Android笔记（十七）：PendingIntent简介

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PendingIntent翻译成中文为“待定意图”，这个翻译很好地表示了它的涵义。PendingIntent描述了封装Intent意图以及该意图要执行的目标操作。PendingIntent封装Intent的目标行为的执行是必须满足一定条件，只有条件满足，才会触发意图的目标操作。

一.获取PendingIntent对象

获取PendingIntent对象有以下几种方式:

• PendingIntent.getActivity(Context, int, Intent, int)：启动活动
• PendingIntent.getActivities(Context, int, Intent[], int)：启动多个活动，意图中为数组
• PendingIntent.getBroadcast(Context, int, Intent, int)：启动广播
• PendingIntent.getService(Context, int, Intent, int)：启动服务

参数说明：

• Context：context上下文，PendingIntent启动活动的上下文
• int：requestCode请求码 ,发送者发送的请求码
• Intent：intent意图：要加载活动的意图
• int：flags 标记

对于其中的标记可以定义为下列形式

• FLAG_ONE_SHOT：PendingIntent对象仅使用一次；
• FLAG_NO_CREATE：如果PendingIntent对象不存在则返回null
• FLAG_CANCEL_CURRENT：如果PendingIntent对象已存在，则取消原有的对象，创建新的PendingIntent对象
• FLAG_UPDATE_CURRENT：如果PendingIntent对象已存在，则保留原有的对象，修改原有对象的属性数据
• FLAG_IMMUTABLE：PendingIntent对象是不可变的
• FLAG_MUTABLE：PendingIntent对象是可变的
• 另外其他Intent中支持的标记都可以在标记参数中使用。

二、应用实例

例如：在MainActivity启动前台服务播放音乐，利用前台服务的通知提供的内容跳转到其他活动例如SongActivity介绍歌曲。界面如下所示。

点击第一张图的播放，会播放音频，同时发布通知如第二张图所示。在第二张图的红色箭头区域点击，可以屏幕会跳转到第三张图。在第三张图中点击“返回”,则返回主活动。

1. AndroidManifest.xml清单配置权限

  <uses-permission android:name="android.permission.POST_NOTIFICATIONS" /><uses-permission android:name="android.permission.ACCESS_NOTIFICATION_POLICY" /><uses-permission android:name="android.permission.FOREGROUND_SERVICE" /><uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />

2. 定义MusicService

class MusicService : Service() {lateinit var mediaPlayer: MediaPlayeroverride fun onCreate() {super.onCreate()mediaPlayer = MediaPlayer.create(this,R.raw.song3)}override fun onBind(intent: Intent): IBinder? {postNotification()playMusic()return null}override fun onUnbind(intent: Intent?): Boolean {stopMusic()return super.onUnbind(intent)}/*** 播放音乐*/private fun playMusic(){mediaPlayer.setOnPreparedListener {mediaPlayer.start()}mediaPlayer.setOnCompletionListener {mediaPlayer.release()}}/*** 停止播放*/private fun stopMusic(){if(mediaPlayer.isPlaying){mediaPlayer.stop()mediaPlayer.release()}}/*** 创建通知渠道* @param id String* @param name String*/private fun createNotificationChannel(id:String,name:String){//创建通知管理器val notificationManager =getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager//定义通知渠道val channel = NotificationChannel(id,name,NotificationManager.IMPORTANCE_DEFAULT)//创建通知渠道notificationManager.createNotificationChannel(channel)}/*** 发布通知*/private fun postNotification(){if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.O) {createNotificationChannel("music_service","歌曲")}//定义跳转SongActivity的PendingIntentval descPendingIntent = getSongPendingIntent()//定义启动控制音乐播放广播接受器的PendingIntentval playPendingIntent = getPlayPendingIntent()//定义启动控制音乐停止播放广播接受器的PendingIntentval stopPendingIntent = getStopPendingIntent()//定义动作val playAction = NotificationCompat.Action(android.R.drawable.ic_media_play,"播放",playPendingIntent)val stopAction = NotificationCompat.Action(android.R.drawable.ic_media_pause,"停止",stopPendingIntent)//创建通知val notification = NotificationCompat.Builder(this,"music_service").apply{setOngoing(true)setOnlyAlertOnce(true)setContentTitle("播放音乐")setContentText("正在播放歌曲...")setSmallIcon(R.mipmap.ic_launcher)setColorized(true)color = resources.getColor(R.color.teal_200,null)setContentIntent(descPendingIntent)//            addAction(android.R.drawable.ic_media_play,"播放",playPendingIntent) //android23开始不支持
//            addAction(android.R.drawable.ic_media_pause,"停止",stopPendingIntent)//android23开始不支持addAction(playAction)addAction(stopAction)}.build()startForeground(1,notification)}/*** 跳转到歌曲介绍的界面* @return PendingIntent*/private fun getSongPendingIntent():PendingIntent{//定义启动服务的意图val intent = Intent(this,SongActivity::class.java)//定义PendingIntentreturn PendingIntent.getActivity(this,1,intent,PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_MUTABLE)}private fun getPlayPendingIntent(): PendingIntent {//创建意图过滤器val intentFilter = IntentFilter()//增加动作intentFilter.addAction("PLAY_ACTION")//创建音乐播放广播接受器val playReceiver = object: BroadcastReceiver(){override fun onReceive(context: Context?, intent: Intent?) {playMusic()}}//注册播放音乐广播器registerReceiver(playReceiver,intentFilter)//创建播放意图val intent = Intent("PLAY_ACTION")return PendingIntent.getBroadcast(this,2,intent,PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT)}private fun getStopPendingIntent():PendingIntent{//创建意图过滤器val intentFilter = IntentFilter()//增加动作intentFilter.addAction("STOP_ACTION")//创建停止播放广播接受器val stopReceiver = object: BroadcastReceiver(){override fun onReceive(context: Context?, intent: Intent?) {stopMusic()}}//注册广播接收器registerReceiver(stopReceiver,intentFilter)//创建意图val intent = Intent("STOP_ACTION")return PendingIntent.getBroadcast(this,3,intent,PendingIntent.FLAG_IMMUTABLE or PendingIntent.FLAG_UPDATE_CURRENT)}
}

3.定义主活动MainActivity

class MainActivity : ComponentActivity() {lateinit var intent1:Intentval conn = object:ServiceConnection{override fun onServiceConnected(name: ComponentName?, service: IBinder?) {}override fun onServiceDisconnected(name: ComponentName?) {}}override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)intent1 = Intent(this,MusicService::class.java)requestNotificationPermission()setContent {Lab03Theme {// A surface container using the 'background' color from the themeSurface(modifier = Modifier.fillMaxSize(),color = MaterialTheme.colorScheme.background) {MainScreen(playAction=::playMusic,stopAction=::stopMusic)}}}}/*** 请求通知权限*/private fun requestNotificationPermission(){if(Build.VERSION.SDK_INT>= Build.VERSION_CODES.TIRAMISU) {ActivityCompat.requestPermissions(this,arrayOf(android.Manifest.permission.POST_NOTIFICATIONS),0)}}/*** 绑定播放音频的服务*/private fun playMusic(){bindService(intent1,conn, Context.BIND_AUTO_CREATE)}/*** 解除绑定*/private fun stopMusic(){unbindService(conn)}
}@Composable
fun MainScreen(playAction:()->Unit,stopAction:()->Unit) {Column(horizontalAlignment = Alignment.CenterHorizontally,verticalArrangement = Arrangement.Center){Row{TextButton(onClick = {playAction.invoke()}){Row{Icon(imageVector = Icons.Filled.PlayArrow,contentDescription = "play")Text("播放")}}TextButton(onClick = {stopAction.invoke()}){Row{Icon(imageVector = Icons.Filled.Stop,contentDescription = "play")Text("停止")}}}}
}

4.定义显示歌曲介绍的SongActivity

class SongActivity : ComponentActivity() {override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContent{Column{Text("正在播放歌曲，歌曲介绍内容描述暂时没有定义")TextButton(onClick = {//结束当前活动finish()}){Text("返回")}}}}
}

参考文献

1.PendingIntent
https://developer.android.google.cn/reference/android/app/PendingIntent

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