Java

Question

我的Java项目中有几个场景和一个我真的不知道如何解决的问题。 First scene called "Zadanie". There are TextFields and ComboBoxes in this first scene called "Zadanie". So, as you can see in image, I wrote some numbers in TextFields and choosed some options in ComboBoxes. Then I switched on other scene by clicking on "Vypočítať" (button up). And then I switched back on first scene "Zadanie", but everything in TextFields and ComboBoxes is gone. Back on first scene "Zadanie". 请给我一些代码示例或如何将它们保留在第一个场景中的方法。谢谢。

Answer 1

问题是当您切换屏幕时，代表屏幕的对象被处理掉了。因此，任何变量（例如用户输入）也将被处理掉。当您切换回屏幕时，它是不同的对象但属于同一类型。这意味着用户输入等变量的值是新鲜的 instantiated/initialized.

解决方法：创建一些存储此信息的全局变量（例如，Main 中的变量，但为了编程习惯，您应该使用不同的类）。当用户点击切换屏幕时，但在屏幕实际切换（卸载）之前，将任何用户输入存储在全局变量中。然后当屏幕切换回时，将这些变量从全局变量重新加载到字段中。

Global.java

class Global {
    public static String nameFieldValue;
    public static String ageFieldValue;
}

PersonForm.java

class PersonForm extends BorderPane {
    Button closeButton;
    TextField nameField;
    TextField ageField;

    public PersonForm() {
        this.nameField = new TextField(...);
        this.ageField = new TextField(...);
        this.closeButton = new Button("Close Window");

        // set layouts of buttons here.

        if (Global.nameFieldValue != null) {
            this.nameField.setText(Global.nameFieldValue);
        }
        if (Global.passwordFieldValue != null) {
            this.passwordField.setText(Global.passwordFieldValue);
        }

        PersonForm thisForm = this; // So that EventHandler cna use this.
        this.closeButton.setOnAction(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                Global.nameFieldValue = thisForm.nameField.getText();
                Global.passwordFieldValue = thisForm.passwordField.getText();
                // switch screens.
            }
        });
    }
}

Java - Scene Builder - TextField 和 ComboBox 中的用户输入在切换场景后消失

Java - Scene Builder - User input in TextField and ComboBox disappears after switching a scenes

combobox

textfield

scenebuilder

gluon