IllegalStateException: Can't get window from the Context

[Queatz]

When I call drawController.saveBitmap() I get this error. Maybe because my DrawBox is in a Dialog?

java.lang.IllegalStateException: Can't get window from the Context
	at io.ak1.drawbox.HelperKt.drawBitmapFromView(Helper.kt:78)
	at io.ak1.drawbox.DrawController$trackBitmaps$$inlined$mapNotNull$1$2.emit(Collect.kt:137)
	at kotlinx.coroutines.flow.SharedFlowImpl.collect$suspendImpl(SharedFlow.kt:392)
	at kotlinx.coroutines.flow.SharedFlowImpl$collect$1.invokeSuspend(Unknown Source:15)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:104)
	at androidx.compose.ui.platform.AndroidUiDispatcher.performTrampolineDispatch(AndroidUiDispatcher.android.kt:81)
	at androidx.compose.ui.platform.AndroidUiDispatcher.access$performTrampolineDispatch(AndroidUiDispatcher.android.kt:41)
	at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.run(AndroidUiDispatcher.android.kt:57)
	at android.os.Handler.handleCallback(Handler.java:966)
	at android.os.Handler.dispatchMessage(Handler.java:110)
	at android.os.Looper.loopOnce(Looper.java:205)
	at android.os.Looper.loop(Looper.java:293)

[Queatz]

I was able to use https://github.com/PatilShreyas/Capturable instead. Maybe we should use this library instead? Then we can remove the AndroidView as well!

[Queatz]

Then we can remove a lot of code, the whole library becomes:

data class PathWrapper(
    var points: SnapshotStateList<Offset>,
    val strokeWidth: Float = 5f,
    val strokeColor: Color,
    val alpha: Float = 1f
)

data class DrawBoxPayLoad(val bgColor: Color, val path: List<PathWrapper>)

fun createPath(points: List<Offset>) = Path().apply {
    if (points.size > 1) {
        var oldPoint: Offset? = null
        this.moveTo(points[0].x, points[0].y)
        for (i in 1 until points.size) {
            val point: Offset = points[i]
            oldPoint?.let {
                val midPoint = calculateMidpoint(it, point)
                if (i == 1) {
                    this.lineTo(midPoint.x, midPoint.y)
                } else {
                    this.quadraticBezierTo(it.x, it.y, midPoint.x, midPoint.y)
                }
            }
            oldPoint = point
        }
        oldPoint?.let { this.lineTo(it.x, oldPoint.y) }
    }
}

private fun calculateMidpoint(start: Offset, end: Offset) =
    Offset((start.x + end.x) / 2, (start.y + end.y) / 2)

/**
 * Created by akshay on 18/01/22
 * https://ak1.io
 */
class DrawController internal constructor(val trackHistory: (undoCount: Int, redoCount: Int) -> Unit = { _, _ -> }) {

    private val _redoPathList = mutableStateListOf<PathWrapper>()
    private val _undoPathList = mutableStateListOf<PathWrapper>()
    internal val pathList: SnapshotStateList<PathWrapper> = _undoPathList
    
    private val _historyTracker = MutableSharedFlow<String>(extraBufferCapacity = 1)
    private val historyTracker = _historyTracker.asSharedFlow()

    fun trackHistory(
        scope: CoroutineScope,
        trackHistory: (undoCount: Int, redoCount: Int) -> Unit
    ) {
        historyTracker
            .onEach { trackHistory(_undoPathList.size, _redoPathList.size) }
            .launchIn(scope)
    }
    
    var opacity by mutableStateOf(1f)
        private set

    var strokeWidth by mutableStateOf(10f)
        private set

    var color by mutableStateOf(Color.Red)
        private set

    var bgColor by mutableStateOf(Color.Black)
        private set

    fun changeOpacity(value: Float) {
        opacity = value
    }

    fun changeColor(value: Color) {
        color = value
    }

    fun changeBgColor(value: Color) {
        bgColor = value
    }

    fun changeStrokeWidth(value: Float) {
        strokeWidth = value
    }

    fun importPath(drawBoxPayLoad: DrawBoxPayLoad) {
        reset()
        bgColor = drawBoxPayLoad.bgColor
        _undoPathList.addAll(drawBoxPayLoad.path)
        _historyTracker.tryEmit("${_undoPathList.size}")
    }

    fun exportPath() = DrawBoxPayLoad(bgColor, pathList.toList())


    fun unDo() {
        if (_undoPathList.isNotEmpty()) {
            val last = _undoPathList.last()
            _redoPathList.add(last)
            _undoPathList.remove(last)
            trackHistory(_undoPathList.size, _redoPathList.size)
            _historyTracker.tryEmit("Undo - ${_undoPathList.size}")
        }
    }

    fun reDo() {
        if (_redoPathList.isNotEmpty()) {
            val last = _redoPathList.last()
            _undoPathList.add(last)
            _redoPathList.remove(last)
            trackHistory(_undoPathList.size, _redoPathList.size)
            _historyTracker.tryEmit("Redo - ${_redoPathList.size}")
        }
    }

    fun reset() {
        _redoPathList.clear()
        _undoPathList.clear()
        _historyTracker.tryEmit("-")
    }

    fun updateLatestPath(newPoint: Offset) {
        val index = _undoPathList.lastIndex
        _undoPathList[index].points.add(newPoint)
    }

    fun insertNewPath(newPoint: Offset) {
        val pathWrapper = PathWrapper(
            points = mutableStateListOf(newPoint),
            strokeColor = color,
            alpha = opacity,
            strokeWidth = strokeWidth,
        )
        _undoPathList.add(pathWrapper)
        _redoPathList.clear()
        _historyTracker.tryEmit("${_undoPathList.size}")
    }
}

@Composable
fun rememberDrawController() = remember { DrawController() }

@Composable
fun DrawBox(
    drawController: DrawController,
    modifier: Modifier = Modifier,
    backgroundColor: Color = MaterialTheme.colorScheme.background,
    trackHistory: (undoCount: Int, redoCount: Int) -> Unit = { _, _ -> }
) {
    LaunchedEffect(drawController, backgroundColor) {
        drawController.changeBgColor(backgroundColor)
        drawController.trackHistory(this, trackHistory)
    }
    Canvas(
        modifier = modifier
        .background(drawController.bgColor)
        .pointerInput(Unit) {
            detectTapGestures(
                onTap = { offset ->
                    drawController.insertNewPath(offset)
                    drawController.updateLatestPath(offset)
                    drawController.pathList
                }
            )
        }
        .pointerInput(Unit) {
            detectDragGestures(
                onDragStart = { offset ->
                    drawController.insertNewPath(offset)
                }
            ) { change, _ ->
                val newPoint = change.position
                drawController.updateLatestPath(newPoint)
            }

        }) {
        drawController.pathList.forEach { pw ->
            drawPath(
                createPath(pw.points),
                color = pw.strokeColor,
                alpha = pw.alpha,
                style = Stroke(
                    width = pw.strokeWidth,
                    cap = StrokeCap.Round,
                    join = StrokeJoin.Round
                )
            )
        }
    }
}