I am having an issue with drawing a cross with JavaFX

问题

I am trying to write code that will draw 3 shapes diagonally across a grid. The first two shapes are a square and a circle, which I was able to do.

The third shape, however, is giving me some grief. I am supposed to draw a cross (T version, not X), and every time I write out the code it comes out looking like a sideways, ⊢. I know I am just missing something simple, but I would really appreciate the help!

Here is the full code for my Shapes program.

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.paint.Color;

public class Shapes extends Application {

    public void start(Stage primaryStage) {
        // This will build the shapes which include a Square, Circle, and 2 Lines.
        // All shapes will have a width of 3.

        // This Rectangle will be colored like the Square on a playstation controller
        Rectangle square = new Rectangle(65, 65, 65, 65);
        square.setStroke(Color.rgb(243, 211, 234));
        square.setStrokeWidth(3);
        square.setFill(Color.rgb(243, 211, 234));

        // A circle colored like the Circle on the playstation controller.
        Circle circle = new Circle(40);
        circle.setStroke(Color.rgb(241, 188, 194));
        circle.setStrokeWidth(3);
        circle.setFill(Color.rgb(241, 188, 194));

        // Lines colored like the Cross button on a playstation controller.
        Line line1 = new Line(-50, 75, 50, 75);
        line1.setStroke(Color.rgb(165, 191, 214));
        line1.setStrokeWidth(3);

        Line line2 = new Line(0, 0, 0, 100);
        line2.setStroke(Color.rgb(165, 191, 214));
        line2.setStrokeWidth(3);


        // Setup the GridPane in the center of the stage which will also pad out from the edge of the window.
        GridPane pane = new GridPane();
        pane.setAlignment(Pos.CENTER);
        pane.setPadding(new Insets(11.5, 12.5, 13.5, 14.5));

        // Place each object in it's respective place on the pane.
        // Square top left, Circle, middle, Cross bottom right.
        pane.add(square, 0, 0);
        pane.add(circle, 1, 1);
        pane.add(line1, 2, 2);
        pane.add(line2, 2, 2);

        // Create the scene to display the program.
        Scene scene = new Scene(pane);
        primaryStage.setTitle("Shapes");
        primaryStage.setScene(scene);
        primaryStage.show();
        primaryStage.setResizable(false);
    }

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

And here is the specific snippet I am having trouble with.

// Lines colored like the Cross button on a playstation controller.
Line line1 = new Line(-50, 75, 50, 75);
line1.setStroke(Color.rgb(165, 191, 214));
line1.setStrokeWidth(3);

Line line2 = new Line(0, 0, 0, 100);
line2.setStroke(Color.rgb(165, 191, 214));
line2.setStrokeWidth(3);

I do need the horizontal line to be a bit higher up on the pane. It should resemble a "Christian cross."

Any help is much appreciated.

回答1:

It looks like the geometry is OK, but the alignment of line2 is wrong. Among the several ways to center it,

Set the alignment explicitly for the relevant GridPane child node:
```
pane.setHalignment(line2, HPos.CENTER);
```
Add the lines to a Pane having the desired layout; StackPane, for example, defaults to Pos.CENTER:
```
StackPane lines = new StackPane(line1, line2);
pane.add(lines, 2, 2);
```

As an aside, judicious use of constants will make tinkering a little easier. For example, use a scale value to keep sizes proportional, as shown here:

private static final int N = 50;
…
Rectangle square = new Rectangle(2 * N, 2 * N);
Circle circle = new Circle(N);
Line line1 = new Line(-N, 0, N, 0);
Line line2 = new Line(0, -N, 0, N);

I do need the horizontal line to be a bit higher up on the pane. It should resemble a "Christian cross."

Using the approach suggested by @fabian, adjust the horizontal line's endpoints as desired; note the changes for a Latin cross, seen in the image below:

Line line1 = new Line(-N, 0, N, 0); // Greek
Line line1 = new Line(-N, -N/3, N, -N/3); // Latin
…
pane.add(new Group(line1, line2), 2, 2);

回答2:

GridPane aligns it's children inside the cells you add them to. This results in the relative position of the Lines changing. To fix this I recommend wrapping the Lines in a parent that does not reposition it's children, e.g. Group.

The following change will result in a "christian cross"-like shape rotated by 180°.

// pane.add(line1, 2, 2);
// pane.add(line2, 2, 2);
pane.add(new Group(line1, line2), 2, 2);

来源：https://stackoverflow.com/questions/55661372/i-am-having-an-issue-with-drawing-a-cross-with-javafx

标签

java

javafx

shapes