How to set the layout_width = screen_width ? And how to manage good size for image compared to the device?
<p>I already read a lot of threads on stackOverflow but I didn't find what I was searching for. I already read too the official documentation but I steel have some questions.</p>

<p>I'm trying to insert some image in my application and I'm trying to make the layout_width to the image equals to the width screen size (in portrait). </p>

<p>So I make many different size for the same image and I put them in
drawable-ldpi, drawable-hdpi .... 
But when I'm trying my image on the emulator (hdpi) it works fine, but when I'm trying this on my tablet (hdpi too) the image don't get all the width screen.</p>

<p>I would like to know if I have to do multiple drawable about the screen size ?
and so then what about the drawable about the dpi ?</p>

<p>I know it's possible to put some vector image but I would like to know if I can choose the layout_width like this: android:layout_width = screen width.</p>

<p>and why is it so important to set the density ? A big tablet can be in mdpi et a phone on hdpi... what is so important in the density ?</p>