AChartEngine transparent background
Try setMarginsColor(Color.argb(0x00, 0x01, 0x01, 0x01)); It looks like there's a bug when setting the color as black transparent
If you want to set transparent background color, you can try:
renderer.setMarginsColor(Color.argb(0x00, 0xff, 0x00, 0x00));
It just be work for me!