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WebView for JetBrains Compose Multiplatform
package com.multiplatform.webview.web
import androidx.compose.runtime.Composable
import androidx.compose.runtime.Stable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
/**
* Created By Kevin Zou On 2023/9/5
*/
/**
* Allows control over the navigation of a WebView from outside the composable. E.g. for performing
* a back navigation in response to the user clicking the "up" button in a TopAppBar.
*
* @see [rememberWebViewNavigator]
*/
@Stable
class WebViewNavigator(private val coroutineScope: CoroutineScope) {
/**
* Sealed class for constraining possible navigation events.
*/
private sealed interface NavigationEvent {
/**
* Navigate back event.
*/
data object Back : NavigationEvent
/**
* Navigate forward event.
*/
data object Forward : NavigationEvent
/**
* Reload event.
*/
data object Reload : NavigationEvent
/**
* Stop loading event.
*/
data object StopLoading : NavigationEvent
/**
* Load url event.
*/
data class LoadUrl(
val url: String,
val additionalHttpHeaders: Map = emptyMap(),
) : NavigationEvent
/**
* Load html event.
*/
data class LoadHtml(
val html: String,
val baseUrl: String? = null,
val mimeType: String? = null,
val encoding: String? = "utf-8",
val historyUrl: String? = null,
) : NavigationEvent
data class LoadHtmlFile(
val fileName: String,
) : NavigationEvent
/**
* Post url event.
*/
data class PostUrl(
val url: String,
val postData: ByteArray,
) : NavigationEvent {
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (other == null || this::class != other::class) return false
other as PostUrl
if (url != other.url) return false
if (!postData.contentEquals(other.postData)) return false
return true
}
override fun hashCode(): Int {
var result = url.hashCode()
result = 31 * result + postData.contentHashCode()
return result
}
}
/**
* Evaluate javascript event.
*/
data class EvaluateJavaScript(
val script: String,
val callback: ((String) -> Unit)?,
) : NavigationEvent
}
/**
* A [MutableSharedFlow] of [NavigationEvent]s that is used to communicate navigation events
* from the composable to the [IWebView].
*/
private val navigationEvents: MutableSharedFlow = MutableSharedFlow(replay = 1)
/**
* Handles navigation events from the composable and calls the appropriate method on the
* [IWebView].
* Use Dispatchers.Main to ensure that the webview methods are called on UI thread
*/
internal suspend fun IWebView.handleNavigationEvents(): Nothing =
withContext(Dispatchers.Main) {
navigationEvents.collect { event ->
when (event) {
is NavigationEvent.Back -> goBack()
is NavigationEvent.Forward -> goForward()
is NavigationEvent.Reload -> reload()
is NavigationEvent.StopLoading -> stopLoading()
is NavigationEvent.LoadHtml ->
loadHtml(
event.baseUrl,
event.html,
event.mimeType,
event.encoding,
event.historyUrl,
)
is NavigationEvent.LoadHtmlFile -> {
loadHtmlFile(event.fileName)
}
is NavigationEvent.LoadUrl -> {
loadUrl(event.url, event.additionalHttpHeaders)
}
is NavigationEvent.PostUrl -> {
postUrl(event.url, event.postData)
}
is NavigationEvent.EvaluateJavaScript -> {
evaluateJavaScript(event.script, event.callback)
}
}
}
}
/**
* True when the web view is able to navigate backwards, false otherwise.
*/
var canGoBack: Boolean by mutableStateOf(false)
internal set
/**
* True when the web view is able to navigate forwards, false otherwise.
*/
var canGoForward: Boolean by mutableStateOf(false)
internal set
/**
* Loads the given URL.
*
* @param url The URL of the resource to load.
*/
fun loadUrl(
url: String,
additionalHttpHeaders: Map = emptyMap(),
) {
coroutineScope.launch {
navigationEvents.emit(
NavigationEvent.LoadUrl(
url,
additionalHttpHeaders,
),
)
}
}
/**
* Loads the given HTML string.
*
* @param html The HTML string to load.
* @param baseUrl The URL to use as the page's base URL.
* @param mimeType The MIME type of the data in the string.
* @param encoding The encoding of the data in the string.
* @param historyUrl The history URL for the loaded HTML. Leave null to use about:blank.
*/
fun loadHtml(
html: String,
baseUrl: String? = null,
mimeType: String? = null,
encoding: String? = "utf-8",
historyUrl: String? = null,
) {
coroutineScope.launch {
navigationEvents.emit(
NavigationEvent.LoadHtml(
html,
baseUrl,
mimeType,
encoding,
historyUrl,
),
)
}
}
fun loadHtmlFile(fileName: String) {
coroutineScope.launch {
navigationEvents.emit(
NavigationEvent.LoadHtmlFile(
fileName,
),
)
}
}
/**
* Posts the given data to the given URL.
*
* @param url The URL to post the data to.
* @param postData The data to post.
*/
fun postUrl(
url: String,
postData: ByteArray,
) {
coroutineScope.launch {
navigationEvents.emit(
NavigationEvent.PostUrl(
url,
postData,
),
)
}
}
/**
* Evaluates the given JavaScript in the context of the currently displayed page.
*
* @param script The JavaScript to evaluate.
* @param callback A callback to be invoked when the script execution completes.
*/
fun evaluateJavaScript(
script: String,
callback: ((String) -> Unit)? = null,
) {
coroutineScope.launch {
navigationEvents.emit(
NavigationEvent.EvaluateJavaScript(
script,
callback,
),
)
}
}
/**
* Navigates the webview back to the previous page.
*/
fun navigateBack() {
coroutineScope.launch { navigationEvents.emit(NavigationEvent.Back) }
}
/**
* Navigates the webview forward after going back from a page.
*/
fun navigateForward() {
coroutineScope.launch { navigationEvents.emit(NavigationEvent.Forward) }
}
/**
* Reloads the current page in the webview.
*/
fun reload() {
coroutineScope.launch { navigationEvents.emit(NavigationEvent.Reload) }
}
/**
* Stops the current page load (if one is loading).
*/
fun stopLoading() {
coroutineScope.launch { navigationEvents.emit(NavigationEvent.StopLoading) }
}
}
/**
* Creates and remembers a [WebViewNavigator] using the default [CoroutineScope] or a provided
* override.
*/
@Composable
fun rememberWebViewNavigator(coroutineScope: CoroutineScope = rememberCoroutineScope()): WebViewNavigator =
remember(coroutineScope) { WebViewNavigator(coroutineScope) }