Question

I have read the “screen support API guide “(http://developer.android.com/guide/practices/screens_support.html) and much more resources, but I cannot understand how the dpi works.

I’m developing a game, and I’m not using any layouts (I’m going to draw all myself with functions like canvas.drawbitmap). But when I use the Canvas.Drawbitmap function I need to specify the pixels of the screen where I want to draw the image.

So I’m working now with a fixed resolution (1280×800) and I’m using the drawable-nodpi folder and adjusting the canvas later if the screen of the phone is wider or narrow. The problem with that is that the images look horrible when the resolution is not the native one (1280×800).

What can I do to solve this problem? I’ve read and read during 3 days, but all explanations and examples are related to Layouts, Nine Patches and so.

Answer 1

Get the density of the device being used and multiply that density by some base size that you pick (how big or small do you actually want it to be drawn?)

Example:

float objectToDrawHeight = 50; //Specified in plain pixels
float objectToDrawWidth = 50; //Specified in plain pixels

float density = getResources().getDisplayMetrics().density;
objectToDrawHeight *= density;
objectToDrawWidth *= density;

//Draw your object using the new (scaled) height and width
//If you are worried about how the object will look on different aspect ratio devices
//  you can get the screen dimensions and use that ratio as a multiplier
//  just as you did with density

Display display = ((Activity)context).getWindowManager().getDefaultDisplay();
float screenDimensionX = display.getWidth();
float screenDimensionY = display.getHeight();

Using density and possibly screen dimensions should allow you to draw anything and keep it scaled correctly. When using canvas, assume everything is in pixels, and that you must do the dpi conversion.