java - 控制不解析到javafx程序中的main

Question

我是java新手。我为 Action 监听器编写的下面的onButtonClick()方法始终执行else block 中的语句。我需要它来验证用户名和密码并执行if-else block 。奇怪的是，当我在每个方法中添加一些 println 时，我注意到控件根本没有解析到 main。当我启动程序时，start 方法中的打印语句首先执行，而不是 main 中的第一个打印语句。 main 中的两个打印语句根本没有被执行。

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;
import javafx.scene.control.Button;

    public class Version3 extends Application {
        public static void main(String args) {
            System.out.println("main called"); //this is not executing
            launch(args);
            System.out.println("Finished"); // this aswell
    }
    Button signInButton;
    Button cancelButton;
    Text userNameText;
    Text passwordText;
    Text Validation;
    TextField userNameField;
    PasswordField passwordField;
    //Using gridpane and intialized all Fields above

    public void start(Stage primaryStage) {
        System.out.println("Stage called"); 
   //added a statement to check when this method was calling. Statement 
   //getting executed as soon as the program started.

        GridPane pane = new GridPane();
        pane.setAlignment(Pos.CENTER);
        pane.setVgap(20);
        pane.setHgap(20);

        userNameText = new Text("Username");
        pane.add(userNameText, 0, 0);

        userNameField = new TextField();
        pane.add(userNameField, 1, 0);

        passwordText = new Text("Password");
        pane.add(passwordText, 0, 1);

        passwordField = new PasswordField();
        pane.add(passwordField, 1, 1);

        signInButton = new Button("Submit");
        pane.add(signInButton, 0, 2);

        signInButton.setOnAction(e -> onButtonClick());
        // calling method for signin button
        Validation = onButtonClick();
        pane.add(Validation, 0, 3);

        cancelButton = new Button("Clear");
        pane.add(cancelButton, 1, 2);

        Scene scene = new Scene(pane, 900, 600);

        primaryStage.setScene(scene);
        primaryStage.setTitle("The Click me app");
        primaryStage.show();

    }

    public Text onButtonClick() {
       System.out.println("onButton called");
       if (userNameField.getText().equals("admin") && 
       passwordField.getText().equals("password")) {
       Text val = new Text("Credentials Validated");
       //this is neither getting validated nor executing
       return val;
       } else {
       Text val = new Text("Invalid Credentials");
       // Always displaying this else block on layout
       return val;
       }
   }
}

Answer 1

1. 首先，您的 main 方法应该像这样

   public static void main(String[] args){
       System.out.println("main called");
       launch(args);
       System.out.println("Finished");
   }
   

2. 第二，更改start(Stage PrimaryStage)方法中的语句来自

   Validation = onButtonClick();
   

   至

   Validation = new Text("Invalid Credentials");
   

3. 第三，将onButtonClick()方法更改为

   public void onButtonClick(){
       System.out.println("onButton called");
       if(userNameField.getText().equals("admin") && passwordField.getText().equals("password")){
         Validation.setText("Credentials Validated");
       }else{
         Validation.setText("Invalid Credentials");
       } 
   }