java - Java中如何使图像居中？

Question

我想将现有三角形居中。提示要求三角形的底边为 Canvas 的长度，顶点接触顶部并居中。这是一个类，并且给出了代码。

public class Triangle {
    private int height;
    private int width;
    private int xPosition;
    private int yPosition;
    private String color;
    private boolean isVisible;

    public Triangle() {
        height = 270;
        width = 270;
        xPosition = 120;
        yPosition = 120;
        color = "green";
        isVisible = false;
    }

    public void makeVisible() {
        isVisible = true;
        draw();
    }

    public void makeInvisible() {
        erase();
        isVisible = false;
    }

    public void moveRight() {
        moveHorizontal(20);
    }

    public void moveLeft() {
        moveHorizontal(-20);
    }

    public void moveUp() {
        moveVertical(-20);
    }

    public void moveDown() {
        moveVertical(20);
    }

    public void moveHorizontal(int distance) {
        erase();
        xPosition += distance;
        draw();
    }

    public void moveVertical(int distance) {
        erase();
        yPosition += distance;
        draw();
    }

    public void slowMoveHorizontal(int distance) {
        int delta;

        if(distance < 0) {
            delta = -1;
            distance = -distance;
        }
        else {
            delta = 1;
        }

        for(int i = 0; i < distance; i++) {
            xPosition += delta;
            draw();
        }
    }

    public void slowMoveVertical(int distance) {
        int delta;

        if(distance < 0) {
            delta = -1;
            distance = -distance;
        }
        else  {
            delta = 1;
        }

        for(int i = 0; i < distance; i++) {
            yPosition += delta;
            draw();
        }
    }

    public void changeSize(int newHeight, int newWidth) {
        erase();
        height = newHeight;
        width = newWidth;
        draw();
    }

    public void changeColor(String newColor) {
        color = newColor;
        draw();
    }

    private void draw() {
        if(isVisible) {
            Canvas canvas = Canvas.getCanvas();
            int[] xpoints = { xPosition, xPosition + (width/2), xPosition + width };
            int[] ypoints = { yPosition + height, yPosition, yPosition + height};
            canvas.draw(this, color, new Polygon(xpoints, ypoints, 3));
            canvas.wait(10);
        }
    }

    private void erase() {
        if(isVisible) {
            Canvas canvas = Canvas.getCanvas();
            canvas.erase(this);
        }
    }
}

Answer 1

三角形的中心位于

xPosition + (width / 2)
yPosition + (height / 2)

要“居中”，您需要移动水平/移动垂直，直到三角形的中心位于要居中的空间的中心