书w3school网站建设教程关于市场营销的100个问题

物联网环境，为了解决不同厂商、不同设备、不同网络情况下使用顺畅，同时也考虑到节约成本，缩小应用体积的好处，我们需要一个服务应用一直存在系统中，保活它以提供服务给其他客户端调用。
开机自启动，通过广播通信，

必要权限

    <!--允许查看所有未启动的应用--><uses-permission android:name="android.permission.QUERY_ALL_PACKAGES"tools:ignore="QueryAllPackagesPermission" /><!--// 添加接收开机广播的权限--><uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" /><!--前台服务--><uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>

开机自启动Service相关代码

import android.content.BroadcastReceiver
import android.content.ComponentName
import android.content.Context
import android.content.Intent
import android.os.Build
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch/*** @date 2023/2/28* @email L2279833535@163.com* @author 小红妹* @package com.xxx.xxx.receiver* @describe 接收开机广播、开机自启动Service* @copyright*/
class BootBroadcastReceiver : BroadcastReceiver() {private val ACTION_BOOT = "android.intent.action.BOOT_COMPLETED"override fun onReceive(context: Context?, intent: Intent?) {if (intent?.action == ACTION_BOOT) {GlobalScope.launch(Dispatchers.Main) {delay(20000L)val intent = Intent()intent.component =ComponentName("com.xxx.xxx.end", "com.xxx.xxx.end.DeviceService")if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {context?.startForegroundService(intent)} else {context?.startService(intent)}}}}}

import android.app.*
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.graphics.Color
import android.os.Build
import android.os.IBinder
import android.util.Log
import androidx.core.app.NotificationCompat
import com.ccbft.pda.reader.RfidUHF
import com.krd.ricemachine.uits.ShareUtil
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch/*** @date 2023/3/16* @email L2279833535@163.com* @author 小红妹* @package com.xxx.xxx.end* @describe* @copyright*/
class DeviceService : Service() {private lateinit var deviceBroadcastReceiver : DeviceBroadcastReceiverprivate lateinit var mContext: Contextprivate val TAG = "DeviceService"/** 标记服务是否启动 */private var serviceIsLive = false/** 唯一前台通知ID */private val NOTIFICATION_ID = 1000override fun onCreate() {super.onCreate()mContext = this//前台显示服务// 获取服务通知val notification: Notification = createForegroundNotification()//将服务置于启动状态 ,NOTIFICATION_ID指的是创建的通知的IDstartForeground(NOTIFICATION_ID, notification)}override fun onBind(p0: Intent?): IBinder? {return null}override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {CoroutineScope(Dispatchers.Main).launch {//delay(1000L)//阻塞时间//receiverRegist()RfidUHF.initUHF()ShareUtil.putString("AES_key", intent?.getStringExtra("key"), mContext)Log.e(TAG, "onStartCommand: "+ intent?.getStringExtra("key"))}// 标记前台服务启动serviceIsLive = truereturn super.onStartCommand(intent, flags, startId)}private fun receiverRegist() {deviceBroadcastReceiver = DeviceBroadcastReceiver()val filter = IntentFilter()filter.addAction("deviceCall")registerReceiver(deviceBroadcastReceiver, filter)}/*** 创建前台服务通知*/private fun createForegroundNotification(): Notification {val notificationManager = getSystemService(NOTIFICATION_SERVICE) as NotificationManager// 唯一的通知通道的id.val notificationChannelId = "notification_channel_id_01"// Android8.0以上的系统，新建消息通道if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {//用户可见的通道名称val channelName = "Foreground Service Notification"//通道的重要程度val importance = NotificationManager.IMPORTANCE_HIGHval notificationChannel =NotificationChannel(notificationChannelId, channelName, importance)notificationChannel.description = "Channel description"//LED灯notificationChannel.enableLights(true)notificationChannel.lightColor = Color.RED//震动notificationChannel.vibrationPattern = longArrayOf(0, 1000, 500, 1000)notificationChannel.enableVibration(true)notificationManager?.createNotificationChannel(notificationChannel)}val builder = NotificationCompat.Builder(this, notificationChannelId)//通知小图标builder.setSmallIcon(R.mipmap.ic_launcher)//通知标题builder.setContentTitle("AndroidServer")//通知内容builder.setContentText("AndroidServer服务正在运行中")//设定通知显示的时间builder.setWhen(System.currentTimeMillis())//设定启动的内容val activityIntent = Intent(this, MainActivity::class.java)val pendingIntent = PendingIntent.getActivity(this,1,activityIntent,PendingIntent.FLAG_IMMUTABLE) /*FLAG_UPDATE_CURRENT*/builder.setContentIntent(pendingIntent)//创建通知并返回return builder.build()}override fun onDestroy() {//unregisterReceiver(deviceBroadcastReceiver)super.onDestroy()// 标记服务关闭serviceIsLive = false// 移除通知stopForeground(true)}

注意
1、Android 8.0后台运行服务需要开启前台显示服务
2、Android 8.0 不再允许后台进程直接通过startService方式去启动服务，改为startForegroundService方式启动。
对应错误提示如下

Context.startForegroundService() did not then call Service.startForeground(): 
ServiceRecord{24fafff u0 com.xxx.xxx.end/.DeviceService}

3、Android O 后台应用想启动服务调用：调用startForegroundService()后 切记调用startForeground()，这个时候会有一个Notification常驻，也就是上面说的1。
权限提示：

Permission Denial: startForeground from pid=2406, uid=10134 requires 
android.permission.FOREGROUND_SERVICE

4、Android 11以上启动服务不能只是这样简单的调用//context?.startService(Intent(context, DeviceService::class.java))
不然会报错，

Process: com.xuanyi.webserver, PID: 2455
java.lang.IllegalStateException: Not allowed to start service Intent { cmp=com.xxx.xxx/.service.WebService }: app is in background uid UidRecord{103aaa1 u0a138 CEM  idle change:cached procs:1 seq(0,0,0)}at android.app.ContextImpl.startServiceCommon(ContextImpl.java:1715)at android.app.ContextImpl.startService(ContextImpl.java:1670)at android.content.ContextWrapper.startService(ContextWrapper.java:720)at android.content.ContextWrapper.startService(ContextWrapper.java:720)at com.xxx.xxx.receiver.BootBroadcastReceiver$onReceive$1.invokeSuspend(BootBroadcastReceiver.kt:26)at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:570)at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:749)at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:677)at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:664)Suppressed: kotlinx.coroutines.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@e0016fc, Dispatchers.Default]

5、Android 12 四大组件含有< intent-filter >< /intent-filter >的需要添加android:exported=“true”，更多情况情况着这篇文章 Android 12适配安全组件导出设置android:exported 指定显式值”

6、Android 11引入了包可见性 ，要么添加QUERY_ALL_PACKAGES权限，要么这样写

<queries>//你要交互的service的包名<package android:name="com.XXX.XXX" />//...等等包名
</queries>

广播通信的前提，1.应用APP要启动过一次，2、要有至少有一个activity ，3、注册广播方式
这就是为什么我们需要服务的意思，首先需要开机自启动服务，这会我们可以在启动的服务中动态注册广播，测试静态注册也可以。
对了，广播的静态注册效果随着版本的升高，效果大打折扣，为了防止小人作弊，系统把君子和小人都设防了。

若是用户手动从后台杀掉应用程序，那么广播无法再次启动服务，哈哈哈哈哈哈，那就想办法让用户无法删除服务吧！