[英]android Bound Service gets frozen when screen is off
我創建了一個非常基本的服務,用於使用TTS播放字典( 請參閱下面的完整代碼 ),並且在我的所有3個android設備(android版本5、7和8)上都遇到了相同的問題。
要點: 該應用程序會播放詞匯表條目,定義和示例。 在每個應用之間,應用需要暫停。
症狀:
大多數情況是在我使用8秒鍾的暫停時間並且應用程序處於后台模式(屏幕關閉)時發生的。 播放只是凍結。
有時播放會繼續進行,長時間的暫停后屏幕會關閉,有時會長達20到30分鍾甚至更長的時間( 但是,如果我們沒有激活屏幕,那么下一個條目也會在非常長的暫停后播放 ) 。 可能還有其他過程會部分喚醒電話嗎?
此外,在按電源按鈕並打開屏幕后,播放將繼續進行。
調試信息:
我估計在應用程序凍結后要在Visual Studio中按一下暫停,以查看是哪段代碼引起的- 不幸的是,調試器似乎使設備保持清醒狀態,而這個問題很難揭示 。
為了防止我的應用程序被凍結,我在服務中獲取了Partial WakeLock (但這仍然無濟於事,即使應用程序清單包含WAKE_LOCK
權限)
private void AcquireWakeLock(MainActivity activity)
{
var mgr = (PowerManager)activity.ApplicationContext.GetSystemService(Context.PowerService);
WakeLock = mgr.NewWakeLock(WakeLockFlags.Partial, "myWakeLock");
WakeLock.Acquire();
}
我的應用程序還具有“播放/暫停”按鈕,我使用TaskCompletionSource
來使該應用程序等待直到恢復播放
public async Task PlayPause(bool isChecked, MainActivity mainActivity)
{
if (isChecked)
{
ReleaseWakeLock();
AppSuspended = new TaskCompletionSource<bool>();
Tts.Stop();
}
else
{
AcquireWakeLock(mainActivity);
AppSuspended.TrySetResult(true);
}
}
然后,在即將播放下一個單詞/詞組之前,我將以下代碼用於我的應用,以等待恢復播放
await AppSuspended.Task;
完整的代碼
[Service(Name = "com.my_app.service.PlaybackService")]
public class PlaybackService : Service, TextToSpeech.IOnInitListener, TextToSpeech.IOnUtteranceCompletedListener
{
public IBinder Binder { get; private set; }
private Java.Util.Locale Lang;
private bool Playing;
private int EntryIndex;
private int DefinitionIndex;
private DictionaryDto Dictionary;
private EntryDto CurrentEntry;
private DefinitionDto CurrentDefinition;
private TaskCompletionSource<bool> AppSuspended;
protected TextToSpeech Tts;
private TaskCompletionSource<bool> PlaybackFinished;
private WakeLock WakeLock;
public override void OnCreate()
{
base.OnCreate();
Tts = new TextToSpeech(this, this);
Lang = Tts.DefaultLanguage;
AppSuspended = new TaskCompletionSource<bool>();
AppSuspended.TrySetResult(true);
}
public override IBinder OnBind(Intent intent)
{
Binder = new PlaybackBinder(this);
return Binder;
}
public override bool OnUnbind(Intent intent)
{
return base.OnUnbind(intent);
}
public override void OnDestroy()
{
Binder = null;
base.OnDestroy();
}
void TextToSpeech.IOnUtteranceCompletedListener.OnUtteranceCompleted(string utteranceId)
{
if (utteranceId.Equals("PlaybackFinished")) { PlaybackFinished.TrySetResult(true); }
}
void TextToSpeech.IOnInitListener.OnInit(OperationResult status)
{
// if we get an error, default to the default language
if (status == OperationResult.Error)
Tts.SetLanguage(Java.Util.Locale.Default);
// if the listener is ok, set the lang
if (status == OperationResult.Success)
{
Tts.SetLanguage(Lang);
Tts.SetOnUtteranceCompletedListener(this);
}
}
public async Task Play(string text)
{
Dictionary<string, string> myHashRender = new Dictionary<string, string>();
myHashRender.Add(TextToSpeech.Engine.KeyParamUtteranceId, "PlaybackFinished");
PlaybackFinished = new TaskCompletionSource<bool>();
Tts.Speak(text, QueueMode.Flush, myHashRender);
await PlaybackFinished.Task;
}
public async Task PlaySilence(long ms)
{
Dictionary<string, string> myHashRender = new Dictionary<string, string>();
myHashRender.Add(TextToSpeech.Engine.KeyParamUtteranceId, "PlaybackFinished");
PlaybackFinished = new TaskCompletionSource<bool>();
Tts.PlaySilence(ms, QueueMode.Flush, myHashRender);
await PlaybackFinished.Task;
}
private async Task PlayDictionary(MainActivity activity)
{
EntryIndex = 0;
for (; EntryIndex < Dictionary.Entries.Count;)
{
CurrentEntry = Dictionary.Entries.ElementAt(EntryIndex);
await AppSuspended.Task;
if (!Playing) { return; }
if (!string.IsNullOrEmpty(CurrentEntry.Text))
{
await AppSuspended.Task;
if (!Playing) { return; }
await Play(CurrentEntry.Text);
}
DefinitionIndex = 0;
for (; DefinitionIndex < CurrentEntry.Definitions.Count();)
{
CurrentDefinition = CurrentEntry.Definitions.ElementAt(DefinitionIndex);
await PlayDefinition();
await PlayExamples();
DefinitionIndex++;
}
if (Playing)
{
DefinitionIndex++;
}
EntryIndex++;
}
}
private async Task PlayExamples()
{
if (!Playing) { return; }
foreach (var example in CurrentDefinition.Examples)
{
if (!string.IsNullOrEmpty(example))
{
await AppSuspended.Task;
if (!Playing) { return; }
await Play(example);
if (Playing)
{
await PlaySilence((long)TimeSpan.FromSeconds(8).TotalMilliseconds);
}
}
}
}
private async Task PlayDefinition()
{
if (!Playing) { return; }
if (!string.IsNullOrEmpty(CurrentEntry.Definitions.ElementAt(DefinitionIndex).Text))
{
await AppSuspended.Task;
if (!Playing) { return; }
await PlayDefinitionText();
if (Playing)
{
await PlaySilence((long)TimeSpan.FromSeconds(7).TotalMilliseconds);
}
}
}
private async Task PlayDefinitionText()
{
await AppSuspended.Task;
await Play($"{CurrentEntry.Definitions.ElementAt(DefinitionIndex).Text}");
}
private void ReleaseWakeLock()
{
if (WakeLock != null)
{
WakeLock.Release();
}
}
private void AcquireWakeLock(MainActivity activity)
{
var mgr = (PowerManager)activity.ApplicationContext.GetSystemService(Context.PowerService);
WakeLock = mgr.NewWakeLock(WakeLockFlags.Partial, "myWakeLock");
WakeLock.Acquire();
}
public async Task PlayPause(bool isChecked, MainActivity mainActivity)
{
if (isChecked)
{
ReleaseWakeLock();
AppSuspended = new TaskCompletionSource<bool>();
Tts.Stop();
}
else
{
AcquireWakeLock(mainActivity);
AppSuspended.TrySetResult(true);
}
}
}
附加信息:
問題發生在我所有的設備上
我徹底調查了此問題,並按照建議改用了“ 前台服務” ,從而完美地解決了我的問題。
經過棒棒糖 , 牛軋糖 , 奧利奧的測試。
將以下方法放在您的MainActivity
類中
public void StartForegroundServiceSafely(Intent intent)
{
if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O)
{
StartForegroundService(intent);
}
else
{
StartService(intent);
}
}
然后,您可以通過Intent
啟動服務
public void PlayFromFile(Android.Net.Uri uri)
{
AcquireWakeLock();
Intent startIntent = new Intent(this, typeof(PlaybackService));
startIntent.SetAction(PlaybackConsts.Start);
startIntent.PutExtra("uri", uri.ToString());
StartForegroundServiceSafely(startIntent);
}
在服務中實現OnStartCommand
方法
public class PlaybackService : Service, TextToSpeech.IOnInitListener, TextToSpeech.IOnUtteranceCompletedListener
[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
if (intent.Action.Equals(PlaybackConsts.Start))
{
var notification =
new Notification.Builder(this)
.SetContentTitle(Resources.GetString(Resource.String.ApplicationName))
.SetContentText("HELLO WORLD")
.SetOngoing(true)
.Build();
StartForeground(SERVICE_RUNNING_NOTIFICATION_ID, notification);
}
if (intent.Action.Equals(PlaybackConsts.Start))
{
var uri = Android.Net.Uri.Parse(intent.GetStringExtra("uri"));
var content = MiscellaneousHelper.GetTextFromStream(ContentResolver.OpenInputStream(uri));
Dictionary = DictionaryFactory.Get(content);
Playing = true;
Task.Factory.StartNew(async () =>
{
await PlayDictionary();
});
}
if (intent.Action.Equals(PlaybackConsts.PlayPause))
{
bool isChecked = intent.GetBooleanExtra("isChecked", false);
PlayPause(isChecked);
}
if (intent.Action.Equals(PlaybackConsts.NextEntry))
{
NextEntry();
}
if (intent.Action.Equals(PlaybackConsts.PrevEntry))
{
PrevEntry();
}
if (intent.Action.Equals(PlaybackConsts.Stop))
{
Task.Factory.StartNew(async () =>
{
await Stop();
});
StopForeground(true);
StopSelf();
}
return StartCommandResult.Sticky;
}
從上面的代碼中,我們學習了如何在OnStartCommand
方法中觸發服務的功能。
定義您的BroadcastReceiver
[BroadcastReceiver(Enabled = true, Exported = false)]
public class PlaybackBroadcastReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
var activity = MainActivity.GetInstance(); // if you need your activity here, see further code below
if (intent.Action == "renderEntry")
{
string entryHtml = intent.GetStringExtra("html");
// omitting code to keep example concise
}
}
}
在MainActivity
類中聲明接收器字段。
另外,如果需要在BroadcastReceiver
類中進行活動,則可以聲明GetInstance
方法(單例方法)。
public class MainActivity : AppCompatActivity
{
PlaybackBroadcastReceiver receiver;
protected DrawerLayout drawerLayout;
protected NavigationView navigationView;
protected WakeLock WakeLock;
private static MainActivity instance;
public static MainActivity GetInstance()
{
return instance;
}
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
receiver = new PlaybackBroadcastReceiver();
instance = this;
}
protected override void OnStart()
{
base.OnStart();
RegisterReceiver(receiver, new IntentFilter("renderEntry"));
}
為了注銷接收者,請使用以下行:
UnregisterReceiver(receiver);
通過服務廣播事件
在您的服務中,您還必須使用意圖
private void SendRenderEntryBroadcast(EntryDto entry)
{
Intent intent = new Intent("renderEntry");
intent.PutExtra("html", GetEntryHtml(entry));
SendBroadcast(intent);
}
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