I am trying to draw the line in the middle. I tried different coordinates

问题

Here is my paintComponent which contains the coordinates

public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g; 
        g2.drawLine(-100,0,500,0);
        g2.drawLine(141,-500,141,500);
        g2.translate(getWidth()/2.0, getHeight()/2.0);
        g2.scale(1,-1);
        g2.rotate(45*Math.PI/180);
        Rectangle2D r = new Rectangle2D.Double(0,0,100,100);
        g2.fill(r);

回答1:

It's a bit of a cheat, but...

protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g.create();
    g2.drawLine(getWidth() / 2, 0, getWidth() / 2, getHeight());
    g2.drawLine(0, getHeight() / 2, getWidth(), getHeight()/ 2);
    g2.translate(getWidth() / 2.0, (getHeight() / 2.0));
    g2.scale(1, -1);
    g2.rotate(45 * Math.PI / 180);
    Rectangle2D r = new Rectangle2D.Double(-50, -50, 100, 100);
    g2.fill(r);
    g2.dispose();
}

Basically, the origin point is now the center of the screen, so in order to draw the rectangle "centered" around the origin point, you need to adjust the x/y accordingly

Now, you also adjust the origin point by 50x50 instead, but then you'd need to change the anchor point around which the Graphics context is rotated to the center of the box

protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g.create();
    g2.drawLine(getWidth() / 2, 0, getWidth() / 2, getHeight());
    g2.drawLine(0, getHeight() / 2, getWidth(), getHeight()/ 2);
    g2.translate((getWidth() / 2.0) - 50, (getHeight() / 2.0) - 50);
    g2.scale(1, -1);
    g2.rotate(45 * Math.PI / 180, 50, 50);
    Rectangle2D r = new Rectangle2D.Double(0, 0, 100, 100);
    g2.fill(r);
    g2.dispose();
}

来源：https://stackoverflow.com/questions/32774263/i-am-trying-to-draw-the-line-in-the-middle-i-tried-different-coordinates

标签

java

swing

paintcomponent