Unable to update row of tableView after connecting to a url - url

Question

I am building a download manager
Here I have shown a test code which tries to update fileNameColumn of a row of tableView but it is not being updated after I connect to url
To be specific, here fileName remains hello1 and it doesnt get updated to hello2. Yhy's that so?
Main.java :
public static TableView<DownloadEntry> downloadsTable;
public TableColumn<DownloadEntry, String> fileNameColumn;
public void initialize(URL location, ResourceBundle resources) {
downloadsTable = new TableView<DownloadEntry>();
fileNameColumn = new TableColumn<>("File Name");
fileNameColumn.setCellValueFactory(new PropertyValueFactory<>("fileName"));
executor = Executors.newFixedThreadPool(4);
}
public void addDownloadButtonClicked() {
try{
String urlText = urlTextBox.getText();
DownloadEntry task = new DownloadEntry(new URL(urlText));
downloadsTable.getItems().add(task);
executor.execute(task);
}
catch(Exception e) {
System.out.println("addDownloadButtonClicked: " + e);
}
}
DownloadEntry.java:
public class DownloadEntry extends Task<Void> {
public SimpleStringProperty fileName;
public URL url;
//Constructor
public DownloadEntry(URL ur) throws Exception{
fileName = new SimpleStringProperty("hello");
url = ur;
}
#Override
protected Void call() {
try {
HttpURLConnection connect=(HttpURLConnection)url.openConnection();
fileName.set("hello1");
connect.connect();
fileName.set("hello2");
}
catch(Exception E) {
this.updateMessage("Error");
E.printStackTrace();
}
return null;
}
public String getFileName() {
return fileName.get();
}
public void setFileName(String fileName) {
this.fileName = new SimpleStringProperty(fileName);
}
}
Please tell if you need more details..

Answer 1

Your model is incorrectly implemented. The setFileName method should be
public void setFileName(String fileName) {
this.fileName.set(fileName);
}
(The problem with your implementation is that the table is still observing the old property, not the new one you create.)
You will also need to provide a "property accessor" method:
public StringProperty fileNameProperty() {
return fileName ;
}
which will allow the table to properly bind to the property (so that it "knows" when its value changes).