Draw From Old Canvas - Android

Question

I\'m making an App that needs to be able to draw new graphics on top of the last set.

This is my current onDraw() method -

protected void onDraw(Canvas          


        

Answer 1

You will have to store the previous image persistently onto a ArrayList, and during ondraw, loop through the ArrayList to redraw all items.

something like this:

for (Graphic graphic : _graphics) {
    bitmap = graphic.getBitmap();
    coords = graphic.getCoordinates();
    canvas.drawBitmap(bitmap, coords.getX(), coords.getY(), null);
}

Answer 2

Found the answer myself :)

@Override
protected void onDraw(Canvas c) {

if(bitmap != null && canvas != null) { 
    canvas.drawLine(p1.x, p1.y, p2.x, p2.y, linePaint);
    c.drawBitmap(bitmap, 0, 0, linePaint);  
}
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

bitmap = Bitmap.createBitmap(width, height, Config.RGB_565);
canvas = new Canvas(bitmap);
canvas.drawColor(Color.WHITE);
}

Works exactly as intended, it creates the effect of drawing on top of the old canvas continuously