Question

我写了一个由以下GUI组成的应用程序该应用程序的目标是在画布上添加一个蓝色矩形到左侧的黑色窗格。因此，我写了一个类预览（也包含黑色窗格）

public class Preview
{
    Canvas can=new Canvas();
    GraphicsContext gc=can.getGraphicsContext2D();
    Pane canvas=new Pane();

    int WIDTH=1920;
    int HEIGHT=1080;
    int y=50;

    public Node area()
    {
       BorderPane container=new BorderPane();
       ScrollPane sp = new ScrollPane(can);
       sp.setFitToHeight(true);
       sp.setFitToWidth(true);

       sp.setStyle("-fx-background: black;");
       container.setCenter(sp);
       return container;
    }

    public void placeCanvas()
    {
        can.setHeight(100);
        can.setWidth(100);
        gc.setFill(Color.BLUE);
        gc.fillRect(0,0,100,100);
        canvas.getChildren().add(can);
    }
}

我在GUI类中创建了一个预览对象。当我尝试在我的GUI类中调用preview.placeCanvas()时，它按预期工作，产生blue rectangle 但是，最终目标是在顶部文本字段（“标题”）失去焦点时使矩形显示。

//Layout of Application
    root.setCenter(preview.area());
    root.setRight(sp);
    root.setBottom(btns);

    //preview.placeCanvas();

    title.focusedProperty().addListener((obs, outFocus, inFocus) ->
    {
        if(outFocus)
        {
            preview.placeCanvas();
            Alert placed=new Alert(AlertType.CONFIRMATION,"Placed Canvas!",ButtonType.OK);
            placed.showAndWait();
        }   
    });

当我运行上面的代码时，警告弹出，告诉我，我输入了if语句，但是我看到no blue rectangle

非常感谢帮助！

P.S。如果有人有兴趣重现这个问题，下面是完整的申请代码：）

import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.Separator;
import javafx.scene.control.TextField;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class GUI extends Application
{

    public static void main(String[] args) 
    {
        launch(args);
    }

    @Override
    public void start(Stage frame) throws Exception 
    {   
        VBox main=new VBox();
        ScrollPane sp = new ScrollPane(main);

        Label header=new Label();
        Label performers=new Label();
        Label crew=new Label();

        TextField title=new TextField();
        TextField subtitle=new TextField();
        TextField roleLabel=new TextField();
        TextField role=new TextField();
        TextField actor=new TextField();
        TextField crewLabel=new TextField();
        TextField job=new TextField();
        TextField name=new TextField();

        Button save=new Button("Speichern ->");
        Button clear=new Button("Clear");

        BorderPane head=new BorderPane();
        BorderPane performersPane=new BorderPane();
        BorderPane crewPane=new BorderPane();
        BorderPane btns=new BorderPane();

        GridPane performersGrid=new GridPane();
        GridPane crewGrid=new GridPane();

        ColumnConstraints col1=new ColumnConstraints();
        ColumnConstraints col2=new ColumnConstraints();
        col1.setPercentWidth(60);

        //Preview Area
        Preview preview=new Preview();

        //Root Pane
        BorderPane root=new BorderPane();

        frame.setTitle("End Credits Generator");

        //VBox Elements
        header.setText("Titel/Untertitel");
        title.setPromptText("Titel des Films eingeben");
        subtitle.setPromptText("Untertitel des Films eingeben");

        performers.setText("Schauspieler");
        roleLabel.setPromptText(performers.getText()+" ändern");
        role.setPromptText("Name des Schauspieler eingeben");
        actor.setPromptText("Name des Schauspieler eingeben");

        crew.setText("Crew");
        crewLabel.setPromptText(crew.getText()+" ändern");
        job.setPromptText("Name des Departments eingeben");
        name.setPromptText("Name der Mitarbeiter eingeben");

        BorderPane.setAlignment(header,Pos.TOP_CENTER);
        BorderPane.setMargin(header,new Insets(5,0,5,0));
        BorderPane.setMargin(title,new Insets(5,0,5,0));
        BorderPane.setMargin(subtitle,new Insets(5,0,5,0));
        head.setTop(header);
        head.setCenter(title);
        head.setBottom(subtitle);

        performersGrid.getColumnConstraints().addAll(col1,col2);
        GridPane.setHalignment(performers,HPos.CENTER);
        performersGrid.add(performers,0,0);
        performersGrid.add(roleLabel,1,0);
        performersGrid.add(role,0,1,2,1);
        performersGrid.add(actor,0,2,2,1);
        performersPane.setCenter(performersGrid);

        crewGrid.getColumnConstraints().addAll(col1,col2);
        GridPane.setHalignment(crew,HPos.CENTER);
        crewGrid.add(crew,0,0);
        crewGrid.add(crewLabel,1,0);
        crewGrid.add(job,0,1,2,1);
        crewGrid.add(name,0,2,2,1);
        crewPane.setCenter(crewGrid);

        btns.setPadding(new Insets(10));
        btns.setRight(save);
        btns.setLeft(clear);

        //Layout of VBox
        main.setPrefWidth(500);
        main.setAlignment(Pos.TOP_CENTER);
        main.getChildren().addAll(head,new Separator(),performersPane,new Separator(),crewGrid,new Separator());

        //Layout of Application
        root.setCenter(preview.area());
        root.setRight(sp);
        root.setBottom(btns);

        //preview.placeCanvas();

        title.focusedProperty().addListener((obs, outFocus, inFocus) ->
        {
            if(outFocus)
            {
                preview.placeCanvas();
                Alert placed=new Alert(AlertType.CONFIRMATION,"Placed Canvas!",ButtonType.OK);
                placed.showAndWait();
            }   
        });

        Scene ui=new Scene(root);
        main.requestFocus();
        frame.setScene(ui);
        frame.setMaximized(true);

        frame.show();
    }
}

import javafx.scene.Node;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;

public class Preview
{
    Canvas can=new Canvas();
    GraphicsContext gc=can.getGraphicsContext2D();
    Pane canvas=new Pane();

    int WIDTH=1920;
    int HEIGHT=1080;
    int y=50;

    public Node area()
    {
        BorderPane container=new BorderPane();
        ScrollPane sp = new ScrollPane(can);
        sp.setFitToHeight(true);
        sp.setFitToWidth(true);

        sp.setStyle("-fx-background: black;");
        container.setCenter(sp);
        return container;
    }

    public void placeCanvas()
    {
        can.setHeight(100);
        can.setWidth(100);
        gc.setFill(Color.BLUE);
        gc.fillRect(0,0,100,100);
        canvas.getChildren().add(can);
    }
}

使用focusedproperty（）监听器时出现问题

0 个答案: