begin making new bt scan gui

app/src/main/java/com/geeksville/mesh/ui/BTScanScreen.kt

@@ -0,0 +1,89 @@
+package com.geeksville.mesh.ui
+
+import android.bluetooth.BluetoothManager
+import android.bluetooth.le.ScanCallback
+import android.bluetooth.le.ScanFilter
+import android.bluetooth.le.ScanResult
+import android.bluetooth.le.ScanSettings
+import android.os.ParcelUuid
+import androidx.compose.Composable
+import androidx.compose.Context
+import androidx.compose.ambient
+import androidx.compose.onActive
+import androidx.ui.core.ContextAmbient
+import androidx.ui.core.Text
+import androidx.ui.layout.Column
+import androidx.ui.tooling.preview.Preview
+import com.geeksville.android.Logging
+import com.geeksville.mesh.service.RadioInterfaceService
+
+object BTLog : Logging
+
+@Composable
+fun BTScanScreen() {
+    val context = ambient(ContextAmbient)
+
+    /// Note: may be null on platforms without a bluetooth driver (ie. the emulator)
+    val bluetoothAdapter =
+        (context.getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager?)?.adapter
+
+    onActive {
+
+        if (bluetoothAdapter == null)
+            BTLog.warn("No bluetooth adapter.  Running under emulation?")
+        else {
+            val scanner = bluetoothAdapter.bluetoothLeScanner
+
+            val scanCallback = object : ScanCallback() {
+                override fun onScanFailed(errorCode: Int) {
+                    TODO() // FIXME, update gui with message about this
+                }
+
+                // For each device that appears in our scan, ask for its GATT, when the gatt arrives,
+                // check if it is an eligable device and store it in our list of candidates
+                // if that device later disconnects remove it as a candidate
+                override fun onScanResult(callbackType: Int, result: ScanResult) {
+
+                    BTLog.info("onScanResult ${result.device.address}")
+
+                    // We don't need any more results now
+                    // scanner.stopScan(this)
+                }
+            }
+
+            BTLog.debug("starting scan")
+
+            // filter and only accept devices that have a sw update service
+            val filter =
+                ScanFilter.Builder()
+                    .setServiceUuid(ParcelUuid(RadioInterfaceService.BTM_SERVICE_UUID))
+                    .build()
+
+            /* ScanSettings.CALLBACK_TYPE_FIRST_MATCH seems to trigger a bug returning an error of
+            SCAN_FAILED_OUT_OF_HARDWARE_RESOURCES (error #5)
+             */
+            val settings =
+                ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY).
+                    // setMatchMode(ScanSettings.MATCH_NUM_ONE_ADVERTISEMENT).
+                    // setCallbackType(ScanSettings.CALLBACK_TYPE_FIRST_MATCH).
+                    build()
+            scanner.startScan(listOf(filter), settings, scanCallback)
+
+            onDispose {
+                BTLog.debug("stopping scan")
+                scanner.stopScan(scanCallback)
+            }
+        }
+    }
+
+    Column {
+        Text("FIXME")
+    }
+}
+
+
+@Preview
+@Composable
+fun btScanScreenPreview() {
+    BTScanScreen()
+}