以编程方式截图Android 13

Question

我有下面的代码，它在Android 12和更低的版本上运行得非常好，但出于一个奇怪的原因，Android 13大约95%的时间都会使用“黑色”屏幕截图。

fun setVirtualDisplay() {
    mImageReader = ImageReader.newInstance(
        deviceScreenUtils.getWidth(),
        deviceScreenUtils.getHeight(),
        PixelFormat.RGBA_8888,
        2
    )

    mImageReader?.let {
        val flags =
            DisplayManager.VIRTUAL_DISPLAY_FLAG_OWN_CONTENT_ONLY or DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC

        try {
            mVirtualDisplay = mMediaProjection?.createVirtualDisplay(
                "screen-mirror", deviceScreenUtils.getWidth(), deviceScreenUtils.getHeight(),
                deviceScreenUtils.getDensity(), flags, it.surface, null, null
            )
        } catch (e: Throwable) {
            Log.i(TAG, "Media Projection not longer available...")
            mMediaProjectionIntent = null
            mImageReader = null
        }
    }
}

fun takeScreenshot() {
    Log.i(TAG, "Taking screenshot...")
    val handler = Handler(Looper.getMainLooper())
    mImageReader?.setOnImageAvailableListener({ imageReader ->
        val image = imageReader.acquireLatestImage()
        Log.i(TAG, "Acquiring image...")
        if (image != null) {
            val planes = image.planes
            val buffer = planes[0].buffer
            val pixelStride = planes[0].pixelStride
            val rowStride = planes[0].rowStride
            val rowPadding: Int = rowStride - pixelStride * deviceScreenUtils.getWidthPixels()
            val bitmap = Bitmap.createBitmap(
                deviceScreenUtils.getWidth() + (rowPadding.toFloat() / pixelStride.toFloat()).toInt(),
                deviceScreenUtils.getHeight(),
                Bitmap.Config.ARGB_8888
            )
            bitmap.copyPixelsFromBuffer(buffer)
            image.close()

            fileUtil.saveImage(bitmap)?.let {
                lastScreenshot.onNext(it)
            }
        }

        imageReader.setOnImageAvailableListener(null, handler)
        releaseBuffer()
    }, handler)
}

这个特定的功能有什么变化吗？或者，我的代码中有什么问题，而且它一直在神奇地处理以前的版本？

Answer 1

在我的测试和观察中，当在Android13上使用ImageReader和媒体投影时，有两个问题

首先，setOnImageAvailableListener的回调结果有时会返回带空像素的缓冲区。因此，我们只需等待下一个图像，直到得到一个非空的位图。

imageReader.setOnImageAvailableListener({ imageReader ->
    val image = imageReader.acquireLatestImage()
    // ... get buffer here
    val bitmap = Bitmap.createBitmap(screenWidth + rowPadding / pixelStride, screenHeight, Bitmap.Config.ARGB_8888)
    bitmap.copyPixelsFromBuffer(buffer)

    // IMPORTANT!
    val isEmptyBitmap = bitmap.isEmptyBitmap()
    if (isEmptyBitmap) {
        // don't stop the listener and let the imageReader continue to run so that we can get next round of image buffer
    } else {
        // save bitmap to file
    }

    }, Handler(Looper.getMainLooper()))

isEmptyBitmap()只是位图的一个扩展：

fun Bitmap.isEmptyBitmap(): Boolean {
    val emptyBitmap = Bitmap.createBitmap(width, height, config)
    return this.sameAs(emptyBitmap)
}

第二个问题是，OnImageAvailableListener有时甚至不回调！在本例中，我设置了一个等待结果的超时，当超时时，从同一个VirtualDisplay实例重新创建MediaProjection对象，它就可以工作了。

我使用的是kotlin协同器，因此代码片段看起来可能如下：

retry(10) {
    val imageVirtualDisplay = createVirtualDisplay(...)
    try {
        withTimeout(100) {
            // awaitImageAvailable will suspend here to get the non-empty bitmap
            val bitmap = imageReader.awaitImageAvailable(screenWidth, screenHeight)
            // save bitmap to file
        }
    } finally {
        Timber.d("screenshot imageVirtualDisplay release")
        imageVirtualDisplay?.release()
    }
}

awaitImageAvailable的实现

suspend fun ImageReader.awaitImageAvailable(screenWidth: Int, screenHeight: Int): Bitmap =
suspendCancellableCoroutine { cont ->
    setOnImageAvailableListener({ imageReader ->

        val image = imageReader.acquireLatestImage() ?: throw Error("get screen image result failed")

        val planes = image.planes
        val buffer = planes[0].buffer

        val pixelStride = planes[0].pixelStride
        val rowStride = planes[0].rowStride
        val rowPadding: Int = rowStride - pixelStride * screenWidth
        var bitmap =
            Bitmap.createBitmap(screenWidth + rowPadding / pixelStride, screenHeight, Bitmap.Config.ARGB_8888)
        bitmap.copyPixelsFromBuffer(buffer)
        bitmap = Bitmap.createBitmap(bitmap, 0, 0, screenWidth, screenHeight)
        image.close()

        if (!bitmap.isEmptyBitmap()) {
            Timber.d("image not empty")
            setOnImageAvailableListener(null, null)
            cont.resume(bitmap)
        } else {
            Timber.w("image empty")
        }
    }, Handler(Looper.getMainLooper()))

    cont.invokeOnCancellation { setOnImageAvailableListener(null, null) }
}