How to display the created flow on corda - corda

when I create a flow, they do not appear in the flow list. Do I need to create them in the cordapp module? Project builds normally.
Project schema1

So without the source code, there's no way for us to really know why it doesn't appear in the list.
It's worth mentioning there are some obscure bugs as well, I suspect that what you're running into here is that your code isn't overriding the progressTracker.
Note the docs here:
Flows cannot be run unless they override the progress tracker
So just try to keep that in mind that it could be causing your issue.
Here's a progressTracker example from the yo cordapp on the corda github.
public class YoFlow extends FlowLogic<SignedTransaction> {
private static final ProgressTracker.Step CREATING = new ProgressTracker.Step("Creating a new Yo!");
private static final ProgressTracker.Step SIGNING = new ProgressTracker.Step("Signing the Yo!");
private static final ProgressTracker.Step VERIFYING = new ProgressTracker.Step("Verfiying the Yo!");
private static final ProgressTracker.Step FINALISING = new ProgressTracker.Step("Sending the Yo!") {
#Nullable
#Override
public ProgressTracker childProgressTracker() {
return FinalityFlow.tracker();
}
};
ProgressTracker progressTracker = new ProgressTracker(
CREATING,
SIGNING,
VERIFYING,
FINALISING
);
#Nullable
#Override
public ProgressTracker getProgressTracker() {
return progressTracker;
}
private final Party target;
public YoFlow(Party target) {
this.target = target;
}
#Suspendable
#Override
public SignedTransaction call() throws FlowException {
progressTracker.setCurrentStep(CREATING);
Source: Docs limitations page: https://docs.corda.net/docs/corda-os/4.4/shell.html#limitations

Related

my custom class implementing ConsumerAwareRebalanceListener is not working

I'm using spring-kafka-2.2.7-RELEASE. I'm trying to capture the event when a consumer is ready to consume message and trying to use ConsumerAwareRebalanceListener but it's not working. Please suggest.
#Component
public class ConsumerAwareRebalanceListenerImpl implements ConsumerAwareRebalanceListener {
public void ConsumerAwareRebalanceListenerImpl(){
System.out.println(" In ConsumerAwareRebalanceListenerImpl constructor");
}
#Override
public void onPartitionsRevoked(Collection<TopicPartition> partitions) {
}
#Override
public void onPartitionsAssigned(Collection<TopicPartition> partitions) {
partitions.forEach( item -> {
TestConsumerConstants.consumerEventsMap.put("key-"+item.partition(), item.partition());
});
}
#Override
public void onPartitionsAssigned(Consumer<?, ?> consumer, Collection<TopicPartition> partitions){
TestConsumerConstants.consumerEventsMap.put(consumer.toString(), partitions);
}
}
I fixed the problem and it's working now. All I had to do is, set the containerProperty 'setConsumerRebalanceListener' of the ConcurrentKafkaListenerContainerFactory to my custom class instance as shown below
ConcurrentKafkaListenerContainerFactory factory = new
ConcurrentKafkaListenerContainerFactory<>();
factory.getContainerProperties().setConsumerRebalanceListener(kafkaConsumerRebalanceListener);

How to test a kafka consumer against a real kafka broker running on a server?

I have difficulty understanding some Kafka concepts in Java Spring Boot. I’d like to test a consumer against a real Kafka broker running on a server, which has some producers that write / have already written data to various topics. I would like to establish a connection with the server, consume the data, and verify or process its content in a test.
An enormous majority of examples (actually all I have seen so far) in the internet refer to embedded kafka, EmbeddedKafkaBroker, and show both a producer and a consumer implemented on one machine, locally. I haven’t found any example that would explain how to make a connection with a remote kafka server and read data from a particular topic.
I've written some code and I've printed the broker address with:
System.out.println(embeddedKafkaBroker.getBrokerAddress(0));
What I got is 127.0.0.1:9092, which means that it is local, so the connection with the remote server has not been established.
On the other hand, when I run the SpringBootApplication I get the payload from the remote broker.
Receiver:
#Component
public class Receiver {
private static final String TOPIC_NAME = "X";
private static final Logger LOGGER = LoggerFactory.getLogger(Receiver.class);
private CountDownLatch latch = new CountDownLatch(1);
public CountDownLatch getLatch() {
return latch;
}
#KafkaListener(topics = TOPIC_NAME)
public void receive(final byte[] payload) {
LOGGER.info("received the following payload: '{}'", payload);
latch.countDown();
}
}
Config:
#EnableKafka
#Configuration
public class ByteReceiverConfig {
#Autowired
EmbeddedKafkaBroker kafkaEmbeded;
#Value("${spring.kafka.bootstrap-servers}")
private String bootstrapServers;
#Value("${spring.kafka.consumer.group-id}")
private String groupIdConfig;
#Bean
public KafkaListenerContainerFactory<?> kafkaListenerContainerFactory() {
final ConcurrentKafkaListenerContainerFactory<Object, Object> factory =
new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory());
return factory;
}
#Bean
ConsumerFactory<Object, Object> consumerFactory() {
return new DefaultKafkaConsumerFactory<>(consumerProperties());
}
#Bean
Map<String, Object> consumerProperties() {
final Map<String, Object> properties =
KafkaTestUtils.consumerProps("junit-test", "true", this.kafkaEmbeded);
properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, ByteArrayDeserializer.class);
properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, ByteArrayDeserializer.class);
properties.put(ConsumerConfig.GROUP_ID_CONFIG, groupIdConfig);
return properties;
}
Test:
#EnableAutoConfiguration
#EnableKafka
#SpringBootTest(classes = {ByteReceiverConfig.class, Receiver.class})
#EmbeddedKafka
#ContextConfiguration(classes = ByteReceiverConfig.class)
#TestPropertySource(properties = { "spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}",
"spring.kafka.consumer.group-id=EmbeddedKafkaTest"})
public class KafkaTest {
#Autowired
private KafkaListenerEndpointRegistry kafkaListenerEndpointRegistry;
#Autowired
EmbeddedKafkaBroker embeddedKafkaBroker;
#Autowired
Receiver receiver;
#BeforeEach
void waitForAssignment() {
for (MessageListenerContainer messageListenerContainer : kafkaListenerEndpointRegistry.getListenerContainers()) {
System.out.println(messageListenerContainer.getAssignedPartitions().isEmpty());
System.out.println(messageListenerContainer.toString());
System.out.println(embeddedKafkaBroker.getTopics().size());
System.out.println(embeddedKafkaBroker.getPartitionsPerTopic());
System.out.println(embeddedKafkaBroker.getBrokerAddress(0));
System.out.println(embeddedKafkaBroker.getBrokersAsString());
ContainerTestUtils.waitForAssignment(messageListenerContainer,
embeddedKafkaBroker.getPartitionsPerTopic());
}
#Test
public void testReceive() {
}
}
I would like somebody to shed some light on the following issues:
1.Can an instance of the class EmbeddedKafkaBroker be used to test data that comes from a remote broker, or is it only used for local tests, in which I would procude i.e send data to a topic that I created and consume data myself?
2.Is it possible to write a test class for a real kafka server? For instance to verify if a connection has been establish, or if a data has been read from a specific topic. What annotations, configurations, and classes would be needed in such case?
3.If I only want to consume data, do I have to provide the producer configuration in a config file (it would be strange, but all examples I have encountered so far did it)?
4.Do you know any resources (books, websites etc.) that show real examples of using kafka i.e. with a remote kafka server, with a procuder or a consumer only?
You don't need an embedded broker at all if you want to talk to an external broker only.
Yes, just set the bootstrap servers property appropriately.
No, you don't need producer configuration.
EDIT
#SpringBootApplication
public class So56044105Application {
public static void main(String[] args) {
SpringApplication.run(So56044105Application.class, args);
}
#Bean
public NewTopic topic() {
return new NewTopic("so56044105", 1, (short) 1);
}
}
spring.kafka.bootstrap-servers=10.0.0.8:9092
spring.kafka.consumer.enable-auto-commit=false
#RunWith(SpringRunner.class)
#SpringBootTest(classes = { So56044105Application.class, So56044105ApplicationTests.Config.class })
public class So56044105ApplicationTests {
#Autowired
public Config config;
#Test
public void test() throws InterruptedException {
assertThat(config.latch.await(10, TimeUnit.SECONDS)).isTrue();
assertThat(config.received.get(0)).isEqualTo("foo");
}
#Configuration
public static class Config implements ConsumerSeekAware {
List<String> received = new ArrayList<>();
CountDownLatch latch = new CountDownLatch(3);
#KafkaListener(id = "so56044105", topics = "so56044105")
public void listen(String in) {
System.out.println(in);
this.received.add(in);
this.latch.countDown();
}
#Override
public void registerSeekCallback(ConsumerSeekCallback callback) {
}
#Override
public void onPartitionsAssigned(Map<TopicPartition, Long> assignments, ConsumerSeekCallback callback) {
System.out.println("Seeking to beginning");
assignments.keySet().forEach(tp -> callback.seekToBeginning(tp.topic(), tp.partition()));
}
#Override
public void onIdleContainer(Map<TopicPartition, Long> assignments, ConsumerSeekCallback callback) {
}
}
}
There are some examples in this repository for bootstrapping real Kafka producers and consumers across a variety of configurations — plaintext, SSL, with and without authentication, etc.
Note: the repo above contains examples for the Effective Kafka book, which I am the author of. However, they can be used freely without the book and hopefully they make just as much sense on their own.
More to the point, here are a pair of examples for a basic producer and a consumer.
/** A sample Kafka producer. */
import static java.lang.System.*;
import java.util.*;
import org.apache.kafka.clients.producer.*;
import org.apache.kafka.common.serialization.*;
public final class BasicProducerSample {
public static void main(String[] args) throws InterruptedException {
final var topic = "getting-started";
final Map<String, Object> config =
Map.of(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092",
ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName(),
ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName(),
ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG, true);
try (var producer = new KafkaProducer<String, String>(config)) {
while (true) {
final var key = "myKey";
final var value = new Date().toString();
out.format("Publishing record with value %s%n",
value);
final Callback callback = (metadata, exception) -> {
out.format("Published with metadata: %s, error: %s%n",
metadata, exception);
};
// publish the record, handling the metadata in the callback
producer.send(new ProducerRecord<>(topic, key, value), callback);
// wait a second before publishing another
Thread.sleep(1000);
}
}
}
}
/** A sample Kafka consumer. */
import static java.lang.System.*;
import java.time.*;
import java.util.*;
import org.apache.kafka.clients.consumer.*;
import org.apache.kafka.common.serialization.*;
public final class BasicConsumerSample {
public static void main(String[] args) {
final var topic = "getting-started";
final Map<String, Object> config =
Map.of(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092",
ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName(),
ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName(),
ConsumerConfig.GROUP_ID_CONFIG, "basic-consumer-sample",
ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest",
ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
try (var consumer = new KafkaConsumer<String, String>(config)) {
consumer.subscribe(Set.of(topic));
while (true) {
final var records = consumer.poll(Duration.ofMillis(100));
for (var record : records) {
out.format("Got record with value %s%n", record.value());
}
consumer.commitAsync();
}
}
}
}
Now, these are obviously not unit tests. But with very little rework they could be turned into one. The next step would be to remove Thread.sleep() and add assertions. Note, since Kafka is inherently asynchronous, naively asserting a published message in a consumer immediately after publishing will fail. For a robust, repeatable test, you may want to use something like Timesert.

Unique Identifier in Obligation Cordapp

I have replicated the Obligation Cordapp Transfer functionality and i am struck with the linearId of Unique Identifier. I have successfully exercised the Issue Cordapp and for transfer of Obligation, i have provided the flow command with linearId of generated Obligation. The parameter which i am passing through linearId is interpreted as the External id [argument in UniqueIdentifier] instead of id and so it is unable to find the Obligation to transfer.
Here are reference for issue.
The generated id for the Obligation created is
**linearId : externalId: null
id: "4799c549-8c2b-401f-90dd-1dc115fbcfba"
Thu Mar 29 18:41:02 IST 2018>>> flow start TransferObligation$Initiator newLender: "O=PartyC,L=Paris,C=FR",anonymous: false,linearId: "4799c549-8c2b-401f-90dd-1dc115fbcfba
The passed argument, linearId has to take as id [argument in UniqueIdentifier and is randomly generated if external id is not equal to null] as per Obligation Cordapp and has to do required transfer functionality. Instead it is taking linearId passed as externalId [argument in UniqueIdentifier] and so total linearId becoming externalId_id.
>Linear Id parameter is:4799c549-8c2b-401f-90dd-1dc115fbcfba_ace60f85-b360-4cf7b198-4d3d471f9d63
>Obtaining IOU from vault.
>States Size:0
Observing that ace60f85-b360-4cf7b198-4d3d471f9d63 is appended as id which is randomly generated and unable to find the Obligation generated.
How corda will interpret linearId passed? as externalId/Id as default?
In Obligation Cordapp it demonstrated in samples took as Id and required job is done.But the cordapp which i am exercising takes the passed parameter as externalId.
Or any changes has to be done in code level to take the linearId parameter as id?
Edit 1:
We are developing the code in java The transfer obligation for reference.Although it is just a replicate.Please have a look at it
package com.example.flow;
import co.paralleluniverse.fibers.Suspendable;
import com.example.contract.ActivityContract;
import com.example.state.Activity;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import net.corda.confidential.IdentitySyncFlow;
import net.corda.confidential.SwapIdentitiesFlow;
import net.corda.core.contracts.Command;
import net.corda.core.contracts.StateAndRef;
import net.corda.core.contracts.UniqueIdentifier;
import net.corda.core.flows.*;
import net.corda.core.identity.AbstractParty;
import net.corda.core.identity.AnonymousParty;
import net.corda.core.identity.Party;
import net.corda.core.transactions.SignedTransaction;
import net.corda.core.transactions.TransactionBuilder;
import net.corda.core.utilities.ProgressTracker;
import net.corda.core.utilities.ProgressTracker.Step;
import java.security.PublicKey;
import java.util.*;
import static com.example.contract.ActivityContract.Activity_Contract_ID;
public class ActivityTransferFlow {
#StartableByRPC
#InitiatingFlow
public static class Initiator extends ActivityBaseFlow{
public final UniqueIdentifier linearId;
public final Party newLender;
public final Boolean anonymous;
private final Step INITIATION = new Step("Obtaining IOU from vault.");
private final Step BUILDING = new Step("Building and Verifying Transaction");
private final Step SIGNING = new Step("Signing gathered transaction");
private final Step SYNCING = new Step("Syncing gathered identities "){
#Override
public ProgressTracker childProgressTracker() {
return IdentitySyncFlow.Send.Companion.tracker();
}
};
private final Step GATHERING = new Step("Gathering counterparty signatures"){
#Override
public ProgressTracker childProgressTracker() {
return CollectSignaturesFlow.Companion.tracker();
}
};
private final Step FINALISING = new Step("Finalising transaction"){
#Override
public ProgressTracker childProgressTracker() {
return FinalityFlow.Companion.tracker();
}
};
private final ProgressTracker progressTracker = new ProgressTracker(
INITIATION,
BUILDING,
SIGNING,
SYNCING,
GATHERING,
FINALISING
);
public Initiator(UniqueIdentifier linearId, Party newLender, Boolean anonymous) {
this.linearId = linearId;
this.newLender = newLender;
this.anonymous = anonymous;
}
#Override
public ProgressTracker getProgressTracker() {
return progressTracker;
}
#Suspendable
#Override
public SignedTransaction call() throws FlowException {
// step1:Retrieve Activity specified by linear id from the vault
progressTracker.setCurrentStep(INITIATION);
final StateAndRef<Activity> activityToTransfer= getObligationByLinearId(linearId);
}
final Activity inputActivity=activityToTransfer.getState().getData();
//step2:This flow can only be initiated by current recipient
final AbstractParty lenderIdentity =getLenderIdentity(inputActivity);
//step3:Abort if the borrower started this flow
if(!getOurIdentity().equals(lenderIdentity))
{
throw new IllegalStateException("Activity transfer can only be initiated by the lender.");
}
//step4:Creating the new obligation state reflecting a new lender
progressTracker.setCurrentStep(BUILDING);
final Activity transferredActivity =createOutputActivity(inputActivity);
//step4:Create transfer command
final List<PublicKey> signerKeys = new ImmutableList.Builder<PublicKey>()
.addAll(inputActivity.getParticipantKeys())
.add(transferredActivity.getLender().getOwningKey()).build();
final Command transferCommand = new Command<>(new ActivityContract.Commands.ActivityTransfer(), signerKeys);
//step5:Create a transaction builder and then add states and commands.
final TransactionBuilder builder = new TransactionBuilder(getNotary())
.addInputState(activityToTransfer)
.addOutputState(transferredActivity, Activity_Contract_ID)
.addCommand(transferCommand);
//step6:Verify and sign the transaction
progressTracker.setCurrentStep(SIGNING);
builder.verify(getServiceHub());
final SignedTransaction ptx=getServiceHub().signInitialTransaction(builder, inputActivity.getLender().getOwningKey());
//step7:Getting party object from the borrower
progressTracker.setCurrentStep(SYNCING);
final Party borrower=getBorrowerIdentity(inputActivity);
//step8:Send any keys or certificates so the signers can verify each other identity
Set<FlowSession> sessions=new HashSet<>();
Set<Party> parties= ImmutableSet.of(borrower,newLender);
for (Party party:parties) {
sessions.add(initiateFlow(party));
}
subFlow(new IdentitySyncFlow.Send(sessions,ptx.getTx(),SYNCING.childProgressTracker()));
//step9:Gathering signatures from the borrower and the new lender
progressTracker.setCurrentStep(GATHERING);
final SignedTransaction stx=subFlow(new CollectSignaturesFlow(
ptx,
sessions,
ImmutableList.of(inputActivity.getLender().getOwningKey()),
GATHERING.childProgressTracker()
));
//Step10:Notarise and record the transaction into vault and broadcast the transaction
progressTracker.setCurrentStep(FINALISING);
return subFlow(new FinalityFlow(stx,ImmutableSet.of(getOurIdentity())));
}
#Suspendable
private AbstractParty getLenderIdentity(Activity inputObligation) {
if (inputObligation.getLender() instanceof AnonymousParty) {
return resolveIdentity(inputObligation.getLender());
} else {
return inputObligation.getLender();
}
}
#Suspendable
private Activity createOutputActivity(Activity inputActivity) throws FlowException {
if (anonymous) {
final HashMap<Party, AnonymousParty> txKeys = subFlow(new SwapIdentitiesFlow(newLender));
if (!txKeys.containsKey(newLender)) {
throw new FlowException("Couldn't get lender's conf. identity.");
}
final AnonymousParty anonymousLender = txKeys.get(newLender);
return inputActivity.withNewLender(anonymousLender);
} else {
return inputActivity.withNewLender(newLender);
}
}
#Suspendable
private Party getBorrowerIdentity(Activity inputActivity) {
if (inputActivity.getBorrower() instanceof AnonymousParty) {
return resolveIdentity(inputActivity.getBorrower());
} else {
return (Party) inputActivity.getBorrower();
}
}
}
#InitiatedBy(Initiator.class)
public static class Responder extends FlowLogic<SignedTransaction> {
private final FlowSession otherFlow;
public Responder(FlowSession otherFlow) {
this.otherFlow = otherFlow;
}
#Suspendable
#Override
public SignedTransaction call() throws FlowException {
subFlow(new IdentitySyncFlow.Receive(otherFlow));
SignedTransaction stx = subFlow(new ActivityBaseFlow.SignTxFlowNoChecking(otherFlow, SignTransactionFlow.Companion.tracker()));
return waitForLedgerCommit(stx.getId());
}
}
}
Edit 2:
The getObligationByLinearId method in ActivityBaseFlow
and the command we use is
flow start ActivityTransferFlow$Initiator linearId: d21827b7-e4be-4874-9383-e9f339d7c9ea,newLender: "O=PartyC,L=Paris,C=FR",anonymous: false
StateAndRef<Activity> getObligationByLinearId(UniqueIdentifier linearId) throws FlowException {
System.out.println("Linear Id parameter is:"+linearId);
QueryCriteria queryCriteria = new QueryCriteria.LinearStateQueryCriteria(
null,
ImmutableList.of(linearId),
Vault.StateStatus.UNCONSUMED,
null);
List<StateAndRef<Activity>> obligations = getServiceHub().getVaultService().queryBy(Activity.class, queryCriteria).getStates();
if (obligations.size() != 1) {
System.out.println("Linear Id 1:"+linearId);
throw new FlowException(String.format("Obligation with id %s not found.", linearId));
}
//System.out.println("Linear Id 2:"+linearId);
return obligations.get(0);
}
The UniqueIdentifier constructor is taking the string input from flow start as the externalId.
Change your flow to accept a string instead and manually parse it using UniqueIdentifier.fromString(inputString). i.e
public Initiator(String inputString, Party newLender, Boolean anonymous) {
this.linearId = UniqueIdentifier.fromString(inputString);
this.newLender = newLender;
this.anonymous = anonymous;
}

setPersistenceEnabled(true) crashes app

I’m creating my first Firebase App. One of its requirements is that it run when the network is not available. The Firebase guide states:
Enabling disk persistence allows our app to also keep all of its state even after an app restart. We can enable disk persistence with just one line of code.
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
With disk persistence enabled, our synced data and writes will be persisted to disk across app restarts and our app should work seamlessly in offline situations.
Another requirement is to use Google Sign In. So in my MainActivity I check if the User is signed in, if not, I launch the SignInActivity. (The SignInActivity is from the Firebase examples.) The SignInActivity works, the user gets logged in, and MainActivity is launched for a second time. Now my app crashes on the code line FirebaseDatabase.getInstance().setPersistenceEnabled(true); with the following message:
Calls to setPersistenceEnabled() must be made before any other usage of FirebaseDatabase instance.
Now if I restart my app, the User is signed in, the SignInActivity is not launched, my app runs fine.
Any suggestions of how I avoid this crash after the User signs in?
As I was posting this question, I received a suggestion to relocate FirebaseDatabase.getInstance().setPersistenceEnabled(true);
to my “Application class”. I get exactly the same result … SignInActivity starts, completes, and I get a crash on the setPersistenceEnabled.
Below is my MainActivity onCreate:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Calls to setPersistenceEnabled() must be made before any other usage of FirebaseDatabase instance.
// Crash here upon returning from SignInActivity.
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
mFirebaseDbReference = FirebaseDatabase.getInstance().getReference();
// Initialize Firebase Auth
mFirebaseAuth = FirebaseAuth.getInstance();
mFirebaseUser = mFirebaseAuth.getCurrentUser();
if (mFirebaseUser == null) {
// Not signed in, launch the Sign In activity
Timber.tag("MainActivity").i("onCreate(): User not signed in, launching SignInActivity");
startActivity(new Intent(this, SignInActivity.class));
finish();
} else {
mUsername = mFirebaseUser.getDisplayName();
Timber.tag("MainActivity").i("onCreate(): User \"%s\" signed in.", mUsername);
if (mFirebaseUser.getPhotoUrl() != null) {
mPhotoUrl = mFirebaseUser.getPhotoUrl().toString();
}
}
A FirebaseApp is initialized by a ContentProvider so it is not initialized at the time onCreate() is called.
Get your FirebaseDatabase like this:
public class Utils {
private static FirebaseDatabase mDatabase;
public static FirebaseDatabase getDatabase() {
if (mDatabase == null) {
mDatabase = FirebaseDatabase.getInstance();
mDatabase.setPersistenceEnabled(true);
}
return mDatabase;
}
}
Then call Utils.getDatabase() from any activity you want.
Read more in this article
I fixed this exception by using setPersistenceEnabled(true) in my Application class.
public class MApplication extends Application {
#Override
public void onCreate() {
super.onCreate();
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
}
In AndroidManifest.xml, set the application name as MApplication:
<application
android:name=".MApplication"
... />
I was facing a similar problem and using a static variable seemed to resolve the issue for me. So at first my code looked something like this
#Override
protected void onCreate(Bundle savedInstanceState) {
//..code
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
FirebaseDatabase database = FirebaseDatabase.getInstance();
//..code
}
and now it looks more like
static boolean calledAlready = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
//..code
if (!calledAlready)
{
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
calledAlready = true;
}
FirebaseDatabase database = FirebaseDatabase.getInstance();
//..code
}
Hope it helps!
I bit late but today i got this issue, I solved by adding
static {
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
to my Activity
To me, it is easier to be handled by creating a separate class for Firebase. This is because Firebase has its own instance and if you are using it in more than one activity, there's the possibility for it to crash if you call setPersistenceEnabled again in another activity.
Another good thing is that you can pass your context or parameters into the FirebaseHandler constructor if required. Or if you have fixed location in the database, they can be called easy without the .child("location") boilerplate.
Example:
public class FirebaseHandler {
// parameters
private Context context;
private String userKey;
private DatabaseReference databaseReference;
private static boolean isPersistenceEnabled = false;
private static String fixedLocationA = "locationA";
private static String fixedLocationB = "locationB";
public FirebaseHandler(Context context, String userKey) {
this.context = context; // context can be used to call PreferenceManager etc.
this.userKey = userKey;
if (!isPersistenceEnabled) {
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
isPersistenceEnabled = true;
}
databaseReference = FirebaseDatabase.getInstance().getReference().child(userKey);
}
public DatabaseReference getRefA() {
return databaseReference.child(fixedLocationA);
}
public DatabaseReference getRefB() {
return databaseReference.child(fixedLocationB);
}
}
This can then be called in any Activity as below.
public class MyActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// get instance
FirebaseHandler firebaseHandler = new FirebaseHander(this, "userKey");
// to set value
firebaseHandler.getRefA().setValue("value");
// to set listener
firebaseHandler.getRefB().addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// TODO here....
// also, can remove listener if required
if (certain condition) {
firebaseHandler.getRefB().removeEventListener(this);
}
}
}
}
}
I'm facing some problem too, but this is my temporary solution for my app.
Create BaseActivity extends AppcompatActivity and override onCreate, put setPersistenceEnabled there.
public class BaseActivity extends AppCompatActivity {
private static String TAG = "BaseActivity";
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try{
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
Log.d(TAG,FirebaseDatabase.getInstance().toString());
}catch (Exception e){
Log.w(TAG,"SetPresistenceEnabled:Fail"+FirebaseDatabase.getInstance().toString());
e.printStackTrace();
}
}
}
And change MainActivity to extend BaseActivity
public class MainActivity extends BaseActivity
EDIT: Follow #imakeApps answer
public class BaseActivity extends AppCompatActivity {
private static String TAG = "BaseActivity";
static boolean isInitialized = false;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try{
if(!isInitialized){
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
isInitialized = true;
}else {
Log.d(TAG,"Already Initialized");
}
}catch (Exception e){
e.printStackTrace();
}
}
}
Solved it by making the Firebase reference a static class field like this:
public class MainActivity extends AppCompatActivity
private static FirebaseDatabase fbDatabase;
#Override
protected void onCreate(Bundle savedInstanceState) {
if(fbDatabase == null) {
fbDatabase = FirebaseDatabase.getInstance();
fbDatabase.setPersistenceEnabled(true);
}
It's no problem to create new Firebase references (without setPersistenceEnabled(true)) in other activities too.
If you don't like the static fields, this did the trick for me:
if (FirebaseApp.getApps(context).isEmpty()) {
FirebaseApp.initializeApp(context);
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
This can be caused be more that one process initializing twice firebase or Multidex apps. For more info see this: https://github.com/firebase/quickstart-android/issues/15
I wouldn't recommend using Application to store the data because like its written in CodePath
There is always data and information that is needed in many places within your app. This might be a session token, the result of an expensive computation, etc. It might be tempting to use the application instance in order to avoid the overhead of passing objects between activities or keeping those in persistent storage.
However, you should never store mutable instance data inside the Application object because if you assume that your data will stay there, your application will inevitably crash at some point with a NullPointerException. The application object is not guaranteed to stay in memory forever, it will get killed. Contrary to popular belief, the app won’t be restarted from scratch. Android will create a new Application object and start the activity where the user was before to give the illusion that the application was never killed in the first place.
Thats the reason I would recommend using a Singleton like this:
public class DataBaseUtil {
private static FirebaseDatabase mDatabase;
public static FirebaseDatabase getDatabase() {
if (mDatabase == null) {
mDatabase = FirebaseDatabase.getInstance();
mDatabase.setPersistenceEnabled(true);
}
return mDatabase;
}}
just use it in your code then like
private FirebaseDatabase fdb = DataBaseUtil.getDatabase();
Create a class called Util.java
and add following code
public class Util {
private static FirebaseDatabase mData;
public static FirebaseDatabase getDatabase() {
if (mData == null) {
mData = FirebaseDatabase.getInstance();
mData.setPersistenceEnabled(true);
}
return mData;
}
}
Now replace FirebaseDatabase.getIntance() with Util.getDatabase() every time in each activity. Calling just once will get the error!
I was facing same issue. i changed code as below.
BEFORE(Causing Crash)
var rootRef = FIRDatabase.database().reference()
override func viewDidLoad() {
super.viewDidLoad()
FIRDatabase.database().persistenceEnabled = true
}
AFTER (Resolved Crash)
var rootRef:FIRDatabaseReference!
override func viewDidLoad() {
super.viewDidLoad()
FIRDatabase.database().persistenceEnabled = true
rootRef = FIRDatabase.database().reference()
}
In Menifest
android:name=".AppName
Create java Class that extends Application
public class AppName extends Application {
#Override
public void onCreate() {
super.onCreate();
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
Make sure that .setpersistenceenabled(true) is not happening twice, while sign in by Google in your case, second care setPersistenceEnabled(true) is must be called before any instance of firebase called this resolve my issue.
For Kotlin Try this:
class DatabaseUtil {
companion object {
private val firebaseDatabase: FirebaseDatabase = FirebaseDatabase.getInstance()
init {
firebaseDatabase.setPersistenceEnabled(true)
}
fun getDatabase() : FirebaseDatabase {
return firebaseDatabase
}
}
}
Simply move you code in ExampleFragment.class from onCreateView method to onCreate method:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container,
#Nullable Bundle savedInstanceState) {
....
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_home, container, false);
The error message describes the problem:
Calls to setPersistenceEnabled() must be made before any other usage
of FirebaseDatabase instance.
The fix to this problem is described into the documentation: As in SDK 2.x, persistence of the disk must be enabled before other calls to the database are made.
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
https://firebase.google.com/support/guides/firebase-android
You can use:
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
before using FirebaseDatabase.getInstance().getReference();

React-native inside a Fragment

How to Start react-native inside of a fragment?
While putting react-native inside Fragment, onCreateView function is unable to return View from mReactRootView.
View view = inflater.inflate(mReactRootView. , container, false);
I've managed to figure this out with much trial and error. I've seen this question asked around the internet and thought that this was the best place to post the answer. Here is how to do with the latest version of React (0.29 as of this writing):
The first thing we'll do is create an abstract ReactFragment class that we will use throughout our app:
public abstract class ReactFragment extends Fragment {
private ReactRootView mReactRootView;
private ReactInstanceManager mReactInstanceManager;
// This method returns the name of our top-level component to show
public abstract String getMainComponentName();
#Override
public void onAttach(Context context) {
super.onAttach(context);
mReactRootView = new ReactRootView(context);
mReactInstanceManager =
((MyApplication) getActivity().getApplication())
.getReactNativeHost()
.getReactInstanceManager();
}
#Override
public ReactRootView onCreateView(LayoutInflater inflater, ViewGroup group, Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
return mReactRootView;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mReactRootView.startReactApplication(
mReactInstanceManager,
getMainComponentName(),
null
);
}
}
We'll now be able to create fragments that render React Native components, e.g.:
public class HelloFragment extends ReactFragment {
#Override
public String getMainComponentName() {
return "hellocomponent"; // name of our React Native component we've registered
}
}
A little more work is required, though. Our parent Activity needs to pass some things into the ReactInstanceManager in order for the React Native lifecycle to work properly. Here's what I ended up with:
public class FragmentActivity extends AppCompatActivity implements DefaultHardwareBackBtnHandler {
/*
* Get the ReactInstanceManager, AKA the bridge between JS and Android
* We use a singleton here so we can reuse the instance throughout our app
* instead of constantly re-instantiating and re-downloading the bundle
*/
private ReactInstanceManager mReactInstanceManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragment);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
/**
* Get the reference to the ReactInstanceManager
*/
mReactInstanceManager =
((MyApplication) getApplication()).getReactNativeHost().getReactInstanceManager();
/*
* We can instantiate a fragment to show for Activity programmatically,
* or using the layout XML files.
* This doesn't necessarily have to be a ReactFragment, any Fragment type will do.
*/
Fragment viewFragment = new HelloFragment();
getFragmentManager().beginTransaction().add(R.id.container, viewFragment).commit();
}
#Override
public void invokeDefaultOnBackPressed() {
super.onBackPressed();
}
/*
* Any activity that uses the ReactFragment or ReactActivty
* Needs to call onHostPause() on the ReactInstanceManager
*/
#Override
protected void onPause() {
super.onPause();
if (mReactInstanceManager != null) {
mReactInstanceManager.onHostPause();
}
}
/*
* Same as onPause - need to call onHostResume
* on our ReactInstanceManager
*/
#Override
protected void onResume() {
super.onResume();
if (mReactInstanceManager != null) {
mReactInstanceManager.onHostResume(this, this);
}
}
#Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_MENU && mReactInstanceManager != null) {
mReactInstanceManager.showDevOptionsDialog();
return true;
}
return super.onKeyUp(keyCode, event);
}
}
Finally, you'll notice the reference to (MyApplication) throughout the code; this is a global Application object to contain our ReactInstanceManager, AKA the bridge between Android and React Native. This is the pattern that the React Native projects use internally, so I simply copied it. Here's how it's implemented:
public class MyApplication extends Application implements ReactApplication {
private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {
#Override
public boolean getUseDeveloperSupport() {
return true;
}
#Override
public List<ReactPackage> getPackages() {
return Arrays.<ReactPackage>asList(
new MainReactPackage()
);
}
};
#Override
public ReactNativeHost getReactNativeHost() {
return mReactNativeHost;
}
}
The trickiest bit was figuring out the lifecycle between the Fragment and the Activity; the ReactRootView needs a reference to the Activity context in order to instantiate, so making sure that getActivity() would not be null was important. Also, registering the onHostPause() and onHostResume() in the parent Activity was unintuitive at first, but ultimately proved simpler once the ReactNativeInstanceManager was abstracted away into a global instead of keeping it on the Activity or Fragment.
Hope this helps someone else out there!
There are libraries available that handle this for you.
One that I use is react-native-android-fragment
As per the instructions on the linked GitHub repository:
Add the following line to your build.gradle compile 'com.github.hudl:react-native-android-fragment:v0.43.2'.
e.g.
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
dependencies {
// Version will correspond to its dependnecy on React Native
compile 'com.github.hudl:react-native-android-fragment:v0.43.2'
}
Build you react code into the fragment
Fragment reactFragment = new ReactFragment.Builder()
.setComponentName("HelloWorld")
.setLaunchOptions(launchOptions) // A Bundle of launch options
.build();
Place the Fragment in a FrameLayout that you would have in your XML layout file. In my case, the FrameLayout ID is react_holder.
getSupportFragmentManager()
.beginTransaction()
.add(R.id.react_holder, reactFragment)
.commit();
There is now an official ReactFragment available here that can be used to host react native inside a fragment.
Just make sure you have your react native host setup correctly, as the fragment tries to access the react native host on the application level, or overload it in a subclass:
// inside the ReactFragment
protected ReactNativeHost getReactNativeHost() {
return ((ReactApplication) getActivity().getApplication()).getReactNativeHost();
}
you can then create the fragment using:
val reactNativeProcessFragment = ReactFragment.Builder()
.setComponentName("nameUsedIn_AppRegistry.registerComponent")
.build()

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