JavaFX Concurrency: How to updateMessage() to the controller with interface? - javafx

Question

Before I learned about running tasks on the background thread I learned how to post messages to my UI via my controller with an Interface. The interface allows me to have a systems messages in any controller. but I cant figure out how to bind it to updateMessage from a task.
My interface:
public interface SystemMessage {
void postMessage(String outText);
}
My controller:
public class MainController implements SystemMessage {
#FXML
public DialogPane systemMessage;
#Override
public void postMessage(String outText) {
systemMessage.setContentText(outText);
}
//***I have tried the following to bind the dialog pane to the updateMessage
systemMessage.contentTextProperty().bind(task.messageProperty());
//***InteliJ tells me that it can not resolve contetTextProperty or task.
}
My Main class with the Task on a new thread.
private SystemMessage mainController;
FXMLLoader loader = new FXMLLoader(getClass().getResource("fxml/entry.fxml"));
Parent root = loader.load();
this.mainController = (SystemMessage) loader.getController();
api = new Api();
machineId = new Identity();
db = new SqLite();
//mainController.postMessage(task.messageProperty()).bind();
Thread th = new Thread(task);
th.setDaemon(true);
th.start();
Task<String> task = new Task<String>() {
#Override protected String call() throws Exception {
checkAsiServer();
updateMessage("API Checked.");
checkMachineId();
updateMessage("Machine Id Checked.");
checkDb();
updateMessage("Server Checked.");
return "done";
}
};
I have tried to bind my DialogPane in the cotroller by:
systemMessage.contentTextProperty().bind(task.messageProperty());
But it can not resolve contentTextProperty and I don't know how to tell the controller about the task object either.

Answer 1

Not sure I understand the problem. Why don't you just expose the property from the controller? You can do
public class MainController implements SystemMessage {
#FXML
private DialogPane systemMessage;
public StringProperty messageProperty() {
return systemMessage.contentTextProperty();
}
// ...
}
and then
FXMLLoader loader = new FXMLLoader(getClass().getResource("fxml/entry.fxml"));
Parent root = loader.load();
MainController mainController = loader.getController();
Task<String> task = new Task<String>() { /* existing code... */};
mainController.messageProperty().bind(task.messageProperty());
Thread thread = new Thread(task);
thread.setDaemon(true);
thread.start();
If you want to keep the type of the controller as SystemMessage and only rely on the postMessage method, then obviously you can't do this with a binding (because you don't have any way to access the property); you would need to use a listener instead:
FXMLLoader loader = new FXMLLoader(getClass().getResource("fxml/entry.fxml"));
Parent root = loader.load();
SystemMessage mainController = loader.getController();
Task<String> task = new Task<String>() { /* existing code... */};
task.messageProperty().addListener((obs, oldMessage, newMessage) ->
mainController.postMessage(newMessage));
Thread thread = new Thread(task);
thread.setDaemon(true);
thread.start();