Let users open a local PDF from their device storage

Trigger the platform file picker with requestOpenFromDevice, observe KPdfOpenDocumentState for results, and load the selected file in the viewer.

KPDF handles the platform file picker for you. Call requestOpenFromDevice() to launch the picker, observe openDocumentState for the result, and call viewerState.open(selectedSource) when the user selects a file. The kpdf-compose module binds the platform effects automatically when you use rememberPdfViewerState, so no additional setup is needed.

Full pattern

The example below shows the complete flow: a button that triggers the picker and a LaunchedEffect that opens the document when the picker returns a selection.

@Composable
fun OpenFromDeviceExample(viewerState: KPdfViewerState) {
    val openState by viewerState.openDocumentState.collectAsState()

    // Open the document as soon as the picker returns a file
    LaunchedEffect(openState) {
        val selectedSource = (openState as? KPdfOpenDocumentState.Success)?.source
            ?: return@LaunchedEffect

        viewerState.open(selectedSource)
    }

    Button(onClick = { viewerState.requestOpenFromDevice() }) {
        Text("Open local PDF")
    }
}

KPdfOpenDocumentState variants

openDocumentState is a StateFlow<KPdfOpenDocumentState>. React to each variant to keep your UI consistent with the picker lifecycle.

State	When it occurs	Suggested UI reaction
Idle	Initial state, no pick in progress	No indicator
AwaitingSelection	Picker is open, waiting for the user	Show a loading or “choosing…” indicator
Success	User selected a file	Call viewerState.open(source) to load it
Cancelled	User dismissed the picker	Dismiss any indicator, restore previous state
Error	Picker failed or the file could not be read	Show an error message

when (openState) {
    KPdfOpenDocumentState.Idle -> Unit
    is KPdfOpenDocumentState.AwaitingSelection -> {
        CircularProgressIndicator()
    }
    is KPdfOpenDocumentState.Success -> {
        // handled in LaunchedEffect above
    }
    KPdfOpenDocumentState.Cancelled -> {
        Text("No file selected.")
    }
    is KPdfOpenDocumentState.Error -> {
        Text("Could not open file: ${openState.reason}")
    }
}

If openDocumentState appears stuck at Idle after tapping the button, the most common cause is that viewerState is being recreated on every recomposition. This happens when you construct KPdfViewerConfig inline, outside a remember block. Wrap the config in remember { KPdfViewerConfig.builder()…build() } to keep the state instance stable.