RxJava gurus, here is your chance to shine!
Can you ensure the following program does not throw an IllegalStateException by only changing the RxJava pipeline starting with Flowable.generate() in the main() method?
class ExportJob {
private static Scheduler singleThread(String threadName) {
return Schedulers.from(newFixedThreadPool(1, r -> {
Thread t = new Thread(r, threadName);
t.setDaemon(true);
return t;
}));
}
public static void main(String[] args) {
Scheduler genSched = singleThread("genThread");
Scheduler mapSched = singleThread("mapThread");
// execute on "genThread"
Flowable.generate(ExportJob::infiniteGenerator)
.subscribeOn(genSched, false)
// execute on "mapThread"
.observeOn(mapSched, false)
.concatMapMaybe(ExportJob::mapping)
// execute on the thread that creates the pipeline, block it until finished
.blockingForEach(ExportJob::terminal);
}
private static int nb;
/** Must execute on "genThread" thread. */
private static void infiniteGenerator(Emitter<Integer> emitter) {
print(nb, "infiniteGenerator");
emitter.onNext(nb++);
checkCurrentThread("genThread");
}
/** Must execute on "mapThread" thread. */
private static Maybe<Integer> mapping(Integer s) {
print(s, "mapping");
checkCurrentThread("mapThread");
return Maybe.just(s);
}
/** Must execute on "terminal" thread. */
private static void terminal(Integer s) {
print(s, "terminal");
checkCurrentThread("main");
}
private static void print(int item, String method) {
System.out.format("%d - %s - %s()%n", item, Thread.currentThread().getName(), method);
}
private static void checkCurrentThread(String expectedThreadName) throws IllegalStateException {
String name = Thread.currentThread().getName();
if (!name.equals(expectedThreadName)) {
throw new IllegalStateException("Thread changed from '" + expectedThreadName + "' to '" + name + "'");
}
}
}
You have to use subscribeOn(scheduler, true) so the requests are routed back to their expected threads as well:
Flowable.generate(ExportJob::infiniteGenerator)
.subscribeOn(genSched, true) // <------------------------------
// execute on "mapThread"
.observeOn(mapSched, false)
.concatMapMaybe(ExportJob::mapping)
.subscribeOn(mapSched, true) // <------------------------------
.blockingForEach(ExportJob::terminal);
Related
I'm trying to use Tesseract in flutter using the following package https://github.com/arrrrny/tesseract_ocr
I've download the app and run in.
The problem is that the extractText hangs the UI.
Looking at the Java code:
Thread t = new Thread(new Runnable() {
public void run() {
baseApi.setImage(tempFile);
recognizedText[0] = baseApi.getUTF8Text();
baseApi.end();
}
});
t.start();
try { t.join(); } catch (InterruptedException e) { e.printStackTrace(); }
result.success(recognizedText[0]);
I can see that it is running on a new thread, so I expect it not to hang the app, but it still does.
I found this example:
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
// Call the desired channel message here.
baseApi.setImage(tempFile);
recognizedText[0] = baseApi.getHOCRText(0);
baseApi.end();
result.success(recognizedText[0]);
}
});
from https://flutter.dev/docs/development/platform-integration/platform-channels#channels-and-platform-threading
but it also hangs the UI.
The docs also say
**Channels and Platform Threading**
Invoke all channel methods on the platform’s main thread when writing code on the platform side.
Can someone clarify this sentence?
According to Richard Heap answer, I tried to call a method from native to dart, passing the result:
Dart side:
_channel.setMethodCallHandler((call) {
print(call);
switch (call.method) {
case "extractTextResult":
final String result = call.arguments;
print(result);
}
var t;
return t;
});
Java side:
channel.invokeMethod("extractTextResult","hello");
if I call this method from the main thread, this works fine, but then the thread is blocking.
If I do
Thread t = new Thread(new Runnable() {
public void run() {
channel.invokeMethod("extractTextResult","test1231231");
}
});
t.start();
result.success("tst"); // return immediately
Then the app crashes with the following message:
I also tried:
Thread t = new Thread(new Runnable() {
public void run() {
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
// Call the desired channel message here.
baseApi.setImage(tempFile);
recognizedText[0] = baseApi.getHOCRText(0);
baseApi.end();
result.success(recognizedText[0]);
// channel.invokeMethod("extractTextResult", "test1231231");
}
});
}
});
t.start();
result.success("tst");
which is what I understand that Richard Heap last comment meant, but It still hangs the ui.
I had the same Issue and fixed it with a MethodCallWrapper in TesseractOcrPlugin.java
This Code works for me (no Dart-code change is needed):
package io.paratoner.tesseract_ocr;
import com.googlecode.tesseract.android.TessBaseAPI;
import android.os.Handler;
import android.os.Looper;
import android.os.AsyncTask;
import java.io.File;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;
import io.flutter.plugin.common.PluginRegistry.Registrar;
/** TesseractOcrPlugin */
public class TesseractOcrPlugin implements MethodCallHandler {
private static final int DEFAULT_PAGE_SEG_MODE = TessBaseAPI.PageSegMode.PSM_SINGLE_BLOCK;
/** Plugin registration. */
public static void registerWith(Registrar registrar) {
final MethodChannel channel = new MethodChannel(registrar.messenger(), "tesseract_ocr");
channel.setMethodCallHandler(new TesseractOcrPlugin());
}
// MethodChannel.Result wrapper that responds on the platform thread.
private static class MethodResultWrapper implements Result {
private Result methodResult;
private Handler handler;
MethodResultWrapper(Result result) {
methodResult = result;
handler = new Handler(Looper.getMainLooper());
}
#Override
public void success(final Object result) {
handler.post(new Runnable() {
#Override
public void run() {
methodResult.success(result);
}
});
}
#Override
public void error(final String errorCode, final String errorMessage, final Object errorDetails) {
handler.post(new Runnable() {
#Override
public void run() {
methodResult.error(errorCode, errorMessage, errorDetails);
}
});
}
#Override
public void notImplemented() {
handler.post(new Runnable() {
#Override
public void run() {
methodResult.notImplemented();
}
});
}
}
#Override
public void onMethodCall(MethodCall call, Result rawResult) {
Result result = new MethodResultWrapper(rawResult);
if (call.method.equals("extractText")) {
final String tessDataPath = call.argument("tessData");
final String imagePath = call.argument("imagePath");
String DEFAULT_LANGUAGE = "eng";
if (call.argument("language") != null) {
DEFAULT_LANGUAGE = call.argument("language");
}
calculateResult(tessDataPath, imagePath, DEFAULT_LANGUAGE, result);
} else {
result.notImplemented();
}
}
private void calculateResult(final String tessDataPath, final String imagePath, final String language,
final Result result) {
new AsyncTask<Void, Void, Void>() {
#Override
protected Void doInBackground(Void... params) {
final String[] recognizedText = new String[1];
final TessBaseAPI baseApi = new TessBaseAPI();
baseApi.init(tessDataPath, language);
final File tempFile = new File(imagePath);
baseApi.setPageSegMode(DEFAULT_PAGE_SEG_MODE);
baseApi.setImage(tempFile);
recognizedText[0] = baseApi.getUTF8Text();
baseApi.end();
result.success(recognizedText[0]);
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
}
}.execute();
}
}
By using join you're making the main thread wait for the background thread, blocking it. You have to remove the join and return a result immediately.
So, how do you return the ocr result, which won't be available immediately. When it becomes available, you then call a method from native to dart, passing the result. At the dart end, you then handle the result as any async event.
The point of the last paragraph of your question is that your result will become available on your background thread, so you'd want to call the native to dart method there. You can't. You have to post the method call code to the main looper - you already show some code for posting to the main looper which you can use as an example.
Based on Richard Heap answer I came up with this:
Dart code:
_channel.setMethodCallHandler((call) {
switch (call.method) {
case "extractTextResult":
final String result = call.arguments;
print(result);
}
var t;
return t;
});
Java code:
Thread t = new Thread(new Runnable() {
public void run() {
baseApi.setImage(tempFile);
recognizedText[0] = baseApi.getHOCRText(0);
baseApi.end();
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
channel.invokeMethod("extractTextResult", recognizedText[0]);
}
});
}
});
t.start();
result.success("tst");
explain:
This code will run the Java extractText in a separate thread, and when the result is ready it will hopp back to the ui thread with the call to Looper.getMainLooper() which will then send the message back to the Dart side which must receive the message on the ui thread, which is what this message means:
**Channels and Platform Threading**
Invoke all channel methods on the platform’s main thread when writing code on the platform side.
NOTE on the Dart side, this is still incomplete example since you then need to report to the ui that a message received, this can be done with a Completer, which is used to create and complete a future
At the end of your method channel just return the response back to dart side
Add this line at the end of method channel result.success(true)
full example
override fun configureFlutterEngine(#NonNull flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
MethodChannel(
flutterEngine.dartExecutor.binaryMessenger,
"method-channel"
).setMethodCallHandler { call, result ->
if (call.method == "getFirebaseAppCheckDebugToken") {
...
result.success(true) // just add this line
}
}
}```
I am testing an application.
My test is complex, and I spawn 2 thread that start 2 process builders which spawn 2 java processes.
Is it possible to write a custom redirect that will be similar to inherit but prepend something to every out and err message, so that I would know its origin.
Example code below:
public class test {
public static void main(String... args){
Thread t = new Thread(new testHelper());
t.start();
t = new Thread(new testHelper());
t.start();
}
}
import java.io.IOException;
public class testHelper implements Runnable {
#Override
public void run() {
Class klass = testWorker.class;
System.out.println(klass.getCanonicalName());
String separator = System.getProperty("file.separator");
String classpath = System.getProperty("java.class.path");
String path = System.getProperty("java.home")
+ separator + "bin" + separator + "java";
ProcessBuilder processBuilder =
new ProcessBuilder(path, "-cp",
classpath,
klass.getCanonicalName());
processBuilder.redirectError(ProcessBuilder.Redirect.INHERIT);
processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
Process process = null;
try {
process = processBuilder.start();
} catch (IOException e) {
e.printStackTrace();
}
try {
process.waitFor();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Child Process is done");
}
}
public class testWorker {
public static void main(String ... args) throws InterruptedException {
System.out.println("Doing some stuff");
Thread.sleep(10000);
System.out.println("Finished doing some stuff");
}
}
No, its not possible. In the source code for java.lang.ProcessBuilder.Redirect the constructor is private and has this to say
/**
* No public constructors. Clients must use predefined
* static {#code Redirect} instances or factory methods.
*/
private Redirect() {}
I Would like to execute a background task which executes multiple background tasks. What i am actually trying to do is execute a background process which executes some code for every Object in a list, and does it within a fixed thread pool. So, for example, i have 100 users in the list and i am executing code for each of them concurrently but no more than 5 at the same time.
Therefore i am using two service/task pairs: One service/task for executing on the whole list of users, this service uses a fixed thread pool as its executor and executes a series of second service/task pairs for every user in the list.
like in the following example:
class MainService extends Service<List<User>> {
private List<User> users;
public MainService(List<User> users) { this.users=users; }
protected Task<List<User>> createTask(){
return new MainTask(this.users)
}
}
class Maintask extends Task<List<User>> {
private List<User> users;
private Executor executor;
public MainTask(List<User> users) {
this.users=users;
this.executor=Executors.newFixedThreadPool(5);
}
protected List<User> call() throws Exception {
for (User user : this.users) {
System.out.println("Starting single service");
SingleService service=new SingleService(user)
service.setExecutor(this.executor);
service.start();
System.out.println("Single service started");
}
}
}
class SingleService extends Service<User> {
private User user;
public SingleService(User user) { this.user=user; }
protected Task<User> createTask() {
return new SingleTask(this.user)
}
}
class SingleTask extends Task<User> {
private User user;
public SingleTask(User user) { this.user=user; }
protected User call() throws Exception() {
// Do some work
}
}
The code executes up to the moment when first "starting single service" is printed, the "single service started" message is not being printed at all. As far as i see the SingleService is started, but its createTask() is not being executed at all. Am i making some mistake here?
Well, I am trying to do the same thing, in different context... launch multiple services from a single main Service.
I've overridden all methods of Service, and this is my printout:
Service must only be used from the FX Application Thread {from onFailed() method}
Service does not run on FX thread, but can only be called from the FX thread.
Therefore, all Services and Tasks called within a Service or Task will not be executed.
This is my work around:
public class FXComponentImporter extends Service<Void> implements JarImporter {
//Scanner<T> = Service<List<Class<T>>>
private Scanner<Node> nodeScanner = null;
private Scanner<Paint> paintScanner = null;
private Scanner<Animation> animationScanner = null;
private static int nodeCount = 0, paintCount = 0, animationCount = 0;
private final ObservableMap<String, Class<?>> foundComponents = FXCollections.observableHashMap();
public FXComponentImporter() {
this(null);
}
public FXComponentImporter(File file) {
if (file != null) {
try {
this.nodeScanner = new Scanner<>(file, Node.class);
this.paintScanner = new Scanner<>(file, Paint.class);
this.animationScanner = new Scanner<>(file, Animation.class);
} catch (IOException ex) {
Logger.getLogger(FXComponentImporter.class.getName()).log(Level.SEVERE, null, ex);
}
} else {
File f = importJar();
try {
this.nodeScanner = new Scanner<>(f, Node.class);
this.paintScanner = new Scanner<>(f, Paint.class);
this.animationScanner = new Scanner<>(f, Animation.class);
} catch (IOException ex) {
Logger.getLogger(FXComponentImporter.class.getName()).log(Level.SEVERE, null, ex);
}
}
this.scanningDone.bind(this.nodeScanningDone.and(this.paintScanningDone.and(this.animationScanningDone)));
this.scanningDone.addListener(new ChangeListener<Boolean>() {
#Override
public void changed(ObservableValue<? extends Boolean> observable, Boolean oldValue, Boolean newValue) {
if (newValue) {
if(scanningDone.isBound()){
scanningDone.unbind();
}
start();
scanningDone.removeListener(this);
}
}
});
startScanning();
}
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
Map<String, Class<?>> map = new HashMap<>();
List<Class<Node>> nodes = new ArrayList<>();
List<Class<Paint>> paints = new ArrayList<>();
List<Class<Animation>> anims = new ArrayList<>();
CountDownLatch latch = new CountDownLatch(1);
//Platform needed due to Service only accessed from FX thread
Platform.runLater(() -> {
try {
//FX Stuff done here
nodes.addAll(nodeScanner.getMatchingClasses());
paints.addAll(paintScanner.getMatchingClasses());
anims.addAll(animationScanner.getMatchingClasses());
} finally {
latch.countDown();
}
});
latch.await();
this.updateMessage("Scanning for Nodes ... ");
nodes.stream().forEach(n -> {
if(n != null){
map.putIfAbsent(n.getSimpleName(), n);
}
nodeCount++;
});
this.updateMessage("Found : " + nodeCount + " Nodes ... ");
this.updateMessage("Scanning for Paints ... ");
paints.stream().forEach(p -> {
if(p != null){
map.putIfAbsent(p.getSimpleName(), p);
}
paintCount++;
});
this.updateMessage("Found : " + paintCount + " Paints ... ");
this.updateMessage("Scanning for Animations ... ");
anims.stream().forEach(a -> {
if(a != null){
map.putIfAbsent(a.getSimpleName(), a);
}
animationCount++;
});
this.updateMessage("Found : " + animationCount + " Animations ... ");
foundComponents.putAll(map);
return null;
}
};
}
#Override
protected void executeTask(Task<Void> task) {
super.executeTask(task);
System.out.println(getClass().getSimpleName() + " is Executing " + task.getTitle());
}
#Override
protected void cancelled() {
super.cancelled();
System.out.println(getClass().getSimpleName() + " was Cancelled ... ");
}
#Override
protected void running() {
super.running();
System.out.println(getClass().getSimpleName() + " is Running ... ");
}
#Override
protected void ready() {
super.ready();
System.out.println(getClass().getSimpleName() + " is Ready! ... ");
}
#Override
protected void scheduled() {
super.scheduled();
System.out.println(getClass().getSimpleName() + " is Scheduled ... ");
}
#Override
protected void failed() {
super.failed();
System.out.println(getException().getMessage());
}
#Override
protected void succeeded() {
super.succeeded();
System.out.println("Importing Succeeded ... with: " + foundComponents.entrySet().size() + " results.\n");
foundComponents.forEach((s, c) -> {
System.out.println(c.getSuperclass().getSimpleName() + " >> " + s + " : " + c.getSimpleName());
});
}
#Override
public void restart() {
super.restart();
System.out.println(getClass().getSimpleName() + " is Restarting ... ");
}
private void startScanning() {
nodeScanner.stateProperty().addListener(nsl);
paintScanner.stateProperty().addListener(psl);
animationScanner.stateProperty().addListener(asl);
nodeScanner.start();
paintScanner.start();
animationScanner.start();
}
private final BooleanProperty scanningDone = new SimpleBooleanProperty(false);
private final BooleanProperty nodeScanningDone = new SimpleBooleanProperty(false);
private final BooleanProperty paintScanningDone = new SimpleBooleanProperty(false);
private final BooleanProperty animationScanningDone = new SimpleBooleanProperty(false);
private final ChangeListener nsl = new ChangeListener<Worker.State>() {
#Override
public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
if (newValue.equals(State.SUCCEEDED)) {
nodeScanningDone.set(true);
nodeScanner.stateProperty().removeListener(this);
}
}
};
private final ChangeListener psl = new ChangeListener<Worker.State>() {
#Override
public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
if (newValue.equals(State.SUCCEEDED)) {
paintScanningDone.set(true);
paintScanner.stateProperty().removeListener(this);
}
}
};
private final ChangeListener asl = new ChangeListener<Worker.State>() {
#Override
public void changed(ObservableValue<? extends State> observable, State oldValue, State newValue) {
if (newValue.equals(State.SUCCEEDED)) {
animationScanningDone.set(true);
animationScanner.stateProperty().removeListener(this);
}
}
};
public ObservableMap<String, Class<?>> getFoundComponents() {
return foundComponents;
}
}
and my Interface if you wanna try it out:
public interface JarImporter {
public static File defaultDirectory = new File(System.getProperty("user.home"));
public static final FileChooser.ExtensionFilter classfilter = new FileChooser.ExtensionFilter("Jar files", "*.jar");
static FileChooser defaultFileChooser(){
FileChooser fc = new FileChooser();
fc.getExtensionFilters().add(classfilter);
fc.setInitialDirectory(defaultDirectory);
return fc;
}
public default File importJar(){
File jar = defaultFileChooser().showOpenDialog(null);
if(jar != null){
return jar;
}else{
return null;
}
}
}
Hope this helps.. though just looked at Question date, and was a while ago...
I have this base class structure:
Base:
public abstract class BackgroundTask
{
protected readonly Logger Logger = LogManager.GetCurrentClassLogger();
protected virtual void Initialize()
{
// initialize database access
}
public void Run()
{
Initialize();
try
{
Execute();
// insert to database or whatever
}
catch (Exception ex)
{
Logger.ErrorException(string.Format("Error proccesing task: {0}\r\n", ToString()), ex);
Exceptions.Add(ex);
}
finally
{
TaskExecuter.Discard();
}
}
protected abstract void Execute();
public abstract override string ToString();
public IList<Exception> Exceptions = new List<Exception>();
}
Task executor:
public static class TaskExecuter
{
private static readonly ThreadLocal<IList<BackgroundTask>> TasksToExecute
= new ThreadLocal<IList<BackgroundTask>>(() => new List<BackgroundTask>());
public static void ExecuteLater(BackgroundTask task)
{
TasksToExecute.Value.Add(task);
}
public static void StartExecuting()
{
foreach (var backgroundTask in TasksToExecute.Value)
{
Task.Factory.StartNew(backgroundTask.Run);
}
}
public static void Discard()
{
TasksToExecute.Value.Clear();
TasksToExecute.Dispose();
}
}
FileTask:
public class FileTask : BackgroundTask
{
protected static string BaseFolder = #"C:\ASCII\";
private static readonly ReaderWriterLockSlim Lock = new ReaderWriterLockSlim();
private readonly string _folder;
private IHistoryRepository _historyRepository;
public string Folder
{
get { return _folder; }
}
public FileTask(string folder)
{
_folder = string.Format("{0}{1}", BaseFolder, folder);
}
protected override void Initialize()
{
_historyRepository = new HistoryRepository();
}
protected override void Execute()
{
// todo: Get institute that are active,
var institute = MockInstitute(); // todo: uncomment _historyRepository.FindInstituteByFolderName(Folder);
// todo: Update institute, lastupdate - [date] | [files amount] | [phonenumbers amount]
if (institute == null)
{
Logger.Warn("Not found data", Folder);
return;
}
// todo: read file get encoding | type and parse it
Task.Factory.StartNew(ReadFile);
}
private void ReadFile()
{
var list = GetFilesByFolder();
StreamReader sr = null;
try
{
Lock.EnterReadLock();
foreach (var fi in list)
{
var fileName = fi.FullName;
Logger.Info("Line: {0}:=> Content: {1}", fileName, Thread.CurrentThread.ManagedThreadId);
sr = new StreamReader(fileName, DetectEncoding(fileName));
string currentLine;
while ((currentLine = sr.ReadLine()).ReturnSuccess())
{
if (string.IsNullOrEmpty(currentLine)) continue;
Logger.Info("Line: {0}:=> Content: {1}", fileName, currentLine);
}
}
Lock.ExitReadLock();
}
finally
{
if (sr != null) sr.Dispose();
Logger.Info("Finished working" + Folder);
}
}
protected IEnumerable<FileInfo> GetFilesByFolder()
{
return Directory.GetFiles(Folder).Select(fileName => new FileInfo(fileName));
}
protected Encoding DetectEncoding(string file)
{
using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
{
var cdet = new Ude.CharsetDetector();
cdet.Feed(fs);
cdet.DataEnd();
return cdet.With(x => x.Charset)
.Return(x => Encoding.GetEncoding(cdet.Charset),
Encoding.GetEncoding("windows-1255"));
}
}
private Institute MockInstitute()
{
return new Institute
{
FromFolderLocation = string.Format("{0}{1}", BaseFolder, Folder)
};
}
public override string ToString()
{
return string.Format("Folder: {0}", Folder);
}
}
When don't read the file every thing ok, the Log is populated and every thing runs smooth,
but when i attach the Task.Factory.StartNew(ReadFile); method i have an exception.
Exception:
Cannot access a disposed object.
Object name: 'The ThreadLocal object has been disposed.'.
How do i solve that issue? might i need to change the LocalThread logic, or what - i have been trying to handle that issue, for almost a day.
BTW: It's an MVC4 project, and C# 5.0 and i'm trying to TDD it all.
You shouldn't be calling TasksToExecute.Dispose();
there.
How can I cancel a thread from another class fetching/refreshing location. I am able to cancel a thread from within the same class. But I am unable to do this across classes. Declaring the GPSThread static did not help. Can anyone please guide?
Class1:
public class GPSListener {
/* Other instantiation code */
Dialog busyDialog1 = new Dialog("Refreshing Location...",
new String [] { "Cancel" },
new int [] { Dialog.CANCEL},
Dialog.CANCEL,
Bitmap.getPredefinedBitmap(Bitmap.HOURGLASS))
{
public void fieldChanged(Field field1, int context1)
{
GPSHandler.requestStop();
busyDialog1.cancel();
}
};
public String refreshCoordinates() {
String test = "nothing";
if (GPSHandler.isStopRequested())
{
GPSHandler.stopRequested = false;
return null;
}
GPSHandler.getInstance().setListener(this);
GPSHandler.getInstance().requestLocationUpdates();
if (GPSHandler.isStopRequested())
{
GPSHandler.stopRequested = false;
return null;
}
busyDialog1.setEscapeEnabled(false);
busyDialog1.show();
return test;
}
public void onLocationReceived(Coordinates location) {
lblLatitude.setText(Double.toString(location.getLatitude()));
lblLongitude.setText(Double.toString(location.getLongitude()));
busyDialog1.cancel();
}
}
Class 2:
public class GPSHandler {
private GPSThread _gpsThread;
private Coordinates _location;
private boolean _gotLocation;
private GPSListener _listener;
/** this class will be a Singleton, as the device only has one GPS system */
private static GPSHandler _instance;
/** #return the Singleton instance of the GPSHandler */
public static GPSHandler getInstance() {
if (_instance == null) {
_instance = new GPSHandler();
}
return _instance;
}
public static boolean stopRequested = false;
public synchronized static void requestStop() {
stopRequested = true;
}
public synchronized static boolean isStopRequested() {
return stopRequested;
}
/** not publicly accessible ... use getInstance() */
private GPSHandler() {
}
/** call this to trigger a new location fix */
public void requestLocationUpdates() {
if (_gpsThread == null || !_gpsThread.isAlive()) {
_gpsThread = new GPSThread();
_gpsThread.start();
}
}
public void setListener(GPSListener listener) {
// only supports one listener this way
_listener = listener;
}
private void setLocation(final Coordinates value) {
_location = value;
if (value.getLatitude() != 0.0 || value.getLongitude() != 0.0) {
_gotLocation = true;
if (_listener != null) {
// this assumes listeners are UI listeners, and want callbacks on the UI thread:
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
_listener.onLocationReceived(value);
}
});
}
}
}
private class GPSThread extends Thread {
private void getLocationFromGoogle() {
try {
int cellID = GPRSInfo.getCellInfo().getCellId();
int lac = GPRSInfo.getCellInfo().getLAC();
String urlString2 = "http://www.google.com/glm/mmap";
// Open a connection to Google Maps API
ConnectionFactory connFact = new ConnectionFactory();
ConnectionDescriptor connDesc;
connDesc = connFact.getConnection(urlString2);
HttpConnection httpConn2;
httpConn2 = (HttpConnection)connDesc.getConnection();
httpConn2.setRequestMethod("POST");
// Write some custom data to Google Maps API
OutputStream outputStream2 = httpConn2.openOutputStream();//getOutputStream();
writeDataGoogleMaps(outputStream2, cellID, lac);
// Get the response
InputStream inputStream2 = httpConn2.openInputStream();//getInputStream();
DataInputStream dataInputStream2 = new DataInputStream(inputStream2);
// Interpret the response obtained
dataInputStream2.readShort();
dataInputStream2.readByte();
final int code = dataInputStream2.readInt();
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Dialog.alert(code + "");
}
});
if (code == 0) {
final double latitude = dataInputStream2.readInt() / 1000000D;
final double longitude = dataInputStream2.readInt() / 1000000D;
setLocation(new Coordinates(latitude, longitude, 0.0f));
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Dialog.alert(latitude+"-----"+longitude);
}
});
dataInputStream2.readInt();
dataInputStream2.readInt();
dataInputStream2.readUTF();
} else {
System.out.println("Error obtaining Cell Id ");
}
outputStream2.close();
inputStream2.close();
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
private void tryGetLocationFromDevice() {
_gotLocation = false;
try {
Criteria myCriteria = new Criteria();
myCriteria.setCostAllowed(false);
LocationProvider myLocationProvider = LocationProvider.getInstance(myCriteria);
try {
Location myLocation = myLocationProvider.getLocation(300);
setLocation(myLocation.getQualifiedCoordinates());
} catch ( InterruptedException iex ) {
System.out.println(iex.getMessage());
} catch ( LocationException lex ) {
System.out.println(lex.getMessage());
}
} catch ( LocationException lex ) {
System.out.println(lex.getMessage());
}
if (!_gotLocation) {
getLocationFromGoogle();
}
}
public void run() {
int bbMapsHandle = CodeModuleManager.getModuleHandle("net_rim_bb_lbs"); // OS 4.5 - 6.0
int bbMapsHandle60 = CodeModuleManager.getModuleHandle("net_rim_bb_maps"); // OS 6.0
if (bbMapsHandle > 0 || bbMapsHandle60 > 0) {
tryGetLocationFromDevice();
} else {
getLocationFromGoogle();
}
}
}
private void writeDataGoogleMaps(OutputStream out, int cellID, int lac) throws IOException {
DataOutputStream dataOutputStream = new DataOutputStream(out);
dataOutputStream.writeShort(21);
dataOutputStream.writeLong(0);
dataOutputStream.writeUTF("en");
dataOutputStream.writeUTF("Android");
dataOutputStream.writeUTF("1.0");
dataOutputStream.writeUTF("Web");
dataOutputStream.writeByte(27);
dataOutputStream.writeInt(0);
dataOutputStream.writeInt(0);
dataOutputStream.writeInt(3);
dataOutputStream.writeUTF("");
dataOutputStream.writeInt(cellID);
dataOutputStream.writeInt(lac);
dataOutputStream.writeInt(0);
dataOutputStream.writeInt(0);
dataOutputStream.writeInt(0);
dataOutputStream.writeInt(0);
dataOutputStream.flush();
}
}
Your GPSThread object is currently declared as a private inner class within GPSHandler. If you want to stop execution (or indeed do anything with it) from outside the scope of GPSHandler you will need to mark it as public. You will also need to provide some public mechanism (e.g. a stop() method) to cancel the thread execution.
The most common way of doing this is to have a boolean flag inside your thread (e.g shouldStop) which is checked within your main execution loop inside run() to see if it should stop. When the stop() method is called shouldStop is set to true and your Thread will stop.
Here's a good example: How to stop threads in Java?
There's two groups of changes you should make.
Change the Stop Requested Flag
First, remember that encapsulation is a good thing in Object-Oriented languages. The isStopRequested() method, or stopRequested variable of the GPSHandler should not be used outside of that class. Your UI's GPSListener should not attempt to use either of those. I would change your GPSHandler to use this:
private static boolean stopRequested = false;
public synchronized static void requestStop() {
stopRequested = true;
}
private synchronized static boolean isStopRequested() {
return stopRequested;
}
Only requestStop() should be public. It looks like you made stopRequested public to allow the GPSListener to reset it. If it needs resetting, let the class that owns that variable do the resetting. For example, in GPSHandler:
/** call this to trigger a new location fix */
public void requestLocationUpdates() {
if (_gpsThread == null || !_gpsThread.isAlive()) {
// reset this stop flag:
stopRequested = false;
_gpsThread = new GPSThread();
_gpsThread.start();
}
}
requestLocationUpdates() is really the method that starts the thread, so it should be where stopRequested gets reset to false.
Also, another reason that you should not make stopRequested public and allow other classes to use it is that this is not generally thread-safe. One of the reasons to wrap stopRequested with the requestStop() and isStopRequested() methods is to add thread-safety. There's many ways to do that, but those two methods achieve thread-safety by being marked with the synchronized keyword.
Change How/Where You Check the Flag
After you make these fixes, you need to change where you check if a stop has been requested. You don't really want to check isStopRequested() in the refreshCoordinates() method. That method involves almost no work. Even though it starts the process of getting a location fix, that only starts a thread, but the actual work of getting the location is done on a background thread (your GPSThread). If requestStop() is called, it's very unlikely that it will be called in the middle of refreshCoordinates(), so that's not where you should check it.
Check isStopRequested() multiple times within the GPSHandler class's methods tryGetLocationFromDevice() and getLocationFromGoogle(). Those are the methods that perform slow processing. Those are the ones you might want to interrupt in the middle. So, something like this:
private void getLocationFromGoogle() {
try {
int cellID = GPRSInfo.getCellInfo().getCellId();
int lac = GPRSInfo.getCellInfo().getLAC();
String urlString2 = "http://www.google.com/glm/mmap";
if (isStopRequested()) return;
// Open a connection to Google Maps API
ConnectionFactory connFact = new ConnectionFactory();
ConnectionDescriptor connDesc;
connDesc = connFact.getConnection(urlString2);
HttpConnection httpConn2;
httpConn2 = (HttpConnection)connDesc.getConnection();
httpConn2.setRequestMethod("POST");
// Write some custom data to Google Maps API
OutputStream outputStream2 = httpConn2.openOutputStream();//getOutputStream();
writeDataGoogleMaps(outputStream2, cellID, lac);
if (isStopRequested()) return;
// Get the response
InputStream inputStream2 = httpConn2.openInputStream();//getInputStream();
DataInputStream dataInputStream2 = new DataInputStream(inputStream2);
// Interpret the response obtained
dataInputStream2.readShort();
dataInputStream2.readByte();
if (isStopRequested()) return;
final int code = dataInputStream2.readInt();
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Dialog.alert(code + "");
}
});
And in tryGetLocationFromDevice(), you could do this (make sure to add the member variable and new method below):
private LocationProvider _locationProvider; // must be a member variable!
public void requestStop() {
if (_locationProvider != null) {
// this will interrupt the _locationProvider.getLocation(300) call
_locationProvider.reset();
}
}
private void tryGetLocationFromDevice() {
_gotLocation = false;
try {
Criteria myCriteria = new Criteria();
myCriteria.setCostAllowed(false);
_locationProvider = LocationProvider.getInstance(myCriteria);
try {
Location myLocation = _locationProvider.getLocation(300);
setLocation(myLocation.getQualifiedCoordinates());
} catch ( InterruptedException iex ) {
// this may be caught if stop requested!!!!
System.out.println(iex.getMessage());
} catch ( LocationException lex ) {
System.out.println(lex.getMessage());
}
} catch ( LocationException lex ) {
System.out.println(lex.getMessage());
}
if (!_gotLocation && !isStopRequested()) {
getLocationFromGoogle();
}
}
Then, call the GPSThread.requestStop() method from the outer GPSHandler.requestStop() method:
public synchronized static void requestStop() {
stopRequested = true;
if (_gpsThread != null) {
_gpsThread.requestStop();
}
}