how to integrate an offline map? am trying this?
private class DownloadTask extends AsyncTask<String, Void, String> {
// Downloading data in non-ui thread
#Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try {
// Fetching the data from web service
data = downloadUrl(url[0]);
Log.d("DownloadTask", "DownloadTask : " + data);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
you can use mapbox, openstreetMap or osmdroid!
https://github.com/osmdroid/osmdroid
https://docs.mapbox.com/android/maps/guides/offline/
https://www.openstreetmap.org/`enter code here`
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 have a pretty simplistic JavaFX application. In it, I have a Java object for handling database activities, mainly executing queries. To prevent my UI from completely freezing while the query executes, I've implemented a background thread using the javafx.concurrent.Service. This works great on my connect method, which doesn't return anything. However, in my query method it immediately jumps to the return line, and of course returns null. Then it goes back and runs the query, but it's already returned an empty arraylist.
What am I doing wrong?
Here's my method:
public ArrayList<Foo> runQuery() throws SQLException {
ArrayList<Foo> result = new ArrayList<Foo>();
backgroundThread = new Service<Void>() {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
protected Void call() throws Exception {
stmt = conn.createStatement();
String query = "Select stuff...
rs = stmt.executeQuery(query);
return null;
}
};
}
};
backgroundThread.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
#Override
public void handle(WorkerStateEvent argo) {
try {
while (rs.next()) {
result.add(new Foo(rs.getString(1)));
}
} catch (SQLException e) {
e.printStackTrace();
}
controller.addLogEntry("done.\n");
}
});
backgroundThread.restart();
return result;
}
I am having trouble coding the socket side of a JavaFX chat client. This is my first time having to deal with socket in any sort of way, so some trouble was expected. I've been following this page to design the server-client side:
http://pirate.shu.edu/~wachsmut/Teaching/CSAS2214/Virtual/Lectures/chat-client-server.html
My problem is getting text I enter into the GUI into a DataInputSteam and DataOutputStream so that others on the same server can see the changes. I do
not understand how to convert the text in the UI to something the sockets
can work with.
Here is part of my controller class:
#FXML
private TextArea messageArea;
#FXML
private Button sendButton;
private ChatClient client;
#FXML
public void initialize() {
client = new ChatClient(ChatServer.HOSTNAME, ChatServer.PORT);
sendButton.setOnAction(event -> {
client.handle(messageArea.getText());
});
}
The ChatClient class is a Runnable with a DataInputStream and DataOutputStream field that connects to a Socket. I haven't changed much from the link:
public class ChatClient implements Runnable {
private Socket socket;
private Thread thread;
private DataInputStream streamIn;
private DataOutputStream streamOut;
private ChatClientThread client;
public ChatClient(String serverName, int port) {
System.out.println("Establishing connection...");
try {
socket = new Socket(serverName, port);
System.out.println("Connected: " + socket);
start();
} catch (UnknownHostException e) {
System.out.println("Unknown host: " + e.getMessage());
} catch (IOException e) {
System.out.println("Unexpected: " + e.getMessage());
}
}
#Override
public void run() {
while (thread != null) {
try {
streamOut.writeUTF(streamIn.readUTF());
streamOut.flush();
} catch (IOException e) {
System.out.println("Sending error: " + e.getMessage());
stop();
}
}
}
public void handle(String msg) {
try {
streamOut.writeUTF(msg);
streamOut.flush();
} catch (IOException e) {
System.out.println("Could not handle message: " + e.getMessage());
}
System.out.println(msg);
}
public void start() throws IOException {
streamIn = new DataInputStream(socket.getInputStream());
streamOut = new DataOutputStream(socket.getOutputStream());
if (thread == null) {
client = new ChatClientThread(this, socket);
thread = new Thread(this);
thread.start();
}
}
So in the controller class, I am calling the handle method which deals with the streams. The original code just wrote to the console, so I had to change the line:
streamIn = new DataInputStream(System.in)
to
streamIn = new DataInputStream(socket.getInputStream());
There is also a ChatClientThread class that extends Thread and just calls ChatClient.handle() in its run method.
I guess my question is how to update a GUI whenever writeUTF and readUTF interact with the DataStreams. I understand that streamOut.writeUTF(msg) changes the DataOutputStream to "have" that string, but I'm not sure how I'm supposed to use that datastream to update my gui so that all clients using the application can see the update. The way I have it now, if I run two instances of the JavaFX app, they dont' communicate through the UI or the console. My program just stalls whenever I click the send button
I've tried two different ways to call a simple REST method from Android; said REST method - which works from other clients - simply returns an int val such as 17.
Both of the following attempts were based on code I found online. One is like so:
public void onFetchBtnClicked(View v){
if(v.getId() == R.id.FetchBtn){
Toast.makeText(getApplicationContext(), "You mashed the button, dude.", Toast.LENGTH_SHORT).show();
new NetworkTask().execute();
}
}
public static class NetworkTask extends AsyncTask {
#Override
protected String doInBackground(Void... params) {
final String TAG;
TAG = "callWebService";
String deviceId = "Android Device";
HttpClient httpclient = new DefaultHttpClient();
HttpGet request = new HttpGet("http://localhost:28642/api/Departments/GetCount");
request.addHeader("deviceId", deviceId);
ResponseHandler<String> handler = new BasicResponseHandler();
String result = "";
try
{
result = httpclient.execute(request, handler);
}
catch (ClientProtocolException e)
{
e.printStackTrace();
Log.e(TAG, "ClientProtocolException in callWebService(). " + e.getMessage());
}
catch (IOException e)
{
e.printStackTrace();
Log.e(TAG, "IOException in callWebService(). " + e.getMessage());
}
httpclient.getConnectionManager().shutdown();
Log.i(TAG, "**callWebService() successful. Result: **");
Log.i(TAG, result);
Log.i(TAG, "*****************************************");
return result;
}
#Override
protected void onPostExecute(String result) {
final String TAG;
TAG = "onPostExecute";
if (null != result)
Log.i(TAG, result);
}
With the code above, after the following line of code fails:
result = httpclient.execute(request, handler) ;
...I get, "*E/callWebService﹕ IOException in callWebService(). Connection to http://localhost:28642 refused*"
This problem may be a threading issue, as I read this in O'Reilly's "Programming Android" book by Mednieks, Dornin, Meike, and Nakamura: "AsyncTask is a convenenient tool for running small, asynchronous tasks. Just remember that the doInBackground method runs on a different thread! It must not write any state visible from another thread or read any state writable from another thread. This includes its parameters."
With my other attempt:
public void onFetchBtnClicked(View v){
if(v.getId() == R.id.FetchBtn){
Toast.makeText(getApplicationContext(), "You mashed the button, dude.", Toast.LENGTH_SHORT).show();
callWebService("http://localhost:28642/api/Departments/GetCount");
}
}
public String callWebService(String requestUrl)
{
final String TAG;
TAG = "callWebService";
String deviceId = "Android Device";
HttpClient httpclient = new DefaultHttpClient();
HttpGet request = new HttpGet(requestUrl);
request.addHeader("deviceId", deviceId);
ResponseHandler<String> handler = new BasicResponseHandler();
String result = "";
try
{
result = httpclient.execute(request, handler);
}
catch (ClientProtocolException e)
{
e.printStackTrace();
Log.e(TAG, "ClientProtocolException in callWebService(). " + e.getMessage());
}
catch (IOException e)
{
e.printStackTrace();
Log.e(TAG, "IOException in callWebService(). " + e.getMessage());
}
httpclient.getConnectionManager().shutdown();
Log.i(TAG, "**callWebService() successful. Result: **");
Log.i(TAG, result);
Log.i(TAG, "*****************************************");
return result;
}
...the debugger dumps me into View.class after hitting that same problem line (result = httpclient.execute(request, handler)). Why it does that, I don't know*, but I think the crux of the problem, as indicated by err msgs in logcat, is: "Caused by: android.os.NetworkOnMainThreadException"
*Maybe because something untoward is being attempted within the UI (View) thread.
Also (not a big deal, but "interesting," perhaps): the Toast doesn't pop up when a method call is made after it (it works otherwise).
The (Web API) server has a breakpoint set in its corresponding Controller method, but it is never reached. As mentioned, the server is running, and responds just fine to other (Windows app) clients.
There must be a somewhat straightforward way of calling a RESTful method from Android. But what/how?
UPDATE
I tried this, now, too, calling it like so:
RestClient client = new RestClient("http://localhost:28642/api/Departments/GetCount");
try {
client.Execute(RestClient.RequestMethod.GET);
} catch (Exception e) {
e.printStackTrace();
}
String response = client.getResponse();
Log.i("CZECH_THIS", response);
...but it also is (or seems, anyway) happy to throw the "NetworkOnMainThread" exception.
UPDATE 2
This is the closest I've gotten so far, I think. Maybe the server is the culprit in this case, because with this code:
public void onFetchBtnClicked(View v){
if(v.getId() == R.id.FetchBtn){
Toast.makeText(getApplicationContext(), "You mashed the button, dude.", Toast.LENGTH_SHORT).show();
new CallAPI().execute("http://localhost:28642/api/Departments/GetCount");
}
}
public static class CallAPI extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... params) {
String urlString=params[0]; // URL to call
String resultToDisplay = "";
InputStream in = null;
// HTTP Get
try {
URL url = new URL(urlString);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
in = new BufferedInputStream(urlConnection.getInputStream());
} catch (Exception e ) {
System.out.println(e.getMessage());
return e.getMessage();
}
return resultToDisplay;
}
protected void onPostExecute(String result) {
Log.i("FromOnPostExecute", result);
}
} // end CallAPI
....the exception that is thrown is:
libcore.io.ErrnoException: connect failed: ECONNREFUSED (Connection refused)
failed to connect to localhost/127.0.0.1 (port 28642): connect failed: ECONNREFUSED (Connection refused)
...and the Android app continues to run (it falls over in the other examples).
Why is my server refusing the connection?
UPDATE 3
I thought for a minute I had it: I forgot to pass the serial Num with the URL. But even after doing so, it fails.
I have a breakpoint in the server app, in the Controller method; also, in the Repository method, but they are never reached.
What could be wrong?
Is "localhost" the wrong thing to use (in the URL)? Should I use the name of the computer instead?
Does the URL (passed literally as "http://localhost:28642/api/Departments/GetCount?serialNum=4242") need to be verbatimized?
UPDATE 4
Changing the "locohost" to the machine name, I get "No address associated with hostname" so that's not the problem...
Oddly, though, this line runs fine:
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
...whereas this is the last line before the exception is thrown/caught:
in = new BufferedInputStream(urlConnection.getInputStream());
Looking at this, though, perhaps I need to escape my whacks; but when you already have double-whacks, as in after "http:", do you have to do triple-whacks? Or quadruple whacks? Surely not ceiling wax...?
I've got it working now. There's an article about it here.
This is the code from there without any explanation:
public class MainActivity extends ActionBarActivity {
private GetDepartmentsCount _getDeptsCount;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button getDeptsCountBtn = (Button)findViewById(R.id.DeptsCountBtn);
getDeptsCountBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
_getDeptsCount = new GetDepartmentsCount();
_getDeptsCount.execute("http://10.0.2.2:28642/api/Departments/GetCount?serialNum=4242");
}
});
}
#Override
public void onStop() {
super.onStop();
_getDeptsCount.cancel(true);
}
private class GetDepartmentsCount extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... params) {
String urlString = params[0]; // URL to call
String result = "";
// HTTP Get
try {
URL url = new URL(urlString);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
if (null != inputStream)
result = IOUtils.toString(inputStream);
} catch (Exception e) {
System.out.println(e.getMessage());
return e.getMessage();
}
return result;
}
#Override
protected void onPostExecute(String result) {
EditText dynCount = (EditText)findViewById(R.id.dynamicCountEdit);
dynCount.setText(result + " records were found");
Log.i("FromOnPostExecute", result);
}
}
}
I'm wondering if anybody can help me with a rather annoying problem regarding creating a background thread in JavaFX! I currently have several SQL queries that add data to the UI which currently run on the JavaFX Application Thread (see example below). However when each of these queries execute it freezes the UI because it isn't running on a background thread. I've looked at various examples that use Task and sort of understand them but I cannot get them to work when doing database queries, some of which take a few seconds to run.
Here is one of the methods that executes a query:
public void getTopOrders() {
customerOrders.clear();
try {
Connection con = DriverManager.getConnection(connectionUrl);
//Get all records from table
String SQL = "EXEC dbo.Get_Top_5_Customers_week";
ResultSet rs;
try (Statement stmt = con.createStatement();) {
rs = stmt.executeQuery(SQL);
while (rs.next()) {
double orderValue = Double.parseDouble(rs.getString(3));
customerOrders.add(new CustomerOrders(rs.getString(1),
rs.getString(2), "£" + formatter.format(orderValue),
rs.getString(4).substring(6, 8) + "/" +
rs.getString(4).substring(4, 6) + "/" +
rs.getString(4).substring(0, 4)));
}
}
} catch (SQLException | NumberFormatException e) {
}
}
Each processed record is added to an ObservableList which is linked to a TableView, or graph or simply sets the text on a label (depends on the query). How can I execute the query on a background thread and still leave the interface free to use and be updated from the queries
Thanks in advance
I created a sample solution for using a Task (as suggested in Alexander Kirov's comment) to access a database on a concurrently executing thread to the JavaFX application thread.
The relevant parts of the sample solution are reproduced below:
// fetches a collection of names from a database.
class FetchNamesTask extends DBTask<ObservableList<String>> {
#Override protected ObservableList<String> call() throws Exception {
// artificially pause for a while to simulate a long
// running database connection.
Thread.sleep(1000);
try (Connection con = getConnection()) {
return fetchNames(con);
}
}
private ObservableList<String> fetchNames(Connection con) throws SQLException {
logger.info("Fetching names from database");
ObservableList<String> names = FXCollections.observableArrayList();
Statement st = con.createStatement();
ResultSet rs = st.executeQuery("select name from employee");
while (rs.next()) {
names.add(rs.getString("name"));
}
logger.info("Found " + names.size() + " names");
return names;
}
}
// loads a collection of names fetched from a database into a listview.
// displays a progress indicator and disables the trigge button for
// the operation while the data is being fetched.
private void fetchNamesFromDatabaseToListView(
final Button triggerButton,
final ProgressIndicator databaseActivityIndicator,
final ListView listView) {
final FetchNamesTask fetchNamesTask = new FetchNamesTask();
triggerButton.setDisable(true);
databaseActivityIndicator.setVisible(true);
databaseActivityIndicator.progressProperty().bind(fetchNamesTask.progressProperty());
fetchNamesTask.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
#Override public void handle(WorkerStateEvent t) {
listView.setItems(fetchNamesTask.getValue());
}
});
fetchNamesTask.runningProperty().addListener(new ChangeListener<Boolean>() {
#Override public void changed(ObservableValue<? extends Boolean> observable, Boolean wasRunning, Boolean isRunning) {
if (!isRunning) {
triggerButton.setDisable(false);
databaseActivityIndicator.setVisible(false);
}
};
});
databaseExecutor.submit(fetchNamesTask);
}
private Connection getConnection() throws ClassNotFoundException, SQLException {
logger.info("Getting a database connection");
Class.forName("org.h2.Driver");
return DriverManager.getConnection("jdbc:h2:~/test", "sa", "");
}
abstract class DBTask<T> extends Task<T> {
DBTask() {
setOnFailed(new EventHandler<WorkerStateEvent>() {
#Override public void handle(WorkerStateEvent t) {
logger.log(Level.SEVERE, null, getException());
}
});
}
}
// executes database operations concurrent to JavaFX operations.
private ExecutorService databaseExecutor = Executors.newFixedThreadPool(
1,
new DatabaseThreadFactory()
);
static class DatabaseThreadFactory implements ThreadFactory {
static final AtomicInteger poolNumber = new AtomicInteger(1);
#Override public Thread newThread(Runnable runnable) {
Thread thread = new Thread(runnable, "Database-Connection-" + poolNumber.getAndIncrement() + "-thread");
thread.setDaemon(true);
return thread;
}
}
Note that once you start doing things concurrently, your coding and your UI gets more complicated than the default mode without Tasks when everything is single threaded. For example, in my sample I disabled the button which initiates the Task so you cannot have multiple Tasks running in the background doing the same thing (this kind of processing is similar to the web world where you might disable a form post button to prevent a form being double posted). I also added an animated progress indicator to the scene while the long running database task was executing so that the user has an indication that something is going on.
Sample program output demonstrating the UI experience when a long running database operation is in progress (note the progress indicator is animating during the fetch which means the UI is responsive though the screenshot does not show this):
To compare the additional complexity and functionality of an implementation with concurrent tasks versus an implementation which executes everything on the JavaFX application thread, you can see another version of the same sample which does not use tasks. Note that in my case with a toy, local database the additional complexity of the task based application is unnecessary because the local database operations execute so quickly, but if you were connecting to a large remote database using long running complex queries, than the Task based approach is worthwhile as it provides users with a smoother UI experience.
Managed to resolve using the solution provided by jewelsea. It is worth noting that if implementing this method when not using lists, tables and/or observable lists where you need to update an item on the UI such as a text field or label then simply add the update code within Platform.runLater. Below are some code snippets that show my working solution.
Code:
public void getSalesData() {
try {
Connection con = DriverManager.getConnection(connectionUrl);
//Get all records from table
String SQL = "EXEC dbo.Order_Information";
try (Statement stmt = con.createStatement(); ResultSet rs =
stmt.executeQuery(SQL)) {
while (rs.next()) {
todayTot = Double.parseDouble(rs.getString(7));
weekTot = Double.parseDouble(rs.getString(8));
monthTot = Double.parseDouble(rs.getString(9));
yearTot = Double.parseDouble(rs.getString(10));
yearTar = Double.parseDouble(rs.getString(11));
monthTar = Double.parseDouble(rs.getString(12));
weekTar = Double.parseDouble(rs.getString(13));
todayTar = Double.parseDouble(rs.getString(14));
deltaValue = Double.parseDouble(rs.getString(17));
yearPer = yearTot / yearTar * 100;
monthPer = monthTot / monthTar * 100;
weekPer = weekTot / weekTar * 100;
todayPer = todayTot / todayTar * 100;
//Doesn't update UI unless you add the update code to Platform.runLater...
Platform.runLater(new Runnable() {
public void run() {
todayTotal.setText("£" + formatter.format(todayTot));
weekTotal.setText("£" + formatter.format(weekTot));
monthTotal.setText("£" + formatter.format(monthTot));
yearTotal.setText("£" + formatter.format(yearTot));
yearTarget.setText("£" + formatter.format(yearTar));
monthTarget.setText("£" + formatter.format(monthTar));
weekTarget.setText("£" + formatter.format(weekTar));
todayTarget.setText("£" + formatter.format(todayTar));
yearPercent.setText(percentFormatter.format(yearPer) + "%");
currentDelta.setText("Current Delta (Week Ends): £"
+ formatter.format(deltaValue));
}
});
}
}
} catch (SQLException | NumberFormatException e) {
}
}
public void databaseThreadTester() {
fetchDataFromDB();
}
private void fetchDataFromDB() {
final testController.FetchNamesTask fetchNamesTask = new testController.FetchNamesTask();
databaseActivityIndicator.setVisible(true);
databaseActivityIndicator.progressProperty().bind(fetchNamesTask.progressProperty());
fetchNamesTask.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
#Override
public void handle(WorkerStateEvent t) {
}
});
fetchNamesTask.runningProperty().addListener(new ChangeListener<Boolean>() {
#Override
public void changed(ObservableValue<? extends Boolean> observable, Boolean wasRunning, Boolean isRunning) {
if (!isRunning) {
databaseActivityIndicator.setVisible(false);
}
}
;
});
databaseExecutor.submit(fetchNamesTask);
}
abstract class DBTask<T> extends Task {
DBTask() {
setOnFailed(new EventHandler<WorkerStateEvent>() {
#Override
public void handle(WorkerStateEvent t) {
}
});
}
}
class FetchNamesTask extends testController.DBTask {
#Override
protected String call() throws Exception {
fetchNames();
return null;
}
private void fetchNames() throws SQLException, InterruptedException {
Thread.sleep(5000);
getTopOrders();
getSalesData();
}
}
The only thing that doesn't appear to work with this implementation is the following, not sure why it doesn't work but it doesn't draw the graph.
public void addCricketGraphData() {
yearChart.getData().clear();
series.getData().clear();
series2.getData().clear();
try {
Connection con = DriverManager.getConnection(connectionUrl);
//Get all records from table
String SQL = "...omitted...";
try (Statement stmt = con.createStatement(); ResultSet rs =
stmt.executeQuery(SQL)) {
while (rs.next()) {
Platform.runLater(new Runnable() {
#Override
public void run() {
try {
series.getData().add(new XYChart.Data<String, Number>(rs.getString(1),
Double.parseDouble(rs.getString(7))));
series2.getData().add(new XYChart.Data<String, Number>(rs.getString(1),
Double.parseDouble(rs.getString(8))));
} catch (SQLException ex) {
Logger.getLogger(testController.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
}
}
} catch (SQLException | NumberFormatException e) {
}
yearChart = createChart();
}
protected LineChart<String, Number> createChart() {
final CategoryAxis xAxis = new CategoryAxis();
final NumberAxis yAxis = new NumberAxis();
// setup chart
series.setName("Target");
series2.setName("Actual");
xAxis.setLabel("Period");
yAxis.setLabel("£");
//Add custom node for each point of data on the line chart.
for (int i = 0; i < series2.getData().size(); i++) {
nodeCounter = i;
final int value = series.getData().get(nodeCounter).getYValue().intValue();
final int value2 = series2.getData().get(nodeCounter).getYValue().intValue();
int result = value2 - value;
Node node = new HoveredThresholdNode(0, result);
node.toBack();
series2.getData().get(nodeCounter).setNode(node);
}
yearChart.getData().add(series);
yearChart.getData().add(series2);
return yearChart;
}