JavaFx程序运行但没有任何东西是空的，为什么？

Question

所以我超级兴奋，我终于想出了这个程序，然后砰的一声启动它=空白屏幕。我在这里调用一个空白窗格，而其他信息没有填充吗？它是在屏幕外填充的吗？出于某种原因，JavaFX真的让我动心了。如果有人也有什么好的地方去读它。（我知道谷歌很管用，我找到的很多网站/地方都不适合我。

package application;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;


public class Main extends Application {

Button button1, button2;
Label label1, label2;
Scene scene1, scene2;
BorderPane border1, border2;
Stage stage;  

ComboBox<String> choseImage;
ImageView mga1 = new ImageView(new 
Image(getClass().getResourceAsStream("/res/mga1.jpg")));
ImageView mga2 = new ImageView(new 
Image(getClass().getResourceAsStream("/res/mga2.jpg")));
ImageView mga3 = new ImageView(new 
Image(getClass().getResourceAsStream("/res/mga3.jpg")));

@Override
public void start(Stage primaryStage) throws Exception {

    primaryStage.setTitle("multi-factor key");
    primaryStage.setScene(scene1);

    //passPhrase
    TextField passPhrase = new TextField();
    button1 = new Button("submit");
    button1.setOnAction(e -> handleButtonAction(e));
    label1 =new Label ("Type in your PassPhrase");

    border1=new BorderPane();
    border1.getChildren().addAll(passPhrase, button1, label1);
    border1.setPadding(new Insets(20));
    BorderPane.setAlignment(passPhrase, Pos.CENTER);
    BorderPane.setAlignment(button1, Pos.BOTTOM_CENTER);
    BorderPane.setAlignment(label1, Pos.TOP_CENTER);
    scene1 = new Scene(border1, 350, 500);


    //combobox
    choseImage = new ComboBox<>();
    choseImage.setPromptText("Select a image.");
    choseImage.getItems().addAll("mga1.png"
    + "mga2.jpg"
        +   "mga3.png");

    choseImage.setValue("mga1.png");
    label2=new Label("Select a image");
    System.out.println(choseImage.getValue());
    String Selection = choseImage.getValue();
    if (Selection == "mga1.png")
            BorderPane.setAlignment(mga1, Pos.CENTER_RIGHT);
    if (Selection == "mga2.jpg")
            BorderPane.setAlignment(mga2, Pos.CENTER_RIGHT);
    if (Selection == "mga3.jpg");
            BorderPane.setAlignment(mga3, Pos.CENTER_RIGHT);



    border2= new BorderPane();
    border2.setPadding(new Insets(20));
    border2.getChildren().addAll(choseImage,label2);
    BorderPane.setAlignment(choseImage, Pos.CENTER);
    BorderPane.setAlignment(label2, Pos.TOP_CENTER);

    scene2 = new Scene(border2, 350, 500);
    primaryStage.show();




}

private void handleButtonAction(ActionEvent event) {
    if (event.getTarget()==button1)
        stage.setScene(scene1);
}




}

Answer 1

有很多问题为什么你启动app时屏幕是空白的

>

当调用primarystage.setScene(scene1)；时，场景为空，因此预期为空，您应该在实例化场景后设置它。在您的示例中，行后:scene1=新场景(border1，350，500)；

即使您执行了前面的步骤，屏幕仍然保持空白，因为您调用了border1.getChildres().addAll(...)，这是错误的。BorderPane有5个区域topbottomleftright和center，因此您应该为这些区域设置一个节点，而不是将它们添加到BorderPane的子区域中。这取决于你想要“看到”它们的地方你应该把它们放在正确的地方。您应该执行类似的操作:border1.settop(...)border1.setbottom(...)等等。