I want to take screenshot of specific composable function on Jetpack Compose. How can I do this? Please, anyone help me. I want to take screenshot of composable function and share with other applications.
Example of my function:
@Composable
fun PhotoCard() {
Stack() {
Image(imageResource(id = R.drawable.background))
Text(text = "Example")
}
}
How to take screenshot of this function?
As @Commonsware mentioned in the comment, and assuming this is not about screenshot testing:
According to official docs you can access the view version of your composable function using LocalView.current, and export that view to a bitmap file like this (the following code goes inside the composable function):
val view = LocalView.current
val context = LocalContext.current
val handler = Handler(Looper.getMainLooper())
handler.postDelayed(Runnable {
val bmp = Bitmap.createBitmap(view.width, view.height,
Bitmap.Config.ARGB_8888).applyCanvas {
view.draw(this)
}
bmp.let {
File(context.filesDir, "screenshot.png")
.writeBitmap(bmp, Bitmap.CompressFormat.PNG, 85)
}
}, 1000)
The writeBitmap method is a simple extension function for File class. Example:
private fun File.writeBitmap(bitmap: Bitmap, format: Bitmap.CompressFormat, quality: Int) {
outputStream().use { out ->
bitmap.compress(format, quality, out)
out.flush()
}
}
I made a small library that screenshots Composables with single shot or periodically.
A state that is used for capturing and storing Bitmap or ImageBitmap
/**
* Create a State of screenshot of composable that is used with that is kept on each recomposition.
* @param delayInMillis delay before each screenshot
* if [ScreenshotState.liveScreenshotFlow] is collected.
*/
@Composable
fun rememberScreenshotState(delayInMillis: Long = 20) = remember {
ScreenshotState(delayInMillis)
}
/**
* State of screenshot of composable that is used with.
* @param timeInMillis delay before each screenshot if [liveScreenshotFlow] is collected.
*/
class ScreenshotState internal constructor(
private val timeInMillis: Long = 20,
) {
val imageState = mutableStateOf<ImageResult>(ImageResult.Initial)
val bitmapState = mutableStateOf<Bitmap?>(null)
internal var callback: (() -> Unit)? = null
/**
* Captures current state of Composables inside [ScreenshotBox]
*/
fun capture() {
callback?.invoke()
}
val liveScreenshotFlow = flow {
while (true) {
callback?.invoke()
delay(timeInMillis)
bitmapState.value?.let {
emit(it)
}
}
}
.map {
it.asImageBitmap()
}
.flowOn(Dispatchers.Default)
val bitmap: Bitmap?
get() = bitmapState.value
val imageBitmap: ImageBitmap?
get() = bitmap?.asImageBitmap()
}
ImageResult that contains error or success depending on process result
sealed class ImageResult {
object Initial : ImageResult()
data class Error(val exception: Exception) : ImageResult()
data class Success(val data: Bitmap) : ImageResult()
}
Composable that captures screenshot of its children Composables
/**
* A composable that gets screenshot of Composable that is in [content].
* @param screenshotState state of screenshot that contains [Bitmap].
* @param content Composable that will be captured to bitmap on action or periodically.
*/
@Composable
fun ScreenshotBox(
modifier: Modifier = Modifier,
screenshotState: ScreenshotState,
content: @Composable () -> Unit,
) {
val view: View = LocalView.current
var composableBounds by remember {
mutableStateOf<Rect?>(null)
}
DisposableEffect(Unit) {
screenshotState.callback = {
composableBounds?.let { bounds ->
if (bounds.width == 0f || bounds.height == 0f) return@let
view.screenshot(bounds) { imageResult: ImageResult ->
screenshotState.imageState.value = imageResult
if (imageResult is ImageResult.Success) {
screenshotState.bitmapState.value = imageResult.data
}
}
}
}
onDispose {
val bmp = screenshotState.bitmapState.value
bmp?.apply {
if (!isRecycled) {
recycle()
}
}
screenshotState.bitmapState.value = null
screenshotState.callback = null
}
}
Box(modifier = modifier
.onGloballyPositioned {
composableBounds = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
it.boundsInWindow()
} else {
it.boundsInRoot()
}
}
) {
content()
}
}
Functions for Capturing screenshot. PixelCopy is required for Devices with version O and above. And you can use these functions without Composables either
fun View.screenshot(
bounds: Rect
): ImageResult {
try {
val bitmap = Bitmap.createBitmap(
bounds.width.toInt(),
bounds.height.toInt(),
Bitmap.Config.ARGB_8888,
)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
// Above Android O not using PixelCopy throws exception
// https://stackoverflow.com/questions/58314397/java-lang-illegalstateexception-software-rendering-doesnt-support-hardware-bit
PixelCopy.request(
(this.context as Activity).window,
bounds.toAndroidRect(),
bitmap,
{},
Handler(Looper.getMainLooper())
)
} else {
val canvas = Canvas(bitmap)
.apply {
translate(-bounds.left, -bounds.top)
}
this.draw(canvas)
canvas.setBitmap(null)
}
return ImageResult.Success(bitmap)
} catch (e: Exception) {
return ImageResult.Error(e)
}
}
fun View.screenshot(
bounds: Rect,
bitmapCallback: (ImageResult) -> Unit
) {
try {
val bitmap = Bitmap.createBitmap(
bounds.width.toInt(),
bounds.height.toInt(),
Bitmap.Config.ARGB_8888,
)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
// Above Android O not using PixelCopy throws exception
// https://stackoverflow.com/questions/58314397/java-lang-illegalstateexception-software-rendering-doesnt-support-hardware-bit
PixelCopy.request(
(this.context as Activity).window,
bounds.toAndroidRect(),
bitmap,
{
when (it) {
PixelCopy.SUCCESS -> {
bitmapCallback.invoke(ImageResult.Success(bitmap))
}
PixelCopy.ERROR_DESTINATION_INVALID -> {
bitmapCallback.invoke(
ImageResult.Error(
Exception(
"The destination isn't a valid copy target. " +
"If the destination is a bitmap this can occur " +
"if the bitmap is too large for the hardware to " +
"copy to. " +
"It can also occur if the destination " +
"has been destroyed"
)
)
)
}
PixelCopy.ERROR_SOURCE_INVALID -> {
bitmapCallback.invoke(
ImageResult.Error(
Exception(
"It is not possible to copy from the source. " +
"This can happen if the source is " +
"hardware-protected or destroyed."
)
)
)
}
PixelCopy.ERROR_TIMEOUT -> {
bitmapCallback.invoke(
ImageResult.Error(
Exception(
"A timeout occurred while trying to acquire a buffer " +
"from the source to copy from."
)
)
)
}
PixelCopy.ERROR_SOURCE_NO_DATA -> {
bitmapCallback.invoke(
ImageResult.Error(
Exception(
"The source has nothing to copy from. " +
"When the source is a Surface this means that " +
"no buffers have been queued yet. " +
"Wait for the source to produce " +
"a frame and try again."
)
)
)
}
else -> {
bitmapCallback.invoke(
ImageResult.Error(
Exception(
"The pixel copy request failed with an unknown error."
)
)
)
}
}
},
Handler(Looper.getMainLooper())
)
} else {
val canvas = Canvas(bitmap)
.apply {
translate(-bounds.left, -bounds.top)
}
this.draw(canvas)
canvas.setBitmap(null)
bitmapCallback.invoke(ImageResult.Success(bitmap))
}
} catch (e: Exception) {
bitmapCallback.invoke(ImageResult.Error(e))
}
}
Implementation
val screenshotState = rememberScreenshotState()
var progress by remember { mutableStateOf(0f) }
ScreenshotBox(screenshotState = screenshotState) {
Column(
modifier = Modifier
.border(2.dp, Color.Green)
.padding(5.dp)
) {
Image(
bitmap = ImageBitmap.imageResource(
LocalContext.current.resources,
R.drawable.landscape
),
contentDescription = null,
modifier = Modifier
.background(Color.LightGray)
.fillMaxWidth()
// This is for displaying different ratio, optional
.aspectRatio(4f / 3),
contentScale = ContentScale.Crop
)
Text(text = "Counter: $counter")
Slider(value = progress, onValueChange = { progress = it })
}
}
Capturing screenshot
Button(onClick = {
screenshotState.capture()
}) {
Text(text = "Take Screenshot")
}
Result
You can create a test, set the content to that composable and then call composeTestRule.captureToImage(). It returns an ImageBitmap.
Example of usage in a screenshot comparator: https://github.com/android/compose-samples/blob/e6994123804b976083fa937d3f5bf926da4facc5/Rally/app/src/androidTest/java/com/example/compose/rally/ScreenshotComparator.kt
You can get position of a composable view inside the root compose view using onGloballyPositioned, and then draw the needed part of the root view into the Bitmap:
val view = LocalView.current
var capturingViewBounds by remember { mutableStateOf<Rect?>(null) }
Button(onClick = {
val bounds = capturingViewBounds ?: return@Button
val image = Bitmap.createBitmap(
bounds.width.roundToInt(), bounds.height.roundToInt(),
Bitmap.Config.ARGB_8888
).applyCanvas {
translate(-bounds.left, -bounds.top)
view.draw(this)
}
}) {
Text("Capture")
}
ViewToCapture(
modifier = Modifier
.onGloballyPositioned {
capturingViewBounds = it.boundsInRoot()
}
)
Note that if you have some view on top of ViewToCapture, like placed with a Box, it'll still be on the image.
p.s. there's a bug which makes Modifier.graphicsLayer effects, offset { IntOffset(...) }(you still can use offset(dp) in this case), scrollable and lazy views position not being displayed correctly on the screenshot. If you've faced it, please star the issue to get more attention.
Using PixelCopy worked for me:
@RequiresApi(Build.VERSION_CODES.O)
suspend fun Window.drawToBitmap(
config: Bitmap.Config = Bitmap.Config.ARGB_8888,
timeoutInMs: Long = 1000
): Bitmap {
var result = PixelCopy.ERROR_UNKNOWN
val latch = CountDownLatch(1)
val bitmap = Bitmap.createBitmap(decorView.width, decorView.height, config)
PixelCopy.request(this, bitmap, { copyResult ->
result = copyResult
latch.countDown()
}, Handler(Looper.getMainLooper()))
var timeout = false
withContext(Dispatchers.IO) {
runCatching {
timeout = !latch.await(timeoutInMs, TimeUnit.MILLISECONDS)
}
}
if (timeout) error("Failed waiting for PixelCopy")
if (result != PixelCopy.SUCCESS) error("Non success result: $result")
return bitmap
}
Example:
val scope = rememberCoroutineScope()
val context = LocalContext.current as Activity
var bitmap by remember { mutableStateOf<Bitmap?>(null) }
Button(onClick = {
scope.launch {
//wrap in a try catch/block
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
bitmap = context.window.drawToBitmap()
}
}
}) {
Text(text = "Take Screenshot")
}
Box(
modifier = Modifier
.background(Color.Red)
.padding(10.dp)
) {
bitmap?.let {
Image(
bitmap = it.asImageBitmap(),
contentDescription = null,
modifier = Modifier.fillMaxSize(),
)
}
}
You can create a preview function with @Preview , run the function on phone or emulator and take the screenshot of the component.
I was looking for how to take screenshot of a composable in tests and this question appeared as the first in results. So, for future users who want to take/save/compare screenshots in tests or do screenshot testing, I put my answer here (thanks to this).
Ensure you have this dependency along with other Compose dependencies:
debugImplementation("androidx.compose.ui:ui-test-manifest:<version>")
Note: Instead of the above dependency, you can simply add an AndroidManifest.xml file in androidTest directory and add <activity android:name="androidx.activity.ComponentActivity" /> in manifest ➜ application element.
Refer to this answer.
The following is a complete example of taking, saving, reading, and comparing screenshots of a composable function called MyComposableFunction:
class ScreenshotTest {
@get:Rule val composeTestRule = createComposeRule()
@Test fun takeAndSaveScreenshot() {
composeTestRule.setContent { MyComposableFunction() }
val node = composeTestRule.onRoot()
val screenshot = node.captureToImage().asAndroidBitmap()
saveScreenshot("screenshot.png", screenshot)
}
@Test fun readAndCompareScreenshots() {
composeTestRule.setContent { MyComposableFunction() }
val node = composeTestRule.onRoot()
val screenshot = node.captureToImage().asAndroidBitmap()
val context = InstrumentationRegistry.getInstrumentation().targetContext
val path = context.getExternalFilesDir(Environment.DIRECTORY_PICTURES)
val file = File(path, "screenshot.png")
val saved = readScreenshot(file)
println("Are screenshots the same: ${screenshot.sameAs(saved)}")
}
private fun readScreenshot(file: File) = BitmapFactory.decodeFile(file.path)
private fun saveScreenshot(filename: String, screenshot: Bitmap) {
val context = InstrumentationRegistry.getInstrumentation().targetContext
// Saves in /Android/data/your.package.name.test/files/Pictures on external storage
val path = context.getExternalFilesDir(Environment.DIRECTORY_PICTURES)
val file = File(path, filename)
file.outputStream().use { stream ->
screenshot.compress(Bitmap.CompressFormat.PNG, 100, stream)
}
}
}
I've also answered a similar question here.