How to boost android canvas performance with a buffered Image

When it comes to drawing to canvas on android one very big performance boost can be gained by using a buffered bitmap image. The idea is to draw lines to a bitmap. And then draw the bitmap to the screen.
This approach avoids unnecessarily redrawing elements that has been drawn already multiple times.

1) Create a bitmap in your view.

2) Remember all touch events.

3) Process all touch events. (Draw lines or something)

4) Draw to buffered bitmap image.

lineManager.draw():

5) And finally draw the buffered bitmap image.

Bonus: invalidate canvas only around finger area and only every 90 milliseconds.

See also

Performance in 2D Canvas App / Game on Android and Traceview War Story