Is there any way of disabling / enabling the touch events in a certain activity
without disabling certain buttons. like if the phone is "frozen" on a certain activity page for limited time?
I need that the user wont be able to go back on page, slide out or any other events.
Is it possible? (I'm using android studio, java)
Thanks in advance!
Any answer would help :)
It's possible.
Actually there is no special function to make it.
To make it, you can make a full screen button with transparent background.
And you will define a function of the button.
Of course, it will be an empty function.
Well, you can do nothing on the screen.
and then you can hide or visible the button according to your necessary.
The app I'm working on shows some sensitive information that must not be shown on the "Recent Tasks" screen when stopping the app by pressing the home button.
I'd like to blur the sensitive data in the screenshot or show the app logo instead.
I am aware of the following approaches but they don't fit my requirements:
Setting the actvitie's android:excludeFromRecents to true in the manifiest prevents the app from being shown at all in the recent tasks. This would disrupt the user experience.
Using FLAG_SECURE results in a blank card on the recents tasks screen. (How do I prevent Android taking a screenshot when my app goes to the background?) I don't like the blank screen. However, I'll stick to this solution if there is no workaround.
Overriding onCreateThumbnail seems like the ideal solution but, unfortunately, doesn't work as it's currently not invoked by the OS :( (https://code.google.com/p/android/issues/detail?id=29370)
And then there are some workarounds that I tried out but that didn't work as hoped:
Start a new activity that shows the app logo in onPause so that it's screenshot is shown instead of the actual activitie's one. But the new activity takes too long to open and it disrupts the user experience.
Set the activitie's content view to an image of the app logo in onPause. That seemed like a great solution to me. Unfortunately, the screenshot for the recent tasks screen is taken at an unspecified time. During testing the app logo quickly appears before the app is closed when pressing 'Home' but the resulting screenshot shows the activity a short time before that.
Removing the sensitive data from the widgets (e.g. textView.setText("")) has the same problem of screenshot timing just mentioned.
Any alternative ideas or solutions to the listed workarounds?
I looked into this a couple of months ago for the same purpose as you.
Unfortunately, I had to conclude that it is simply not possible. I dug through the android source code and confirmed it.
There is no callbacks or methods from android that allows you to customize it (that works anyway). Besides FLAG_SECURE, this part of the code does not accept any input or change.
OnPause and similar lifecycle methods are called too late (the screenshot is taken already). All lifecycle methods that would hint that you're about to go into the background runs too late.
The image you see in the recent tasks is an actual screenshot - and thus isn't affected by changes you do (too late) to your view. That means you can't modify your view just-in-time (like making it invisible, replacing with something else, adding SECURE_FLAG, or any other obstruction of the view). As an aside, these images can be found on an emulator at /data/system_ce/0/recent_images.
The only exception is using FLAG_SECURE, which will prevent the screenshot from being taken of your application. I experimented with setting this FLAG in onPause and removing it in onResume, however as mentioned already these lifecycle methods runs after the screenshot is taken already, and thus had absolutely no effect.
As discussed in How to change the snapshot shown by recent apps list? there used to be a callback that you could use to customize the thumbnail: onCreateThumbnail. However, this does not work and it is never called. To be clear, the callback is still there, it is simply never called by the OS. The fact that it stopped working is poorly documented, but apparently was silently deprecated/removed in 4.0.3
As for the thumbnail itself, it is a screenshot taken serverside. It is taken before onPause is called (or in fact before any callbacks indicating that your activity is about to go into the background is called).
When your app does go into the background, your actual view is animated (to get that zoom-out transition). That animation can be affected through changes you do in onPause (if you're fast enough that is) (I experimented with setting opacity to 0 on the window among other things). This will however only affect the animation. When the animation is finished, the view is replaced by the screenshot taken earlier.
Also see these questions that discuss this:
When does Android take its recent apps switcher screenshot?
Show custom application image in task manager on ICS or JB
Android never call method onCreateThumbnail
Currently (28/10/2020) is impossibile customizing app thumbnail in recent apps screen.
As explained by #Dellkan in the previous answer, the onCreateThumbnail method is not called anymore by the OS.
Unfortunately, also the suggestion to create a kind of launcher/splash screen without the FLAG_SECURE flag to let the app take a screenshot of that activity is not working, because the screenshot is taken on the activity you see and not at the launch of the app.
You cannot even customize the color of window background when using FLAG_SECURE as reported here.
How about implementing a layout overlay on top of your entire activity?
Make it transparent, it's click-through by default, so no negative impact on UX while in use.
In onPause() set a half-transparent, blurred image as the background of that layout, the data will be scrambled behind it. In onResume() change the background to fully transparent again. Voila.
It might be faster than other types of overlays. The positive side effect is, if you do the unblurring as a short animation effect when the user goes back (with a proper library that uses C++ instead of Java), it might even look cool and the users wouldnt even mind seeing it.
I haven't tried this myself, but it's something you haven't tried yet.
Since onPause is called to late, I use WindowFocusChangeListener to observe when the Fragment loses focus. At this moment we can hide all view which show sensitive data:
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
view.getViewTreeObserver().addOnWindowFocusChangeListener(new ViewTreeObserver.OnWindowFocusChangeListener() {
#Override
public void onWindowFocusChanged(boolean hasFocus) {
// hide sensitive data when window moves to background (before system screenshot is captured)
myViewWithSensitiveData.setVisibility(hasFocus ? View.VISIBLE : View.INVISIBLE);
}
});
There is a way to customize it. You need your Activities with sensitive data to FLAG_SECURE in onCreate before you setContentView. Then you need an empty Activity, which renders whatever you want to have as the customized thumbnail. This usually is some sort of splash screen. This new Activity needs to be the launcher and is the only Activity not FLAG_SECURE. This Activity is launched and in onResume starts your actual Activity with the sensitive data.
Android OS will take a screenshot of that new Activity at the beginning of your App. Unfortunately the users will also see this Activity for a short moment. Since every other Activity is FLAG_SECURE, Android OS will use the only available screenshot it made at the beginning.
Was looking for a solution and found some dirty things in case you don't want to use 'FLAG_SECURE'. It doesn't give a nice picture but protects data and doesn't prevent making screenshots for the user while they are in the app.
protected void onPause () {
this.getWindow().getDecorView().getRootView().setScaleX((float)200);
this.getWindow().getDecorView().getRootView().setScaleY((float)200);
super.onPause();
}
protected void onResume () {
this.getWindow().getDecorView().getRootView().setScaleX((float)1);
this.getWindow().getDecorView().getRootView().setScaleY((float)1);
super.onResume();
}
I think this can only achieve through BroadCastReceiver but there is no receiver present. So therefore you first disable default screenshot functionality in android and then implementing your own functionality to take screenshot and before taking screenshot you should blur your secure information.
What is the proper way of completely disposing of a screen in Libgdx? Currently If I click where a button was on my previous screen the button still does what it would of done if I were on that screen. Should I be .dispose()-ing everything I can in the dispose() method? or is there a simpler way to dispose of everything on screen?
Unfortunately there is no easier way. These classes do not share any kind of common "Disposable" interface, or anything like that, to do it automatically. Everything that has a dispose() method needs to be disposed manually when it's not needed anymore.
This is also valid for the Screens themselves. When switching Screens they do not get disposed automatically, but you need to do that yourself (before calling Game.setScreen()).
On the other hand, this is not a big deal. Just look through everything in your Screen and check whether it has to be disposed or not. If there is a dispose method, call it in dispose() of the Screen.
BUT this does not explain your behaviour about invisible buttons from the last Screen. I suppose you use a Stage and used Gdx.input.setInputProcessor(stage);. This setting will not be changed when you change the screen and you have to set the input processor to the Stage of your current Screen, or to whatever that handles the input in your current Screen. That way the "old" stage will not catch any inputs anymore.
I can confirm that this issue is not passing the inpur processor a new stage. this will result in "ghost" buttons as described.
Unfortunately LibGDX API documentation says
Note that dispose() is not called automatically.
So what I do is disposing all disposables (such as Stage, Skin, Texture ... etc) inside the hide() method in the Screen because hide() is called automatically and it works very well!
example:
public class GameScreen implements Screen {
...
#Override
public void hide() {
mainStage.dispose();
playGroundStage.dispose();
controller.dispose();
labelActor.dispose();
}
...
}
I know this may not be an appropriate question, but I want to know how a touch enabled OS like
android detects a button in an app and calls the appropriate handler? When programming an app we just give the alignment information of a particular button. So, how android keeps the mapping between a button and screen position? I think this is kindof dynamic because if you change the screen orientation or use zoom or something like that the button positions are changed dynamically. So, android must look at the touch position and decide whether a button is there or not and call the appropriate handler. How this all things put together?
I appreciate any reply.
In the method "OnCreate" of my actvity, I'm displaying a little progress dialog while loading data. It's done every time the "OnCreate" method is called so even when the screen orientation change.$
In the nominal case, there is no problem even if the user change the screen orientation.
But, if the user opens another dialog (used to select an item in a list), then change the orientation, the progress dialog is displayed behind the "list" dialog and is not impacted by the "removeDialog".
Do you have any clues on that behavior ?
Thanks
call "removeDialog" or "dismissDialog" before "startDialog" with try-catch and so on. You can call "removeDialog" or "dismissDialog" several times...