Drawing dashed line in java

Question

My problem is that I want to draw a dashed line in a panel. I'm able to do it, but it drew my border in a dashed line as well.

Can someone please explain why? I'm using paintComponent to draw and draw straight to the panel.

This is the code to draw a dashed line:

public void drawDashedLine(Graphics g, int x1, int y1, int x2, int y2){         Graphics2D g2d = (Graphics2D) g;         //float dash[] = {10.0f};         Stroke dashed = new BasicStroke(3, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL, 0, new float[]{9}, 0);         g2d.setStroke(dashed);         g2d.drawLine(x1, y1, x2, y2);     } 

Answer 1

You're modifying the Graphics instance passed into paintComponent(), which is also used to paint the borders.

Instead, make a copy of the Graphics instance and use that to do your drawing:

public void drawDashedLine(Graphics g, int x1, int y1, int x2, int y2){    // Create a copy of the Graphics instance   Graphics2D g2d = (Graphics2D) g.create();    // Set the stroke of the copy, not the original    Stroke dashed = new BasicStroke(3, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL,                                   0, new float[]{9}, 0);   g2d.setStroke(dashed);    // Draw to the copy   g2d.drawLine(x1, y1, x2, y2);    // Get rid of the copy   g2d.dispose(); } 

Answer 2

Another possibility would be to store the values used in swap local variables (Ex. Color , Stroke etc...) and set them back to the on use Graphics.

something like :

Color original = g.getColor(); g.setColor( // your color //);  // your drawings stuff  g.setColor(original); 

this will work for whatever change you decide to do to the Graphics.