iOS Question Problem mit B4XCanvas or iPhone-X ?

Deleted member 103 · Oct 31, 2019

Hi,
attached is a test project with B4XCanvas. Only one arrow is drawn here.
1) test with iPhone-X
When the app starts, the arrows are visible, after a change to Page-2 and back to Page-1, the arrows are no longer visible.

2) Test with iPhone 6 and iPad mini
When the app starts, the arrows are visible, after a change to Page-2 and back to Page-1, the arrows are always visible.

Is this a Canvas problem or does my iPhone X have a problem or am I doing something wrong?

Erel · Oct 31, 2019

Why are you initializing the canvas multiple times?

Initialize it once when the app starts and change Page1_Resize to:

B4X:

Private Sub Page1_Resize(Width As Int, Height As Int)
   cvsArrow.Resize(pnlCrono.Width, pnlCrono.Height)
   CreateArrow(0)
End Sub

Don't resize it in other places.

Deleted member 103 · Oct 31, 2019

Erel said:
Why are you initializing the canvas multiple times?

Initialize it once when the app starts and change Page1_Resize to:

B4X:

Private Sub Page1_Resize(Width As Int, Height As Int) cvsArrow.Resize(pnlCrono.Width, pnlCrono.Height) CreateArrow(0) End Sub

Don't resize it in other places.

Unfortunately, the change brings no improvement, the error remains.

Does anyone have an iPhone-X with which he can reproduce the mistake?

Erel · Oct 31, 2019

Please upload the updated project. I'll test it with iPhone X (though it is probably not related to any specific version).

Deleted member 103 · Oct 31, 2019

Hi Erel,

here is the modified project.

angel_ · Oct 31, 2019

Did you try this?:

https://www.b4x.com/android/forum/threads/white-bar-on-iphone-xs.107514/#post-672963

Erel · Nov 1, 2019

I see the behavior you are describing. It looks like a caching issue related to ImageView. It will work properly if you initialize the canvas with the underlying panel instead of an ImageView.

I will further check it. Use a panel for now (all custom views that use a canvas are drawing on panels).

Deleted member 103 · Nov 1, 2019

Use a panel for now (all custom views that use a canvas are drawing on panels).

Thanks Erel, it works well with panel.
Can it be a problem with iOS-13?

Erel · Nov 1, 2019

Not sure. Probably related to an optimization of ImageViews visual layers.

iOS Question Problem mit B4XCanvas or iPhone-X ?

Deleted member 103

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