java - 自制油漆应用程序中的绘图错误

Question

我有一个愚蠢的错误，我无法在用 Java 开发的类似 Paint 的应用程序中弄清楚。我现在的问题是，当我绘制形状(比如说矩形)时，矩形应该在所有 4 个方向上绘制(无论拖动什么方式)，但现在它仅在右下方向上绘制。我把它编码为所有方向。在找出错误时，我意识到当您向左上方拖动时，初始 x 和 y 会取 x2、y2 的值​​。我不知道为什么会发生这种情况，因为我没有代码可以做到这一点。请帮忙，我整夜都在处理这个错误((

这个类负责所有的形状

public abstract class DrawShapes implements DrawListenerInterface {

private final Canvas canvas;

protected int x;
protected int y;
protected int x2;
protected int y2;
protected int w;
private boolean prev;

protected int h;

public DrawShapes(Canvas canvas) {
    this.canvas = canvas;
}

@Override
public void preview(Graphics2D g2) {
    g2.setColor(Color.black);
    if (prev) {
        draw(g2);
    }
}

@Override
public void draw(Graphics2D g2) {

    System.out.println("before " + x + " " + y + " " + x2 + " " + y2);
    x = Math.min(x, x2);
    y = Math.min(y, y2);
    w = Math.abs(x - x2);
    h = Math.abs(y - y2);
    //
    System.out.println("after " + x + " " + y + " " + x2 + " " + y2);

}

@Override
public void mousePressed(MouseEvent e) {
    prev = true;

    this.x = e.getX();
    this.y = e.getY();
    this.x2 = e.getX();
    this.y2 = e.getY();
    System.out.println("PRESSED " + x + " " + x2 + " " + y + " " + y2);

    canvas.repaint();
}

@Override
public void mouseReleased(MouseEvent e) {

    // this.x2 = e.getX();
    // this.y2 = e.getY();
    final Graphics2D g2 = (Graphics2D) canvas.getImage().getGraphics();
    canvas.defaultSettings(g2);
    prev = false;
    draw(g2);
    // canvas.repaint();

}

@Override
public void mouseDragged(MouseEvent e) {

    this.x2 = e.getX();
    this.y2 = e.getY();
    System.out.println("dragging " + x2 + " " + y2);
    this.canvas.repaint();

}

这个类是 DrawShapes 的子类，它正在绘制自己的形状

public class SquareListener extends DrawShapes {



@Override
public void draw(Graphics2D g2) {
    // TODO Auto-generated method stub

    super.draw(g2);
        g2.drawRect(x, y, w, h);
// System.out.println(x + " " + y + " " + x2 + " " + y2);
}

Answer 1

您必须将 X1 与 X2 以及 Y1 与 Y2 进行比较，如果 *1 > *2 - 将它们交换为 drawRect()。