JavaFX -移除形状与按钮setOnAction

Question

我正在尝试创建一个应用程序，其中用户输入一些方面，并在单击按钮时，从场景中删除任何当前形状，并生成具有指定数量的方面的形状。

虽然生成形状的逻辑正在工作，但实现root.getChildren().remove(shape);似乎没有工作?

public class genShape extends Application 
{
@Override    
public void start(Stage stage) 
{       
// configure text fields for input         
TextField shapeNoSidesField = new TextField();         
shapeNoSidesField.setMaxWidth(23);         

// configure label fields        
Label shapeNoSidesLabel = new Label("Enter Desired Number Of Shape Sides:");         
shapeNoSidesLabel.setTextFill(Color.RED);         
shapeNoSidesLabel.setFont(Font.font("Arial", 10));   
// configure generate shape button         
Button generateShapeButton = new Button();         
generateShapeButton.setText("Generate Shape");

// configure an HBox input components                       
HBox inputComponents = new HBox(40);
inputComponents.setAlignment(Pos.CENTER);        
inputComponents.getChildren().addAll(shapeNoSidesLabel, shapeNoSidesField);  

// configure vbox
VBox root = new VBox(50);         
root.setAlignment(Pos.CENTER);        
root.getChildren().addAll(inputComponents, generateShapeButton); 


// Generate shape based on user Integral input. Perform input checks.
generateShapeButton.setOnAction( e ->                     
{   
Shape shape = null;
root.getChildren().remove(shape);
// Perform input checks using helper variables. Assert no of sides field not null.
boolean shapeFieldIsEmpty = shapeNoSidesField.getText().isEmpty();
if(shapeFieldIsEmpty)        
{                               
System.out.println("Number of Sides Field Cannot Be Empty. Please Enter a Number Between 3 and 5 Inclusive.");
display.setText("Number of Sides Field Cannot Be Empty. Please Enter a Number Between 3 and 5 Inclusive.");
}
else 
{
// Retrieve user required number of sides
int numberOfSides = Integer.parseInt(shapeNoSidesField.getText());
switch(numberOfSides) 
{
// User enters shape requirement of three sides (Polygon object)
case 3:
shape = new Polygon();
((Polygon) shape).getPoints().addAll(new Double[]
{
100., 70.,
100., 250.,
400., 250.
});
root.getChildren().add(shape);
break;
case 4:
shape = new Rectangle();
((Rectangle) shape).setX(150f);
((Rectangle) shape).setY(75.0f); 
((Rectangle) shape).setWidth(300.0f); 
((Rectangle) shape).setHeight(150.0f);
root.getChildren().add(shape);
break;
default:
break;
}

}                                                                        
}                                     
); 

// create a new scene and add it to the stage         
Scene scene = new Scene(root, 500, 500);         
stage.setScene(scene);         
stage.setTitle("Shapes");        
stage.show();             
}
public static void main(String[] args) 
{
// TODO Auto-generated method stub
launch(args);     
}
}

任何帮助都非常感激，谢谢!

Answer 1

将shape设置为实例变量。还需要注意的是，没有必要使用所有丑陋的向下转换。

public class GenShape extends Application 
{
private Shape shape ;
@Override    
public void start(Stage stage) 
{       
// configure text fields for input         
TextField shapeNoSidesField = new TextField();         
shapeNoSidesField.setMaxWidth(23);         

// configure label fields        
Label shapeNoSidesLabel = new Label("Enter Desired Number Of Shape Sides:");         
shapeNoSidesLabel.setTextFill(Color.RED);         
shapeNoSidesLabel.setFont(Font.font("Arial", 10));   
// configure generate shape button         
Button generateShapeButton = new Button();         
generateShapeButton.setText("Generate Shape");

// configure an HBox input components                       
HBox inputComponents = new HBox(40);
inputComponents.setAlignment(Pos.CENTER);        
inputComponents.getChildren().addAll(shapeNoSidesLabel, shapeNoSidesField);  

// configure vbox
VBox root = new VBox(50);         
root.setAlignment(Pos.CENTER);        
root.getChildren().addAll(inputComponents, generateShapeButton); 


// Generate shape based on user Integral input. Perform input checks.
generateShapeButton.setOnAction( e ->                     
{   
if (shape != null) {
root.getChildren().remove(shape);
}
// Perform input checks using helper variables. Assert no of sides field not null.
boolean shapeFieldIsEmpty = shapeNoSidesField.getText().isEmpty();
if(shapeFieldIsEmpty)        
{                               
System.out.println("Number of Sides Field Cannot Be Empty. Please Enter a Number Between 3 and 5 Inclusive.");
display.setText("Number of Sides Field Cannot Be Empty. Please Enter a Number Between 3 and 5 Inclusive.");
}
else 
{
// Retrieve user required number of sides
int numberOfSides = Integer.parseInt(shapeNoSidesField.getText());
switch(numberOfSides) 
{
// User enters shape requirement of three sides (Polygon object)
case 3:
Polygon poly = new Polygon();
poly.getPoints().addAll(new Double[]
{
100., 70.,
100., 250.,
400., 250.
});
root.getChildren().add(poly);
this.shape = poly ;
break;
case 4:
Rectangle rect = new Rectangle();
rect.setX(150f);
rect.setY(75.0f); 
rect.setWidth(300.0f); 
rect.setHeight(150.0f);
root.getChildren().add(rect);
this.shape = rect ;
break;
default:
break;
}

}                                                                        
}                                     
); 

// create a new scene and add it to the stage         
Scene scene = new Scene(root, 500, 500);         
stage.setScene(scene);         
stage.setTitle("Shapes");        
stage.show();             
}
public static void main(String[] args) 
{
// TODO Auto-generated method stub
launch(args);     
}
}