问题：
Flutter静态编程语言从广播接收机获取数据
陆野
我正在尝试拥有自己的蓝牙kotlin实现，但遇到了一个问题。
我正在按照这里的kotlin教程启动一个用于扫描蓝牙设备的广播接收器。
问题是，当我试图从广播接收器将每个发现的设备添加到主活动范围内的可变列表中，以便将列表发送到颤振端时，我总是得到一个空值。
由于我是kotlin和android的新手，我无法真正理解我到底哪里出错了，以及我需要了解哪些概念才能做我需要做的事情。
Kotlin主要活动。千吨级
class MainActivity : FlutterActivity() {
private val CHANNEL = "bluetooth.channel"
var deviceList: MutableList<BluetoothDevice>?=null;
override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
GeneratedPluginRegistrant.registerWith(flutterEngine);
MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
when (call.method) {
"getBlue" -> bluetoothWrapper(result)
"discoverBlue" -> discoverDevices(deviceList,result)
}
}
}
private fun bluetoothWrapper(result: MethodChannel.Result) {
val defaultAdapter: BluetoothAdapter? = BluetoothAdapter.getDefaultAdapter()
checkAdapter(result, defaultAdapter);
enableAdapter(defaultAdapter!!);
}
private fun checkAdapter(result: MethodChannel.Result, defaultAdapter: BluetoothAdapter?) { // check if adapter exists
if (defaultAdapter == null) {
result.error("Bluetooth adapter doesn't exist on this device", null, null)
} else {
result.success("bluetooth adapter exists on device")
}
}
// check if adapter is enabled if it exists, enable it if it isnt
@SuppressLint("MissingPermission")
private fun enableAdapter(bluetoothAdapter: BluetoothAdapter) {
val requestEnableBt = 1;
if (!bluetoothAdapter.isEnabled) {
val enableIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
startActivityForResult(enableIntent, requestEnableBt)
}
}
// register broadcast receiver in order to discover available devices
private fun discoverDevices(deviceList: MutableList<BluetoothDevice>?, result: MethodChannel.Result) {
val filter = IntentFilter(BluetoothDevice.ACTION_FOUND)
registerReceiver(receiver, filter);
result.success(deviceList)
}
private val receiver = object : BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
when (intent.action) {
BluetoothDevice.ACTION_FOUND -> {
val device: BluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE)
deviceList?.add(device)
println("device found has selected parameters inside the broadcast receivver function $device")
}
"" -> println("broadcast receiver intent.action has no attribute")
null -> println("broadcast receiver intent.action was null")
}
}
}
}
颤振总管。飞奔
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() => runApp(MaterialApp(home: HomePage()));
class HomePage extends StatelessWidget {
static const platform = const MethodChannel('bluetooth.channel');
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Bluetooth Native'),
centerTitle: true,
),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
color: Colors.blue[500],
onPressed: () {
printMethod();
},
child: Text('connect to Devices'),
)
],
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
color: Colors.blue[500],
onPressed: () {
discoverBlue();
},
child: Text('Discover devices'),
)
],
)
],
),
);
}
void printMethod() async {
String value;
try {
value = await platform.invokeMethod("getBlue");
} catch (e) {
print(e);
}
print('printing from dart: $value');
}
void discoverBlue() async {
Future<List> list;
list = platform.invokeListMethod("discoverBlue", list);
list.then((val) {
print("got values from kotlin $val");
});
}
}
共有1个答案
田修为
我看到你还没有触发启动发现过程。你需要做
val myAdapter = BluetoothAdapter.getDefaultAdapter();
myAdapter.startDiscovery();
另外，因为它在kotlin中是异步任务。返回结果
BluetoothAdapter.ACTION_DISCOVERY_FINISHED
所以你的MainActivity.kt会是
package com.example.testapp
import android.annotation.SuppressLint
import android.app.Activity
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothDevice
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import androidx.annotation.NonNull
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant
class MainActivity : FlutterActivity() {
private val CHANNEL = "bluetooth.channel"
var deviceList: MutableList<BluetoothDevice>? = null;
override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
GeneratedPluginRegistrant.registerWith(flutterEngine);
MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
when (call.method) {
"getBlue" -> bluetoothWrapper(result)
"discoverBlue" -> discoverDevices(deviceList, result)
"allPaired" -> getConnectedDevices(result)
}
}
}
private fun getConnectedDevices(result: MethodChannel.Result) {
val mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
val pairedDevices = mBluetoothAdapter.bondedDevices
val s: MutableList<String> = ArrayList()
for (bt in pairedDevices) s.add(bt.name)
result.success(s);
}
private fun bluetoothWrapper(result: MethodChannel.Result) {
val defaultAdapter: BluetoothAdapter? = BluetoothAdapter.getDefaultAdapter()
checkAdapter(result, defaultAdapter);
enableAdapter(defaultAdapter!!);
}
private fun checkAdapter(result: MethodChannel.Result, defaultAdapter: BluetoothAdapter?) { // check if adapter exists
if (defaultAdapter == null) {
result.error("Bluetooth adapter doesn't exist on this device", null, null)
} else {
result.success("bluetooth adapter exists on device")
}
}
// check if adapter is enabled if it exists, enable it if it isnt
@SuppressLint("MissingPermission")
private fun enableAdapter(bluetoothAdapter: BluetoothAdapter) {
val requestEnableBt = 1;
if (!bluetoothAdapter.isEnabled) {
val enableIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
startActivityForResult(enableIntent, requestEnableBt)
}
}
// register broadcast receiver in order to discover available devices
private fun discoverDevices(deviceList: MutableList<BluetoothDevice>?, result: MethodChannel.Result) {
val myAdapter = BluetoothAdapter.getDefaultAdapter();
myAdapter.startDiscovery();
val filter = IntentFilter(BluetoothDevice.ACTION_FOUND)
val receiver = object : BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
when (intent.action) {
BluetoothDevice.ACTION_FOUND -> {
val device: BluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE)
deviceList?.add(device)
println("device found has selected parameters inside the broadcast receivver function $device")
}
BluetoothAdapter.ACTION_DISCOVERY_FINISHED -> {
result.success(deviceList)
}
"" -> println("broadcast receiver intent.action has no attribute")
null -> println("broadcast receiver intent.action was null")
}
}
}
registerReceiver(receiver, filter)
}
}
和main。dart将是
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
void main() => runApp(MaterialApp(home: HomePage()));
class HomePage extends StatelessWidget {
static const platform = const MethodChannel('bluetooth.channel');
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Bluetooth Native'),
centerTitle: true,
),
body: Container(
width: double.infinity,
child: Column(
mainAxisSize: MainAxisSize.max,
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
color: Colors.blue[500],
onPressed: () {
printMethod();
},
child: Text('connect to Devices'),
),
RaisedButton(
color: Colors.blue[500],
onPressed: () {
discoverBlue();
},
child: Text('Discover devices'),
),
RaisedButton(
color: Colors.blue[500],
onPressed: () {
getAllPaired();
},
child: Text('All paired devices'),
)
],
),
),
);
}
void printMethod() async {
String value;
try {
value = await platform.invokeMethod("getBlue");
} catch (e) {
print(e);
}
print('printing from dart: $value');
}
void discoverBlue() async {
Future<List> list;
list = platform.invokeListMethod("discoverBlue", list);
list.then((val) {
print("got values from kotlin $val");
});
}
void getAllPaired() async {
var value = await platform.invokeListMethod("allPaired");
print(value);
}
}
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