Android DPI - a lie?

So I create sets of assets for an Android UI - 320 x 400 & 480 x 800 both of these at 160 and 240 dpi...

After Drawing some of the assets as 9 patch a weird thing happene开发者_JS百科d. The 9 patch graphics all 'came out' as 72 dpi but with different dimensions!

So my conclusion is that android asset creation works similiar to iPhone. Creatings assets to dimensions and ignore DPI (using 72 as a base - as this is what the 9 patch programme converted them too!) RIGHT?

Anyone else experimented with this?

Just think for a minute about what DPI is. Dots per Inch. For displays, it's actually Pixels per Inch, or PPI.

A 320 pixel wide image at 160 pixels per inch is 320 pixels wide. How many pixels wide is a 320 pixel image at 240 pixels? The PPI density only matters on the actual output device. Your display has a fixed number of pixels at a fixed physical size. The number of pixels that fit into 1 inch is its PPI density. The reason this is modifiable for graphics is for when the density can differ. Most commonly, this is for printing (which is where the dots come in). Most printers can print at a variety of resolutions. The typical is something like 300 dpi for images, 1200 dpi or higher for vector graphics and line art. When you set the dpi before printing an image, it tells the printer how many dots per inch it should lay out. The higher the dpi, the sharper the image -- assuming the input image is actually large enough to accomodate this resolution.