Qt app started from android device shows white screen

simgunz · wrote on 8 Apr 2014, 15:47

If I deploy and application from QtCreator to an android device (tested on two different devices, same result) the app starts fine. Then I hit the home button and I get to the android menu. So I hit the application launcher and I start it a second time, at this point I see a white screen and the application won't load. If I rotate the screen the application crashes and soon after it is reloaded and starts correctly. This happens all the time the application is started from the launcher.

Anyone know how can I solve this?

Xander84 · wrote on 8 Apr 2014, 18:33

I think I have the same problem, seems like android tries to start the app again, even though it is already running. I don't know why that is happening but to me android should manage the running apps and just show the running app instead of launching another instance. if you use the app switcher it works like expected, maybe some weird Qt bug or feature but seems weird behavior to me, yes.

simgunz · wrote on 8 Apr 2014, 18:42

I've noticed that after a phone reboot the app seems to work fine both using app switcher and launching it from app launcher.

Xander84 · wrote on 8 Apr 2014, 19:00

Yeah well if you close the app you can start it from the launcher obviously (I think if you restart the phone it will close all apps). You know you can manually close an app from the app switcher? then you can start it again :D
I don't know what exactly happens and why it stays "white" I just assumed Qt/Android tries to start another instance of the app instead of switching to the running app, because it works with the app switcher or if you run another app from your app (like the browser) and use the back button also works fine!

simgunz · wrote on 8 Apr 2014, 19:46

No I meant a different thing:

The first time you load the app on the android device:
1.the first time the app starts fine
2.press the home button
3.press the app launcher -> white screen
4.press the home button
5.select the app from the app switcher -> app starts fine

Reboot the android device:
1.the first time the app starts fine
2.press the home button
3.press the app launcher -> the app starts fine! (it's recalled from it previous state)
4.press the home button
5.select the app from the app switcher -> app starts fine

So after rebooting the phone the problem seems disappeared.

Iktwo · wrote on 10 Apr 2014, 17:46

I'm having a similar issue, I wrote a launcher with qml, when it is deployed and start from qtcreator I can see it, if I then go to the app switcher and then press home, it looks like my application is trying to start again and it fails, I see just a white screen :S the worst part is that if I set my launcher as default and I reboot I will see nothing but a white screen

This is what I get

@
W/Adreno-EGLSUB(18476): DequeueBuffer:606: dequeue native buffer fail: No such device, buffer=0x0, handle=0x0
W/Adreno-ES20(18476): <gl2_surface_swap:43>: GL_OUT_OF_MEMORY
W/Adreno-EGL(18476): <qeglDrvAPI_eglSwapBuffers:3597>: EGL_BAD_SURFACE
W/Qt (18476): eglconvenience/qeglplatformcontext.cpp:332 (virtual void QEGLPlatformContext::swapBuffers(QPlatformSurface*)): QEGLPlatformContext::swapBuffers(): eglError: 12301, this: 0x774d0da8
W/Qt (18476):
E/Qt JAVA (18476): Surface 1 not found!
I/Timeline(18476): Timeline: Activity_idle id: android.os.BinderProxy_41b4ac00 time:1784196
@

This is how it looks when everything is ok

http://imgur.com/jakTR8J

This is what I gett when it fails

http://imgur.com/0G44W9E

pkoretic · wrote on 28 Oct 2014, 19:20

This may be late but since nobody replied, setting:
android:launchMode="singleInstance"
fixes the problem above.

more information here:
http://developer.android.com/guide/topics/manifest/activity-element.html#lmode

Using qt 5.4.

simgunz · wrote on 30 Oct 2014, 09:27

Thank you. I haven't work anymore on that project so I haven't fixed that. I'll try.

ahmad88me · wrote on 31 Jul 2016, 22:02

This post is deleted!