The Android coordinate system
As you will see, drawing a bitmap graphic is trivial. However, the coordinate system that we use to draw our graphics on requires a brief explanation.
Plotting and drawing
When we draw a bitmap graphic on the screen, we pass in the coordinates that we want to draw the object to. The available coordinates of a given Android device depend upon the resolution of its screen.
For example, the Google Pixel phone has a screen resolution of 1,920 pixels (across) by 1,080 pixels (down) when held in landscape orientation.
The numbering system of these coordinates starts in the top left-hand corner at 0,0, and proceeds downward and to the right until the bottom-right corner is pixel 1919, 1079. The apparent 1-pixel disparity between 1,920/1,919 and 1,080/1,079 is because the numbering starts at 0.
So, when we draw a bitmap graphic or anything else on the screen (such as Canvas circles and rectangles), we must specify an x, y coordinate.
Furthermore, a bitmap graphic (or...
