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Zebra RFID API Read Access Operation Code return null

I'm trying to develop a small Application for a Zebra handheld rfid reader and can't find a way to access the MemoryBank of the tag. My reader configuration is as follows:
private void ConfigureReader() {
if (reader.isConnected()) {
TriggerInfo triggerInfo = new TriggerInfo();
triggerInfo.StartTrigger.setTriggerType(START_TRIGGER_TYPE.START_TRIGGER_TYPE_IMMEDIATE);
triggerInfo.StopTrigger.setTriggerType(STOP_TRIGGER_TYPE.STOP_TRIGGER_TYPE_IMMEDIATE);
try {
// receive events from reader
if (eventHandler == null){
eventHandler = new EventHandler();
}
reader.Events.addEventsListener(eventHandler);
// HH event
reader.Events.setHandheldEvent(true);
// tag event with tag data
reader.Events.setTagReadEvent(true);
reader.Events.setAttachTagDataWithReadEvent(true);
// set trigger mode as rfid so scanner beam will not come
reader.Config.setTriggerMode(ENUM_TRIGGER_MODE.RFID_MODE, true);
// set start and stop triggers
reader.Config.setStartTrigger(triggerInfo.StartTrigger);
reader.Config.setStopTrigger(triggerInfo.StopTrigger);
} catch (InvalidUsageException e) {
e.printStackTrace();
} catch (OperationFailureException e) {
e.printStackTrace();
}
}
}
And the eventReadNotify looks like this:
public void eventReadNotify(RfidReadEvents e) {
// Recommended to use new method getReadTagsEx for better performance in case of large tag population
TagData[] myTags = reader.Actions.getReadTags(100);
if (myTags != null) {
for (int index = 0; index < myTags.length; index++) {
Log.d(TAG, "Tag ID " + myTags[index].getTagID());
ACCESS_OPERATION_CODE aoc = myTags[index].getOpCode();
ACCESS_OPERATION_STATUS aos = myTags[index].getOpStatus();
if (aoc == ACCESS_OPERATION_CODE.ACCESS_OPERATION_READ && aos == ACCESS_OPERATION_STATUS.ACCESS_SUCCESS) {
if (myTags[index].getMemoryBankData().length() > 0) {
Log.d(TAG, " Mem Bank Data " + myTags[index].getMemoryBankData());
}
}
}
}
}
When I'm scanning a tag I get the correct TagID but both myTags[index].getOpCode() and myTags[index].getOpStatus() return null values.
I appreciate every suggestion that might lead to a successful scan.
Thanks.

I managed to find a solution for my problem. To perform any Read or Write task with Zebra Handheld Scanners the following two conditions must be satisfied. Look here for reference: How to write to RFID tag using RFIDLibrary by Zebra?
// make sure Inventory is stopped
reader.Actions.Inventory.stop();
// make sure DPO is disabled
reader.Config.setDPOState(DYNAMIC_POWER_OPTIMIZATION.DISABLE);
You have to stop the inventory and make sure to disable dpo in order to get data other than the TagID from a Tag. Unfortunately this isn't mentioned in the docu for Reading RFID Tags.

How to fix "GetStatus Write RFID_API_UNKNOWN_ERROR data(x)- Field can Only Take Word values" Android RFID 8500 Zebra

I am trying to develop and application to read and write to RF tags. Reading is flawless, but I'm having issues with writing. Specifically the error "GetStatus Write RFID_API_UNKNOWN_ERROR data(x)- Field can Only Take Word values"
I have tried reverse-engineering the Zebra RFID API Mobile by obtaining the .apk and decoding it, but the code is obfuscated and I am not able to decypher why that application's Write works and mine doesn't.
I see the error in the https://www.ptsmobile.com/rfd8500/rfd8500-rfid-developer-guide.pdf at page 185, but I have no idea what's causing it.
I've tried forcefully changing the writeData to Hex, before I realized that the API does that on its own, I've tried changing the Length of the writeData as well, but it just gets a null value. I'm so lost.
public boolean WriteTag(String sourceEPC, long Password, MEMORY_BANK memory_bank, String targetData, int offset) {
Log.d(TAG, "WriteTag " + targetData);
try {
TagData tagData = null;
String tagId = sourceEPC;
TagAccess tagAccess = new TagAccess();
tagAccess.getClass();
TagAccess.WriteAccessParams writeAccessParams = tagAccess.new WriteAccessParams();
String writeData = targetData; //write data in string
writeAccessParams.setAccessPassword(Password);
writeAccessParams.setMemoryBank(MEMORY_BANK.MEMORY_BANK_USER);
writeAccessParams.setOffset(offset); // start writing from word offset 0
writeAccessParams.setWriteData(writeData);
// set retries in case of partial write happens
writeAccessParams.setWriteRetries(3);
// data length in words
System.out.println("length: " + writeData.length()/4);
System.out.println("length: " + writeData.length());
writeAccessParams.setWriteDataLength(writeData.length()/4);
// 5th parameter bPrefilter flag is true which means API will apply pre filter internally
// 6th parameter should be true in case of changing EPC ID it self i.e. source and target both is EPC
boolean useTIDfilter = memory_bank == MEMORY_BANK.MEMORY_BANK_EPC;
reader.Actions.TagAccess.writeWait(tagId, writeAccessParams, null, tagData, true, useTIDfilter);
} catch (InvalidUsageException e) {
System.out.println("INVALID USAGE EXCEPTION: " + e.getInfo());
e.printStackTrace();
return false;
} catch (OperationFailureException e) {
//System.out.println("OPERATION FAILURE EXCEPTION");
System.out.println("OPERATION FAILURE EXCEPTION: " + e.getResults().toString());
e.printStackTrace();
return false;
}
return true;
}
With
Password being 00
sourceEPC being the Tag ID obtained after reading
Memory Bank being MEMORY_BANK.MEMORY_BANK_USER
target data being "8426017056458"
offset being 0
It just keeps giving me "GetStatus Write RFID_API_UNKNOWN_ERROR data(x)- Field can Only Take Word values" and I have no idea why this is the case, nor I know what a "Word value" is, and i've searched for it. This is all under the "OperationFailureException", as well. Any help would be appreciated, as there's almost no resources online for this kind of thing.

Even this question is a bit older, I had the same problem so as far as I know this should be the answer.
Your target data "8426017056458" length is 13 and at writeAccessParams.setWriteDataLength(writeData.length()/4)
you are devide it with four. Now if you are trying to write the target data it is longer than the determined WriteDataLength. And this throws the Error.
One 'word' is 4 Hex => 16 Bits long. So your Data have to be filled up first and convert it to Hex.

How to transcribe bandwidth call recordings in java

My application uses https://app.bandwidth.com/ for receiving incoming calls. I have an api to handle the incoming calls which record the calls when the call is not answered(This recording is treated as a voice mail).
if (eventType.equalsIgnoreCase(EventType.ANSWER.toString())) {
Timestamp callStartTime = new Timestamp(TimeUtil.now().getTime());
incomingCall.setCallTime(callStartTime);
callStatus = transferCall(callId, incomingCall.getVoiceForwardNumber(), 1);
}
else if (eventType.equalsIgnoreCase(EventType.TIMEOUT.toString())) {
voiceMailIntro(callId);
}
else if (eventType.equalsIgnoreCase(EventType.SPEAK.toString()) && PLAYBACK_STOP.equalsIgnoreCase(callState)) {
recordVoiceMail(callId);
}
else if (eventType.equalsIgnoreCase(EventType.RECORDING.toString()) &&
state.equalsIgnoreCase(BandwidthCallStatus.COMPLETE.toString())) {
createTranscription(recordingId);
}
else if (eventType.equalsIgnoreCase(EventType.TRANSCRIPTION.toString()) && status.equalsIgnoreCase(BandwidthCallStatus.COMPLETED.toString())) {
incomingCall.setVoiceMail(text);
}
This is the code for recording call
private void recordVoiceMail(String callId) {
BandwidthClient client = BandwidthClient.getInstance();
client.setCredentials(bandwidthUserId, bandwidthApiToken, bandwidthApiSecret);
try {
Call call = Call.get(client, callId);
call.recordingOn();
} catch (Exception e) {
log.error("An exception occurred while recording voice mail : " +
e.getMessage(), e);
}
}
Now i need to transcribe these vocie mails.
From documentation i got methods in python, js, c#, ruby etc. to transcribe the recordings using the recordings.
For example in js,
client.Recording.createTranscription(recordingId, function(err, transcription){});
I searched every where, but i couldn't find any method in java for that.
Can any one help me if you know ?

Anyway, as I see, you need that link for java doc.
And here you can follow to java sdk located on Github.
And, also, you can find some more information about transcriptions API here which you are looking for.
First of all, why do you need that? Perhaps, you do not need that.
As I find, you can't do transcribe with POJO, but you can do something like that.
If you want to do that, you can make it with
public void transcribeOn() throws Exception {
final List<Recording> list = Recording.list(0, 5);
if (!list.isEmpty()) {
final Recording recording = Recording.get(list.get(0).getId());
System.out.println("\nRecording by Id");
System.out.println(recording);
final String recordingUri = mockClient.getUserResourceUri(BandwidthConstants.RECORDINGS_URI_PATH);
client.post(recordingUri + "/" + list.get(0).getId() + "/transcriptions", null);
final JSONObject jsonObject = call.toJSONObject(client.get(recordingUri, null));
call.updateProperties(jsonObject);
}
}
I'm not sure it works correctly, but I hope it put you on correct way

Parrot AR.Drone 2.0 - JavaDrone (Get the drone details E.G. Battery Level, Altitude, Speed etc)?

I am working on Parrot AR. Drone project. The libraries are downloaded and implemented in this project from JavaDrone website (https://code.google.com/p/javadrone/downloads/list). However, although I did included the all the correct libraries and make the right class call to get the method, it still cannot return me the correct information. All the results returned appeared to be "false". Any idea what happening on this code? Please help me :(
So what I did is I have 2 buttons : (i) connect (ii) take off buttons. The Connect button function is for establish connection to drone while Take off button is used for make the drone fly move a bit and return me the drone's NAV navigation data. Sadly all the returned NAV data appears not working.
Note : This code is working fine upon code compilation. But it just cannot return me the correct & valid NAV data from drone.
private void jButtonConnectActionPerformed(java.awt.event.ActionEvent evt) {
System.out.println("Connect?");
drone = new ARDrone();
data = new NavData();
drone.playLED(10,10,10);
drone.connect();
drone.clearEmergencySignal();
System.err.println("Ready to connect!!");
// Wait until drone is ready
drone.waitForReady(CONNECT_TIMEOUT);
System.err.println("Drone State: " + drone.getState());
// do TRIM operation
drone.trim();
System.err.println("Congratulation! You have connected to Drone!");
System.out.println("You can issue flight commands now!");
batteryStatus.setText("0" + "%");
batteryStatus.setForeground(Color.ORANGE);
batteryStatus.setText("" + data.getBattery());
}
private void jButtonTakeOffActionPerformed(java.awt.event.ActionEvent evt) {
System.err.println("Current Drone State : " + drone.getState().toString());
System.err.println("Taking off");
drone.takeOff();
Thread.sleep(4000);
System.err.println("**********\nMOVE\n**********");
drone.move(0.0f, 150.5f, 500.0f, 0.0f);
Thread.sleep(1000);
System.err.println("******************************************");
System.err.println("Drone Infomation");
System.err.println("Battery Too High ? " + data.isBatteryTooHigh());
System.err.println("Battery Too Low ? " + data.isBatteryTooLow());
System.err.println("Drone Flying ? " + data.isFlying());
System.err.println("Control Received ? " + data.isControlReceived());
System.err.println("Motor Down ? " + data.isMotorsDown());
System.err.println("Not Enough Power ?" + data.isNotEnoughPower());
System.err.println("Trim Received ? " + data.isTrimReceived());
System.err.println("Trim Running? " + data.isTrimRunning());
System.err.println("Trim succeded? " + data.isTrimSucceeded());
System.err.println("PIC Number OK? "+ data.isPICVersionNumberOK());
System.err.println("******************************************");
Thread.sleep(5000);
drone.sendAllNavigationData();
drone.land();
}
Output :
******************************************
Drone Infomation
Battery Life: 0.0%
Battery Too High ? false
Battery Too Low ? false
Drone Flying ? false
Control Received ? false
Motor Down ? false
Not Enough Power ?false
Trim Received ? false
Trim Running? false
Trim succeded? false
PIC Number OK? false
********************************************
Update:
What I did was followed John's suggestion. I did implemented all the neccessary methods and NavDataListener for getting the NavData from drone.
import com.codeminders.ardrone.ARDrone;
import com.codeminders.ardrone.ARDrone.VideoChannel;
import com.codeminders.ardrone.NavData;
import com.codeminders.ardrone.NavDataListener;
public class arDrone extends javax.swing.JFrame implements Runnable, NavDataListener{
public ARDrone drone;
public NavData data = new NavData();
public arDrone(String text) {
//FreeTTS speech text
this.text=text;
}
public arDrone() {
initComponents();
setIcon();
initDrone();
}
private void initDrone() {
try {
drone = new ARDrone();
data = new NavData();
drone.addNavDataListener(this);
} catch (UnknownHostException ex) {
System.err.println(ex);
return;
}
}
public void navDataReceived(NavData nd) {
System.err.println("Testing navDataReceived is running...");
updateBatteryStatus(nd.getBattery());
this.flying.set(nd.isFlying());
}
private void updateBatteryStatus(final int value) {
java.awt.EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
batteryStatus.setText(value + "%");
if (value < 15) {
batteryStatus.setForeground(Color.RED);
} else if (value < 50) {
batteryStatus.setForeground(Color.ORANGE);
} else {
batteryStatus.setForeground(Color.GREEN);
}
}
});
}

The problem is that you are not doing anything to actually get navdata. You can't just create a NavData object and hope it gets filled in with valid data--It won't.
You need to use the com.codeminders.ardrone.NavDataListener interface.
Implement the NavDataListener interface, and the
navDataReceived method.
Add your listener using the ARDrone
method addNavDataListener.
In your navDataRecieved method
you will receive a NavData object with valid telemetry data.

Do you set the Drone IP address? According to sources the default IP for the drone is 192.168.1.1.
You can call another constructor to set the IP:
drone = new ARDrone(InetAddress.getByName("xxx.xxx.xxx.xxx"));
replace xxx.xxx.xxx.xxx with the actual drone IP.

Max 20 Friends Information on Twitter4J

Like you see in this code, I want to get all the information about friends in twitter, people I follow.
But doing this :
PagableResponseList<User> users = twitter.getFriendsList(USER_ID, CURSOR);
... only gives me the first 20 recent friends... What can I do?
Complete code about it :
PagableResponseList<User> users = twitter.getFriendsList(USER_ID, CURSOR);
User user = null;
max = users.size();
System.out.println("Following: "+max);
for (int i = 0 ; i < users.size() ; i++){
user = users.get(i);
System.out.print("\nID: "+user.getId()+" / User: "+user.getName()+" /");
System.out.print("\nFollowers: "+user.getFollowersCount()+"\n");
tid.add(Long.parseLong(String.valueOf(user.getId())));
tusername.add(user.getName());
tfollowers.add(Long.parseLong(String.valueOf(user.getFollowersCount())));
tname.add(user.getScreenName());
}
Thanks..

you can try this code to get the list of people you follow.
long cursor = -1;
PagableResponseList<User> users;
while ((cursor = followers.getNextCursor()) != 0);
{
users = twitter.getFriendsList(userId, cursor);
}

I've taken a peek at the documentation at Twitter4J and Twitter themselves and it's all about that cursor.
To prevent you're getting loaded with a whole bunch of friends at once, Twitter only returns the first 20 results. It doesn't return just the first 20 results, but it also returns a cursor. That cursor is just a random number that's managed by Twitter. When you make a call again and pass this cursor, the next 20 entries (friends) will be returned, again with a cursor that's different now. You can repeat this until the cursor returned is zero. That means there are no more entries available.
In case you want to know more, check these two links: Twitter DEV and Twitter4J documentation.
Concerning your Java, you just need to find a way to get the current cursor, and pass that cursor to your method again, making the app load the next 20 entries. According to this piece of information, that should do the trick.
List<User> allUsers = new ArrayList<User>();
PagableResponseList<User> users;
long cursor = -1;
while (cursor != 0) {
users = twitter.getFriendsList(USER_ID, cursor);
cursor = users.getNextCursor();
allUsers.add(users);
}

You should be able to request up to 200 results at a time:
final PagableResponseList<User> users = twitter.getFriendsList(USER_ID, cursor, 200);
cursor = users.getNextCursor();
If you need to start from where you left off between invocations of your program then you need to store the value of cursor somewhere.

Improvements to Sander's answer!
You can set a count value to the getFriendsList method as in Jonathan's Answer. The maximum value allowed for count is 200. The loop construct will help to collect more than 200 friends now. 200 friends per page or per iteration!
Yet, there are rate limits for any request you make. The getFriendsList method will use this api endpoint: GET friends/list which has a rate limit of 15 hits per 15 minutes. Each hit can fetch a maximum of 200 friends which equates to a total of 3000 friends (15 x 200 = 3000) per 15 minutes. So, there will be no problem if you have only 3000 friends. If you have more than 3000 friends, an exception will be thrown. You can use the RateLimitStatus class to avoid that exception. The following code is an example implementation to achieve this.
Method 1: fetchFriends(long userId)
public List<User> fetchFriends(long userId) {
List<User> friends = new ArrayList<User>();
PagableResponseList<User> page;
long cursor = -1;
try {
while (cursor != 0) {
page = twitter.getFriendsList(userId, cursor, 200);
friends.addAll(page);
System.out.println("Total number of friends fetched so far: " + friends.size());
cursor = page.getNextCursor();
this.handleRateLimit(page.getRateLimitStatus());
}
} catch (TwitterException e) {
e.printStackTrace();
}
return friends;
}
Method 2: handleRateLimit(RateLimitStatus rls)
private void handleRateLimit(RateLimitStatus rls) {
int remaining = rls.getRemaining();
System.out.println("Rate Limit Remaining: " + remaining);
if (remaining == 0) {
int resetTime = rls.getSecondsUntilReset() + 5;
int sleep = (resetTime * 1000);
try {
if(sleep > 0) {
System.out.println("Rate Limit Exceeded. Sleep for " + (sleep / 1000) + " seconds..");
Thread.sleep(sleep);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
By doing so, your program will sleep for some time period based on the rate limiting threshold. It will continue to run from where it left after the sleep. This way we can avoid our program stopping in the midway of collecting friends counting more than 3000.

I have the solution to my post... thanks to Sander, give me some ideas...
The thing was change the for to while ((CURSOR = ids.getNextCursor()) != 0);.
And... user = twitter.showUser(id);
Playing with showUser makes it possible to get, with a slowly time, all the info about all my friends...
That's all. Don't use user.get(i);