java - Panel not shown for 2D Animation -

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i trying create 2d animation in java of moving line on panel(a line moving 1 point in panel). hope possible. here's code used.

private void movingline(int length) throws interruptedexception {         for(int = 0; + length < width; i++){             for(int j = 0; j + length < height; j++){                  eraseline();                   drawline(color.cyan, i, j, i+length, j+length);                  erase = true;             }         }     }      private void eraseline() {         if(erase){             fillcanvas(color.blue);         }     }

on running code, panel doesn't show up.

here's code draw line.

 public void drawline(color c, int x1, int y1, int x2, int y2) {         int pix = c.getrgb();         int dx = x2 - x1;         int dy = y2 - y1;         canvas.setrgb(x1, y1, pix);         if (dx != 0) {             float m = (float) dy / (float) dx;             float b = y1 - m*x1;             dx = (x2 > x1) ? 1 : -1;             while (x1 != x2) {                 x1 += dx;                 y1 = math.round(m*x1 + b);                 canvas.setrgb(x1, y1, pix);             }         }         repaint();     }

on running code panel doesn't show moving line. appreciated.

i think biggest problem you're trying change appearance of gui (i'm guessing) thread that's not event dispatching thread.

the solution wrap activity (specifically, calls eraseline , drawline) in runnable , call runnable using swingutilities.invokeandwait().

edit: java's graphics components don't let manipulate canvas yourself. components drawing, , when called on paint themselves. directly drawing on canvas, if work, work badly because you'd interfering component does.

rather go lot more explanation, i've gone , implemented think "proper" way this.

http://pastebin.com/etfmkbjj

the coding's commented necessary, hope gives ideas. more background, read official tutorials on swing , graphics.


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