Other [quiz] Find the bug

[Erel]

Sub Process_Globals
   Public Image As Bitmap 'public image
   Private SQL1 As SQL 'private sql object
End Sub

Sub Activity_Create(FirstTime As Boolean)
   If FirstTime Then
     Image = LoadBitmap(File.DirAssets, "Image.jpg")
     SQL1.Initialize(File.DirInternal, "1.db", True)
   End If
End Sub

Solution: https://www.b4x.com/android/forum/threads/quiz-find-the-bug.56132/page-2#post-353562

 

[imbault]

First DirInternal is not the place I would put the DB, it could be deleted in case of uninstall... I would use File.DirDefaultExternal

I don't know it's a really a bug, but I should load the image file with a Initialize, like this

Image.Initialize(File.DirAssets, "Image.jpg")

And Scope of SQL1 to be private, will exclude it from others modules..., so I would put it Public

 

[ArminKH]

we should not store an private variable on Process_Global because this sub is for public variables which we want to be accessable from another activity

Public Sql1 as SQL

IS Correct i think
and also i think we should not store an ui element on process_global because it will be kept alive when the activity is recreated and maybe be a reason for memory leak

 

[Erel]

We are not there yet...

we should not store an private variable on Process_Global because this sub is for public variables which we want to be accessable from another activity

ActuallySQL objects should always be declared as process global variables.
It is also completely fine to declare it a private variable.
Bitmaps are not "activity objects". It is better to declare them as process global variables.

First DirInternal is not the place I would put the DB, it could be deleted in case of uninstall... I would use File.DirDefaultExternal

It really depends on your app requirements. In most cases it is better not to leave any file on the device after your app is uninstalled. Also note that File.DirDefaultExternal folder will also be cleaned when your app is uninstalled.

LoadBitmap is identical to Bitmap.Initialize.

And Scope of SQL1 to be private, will exclude it from others modules..., so I would put it Public

This again depends on the requirements. If the SQL object will only be used in the current activity then it is better to declare it as a private variable.

Hint: The image will be used from other activities as well.

 

[ArminKH]

We are not there yet...


ActuallySQL objects should always be declared as process global variables.
It is also completely fine to declare it a private variable.
Bitmaps are not "activity objects". It is better to declare them as process global variables.


It really depends on your app requirements. In most cases it is better not to leave any file on the device after your app is uninstalled. Also note that File.DirDefaultExternal folder will also be cleaned when your app is uninstalled.

LoadBitmap is identical to Bitmap.Initialize.


This again depends on the requirements. If the SQL object will only be used in the current activity then it is better to declare it as a private variable.

Hint: The image will be used from other activities as well.

so maybe we should use LoadBitmapSample instead LoadBitmap?I'm not sure exactly this can be a bug or not

 

[sorex]

Image.jpg should be image.jpg ?

 

[ArminKH]

Image.jpg should be image.jpg ?

why?!

 

[sorex]

wasn't there a limitation that some things only worked with lower cased filenames?

 

[ArminKH]

wasn't there a limitation that some things only worked with lower cased filenames?

no i test it with upercase name and still works
maybe the bug be in Initialize and is related to Activity LifeCycle

 

[eurojam]

I am missing the file copy from File.DirAssets to File.DirInternal:

File.Copy(File.DirAssets,"1.db", File.DirInternal,"1.db")

 

[sorex]

maybe he want to start with an empty one?

 

[ArminKH]

I am missing the file copy from File.DirAssets to File.DirInternal:

File.Copy(File.DirAssets,"1.db", File.DirInternal,"1.db")

no,then a new database will be created if it dosn't exist any database named 1.db on DirInternal and if CreateIsNecessary is true

 

[eurojam]

no,then a new database will be created if it dosn't exist any database named 1.db on DirInternal and if CreateIsNecessary is true

yes you are right, I missed that

 

[Erel]

so maybe we should use LoadBitmapSample instead LoadBitmap?

LoadBitmapSample is indeed better than LoadBitmap in many cases. However lets assume that the image file is at the exact required size.

 

[sorex]

I don't have a 5.x device but on 2.x-4. file.dirinternal was read only, not? so that would lead to an init error.

 

[Erel]

file.dirinternal was read only, not?

No. Don't confuse File.DirInternal with File.DirAssets.

 

[eurojam]

....if running the code from Erel, there will be no error on my nexus, there is only this wonderfull app, doing nothing beside creating and opening a database and an image....mmmhhhh....

 

[Erel]

if running the code from Erel, there will be no error on my nexus, there is only this wonderfull app, doing nothing beside creating and opening a database and an image

This is exactly the problem with this bug. It will almost never reveal itself during development. However it will easily crash your app when it runs on the users phone.

Let me repeat the hint I posted:
The image (as Main.Image) will be used from other activities as well.

 

[sorex]

I just copied it to a project aswell, no errors and the image displayed fine.

 

[sorex]

Image is an existing type in java or something?