Java FX - can't close window in loop - file

Question

I write short program in JavaFX which monitors folder for every 5 seconds . When it finds any PDF file then shows informations about number of finds files. And everything works fine, but when in folder is any files, then I will see window (and this is ok), but after this, when I will delete files (folder will be empty) then window is still showing (but is inactiv). Why this window doesn't close? Have you any idea?
Below is my code:
package testFolder;
import java.io.*;
import javafx.application.Application;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Alert;
import javafx.stage.Stage;
public class App extends Application{
private static String searchPath;
private File[] childrenFiles;
#Override
public void init(){
setPath();
}
#Override
public void start(Stage primaryStage){
run();
}
public File[] findPDFFiles(){
System.out.println("Find file in: " + searchPath);
File directory = new File(searchPath);
File[] childrenFiles = directory.listFiles(
(dir, name) -> {
return name.toLowerCase().endsWith(".pdf");
}
);
System.out.println("Number files: " + childrenFiles.length);
return childrenFiles;
}
// search folder
public void run(){
while (true){
childrenFiles = findPDFFiles();
if ((childrenFiles.length > 0)){
String countFile = "Number files: " + childrenFiles.length;
showAndWait(AlertType.INFORMATION, "FILES FOUND", countFile);
}
// wait 5 seconds
try{
Thread.sleep(5000);
}
catch (InterruptedException iex){
iex.printStackTrace();
};
}
}
// shows window with information about number of found files
private static void showAndWait(
AlertType alertType,
String title,
String content) {
Alert alert = new Alert(alertType);
alert.setTitle(title);
alert.setHeaderText(null);
alert.setContentText(content);
alert.getDialogPane().setPrefWidth(800);
alert.showAndWait();
}
// set folder to search files
public void setPath(){
searchPath = "/Users/Marcin/Desktop/IN/";
}
public static void main(final String[] args){
launch();
}
}

Answer 1

I tried your code and it worked fine for me even after deleting all pdf files it will print Number files: 0 in the console and no alerts are showing.
however, i will suggest using an AnimationTimer instead of the while(true) loop
an animationTimer has a handle method which is an abstract method that you'll have to override when you create the AnimationTimer
the code inside handle will be executed every frame so it will work like your while(true) but better
but be careful ! you can't directly call showAndWait inside an AnimationTimer handle so you'll do it by calling Platform.runLater, and this won't stop the animation timer from executing its handle method
so you can stop the animationTimer whenever you have to show an alert, and start it back when the alert gets hidden (closed) mainly to prevent the timer from creating a lot of alerts if you do not close old ones
one last problem is that the javafx platform will automatically shutdown whenever there is no javafx context shown so you can stop that by setting ImplicitExit to false in your start method !
after applying all of the above explained stuff, your code will look like this
package testFolder;
import java.io.*;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Alert;
import javafx.stage.Stage;
public class App extends Application{
private static String searchPath;
private static File[] childrenFiles;
static AnimationTimer timer;
static long then = 0;
#Override
public void init(){
setPath();
}
#Override
public void start(Stage primaryStage){
Platform.setImplicitExit(false);
run();
}
public static File[] findPDFFiles(){
System.out.println("Find file in: " + searchPath);
File directory = new File(searchPath);
File[] childrenFiles = directory.listFiles((dir, name) -> {
return name.toLowerCase().endsWith(".pdf");
});
System.out.println("Number files: " + childrenFiles.length);
return childrenFiles;
}
// search folder
public static void run(){
timer = new AnimationTimer() {
long sum = 0;
#Override
public void handle(long now) {
long dt = now - then;
sum+=dt;
if(sum/1000000 > 5000) {
childrenFiles = findPDFFiles();
if ((childrenFiles.length > 0)){
this.stop();
String countFile = "Number files: " + childrenFiles.length;
showAndWait(AlertType.INFORMATION, "FILES FOUND", countFile);
}
sum=0;
}
then = now;
}
};
timer.start();
}
// shows window with information about number of found files
private static void showAndWait(AlertType alertType, String title, String content) {
Alert alert = new Alert(alertType);
alert.setTitle(title);
alert.setHeaderText(null);
alert.setContentText(content);
alert.getDialogPane().setPrefWidth(800);
alert.setOnHidden(e->{
then = System.nanoTime();
timer.start();
});
Platform.runLater(alert::showAndWait);
}
// set folder to search files
public void setPath(){
searchPath = "/Users/Marcin/Desktop/IN/";
}
public static void main(final String[] args){
launch(args);
}
}
hope this solves you're problem