IssueTracker

Hi macocco124,

CameraX PreviewView supports two modes - PERFORMANCE and COMPATIBLE. By default, the PERFORMANCE mode is used. I find the issue disappeared when using COMPATIBLE mode. Please have a try and maybe you can consider to use the COMPATIBLE mode for your application.

The major difference between PERFORMANCE and COMPATIBLE is that PERFORMANCE mode uses SurfaceView but the COMPATIBLE mode uses TextureView to implement the PreviewView. The issue looks only happen when using SurfaceView.

I tried to clarify the issue via Android Studio Layout Inspector tool. The dimensions of SurfaceView seem correct, but the inside preview images are really stretched by unknown reason. Please refer to the attached screenshots of the PointerGun and CameraXBasic sample apps' layout inspector information. You can see the width and height are all the same. The preview images can be displayed correctly in full screen while it has problem in PointerGun sample app. I will need more time to clarify why CameraX plus Compose UI will cause the issue.

Thank you Charcoal for looking at this. FYI one more report for a similar issue: bug 183864890.

This is a redraw timing related issue which happens when using PreviewView's SurfaceViewImplementation mode together with Compose UI.

Based on the PointerGun sample project provide in comment#1, if the following two lines of code are moved to be done after the bindPreview() call, the preview stretched issue disappeared.

Original code:

            PreviewView(context).apply {
                setBackgroundColor(Color.GREEN)
                layoutParams = LinearLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT)
                scaleType = PreviewView.ScaleType.FILL_CENTER
                post {
                    cameraProviderFuture.addListener(Runnable {
                        val cameraProvider = cameraProviderFuture.get()
                        bindPreview(
                            cameraProvider,
                            lifecycleOwner,
                            this,
                        )
                    }, ContextCompat.getMainExecutor(context))
                }
            }

New code:

            PreviewView(context).apply {
                setBackgroundColor(Color.GREEN)
                post {
                    cameraProviderFuture.addListener(Runnable {
                        val cameraProvider = cameraProviderFuture.get()
                        bindPreview(
                            cameraProvider,
                            lifecycleOwner,
                            this,
                        )

                        // Updated layoutParams and ScaleType after bindPreview() call
                        layoutParams = LinearLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT)
                        scaleType = PreviewView.ScaleType.FILL_CENTER
                    }, ContextCompat.getMainExecutor(context))
                }
            }

But, the above solution won't work if the compose related library version is updated from 1.0.0-beta03 to 1.0.0-beta09.

I also tried to add onClickListener to the PreviewView and change its ScaleType. The preview can be displayed correctly if ScaleType is changed to a different type when receiving a click event. It means that the SurfaceViewImplementation's transformation calculation should be correct and the issue might be caused by calling setScaleX/Y and setTranslationX/Y too early.

            PreviewView(context).apply {
                setBackgroundColor(Color.GREEN)
                layoutParams = LinearLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT)
                scaleType = PreviewView.ScaleType.FILL_CENTER

                // Adds onClickListener to change its ScaleType
                setOnClickListener { v ->
                    if (scaleType == PreviewView.ScaleType.FILL_CENTER) {
                        scaleType = PreviewView.ScaleType.FIT_CENTER
                    } else {
                        scaleType = PreviewView.ScaleType.FILL_CENTER
                    }
                }

                post {
                    cameraProviderFuture.addListener(Runnable {
                        val cameraProvider = cameraProviderFuture.get()
                        bindPreview(
                            cameraProvider,
                            lifecycleOwner,
                            this,
                        )
                    }, ContextCompat.getMainExecutor(context))
                }
            }

The SurfaceView's javadoc has the following description. Therefore, I tried to add a callback to SurfaceHolder to make setScaleX/Y and setTranslationX/Y only called after surfaceCreated event is received. But the issue still exists.

You must ensure that the drawing thread only touches the underlying Surface while it is valid -- between SurfaceHolder.Callback.surfaceCreated() and SurfaceHolder.Callback.surfaceDestroyed().

After the surface is created, it will provide the surface to the SurfaceRequest requested by the PreviewView's SurfaceProvider. Therefore, I tried to only call setScaleX/Y and setTranslationX/Y when the surface has been provided. I found the issue disappeared by this change. This might be the solution for this issue and this might also be a reasonable timing to start calling setScaleX/Y and setTranslationX/Y since the preview content can be displayed only if the surface has been provided.

The solution has been merged in https://android-review.googlesource.com/1747943. It can't be included in June's release but will be included in July's release.

Update some more information. After doing more testing for this issue, this issue looks only happen on Android 10 and 11 devices.

Attached PointerGun-Original.apk is built by the original CameraX library setting.

Attached PointerGun-BuiltWithSolution.apk is built by the local verifying library with the solution.

Hi Mihai,

Could you also help to double check this issue in the Compose UI part? It is because that:

1. The issue doesn't happen when using only CameraX's PreviewView (SurfaceViewImplementation mode).
2. As mentioned in comment#5, the same code might have the issue when using 1.0.0-beta09 but doesn't have the issue when using 1.0.0-beta03.

If the issue could also possibly have a solution in the Compose UI side, it will benefit the applications which have their own SurfaceView widget implementation and use it together with Compose UI. Or, maybe we can know what we should take care of when using SurfaceView together with Compose UI.