我有一个奇怪的问题，我现在在寻找如何追踪它的想法。
问题：
为了解决性能问题，该应用程序使用服务，线程和AyncTasks。到现在为止还挺好。一切都按预期工作，但最近我引入了回归
我有一个包含Google Maps Fragment的片段。
在该片段的onStart方法中，我创建并启动一个AsyncTask，它向我的内容提供者查询当前数据，将其存储在私有成员变量中，以便在重绘时快速访问。
现在我遇到的问题是这个异步任务突然被推迟了，我不知道为什么。
AFAIK AsyncTasks使用线程池，当此池耗尽时，任务会延迟。所以我检查了AsyncTasks的代码 - 特别是长时间运行的代码。添加了一堆日志消息，但当时似乎没有其中任何一个正在运行。
然后我注意到延迟只发生在我启动了一个服务监视某些目录以进行更改时（使用FileObservers）。但在该服务中，我不使用任何AsyncTasks或线程。在那里，我为我感兴趣的目录创建FileObservers，并将它们存储在私有列表中。该代码直接从onStartCommand调用。所以异步任务不应受此影响。
其次，这似乎只在特殊情况下发生。大多数情况下都会立即更新。只有在我从Play商店更新或从Android-Studio启动后第一次启动应用程序时，才会发生延迟。
我可以将它从最近的应用程序列表中删除（这应该会杀死应用程序线程（但如果服务在该进程中运行则不会处理））并且继续及时查询更新（只要该服务仍在运行）。
如果我停止然后重新启动服务，我又遇到了这个问题。
问题似乎与此filewatcher-service的启动有关。
所以看起来这个服务的开始会阻止AsyncTasks一段时间。 ......但是为什么？
这里是应用程序第一次启动时日志文件的摘录：
（为了便于阅读，我插入了一些空行）
02-05 22:00:54.361 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: onStart
02-05 22:00:54.672 24041-24041/de.leo.android.buddy_tracker I/TextToSpeech: Connected to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
02-05 22:00:54.679 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: onStartCommand: Start service (with intent)
02-05 22:00:54.700 24041-24045/de.leo.android.buddy_tracker I/art: Do full code cache collection, code=125KB, data=92KB
02-05 22:00:54.702 24041-24045/de.leo.android.buddy_tracker I/art: Starting a blocking GC JitCodeCache
02-05 22:00:54.702 24041-24045/de.leo.android.buddy_tracker I/art: After code cache collection, code=112KB, data=67KB
02-05 22:00:54.774 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: initWatchers
02-05 22:00:54.899 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: initWatchers1: Watcher for root /storage/emulated/0/Sync/BT-Shares/Leo intern created
02-05 22:00:54.973 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: initWatchers1: Watcher for subdirectory /storage/emulated/0/Sync/BT-Shares/Leo intern/Leo#GN created
02-05 22:00:55.047 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: initWatchers1: Watcher for subdirectory /storage/emulated/0/Sync/BT-Shares/Leo intern/Leo#N5x created
02-05 22:00:55.194 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: initWatchers finished
02-05 22:00:55.268 24041-24041/de.leo.android.buddy_tracker I/Receive_SharedFolderService: onStartCommand finished
02-05 22:00:55.350 24041-24041/de.leo.android.buddy_tracker I/SpeechHandler: startTextToSpeechService
02-05 22:00:55.515 24041-24041/de.leo.android.buddy_tracker I/TextToSpeech: Sucessfully bound to com.google.android.tts
02-05 22:00:55.557 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawContents (onMapReady)
02-05 22:00:55.800 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawContents: calculate bounds and move camera
02-05 22:00:55.891 24041-24041/de.leo.android.buddy_tracker I/Choreographer: Skipped 72 frames! The application may be doing too much work on its main thread.
02-05 22:00:56.040 24041-24211/de.leo.android.buddy_tracker I/Adreno: QUALCOMM build : 6818200, Idb2b4cb785
Build Date : 11/18/16
OpenGL ES Shader Compiler Version: XE031.09.00.04
Local Branch : N25
Remote Branch :
Remote Branch :
Reconstruct Branch :
02-05 22:00:56.047 24041-24211/de.leo.android.buddy_tracker I/OpenGLRenderer: Initialized EGL, version 1.4
02-05 22:00:56.047 24041-24211/de.leo.android.buddy_tracker D/OpenGLRenderer: Swap behavior 1
02-05 22:00:56.248 24041-24045/de.leo.android.buddy_tracker I/art: Do partial code cache collection, code=124KB, data=101KB
02-05 22:00:56.249 24041-24045/de.leo.android.buddy_tracker I/art: After code cache collection, code=122KB, data=99KB
02-05 22:00:56.249 24041-24045/de.leo.android.buddy_tracker I/art: Increasing code cache capacity to 512KB
02-05 22:00:56.367 24041-24199/de.leo.android.buddy_tracker W/DynamiteModule: Local module descriptor class for com.google.android.gms.googlecertificates not found.
02-05 22:00:56.379 24041-24041/de.leo.android.buddy_tracker I/TextToSpeech: Connected to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
02-05 22:00:56.380 24041-24199/de.leo.android.buddy_tracker I/DynamiteModule: Considering local module com.google.android.gms.googlecertificates:0 and remote module com.google.android.gms.googlecertificates:2
02-05 22:00:56.380 24041-24199/de.leo.android.buddy_tracker I/DynamiteModule: Selected remote version of com.google.android.gms.googlecertificates, version >= 2
02-05 22:00:56.404 24041-24253/de.leo.android.buddy_tracker W/f: Suppressed StrictMode policy violation: StrictModeDiskReadViolation
02-05 22:00:56.553 24041-24045/de.leo.android.buddy_tracker I/art: Compiler allocated 7MB to compile void android.widget.TextView.<init>(android.content.Context, android.util.AttributeSet, int, int)
02-05 22:00:56.704 24041-24041/de.leo.android.buddy_tracker W/f: Suppressed StrictMode policy violation: StrictModeDiskReadViolation
02-05 22:00:56.704 24041-24041/de.leo.android.buddy_tracker W/f: Suppressed StrictMode policy violation: StrictModeDiskWriteViolation
02-05 22:00:58.533 24041-24213/de.leo.android.buddy_tracker I/Receive_SharedFolderService: Leo#N5x was opened
02-05 22:00:58.577 24041-24213/de.leo.android.buddy_tracker I/Receive_SharedFolderService: Leo#N5x was closed (no write)
02-05 22:00:58.600 24041-24213/de.leo.android.buddy_tracker I/Receive_SharedFolderService: Leo#N5x was opened
02-05 22:00:58.695 24041-24213/de.leo.android.buddy_tracker I/Receive_SharedFolderService: Leo#N5x was closed (no write)
02-05 22:00:59.522 24041-24048/de.leo.android.buddy_tracker W/art: Suspending all threads took: 7.092ms
02-05 22:01:00.344 24041-24045/de.leo.android.buddy_tracker I/art: Do full code cache collection, code=241KB, data=221KB
02-05 22:01:00.345 24041-24045/de.leo.android.buddy_tracker I/art: Starting a blocking GC JitCodeCache
02-05 22:01:00.346 24041-24045/de.leo.android.buddy_tracker I/art: After code cache collection, code=217KB, data=173KB
02-05 22:01:00.346 24041-24045/de.leo.android.buddy_tracker I/art: Compiler allocated 6MB to compile void android.view.ViewRootImpl.performTraversals()
02-05 22:01:02.259 24041-24045/de.leo.android.buddy_tracker I/art: Do partial code cache collection, code=249KB, data=197KB
02-05 22:01:02.260 24041-24045/de.leo.android.buddy_tracker I/art: After code cache collection, code=247KB, data=197KB
02-05 22:01:02.260 24041-24045/de.leo.android.buddy_tracker I/art: Increasing code cache capacity to 1024KB
02-05 22:01:17.217 24041-24969/de.leo.android.buddy_tracker I/Fragment_Map: UpdateData.doInBackground (--start)
02-05 22:01:17.256 24041-24969/de.leo.android.buddy_tracker I/BuddyTrackerHelper: readBuddyPositions from 04.02.2017 22:01 to 17.08.292278994 08:12
02-05 22:01:17.518 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawContents (UpdateData.onPostExecute)
02-05 22:01:17.549 24041-24978/de.leo.android.buddy_tracker I/TextToSpeech: Set up connection to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
02-05 22:01:17.560 24041-24979/de.leo.android.buddy_tracker I/TextToSpeech: Set up connection to ComponentInfo{com.google.android.tts/com.google.android.tts.service.GoogleTTSService}
02-05 22:01:18.150 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawTrack: Track Leo#GN mit 77 Punkten eingetragen
02-05 22:01:18.601 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawTrack: Track Leo#N5x mit 239 Punkten eingetragen
02-05 22:01:18.618 24041-24041/de.leo.android.buddy_tracker I/Fragment_Map: drawContents: calculate bounds and move camera
有趣的部分：
在22：00：54.361输入了我的map-fragment的onStart方法。此方法以调用AsyncTask查询我的数据结束
在后台其他任务正在运行。其中一个是我在22：00：54.679开始的filewatcher服务。这是在22：00：55.268完成的
然后地图就绪，第一次尝试将数据绘制到地图是在22：00：55：557。那里没有数据 - 没问题！
在22：00：58.533，访问被监视的文件夹，并触发来自文件服务器的回调
最后在22：01：17.217开始片段的onStart方法的AsyncTask。
所以问题：
是什么原因造成22秒的延迟？
重复：仅当filewatcher-service处于活动状态时才会发生这种情况。
onStart方法：
@Override
public void onStart() {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, "onStart");
super.onStart();
if (Application_Buddy_Tracker.getLocationProvider() != null)
Application_Buddy_Tracker.getLocationProvider().registerClientIfLocationhandlerActive(this);
getActivity().getContentResolver().registerContentObserver(CONTENT_POSITIONS_URI, true, buddyPositionContentObserver);
new UpdateData().execute("--start");
LeoCommunication.collectGarbage(getActivity());
final SharedPreferences prefs = Application_Buddy_Tracker.getPreferences(getActivity());
setMapType(prefs);
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) LeoLog.i(LOG_TAG, "onStart completed");
}
我的服务：
public class Receive_SharedFolderService extends Service {
private final static String LOG_TAG = Receive_SharedFolderService.class.getSimpleName();
private final static @GlobalConstants.Debuglevels int DEBUG_LEVEL = DEBUGLEVEL_VERBOSE;
public class MyFileObserver extends FileObserver {
String absolutePath;
MyFileObserver(String path) {
super(path, FileObserver.ALL_EVENTS);
absolutePath = path;
}
@Override
public void onEvent(int event, String path) {
if (path == null) return;
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) {
if ((FileObserver.ACCESS & event) != 0) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was accessed/read"); //data was read from a file
if ((FileObserver.ATTRIB & event) != 0) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was changed (permissions, owner, timestamp)"); //Metadata (permissions, owner, timestamp) was changed explicitly
if ((FileObserver.CLOSE_NOWRITE & event) != 0) LeoLog.i(LOG_TAG, path + " was closed (no write)"); //someone has a file or directory open read-only, and closed it
if ((FileObserver.DELETE_SELF & event) != 0) LeoLog.i(LOG_TAG, absolutePath + "/" + " was deleted"); //the monitored file or directory was deleted, monitoring effectively stops
if ((FileObserver.MODIFY & event) != 0) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was modified"); //data was written to a file
if ((FileObserver.MOVED_FROM & event) != 0) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was moved to somewhere"); //a file or subdirectory was moved from the monitored directory
if ((FileObserver.MOVE_SELF & event) != 0) LeoLog.i(LOG_TAG, path + " was moved"); //the monitored file or directory was moved; monitoring continues
if ((FileObserver.OPEN & event) != 0) LeoLog.i(LOG_TAG, path + " was opened"); //a file or directory was opened
//TODO: consider combine this one with one below
//a file was deleted from the monitored directory
if ((FileObserver.DELETE & event) != 0) {
//for testing copy file
// FileUtils.copyFile(absolutePath + "/" + path);
LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was deleted");
}
}
if ((FileObserver.CREATE & event) != 0) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was created"); //a new file or subdirectory was created under the monitored directory
if ((new File(absolutePath + "/" + path)).isDirectory()) {
final SharedPreferences prefs = Application_Buddy_Tracker.getPreferences(getApplicationContext());
initWatchers(getApplicationContext(), prefs.getString(getString(R.string.prefs_buddymessages_share_folder_root_key), ""));
}
}
//a file or subdirectory was moved to the monitored directory
if ((FileObserver.MOVED_TO & event) != 0) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, "File was moved to " + absolutePath + "/" + path);
if (path.endsWith(".json")) newMessage(absolutePath, path); // Final action for new file in Bittorrent-Sync
}
//someone has a file or directory open for writing, and closed it
if ((FileObserver.CLOSE_WRITE & event) != 0) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, absolutePath + "/" + path + " was written and closed (== changed)");
if (path.endsWith(".json")) newMessage(absolutePath, path); // Final action for new file in Bittorrent-Sync
}
}
private void newMessage(String absolutePath, String path) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, "Check if received message is new: " + path);
if (BuddyMessage.addMessage(getApplicationContext(), absolutePath + "/" + path)) {
//noinspection ConstantConditions
if (DEBUG_LEVEL > DEBUGLEVEL_NONE) LeoLog.i(LOG_TAG, "New message added to message-store: " + path);
LeoCommunication.notifyNewMsg(getApplicationContext(), Application_Buddy_Tracker.RQ_NEW_MESSAGE_ARRIVED, Application_Buddy_Tracker.ID_NOTIFICATION_BUDDYTRACKER_MESSAGE_RECEIVED);
}
}
}
private static boolean _isRunning = false;
public static boolean isRunning() { return _isRunning; }
/**
* FileObservers that monior shared folders.
* <p>Important: Keep (this) reference in order to not have the observers garbage collected!</p>
*/
private final List<MyFileObserver> fileObservers = new ArrayList<>();
@Override
public IBinder onBind(Intent intent) { return null; }
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (intent == null) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_STANDARD) LeoLog.i(LOG_TAG, "onStartCommand: Restarting Service (without intent)");
} else {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_STANDARD) LeoLog.i(LOG_TAG, "onStartCommand: Start service (with intent)");
}
final Context context = getApplicationContext();
final NotificationCompat.Builder nb = new NotificationCompat.Builder(context)
.setSmallIcon(context.getApplicationInfo().icon)
.setWhen(System.currentTimeMillis()) // Zeitpunkt der Notification
.setContentTitle(context.getText(context.getApplicationInfo().labelRes))
.setContentText(getResources().getString(de.leo.android.buddy_tracker.R.string.app_receiving_by_shared_folder))
.setTicker(getResources().getString(de.leo.android.buddy_tracker.R.string.app_receiving_by_shared_folder));
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) nb.setCategory(Notification.CATEGORY_SERVICE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) nb.setPriority(Notification.PRIORITY_MIN);
final Intent intent1 = new Intent(context, Activity_Main.class);
intent1.putExtra(DISPLAY_TAB, Activity_Main.TABPOSITION_SHARE);
final PendingIntent pIntent = PendingIntent.getActivity(context, Application_Buddy_Tracker.RQ_SERVICE_RECEIVE_POSITIONS, intent1, PendingIntent.FLAG_UPDATE_CURRENT);
nb.setContentIntent(pIntent);
this.startForeground(Application_Buddy_Tracker.ID_NOTIFICATION_BUDDYTRACKER_RECEIVE, nb.build());
final SharedPreferences prefs = Application_Buddy_Tracker.getPreferences(context);
final String buddyMessages_Root = prefs.getString(getString(R.string.prefs_buddymessages_share_folder_root_key), "");
if (!initWatchers(context, buddyMessages_Root)) {
LeoLog.e(LOG_TAG, "onStartCommand: initWatchers failed - stopping Service");
stopSelf(startId);
return Service.START_NOT_STICKY;
}
_isRunning = true;
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) LeoLog.i(LOG_TAG, "onStartCommand finished");
return Service.START_STICKY;
}
@Override
public void onDestroy() {
synchronized (fileObservers) {
for (FileObserver fileObserver : fileObservers)
fileObserver.stopWatching();
fileObservers.clear();
}
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_STANDARD) LeoLog.i(LOG_TAG, "disconnect: Fileobservers and Service stopped");
_isRunning = false;
stopForeground(true);
}
private boolean initWatchers(Context context, String buddyMessages_Root) {
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_EXTENDED) LeoLog.i(LOG_TAG, "initWatchers");
if (buddyMessages_Root == null || buddyMessages_Root.length() == 0) return false;
final File rootDir = new File(buddyMessages_Root);
synchronized (fileObservers) {
fileObservers.clear();
initWatchers1(rootDir.getAbsolutePath());
final Cursor c = context.getContentResolver().query(CONTENT_BUDDIES_URI, new String[]{COL_BUDDY_SHARED_FOLDER},
COL_BUDDY_ACTIVE + " != 0 AND " + COL_BUDDY_SHARED_FOLDER_RECEIVE + " != 0 AND " + COL_BUDDY_SHARED_FOLDER + " IS NOT NULL",
null,
null);
assert c != null;
while (c.moveToNext())
initWatchers1(c.getString(0));
c.close();
}
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) LeoLog.i(LOG_TAG, "initWatchers finished");
return true;
}
private boolean initWatchers1(String rootpath) {
if (rootpath == null) return true;
// Watcher for the rootdir -> monitor add and remove of buddies
final MyFileObserver fileObserver1 = new MyFileObserver(rootpath);
fileObservers.add(fileObserver1);
fileObserver1.startWatching();
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) LeoLog.i(LOG_TAG, "initWatchers1: Watcher for root " + rootpath + " created");
File dir1 = new File(rootpath);
for (File f : dir1.listFiles())
if (f.isDirectory()) {
MyFileObserver fileObserver = new MyFileObserver(f.getAbsolutePath());
fileObservers.add(fileObserver);
fileObserver.startWatching();
//noinspection ConstantConditions
if (DEBUG_LEVEL >= DEBUGLEVEL_VERBOSE) LeoLog.i(LOG_TAG, "initWatchers1: Watcher for subdirectory " + f.getAbsolutePath() + " created");
}
return true;
}
}
答案 0 :(得分：0)
很少有建议：
AsyncTask应该用于短期运行任务。
AsyncTask旨在成为Thread和Handler的辅助类，并不构成通用的线程框架。理想情况下，AsyncTasks应该用于短操作（最多几秒钟）。如果需要保持线程长时间运行，强烈建议您使用java.util提供的各种API。并发包，例如Executor，ThreadPoolExecutor和FutureTask。
默认情况下，您的Service在UI线程上运行
请注意，服务与其他应用程序对象一样，在其托管进程的主线程中运行。这意味着，如果您的服务要进行任何CPU密集型（例如MP3播放）或阻止（例如网络）操作，它应该生成自己的线程来执行该工作。有关此内容的更多信息，请参见进程和线程。 IntentService类可用作Service的标准实现，它具有自己的线程，用于调度其工作。
在单独的线程中启动您的服务或将其转换为IntentService。如果您的AsyncTask执行任务需要更长的时间，请将其替换为建议1中建议的其他替代方案。