I try to eject external USB drives and Disk Images after being unmounted in the following callback function:
void __unmountCallback(DADiskRef disk, DADissenterRef dissenter, void *context )
{
...
if (!dissenter)
{
DADiskEject(disk,
kDADiskEjectOptionDefault,
__ejectCallback,
NULL);
}
}
Unfortunately I get an error in __ejectCallback...
void __ejectCallback(DADiskRef disk, DADissenterRef dissenter, void * context)
{
if(dissenter)
{
DAReturn status = DADissenterGetStatus(dissenter);
if(unix_err(status))
{
int code = err_get_code(status);
...
}
}
}
The error code is 12 meaning kDAReturnUnsupported. I don't really know what is going wrong. Can anyone please comment on this? Does this mean disk images can not be ejected???
Many thanks in advance!!
The documentation is pretty unclear on this. Therefore, it's a good idea to look into the actual source code of the DARequest class to find out what causes the kDAReturnUnsupported response.
It reveals the following conditions that return a kDAReturnUnsupported response:
Does your DADisk instance represent the entire volume or not?
if ( DADiskGetDescription(disk, kDADiskDescriptionMediaWholeKey) == NULL )
{
status = kDAReturnUnsupported;
}
if ( DADiskGetDescription(disk, kDADiskDescriptionMediaWholeKey) == kCFBooleanFalse )
{
status = kDAReturnUnsupported;
}
Looking into the IO Kit documentation (for which DiscArbitation.framework is a wrapper for), we find that kDADiskDescriptionMediaWholeKey describes whether the media is whole or not (that is, it represents the whole disk or a partition on it), so check that you're ejecting the entire disc and not a partition. Remember, you can unmount a partition, but you can't eject it. (that wouldn't make sense)
Is the disc mountable?
Another condition in DARequest.c is whether the volume is mountable or not, so make sure it is:
if (DADiskGetDescription(disk, kDADiskDescriptionVolumeMountableKey) == kCFBooleanFalse )
{
status = kDAReturnUnsupported;
}
Is the DADisk instance's name valid?
A third check validates the volume's name. Some system provided (internal) volumes don't have a name and can't be ejected. The check is very simple and simply looks for any name, so this shouldn't be a big deal.
if (DARequestGetArgument2(request) == NULL)
{
status = kDAReturnUnsupported;
}
Go through these three checks and see if they apply to you. This way you're bound to find out what's wrong.
Related
I am attempting to get the address out of the callback function. I have been reading the documentation for CallBacks and some posts but still don't get why this is not working, as at the moment of returning the 'address' variable the callback has already finished.
private fun getAddressForCoordinates(geoCoordinates: GeoCoordinates):String {
address = "unchanged"
val maxItems = 1
val reverseGeocodingOptions = SearchOptions(LanguageCode.EN_GB, maxItems)
searchEngine.search(geoCoordinates, reverseGeocodingOptions, addressSearchCallback)
return address
}
private val addressSearchCallback =
SearchCallback { searchError, list ->
if (searchError != null) {
//showDialog("Reverse geocoding", "Error: $searchError")
Toast.makeText(context, "Error: $searchError", Toast.LENGTH_LONG).show()
return#SearchCallback
}
Toast.makeText(
context,
"Reverse geocoded address:" + list!![0].address.addressText,
Toast.LENGTH_LONG
).show()
address = list[0].address.addressText
}
From your code and comment I assume you are not familiar with the concept of asynchronous execution. That concept was well described here. I'll quote the main point:
When you execute something synchronously, you wait for it to finish
before moving on to another task. When you execute something
asynchronously, you can move on to another task before it finishes.
The fact that search() requires providing a callback and it doesn't simply return search results, is a good indication that it is most probably asynchronous. Invoking it is like saying: "Search for the data in the background and let me know when you have it. This is my email address - please send me my results there". Where email address is your callback. Invoking search() method does not block execution of your code, it does not wait for results - it only schedules searching and returns almost immediately.
Asynchronous processing is usually more tricky than a regular, synchronous code, but in many cases it is more efficient. In your case you can either try to "convert" original async API of the library to sync API that your code expects - but this is not recommended approach. Or you can redesign your code, so it will work asynchronously. For example, instead of doing this:
fun yourMethodThatNeedsAddress() {
val address = getAddressForCoordinates()
doSomethingWithAddress(address)
}
You need to do this:
fun yourMethodThatNeedsAddress() {
scheduleGetAddressForCoordinates() // renamed getAddressForCoordinates()
}
fun addressSearchCallback() {
...
doSomethingWithAddress(address)
}
So, whatever you planned to do with the acquired address, you can't do this straight after you started searching. You need to wait for a callback and then continue with processing of your address from there.
The SearchEngine from the 4.x HERE SDK needs an online connection as it is fetching results from a remote backend. This may take a few milliseconds, depending on your network connection. So, whenever you perform a search request, you need to wait until the callback is called:
searchEngine.search(geoCoordinates, reverseGeocodingOptions, addressSearchCallback)
When you call this, you pass addressSearchCallback as parameter. The implementation for addressSearchCallback can look like in your example. It will be called whenever the operation has finished. If the device is offline, then an error will be shown.
Note that the search() method is not returning any results immediately. These are passed to the callback, which happens asynchronously on a background thread. Thus, your application can continue to work without blocking any UI.
Once results are retrieved, the callback will be executed by the HERE SDK on the main thread.
So, if your code needs to do something with the address result, you have to do it inside the onSearchCompleted() method defined by the SearchCallback. If you write it in plain Java without lambda notation, it is more visible: You create a new SearchCallback object and pass it as parameter to the SearchEngine. The SearchEngine stores the object and executes the object's onSearchCompleted() whenever it thinks it's the right time:
private SearchCallback addressSearchCallback = new SearchCallback() {
#Override
public void onSearchCompleted(#Nullable SearchError searchError, #Nullable List<Place> list) {
if (searchError != null) {
showDialog("Reverse geocoding", "Error: " + searchError.toString());
return;
}
// If error is null, list is guaranteed to be not empty.
showDialog("Reverse geocoded address:", list.get(0).getAddress().addressText);
// Here is the place to do something more useful with the Address object ...!
}
};
I took this from this GitHub code snippet. Note that there is also an OfflineSearchEngine, that works without an internet connection, but for some reason it follows the same pattern and executes the task asynchronously.
private void getAddressForCoordinates(GeoCoordinates geoCoordinates) {
int maxItems = 1;
SearchOptions reverseGeocodingOptions = new SearchOptions(LanguageCode.EN_GB, maxItems);
searchEngine.search(geoCoordinates, reverseGeocodingOptions, new SearchCallback() {
#Override
public void onSearchCompleted(#Nullable SearchError searchError, #Nullable List<Place> list) {
if (searchError != null) {
showDialog("Reverse geocoding", "Error: " + searchError.toString());
return;
}
// If error is null, list is guaranteed to be not empty.
showDialog("Reverse geocoded address:", list.get(0).getAddress().addressText);
}
});
}
SearchEngine, a SearchOptions instance needs to be provided to set the desired LanguageCode. It determines the language of the resulting address. Then we can make a call to the engine's search()-method to search online for the address of the passed coordinates. In case of errors, such as when the device is offline, SearchError holds the error cause.
The reverse geocoding response contains either an error or a result: SearchError and the result list can never be null at the same time - or non-null at the same time.
The Address object contained inside each Place instance is a data class that contains multiple String fields describing the address of the raw location, such as country, city, street name, and many more. Consult the API Reference for more details. If you are only interested in receiving a readable address representation, you can access addressText, as shown in the above example. This is a String containing the most relevant address details, including the place's title.
Please refer to following link for detailed documentation on search() function and parameters associated with it.
https://developer.here.com/documentation/android-sdk-explore/4.4.0.2/dev_guide/topics/search.html
I am building a Capacited Vehicle Routing Problem with Time Windows, but with one small difference when compared to the one provided in examples from the documentation: I don't have a depot. Instead, each order has a pickup step, and a delivery step, in two different locations.
(like in the Vehicle Routing example from the documentation, the previousStep planning variable has the CHAINED graph type, and its valueRangeProviderRefs includes both Drivers, and Steps)
This difference adds a couple of constraints:
the pickup and delivery steps of a given order must be handled by the same driver
the pickup must be before the delivery
After experimenting with constraints, I have found that it would be more efficient to implement two types of custom moves:
assign both steps of an order to a driver
rearrange the steps of a driver
I am currently implementing that first custom move. My solver's configuration looks like this:
SolverFactory<RoutingProblem> solverFactory = SolverFactory.create(
new SolverConfig()
.withSolutionClass(RoutingProblem.class)
.withEntityClasses(Step.class, StepList.class)
.withScoreDirectorFactory(new ScoreDirectorFactoryConfig()
.withConstraintProviderClass(Constraints.class)
)
.withTerminationConfig(new TerminationConfig()
.withSecondsSpentLimit(60L)
)
.withPhaseList(List.of(
new LocalSearchPhaseConfig()
.withMoveSelectorConfig(CustomMoveListFactory.getConfig())
))
);
My CustomMoveListFactory looks like this (I plan on migrating it to an MoveIteratorFactory later, but for the moment, this is easier to read and write):
public class CustomMoveListFactory implements MoveListFactory<RoutingProblem> {
public static MoveListFactoryConfig getConfig() {
MoveListFactoryConfig result = new MoveListFactoryConfig();
result.setMoveListFactoryClass(CustomMoveListFactory.class);
return result;
}
#Override
public List<? extends Move<RoutingProblem>> createMoveList(RoutingProblem routingProblem) {
List<Move<RoutingProblem>> moves = new ArrayList<>();
// 1. Assign moves
for (Order order : routingProblem.getOrders()) {
Driver currentDriver = order.getDriver();
for (Driver driver : routingProblem.getDrivers()) {
if (!driver.equals(currentDriver)) {
moves.add(new AssignMove(order, driver));
}
}
}
// 2. Rearrange moves
// TODO
return moves;
}
}
And finally, the move itself looks like this (nevermind the undo or the isDoable for the moment):
#Override
protected void doMoveOnGenuineVariables(ScoreDirector<RoutingProblem> scoreDirector) {
assignStep(scoreDirector, order.getPickupStep());
assignStep(scoreDirector, order.getDeliveryStep());
}
private void assignStep(ScoreDirector<RoutingProblem> scoreDirector, Step step) {
StepList beforeStep = step.getPreviousStep();
Step afterStep = step.getNextStep();
// 1. Insert step at the end of the driver's step list
StepList lastStep = driver.getLastStep();
scoreDirector.beforeVariableChanged(step, "previousStep"); // NullPointerException here
step.setPreviousStep(lastStep);
scoreDirector.afterVariableChanged(step, "previousStep");
// 2. Remove step from current chained list
if (afterStep != null) {
scoreDirector.beforeVariableChanged(afterStep, "previousStep");
afterStep.setPreviousStep(beforeStep);
scoreDirector.afterVariableChanged(afterStep, "previousStep");
}
}
The idea being that at no point I'm doing an invalid chained list manipulation:
However, as the title and the code comment indicate, I am getting a NullPointerException when I call scoreDirector.beforeVariableChanged. None of my variables are null (I've printed them to make sure). The NullPointerException doesn't occur in my code, but deep inside Optaplanner's inner workings, making it difficult for me to fix it:
Exception in thread "main" java.lang.NullPointerException
at org.drools.core.common.NamedEntryPoint.update(NamedEntryPoint.java:353)
at org.drools.core.common.NamedEntryPoint.update(NamedEntryPoint.java:338)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:1579)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:1551)
at org.optaplanner.core.impl.score.stream.drools.DroolsConstraintSession.update(DroolsConstraintSession.java:49)
at org.optaplanner.core.impl.score.director.stream.ConstraintStreamScoreDirector.afterVariableChanged(ConstraintStreamScoreDirector.java:137)
at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.retract(SingletonInverseVariableListener.java:96)
at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.beforeVariableChanged(SingletonInverseVariableListener.java:46)
at org.optaplanner.core.impl.domain.variable.listener.support.VariableListenerSupport.beforeVariableChanged(VariableListenerSupport.java:170)
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.beforeVariableChanged(AbstractScoreDirector.java:430)
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.beforeVariableChanged(AbstractScoreDirector.java:390)
at test.optaplanner.solver.AssignMove.assignStep(AssignMove.java:98)
at test.optaplanner.solver.AssignMove.doMoveOnGenuineVariables(AssignMove.java:85)
at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:35)
at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:30)
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.doAndProcessMove(AbstractScoreDirector.java:187)
at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.doMove(LocalSearchDecider.java:132)
at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.decideNextStep(LocalSearchDecider.java:116)
at org.optaplanner.core.impl.localsearch.DefaultLocalSearchPhase.solve(DefaultLocalSearchPhase.java:70)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:98)
at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:189)
at test.optaplanner.OptaPlannerService.testOptaplanner(OptaPlannerService.java:68)
at test.optaplanner.App.main(App.java:13)
Is there something I did wrong? It seems I am following the documentation for custom moves fairly closely, outside of the fact that I am using exclusively java code instead of drools.
The initial solution I feed to the solver has all of the steps assigned to a single driver. There are 15 drivers and 40 orders.
In order to bypass this error, I have tried a number of different things:
remove the shadow variable annotation, turn Driver into a problem fact, and handle the nextStep field myself => this makes no difference
use Simulated Annealing + First Fit Decreasing construction heuristics, and start with steps not assigned to any driver (this was inspired by looking up the example here, which is more complete than the one from the documentation) => the NullPointerException appears on afterVariableChanged instead, but it still appears.
a number of other things which were probably not very smart
But without a more helpful error message, I can't think of anything else to try.
Thank you for your help
I have a process where I have 3 sequential user tasks (something like Task 1 -> Task 2 -> Task 3). So, to validate the Task 3, I have to validate the Task 1, then the Task 2.
My goal is to implement a workaround to go back in an execution of a process instance thanks to a Command like suggested in this link. The problem is I started to implement the command by it does not work as I want. The algorithm should be something like:
Retrieve the task with the passed id
Get the process instance of this task
Get the historic tasks of the process instance
From the list of the historic tasks, deduce the previous one
Create a new task from the previous historic task
Make the execution to point to this new task
Maybe clean the task pointed before the update
So, the code of my command is like that:
public class MoveTokenCmd implements Command<Void> {
protected String fromTaskId = "20918";
public MoveTokenCmd() {
}
public Void execute(CommandContext commandContext) {
HistoricTaskInstanceEntity currentUserTaskEntity = commandContext.getHistoricTaskInstanceEntityManager()
.findHistoricTaskInstanceById(fromTaskId);
ExecutionEntity currentExecution = commandContext.getExecutionEntityManager()
.findExecutionById(currentUserTaskEntity.getExecutionId());
// Get process Instance
HistoricProcessInstanceEntity historicProcessInstanceEntity = commandContext
.getHistoricProcessInstanceEntityManager()
.findHistoricProcessInstance(currentUserTaskEntity.getProcessInstanceId());
HistoricTaskInstanceQueryImpl historicTaskInstanceQuery = new HistoricTaskInstanceQueryImpl();
historicTaskInstanceQuery.processInstanceId(historicProcessInstanceEntity.getId()).orderByExecutionId().desc();
List<HistoricTaskInstance> historicTaskInstances = commandContext.getHistoricTaskInstanceEntityManager()
.findHistoricTaskInstancesByQueryCriteria(historicTaskInstanceQuery);
int index = 0;
for (HistoricTaskInstance historicTaskInstance : historicTaskInstances) {
if (historicTaskInstance.getId().equals(currentUserTaskEntity.getId())) {
break;
}
index++;
}
if (index > 0) {
HistoricTaskInstance previousTask = historicTaskInstances.get(index - 1);
TaskEntity newTaskEntity = createTaskFromHistoricTask(previousTask, commandContext);
currentExecution.addTask(newTaskEntity);
commandContext.getTaskEntityManager().insert(newTaskEntity);
AtomicOperation.TRANSITION_CREATE_SCOPE.execute(currentExecution);
} else {
// TODO: find the last task of the previous process instance
}
// To overcome the "Task cannot be deleted because is part of a running
// process"
TaskEntity currentUserTask = commandContext.getTaskEntityManager().findTaskById(fromTaskId);
if (currentUserTask != null) {
currentUserTask.setExecutionId(null);
commandContext.getTaskEntityManager().deleteTask(currentUserTask, "jumped to another task", true);
}
return null;
}
private TaskEntity createTaskFromHistoricTask(HistoricTaskInstance historicTaskInstance,
CommandContext commandContext) {
TaskEntity newTaskEntity = new TaskEntity();
newTaskEntity.setProcessDefinitionId(historicTaskInstance.getProcessDefinitionId());
newTaskEntity.setName(historicTaskInstance.getName());
newTaskEntity.setTaskDefinitionKey(historicTaskInstance.getTaskDefinitionKey());
newTaskEntity.setProcessInstanceId(historicTaskInstance.getExecutionId());
newTaskEntity.setExecutionId(historicTaskInstance.getExecutionId());
return newTaskEntity;
}
}
But the problem is I can see my task is created, but the execution does not point to it but to the current one.
I had the idea to use the activity (via the object ActivityImpl) to set it to the execution but I don't know how to retrieve the activity of my new task.
Can someone help me, please?
Unless somethign has changed in the engine significantly the code in the link you reference should still work (I have used it on a number of projects).
That said, when scanning your code I don't see the most important command.
Once you have the current execution, you can move the token by setting the current activity.
Like I said, the code in the referenced article used to work and still should.
Greg
Referring the same link in your question, i would personally recommend to work with the design of you your process. use an exclusive gateway to decide whether the process should end or should be returned to the previous task. if the generation of task is dynamic, you can point to the same task and delete local variable. Activiti has constructs to save your time from implementing the same :).
What I try to achieve here is to get the number of relationships of a particular node, while other threads adding new relationships to it concurrently. I run my code in a unit test with
TestGraphDatabaseFactory().newImpermanentDatabase() graph service.
My code is executed by ~50 threads, and it looks something like this:
int numOfRels = 0;
try {
Iterable<Relationship> rels = parentNode.getRelationships(RelTypes.RUNS, Direction.OUTGOING);
while (rels.iterator().hasNext()) {
numOfRels++;
rels.iterator().next();
}
}
catch(Exception e) {
throw e;
}
// Enforce relationship limit
if (numOfRels > 10) {
// do something
}
Transaction tx = graph.beginTx();
try {
Node node = createMyNodeAndConnectToParentNode(...);
tx.success();
return node;
}
catch (Exception e) {
tx.failure();
}
finally {
tx.finish();
}
The problem is once a while I get a "ArrayIndexOutOfBoundsException: 1" in the try-catch block above (the one surrounding the getRelationships()). If I understand correctly Iterable is not thread-safe and causing this problem.
My question is what is the best way to iterate over constantly changing relationships and nodes using Neo4j's Java API?
I am getting the following errors:
Exception in thread "Thread-14" org.neo4j.helpers.ThisShouldNotHappenError: Developer: Stefan/Jake claims that: A property key id disappeared under our feet
at org.neo4j.kernel.impl.core.NodeProxy.setProperty(NodeProxy.java:188)
at com.inbiza.connio.neo4j.server.extensions.graph.AppEntity.createMyNodeAndConnectToParentNode(AppEntity.java:546)
at com.inbiza.connio.neo4j.server.extensions.graph.AppEntity.create(AppEntity.java:305)
at com.inbiza.connio.neo4j.server.extensions.TestEmbeddedConnioGraph$appCreatorThread.run(TestEmbeddedConnioGraph.java:61)
at java.lang.Thread.run(Thread.java:722)
Exception in thread "Thread-92" java.lang.ArrayIndexOutOfBoundsException: 1
at org.neo4j.kernel.impl.core.RelationshipIterator.fetchNextOrNull(RelationshipIterator.java:72)
at org.neo4j.kernel.impl.core.RelationshipIterator.fetchNextOrNull(RelationshipIterator.java:36)
at org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55)
at com.inbiza.connio.neo4j.server.extensions.graph.AppEntity.create(AppEntity.java:243)
at com.inbiza.connio.neo4j.server.extensions.TestEmbeddedConnioGraph$appCreatorThread.run(TestEmbeddedConnioGraph.java:61)
at java.lang.Thread.run(Thread.java:722)
Exception in thread "Thread-12" java.lang.ArrayIndexOutOfBoundsException: 1
at org.neo4j.kernel.impl.core.RelationshipIterator.fetchNextOrNull(RelationshipIterator.java:72)
at org.neo4j.kernel.impl.core.RelationshipIterator.fetchNextOrNull(RelationshipIterator.java:36)
at org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55)
at com.inbiza.connio.neo4j.server.extensions.graph.AppEntity.create(AppEntity.java:243)
at com.inbiza.connio.neo4j.server.extensions.TestEmbeddedConnioGraph$appCreatorThread.run(TestEmbeddedConnioGraph.java:61)
at java.lang.Thread.run(Thread.java:722)
Exception in thread "Thread-93" java.lang.ArrayIndexOutOfBoundsException
Exception in thread "Thread-90" java.lang.ArrayIndexOutOfBoundsException
Below is the method responsible of node creation:
static Node createMyNodeAndConnectToParentNode(GraphDatabaseService graph, final Node ownerAccountNode, final String suggestedName, Map properties) {
final String accountId = checkNotNull((String)ownerAccountNode.getProperty("account_id"));
Node appNode = graph.createNode();
appNode.setProperty("urn_name", App.composeUrnName(accountId, suggestedName.toLowerCase().trim()));
int nextId = nodeId.addAndGet(1); // I normally use getOrCreate idiom but to simplify I replaced it with an atomic int - that would do for testing
String urn = App.composeUrnUid(accountId, nextId);
appNode.setProperty("urn_uid", urn);
appNode.setProperty("id", nextId);
appNode.setProperty("name", suggestedName);
Index<Node> indexUid = graph.index().forNodes("EntityUrnUid");
indexUid.add(appNode, "urn_uid", urn);
appNode.addLabel(LabelTypes.App);
appNode.setProperty("version", properties.get("version"));
appNode.setProperty("description", properties.get("description"));
Relationship rel = ownerAccountNode.createRelationshipTo(appNode, RelTypes.RUNS);
rel.setProperty("date_created", fmt.print(new DateTime()));
return appNode;
}
I am looking at org.neo4j.kernel.impl.core.RelationshipIterator.fetchNextOrNull()
It looks like my test generates a condition where else if ( (status = fromNode.getMoreRelationships( nodeManager )).loaded() || lastTimeILookedThereWasMoreToLoad ) is not executed, and where currentTypeIterator state is changed in between.
RelIdIterator currentTypeIterator = rels[currentTypeIndex]; //<-- this is where is crashes
do
{
if ( currentTypeIterator.hasNext() )
...
...
while ( !currentTypeIterator.hasNext() )
{
if ( ++currentTypeIndex < rels.length )
{
currentTypeIterator = rels[currentTypeIndex];
}
else if ( (status = fromNode.getMoreRelationships( nodeManager )).loaded()
// This is here to guard for that someone else might have loaded
// stuff in this relationship chain (and exhausted it) while I
// iterated over my batch of relationships. It will only happen
// for nodes which have more than <grab size> relationships and
// isn't fully loaded when starting iterating.
|| lastTimeILookedThereWasMoreToLoad )
{
....
}
}
} while ( currentTypeIterator.hasNext() );
I also tested couple locking scenarios. The one below solves the issue. Not sure if I should use a lock every time I iterate over relationships based on this.
Transaction txRead = graph.beginTx();
try {
txRead.acquireReadLock(parentNode);
long numOfRels = 0L;
Iterable<Relationship> rels = parentNode.getRelationships(RelTypes.RUNS, Direction.OUTGOING);
while (rels.iterator().hasNext()) {
numOfRels++;
rels.iterator().next();
}
txRead.success();
}
finally {
txRead.finish();
}
I am very new to Neo4j and its source base; just testing as a potential data store for our product. I will appreciate if someone knowing Neo4j inside & out explains what is going on here.
This is a bug. The fix is captured in this pull request: https://github.com/neo4j/neo4j/pull/1011
Well I think this a bug. The Iterable returned by getRelationships() are meant to be immutable. When this method is called, all the available Nodes till that moment will be available in the iterator. (You can verify this from org.neo4j.kernel.IntArrayIterator)
I tried replicating it by having 250 threads trying to insert a relationship from a node to some other node. And having a main thread looping over the iterator for the first node. On careful analysis, the iterator only contains the relationships added when getRelationship() was last called. The issue never came up for me.
Can you please put your complete code, IMO there might some silly error. The reason it cannot happen is that the write locks are in place when adding a relationship and reads are hence synchronized.
I'm currently developing a camera application for Android on which some problems have occurred. I need it to work on all Android devices and since all of these works in different ways specially with the camera hardware, I'm having a hard time finding a solution that works for every device.
My application main goal is to launch the camera on a button click, take a photo and upload it to a server. So I don't really need the functionality of saving the image on the device, but if that's needed for further image use I might as well allow it.
For example I'm testing my application on a Samsung Galaxy SII and a Motorola Pad. I got working code that launches the camera, which is by the way C# code since I'm using Monodroid:
Intent cameraIntent = new Intent(Android.Provider.MediaStore.ActionImageCapture);
StartActivityForResult(cameraIntent, PHOTO_CAPTURE);
And I fetch the result, similar to this guide I followed:
http://kevinpotgieter.wordpress.com/2011/03/30/null-intent-passed-back-on-samsung-galaxy-tab/
Why I followed this guide is because the activity returns null on my galaxy device (Another device oriented problem).
This code works fine on the Galaxy device. It takes a photo and saves the photo in the gallery from which i can upload to a server. By further research this is apparently galaxy standard behaviour, so this doesn't work on my Motorola pad. The camera works fine, but no image is saved to gallery.
So with this background my question is, am I on the right path here? Do I need to save the image to gallery in order for further use in my application? Is there any solution that works for every Android device, cause that's the solution i need.
Thanks for any feedback!
After reading the linked article, the approach taken in that article is geared toward the Galaxy line, since they appear to write to the gallery automatically.
This article discusses some other scenarios in detail:
Android ACTION_IMAGE_CAPTURE Intent
So, I don't necessarily think that following the linked article that you provided is the right path. Not all devices automatically write to the gallery as described in that article, afaik. The article I linked to points to the issues being related to security and suggests writing the image to a /sdcard/tmp folder for storing the original image. Going down a similar path would more than likely lead to code that is going to work reliably across many devices.
Here are some other links for reference:
Google discussion regarding this subject: http://code.google.com/p/android/issues/detail?id=1480
Project with potential a solution to the problem: https://github.com/johnyma22/classdroid
While that discussion/project are in Java/Android SDK, the same concepts should apply to Monodroid. I'd be happy to help you adapt the code to a working Mono for Android solution if you need help.
To long2know:
Yes the same concepts applies to Monodroid. I've already read the stack article you linked among with some other similar. However i don't like the approach in that particular post since it checks for bugs for some devices that are hardcoded into a collection. Meaning it might fail to detect bugs in future devices. Since i won't be doing maintenance on this application, i can't allow this. I found a solution elsewhere and adapted it to my case and i'll post it below if someone would need it. It works on both my devices, guessing it would work for the majority of other devices. Thanks for your post!
Solution that allows you to snap a picture and use, also with the option of using a image from gallery. Solution uses option menu for these purposes, just for testing. (Monodroid code).
Camera code is inspired by:
access to full resolution pictures from camera with MonoDroid
namespace StackOverFlow.UsingCameraWithMonodroid
{
[Activity(Label = "ImageActivity")]
public class ImageActivity
private readonly static int TakePicture = 1;
private readonly static int SelectPicture = 2;
private string imageUriString;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
this.SetContentView(Resource.Layout.ImageActivity);
}
public override bool OnCreateOptionsMenu(IMenu menu)
{
MenuInflater flate = this.MenuInflater;
flate.Inflate(Resource.Menu.ImageMenues, menu);
return base.OnCreateOptionsMenu(menu);
}
public override bool OnOptionsItemSelected(IMenuItem item)
{
switch (item.ItemId)
{
case Resource.Id.UseExisting:
this.SelectImageFromStorage();
return true;
case Resource.Id.AddNew:
this.StartCamera();
return true;
default:
return base.OnOptionsItemSelected(item);
}
}
private Boolean isMounted
{
get
{
return Android.OS.Environment.ExternalStorageState.Equals(Android.OS.Environment.MediaMounted);
}
}
private void StartCamera()
{
var imageUri = ContentResolver.Insert(isMounted ? MediaStore.Images.Media.ExternalContentUri
: MediaStore.Images.Media.InternalContentUri, new ContentValues());
this.imageUriString = imageUri.ToString();
var cameraIntent = new Intent(MediaStore.ActionImageCapture);
cameraIntent.PutExtra(MediaStore.ExtraOutput, imageUri);
this.StartActivityForResult(cameraIntent, TakePicture);
}
private void SelectImageFromStorage()
{
Intent intent = new Intent();
intent.SetType("image/*");
intent.SetAction(Intent.ActionGetContent);
this.StartActivityForResult(Intent.CreateChooser(intent,
"Select Picture"), SelectPicture);
}
// Example code of using the result, in my case i want to upload in another activity
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
// If a picture was taken
if (resultCode == Result.Ok && requestCode == TakePicture)
{
// For some devices data can become null when using the camera activity.
// For this reason we save pass the already saved imageUriString to the upload activity
// in order to adapt to every device. Instead we would want to use the data intent
// like in the SelectPicture option.
var uploadIntent = new Intent(this.BaseContext, typeof(UploadActivity));
uploadIntent.PutExtra("ImageUri", this.imageUriString);
this.StartActivity(uploadIntent);
}
// User has selected a image from storage
else if (requestCode == SelectPicture)
{
var uploadIntent = new Intent(this.BaseContext, typeof(UploadActivity));
uploadIntent.PutExtra("ImageUri", data.DataString);
this.StartActivity(uploadIntent);
}
}
}
}