Android: Handling images size for multiple screens

Question

I find it really hard to handle images with Android, I think it's the hardest part of Android development...

1) I have an image, I want it to be the background of my application so I do

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context=".MainActivity" 
    android:background="@drawable/accueil">
</RelativeLayout>

The background should fill the entire screen but it's not the cas. Only a part of the background is shown on some (small) screens. How could I say: I want the image to fill all the screen even if the image is bigger then the screen the image should be reduced so I see all the background?

Maybe I should put my background instead of using it as a background

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context=".MainActivity">


       <ImageView
           android:id="@+id/imageView1"
           android:layout_width="500dp"
           android:layout_height="500dp"
           android:adjustViewBounds="false"
           android:src="@drawable/accueil" />

</RelativeLayout>

Yet in some devices the image is a bit cropped.

2) I have to place a layout in another layout but I want its position to be precise, its width to be relative to the parent layout. Yet if I do

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/fond">

 <LinearLayout
     android:layout_width="300dp"
     android:layout_height="350dp"
     android:layout_marginTop="20dp"
     android:background="@drawable/fondshare"
     android:orientation="vertical" >

you can see the result is not what I expected (the linear layout being the rectangle with the smiley and all the buttons)

Answer 1

Android categorizes device screens using two general properties: size and density. You should expect that your app will be installed on devices with screens that range in both size and density. As such, you should include some alternative resources that optimize your app’s appearance for different screen sizes and densities. There are four generalized sizes: small, normal, large, xlargeAnd four generalized densities: low (ldpi), medium (mdpi), high (hdpi), extra high (xhdpi)

To declare different layouts and bitmaps you'd like to use for different screens, you must place these alternative resources in separate directories, similar to how you do for different language strings.

Also be aware that the screens orientation (landscape or portrait) is considered a variation of screen size, so many apps should revise the layout to optimize the user experience in each orientation.

See android.com's "Supporting Different Screens" article for more information.