among the mass of system log messages.
The short answer to the original question is 'no'. This is largely because, unfortunately, not every developer follows the guidelines referenced by previous answers.
Yet the guidleines themselves mention exceptions, when the Back key should not call finish(). the most prominent exception is the Web browser, which has its own "back stack" for each window, so it must have its own custom handling of the Back key.
If there are no fragments on the back stack and a developer has not overridden onBackPressed, the activity will finish when the back button is pressed.
Here is the source code for Android 4.4.2 Activity.onBackPressed():
public void onBackPressed() {
if (!mFragments.popBackStackImmediate()) {
finish();
}
}
just override onbackpressed().. on back press this method will get execute remove super and do what u want to do.