[FIXED] How do you edit the color of a label in main class from a different class?

Issue

I'm a beginner java programmer and I'm making a small app where I can enter my school marks and see my total score. I have 2 classes in total (1 for javafx layout and 1 for my Methods), and I'm trying to change the color of a label (.setTextFill) which is in the main class with a method in the methods class.

I have tried making an object of the main class but this gives an error: java.lang.reflect.InvocationTargetException.

public void start(Stage primaryStage)throws Exception{
  totalPercent = new Label(Methods.getTotalPercent());
  totalPercent.setTextFill(Color.web("#4ecf17"));
}

//next code is in a different class
public void setPercentColor(){
    if(percent <  50){
        totalPercent.setTextFill(Color.web("#ff0000"));
    }else if(percent >=  50 && percent <  60){
        totalPercent.setTextFill(Color.web("#ff7700"));
    }else if (percent >=  60 && percent <  100){
        totalPercent.setTextFill(Color.web("#59ff00"));
    }else{
        totalPercent.setTextFill(Color.web("#000000"));
    }
}

So basically I don't know how to change the color from the label 'totalPercent' with a method that's located in a different class.

Solution

The design of your classes is not done well considering the setPercentColor method: It controls the details of the representation of some view managed by another class.

I recommend redesigning Methods to provide a property and letting the other class decide on what to do with this value.

In this case you could add a ReadOnlyIntegerProperty percent instead of using a field. This way the other class can use bindings/listeners to update the view and the only thing Methods needs to worry about is updating the property.

In Methods

// private int percent;
private final ReadOnlyIntegerWrapper percent = new ReadOnlyIntegerWrapper();

public ReadOnlyIntegerProperty percentProperty() {
    return percent.getReadOnlyProperty();
}

public int getPercent() {
    return percent.get();
}

...
// percent = i
percent.set(i); // replace assinment to int field with setting the property

Other class

public void start(Stage primaryStage)throws Exception{
    totalPercent = new Label();

    totalPercent.textProperty().bind(Methods.percentProperty().asString());

    final Color color560 = Color.web("#ff7700");
    final Color color100 = Color.web("#59ff00");
    totalPercent.textFillProperty().bind(Bindings.createObjectBinding(() -> {
              int percent = Methods.getPercent();
              if(percent <  50) {
                  return Color.RED;
              } else if(percent < 60) {
                  return color60;
              }else if (percent < 100){
                  return color100;
              } else {
                  return Color.BLACK;
              }
          }, Methods.percentProperty()));
}

BTW: I recommend choosing a more meaningful name for the Methods class: Most classes contain method implementations, so the name contains basically no valuable info to someone reading the code.

Answered By - fabian
Answer Checked By - Mary Flores (JavaFixing Volunteer)