Add UnitEmitter

Author: colemancda

Demo/app/src/main/java/com/pureswift/swiftandroid/MainActivity.kt

@@ -4,17 +4,41 @@ import android.os.Bundle
 import android.util.Log
 import android.view.View
 import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.width
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import java.util.Date
 
 class MainActivity : ComponentActivity() {
 
     init {
         NativeLibrary.shared()
     }
 
+    val emitter = UnitEmitter()
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         onCreateSwift(savedInstanceState)
         //enableEdgeToEdge()
+
+        // set composable root view
+        setContent {
+            EventReceiver(emitter = emitter)
+        }
     }
 
     external fun onCreateSwift(savedInstanceState: Bundle?)
@@ -24,3 +48,29 @@ class MainActivity : ComponentActivity() {
         setContentView(view)
     }
 }
+
+@Composable
+fun EventReceiver(emitter: UnitEmitter) {
+
+    val tick by emitter.flow.collectAsState(initial = Unit)
+
+    var date by remember { mutableStateOf(Date()) }
+
+    LaunchedEffect(Unit) {
+        emitter.flow.collect {
+            date = Date()
+        }
+    }
+
+    Box(
+        modifier = Modifier.fillMaxSize(),
+        contentAlignment = Alignment.Center
+    ) {
+        Column(
+            horizontalAlignment = Alignment.CenterHorizontally
+        ) {
+            Text("Hello Swift!")
+            Text(date.toString())
+        }
+    }
+}

Demo/app/src/main/java/com/pureswift/swiftandroid/UnitEmitter.kt

@@ -0,0 +1,15 @@
+package com.pureswift.swiftandroid
+
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.SharedFlow
+
+class UnitEmitter() {
+
+    private val _flow = MutableSharedFlow<Unit>(extraBufferCapacity = 64)
+    val flow: SharedFlow<Unit> get() = _flow
+
+    fun emit() {
+        //println("Emit")
+        _flow.tryEmit(Unit)
+    }
+}

Demo/app/src/main/swift/MainActivity.swift

@@ -16,6 +16,9 @@ open class MainActivity: AndroidApp.Activity {
     @JavaMethod
     open func setRootView(_ view: AndroidView.View?)
 
+    @JavaMethod
+    open func getEmitter() -> UnitEmitter!
+    
     static private(set) var shared: MainActivity!
 
     lazy var textView = TextView(self)
@@ -25,6 +28,8 @@ open class MainActivity: AndroidApp.Activity {
     lazy var recyclerView = RecyclerView(self)
 
     lazy var button = AndroidWidget.Button(self)
+
+    lazy var emitter = getEmitter()!
 
     lazy var rootViewID: Int32 = try! JavaClass<AndroidView.View>().generateViewId()
 }
@@ -56,7 +61,8 @@ private extension MainActivity {
         }
 
         // need to recreate views
-        setRootView()
+        //setRootView()
+        startEmitterTimer()
 
         Task {
             printBinderVersion()
@@ -105,6 +111,22 @@ private extension MainActivity {
         }
     }
 
+    func startEmitterTimer() {
+        // update view on timer
+        Task { [weak self] in
+            while let self {
+                emit()
+                try? await Task.sleep(for: .seconds(1))
+            }
+        }
+    }
+
+    @MainActor
+    func emit() {
+        Self.log("\(self).\(#function)")
+        emitter.emit()
+    }
+    
     func setupNavigationStack() {
 
         let fragmentContainer = FrameLayout(self)

Demo/app/src/main/swift/UnitEmitter.swift

@@ -0,0 +1,19 @@
+//
+//  UnitEmitter.swift
+//  SwiftAndroidApp
+//
+//  Created by Alsey Coleman Miller on 7/13/25.
+//
+
+import JavaKit
+
+/// Bridge from Swift to Kotlin Coroutines
+@JavaClass("com.pureswift.swiftandroid.UnitEmitter")
+open class UnitEmitter: JavaObject {
+    
+    @JavaMethod
+    @_nonoverride public convenience init(environment: JNIEnvironment? = nil)
+    
+    @JavaMethod
+    func emit()
+}