Question

Trying to use LayerDrawable (defined in XML as layer-list) to layer several shape drawables onto one another; to be used as a background for a layout.

The Android guide (for LayerList) says:

All drawable items are scaled to fit the size of the containing View,
by default. Thus, placing your images in a layer list at different
positions might increase the size of the View and some images scale as
appropriate. To avoid scaling items in the list, use a <bitmap>
element inside the <item> element to specify the drawable and define
the gravity to something that does not scale, such as “center”.

I don’t want my shapes to scale, but I’m unsure how to wrap them in bitmap tags correctly: it produces an error if I do it as follows:

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <bitmap
            android:src="@drawable/layer_one"
            android:gravity="center" />
    </item>
    <item>
        <bitmap
            android:src="@drawable/layer_two"
            android:gravity="center" />
    </item>
    <item>
        <bitmap
            android:src="@drawable/layer_three"
            android:gravity="center" />
    </item>
    <item>
        <bitmap
            android:src="@drawable/layer_four"
            android:gravity="center" />
    </item>
</layer-list>

Complaining:

Binary XML file line #25: <bitmap> requires a valid src attribute

An example of one of the drawables, e.g. res/drawable/layer_one.xml:

<?xml version="1.0" encoding="utf-8"?>

<!--  res/drawable/layer_one.xml -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <solid android:color="#FFFFFF"/>
    <corners
        android:bottomRightRadius="15dp"
        android:bottomLeftRadius="15dp"
        android:topLeftRadius="15dp"
        android:topRightRadius="15dp" />
</shape>

The example used on the Android site uses images as drawables, not XML-defined shapes (not to say that my error is specific to these, and that I haven’t made a silly mistake somewhere). Any clues appreciated, thanks.

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Using drawable resources
This question’s answer states that you cannot use an XML drawable as the src for a Bitmap. I’ve amended the title of the question, to now ask how you can prevent shapes from scaling (thereby resizing the container view) without using bitmap, or am I forced to use actual image resources?

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Added an image of the desired outcome – the ability to have a background with a regular rectangle filled shape or whatever, and then layered on top of this, more shape drawables (here there are 3 ellipses). On the left is ideal, where top and left offsets are allowed, and on the right is fine, where all shapes just go to a default position:

Answer 1

Yes, (as per my previous answer) you cant use xml drawable for bitmaps. It is fine to build, but when you run the app, it crashes.

Regarding the statement use a <bitmap> element inside the <item> element means that you can define further shapes in your layer-list and that’s what it is for. Though you can also define Bitmaps but then your bitmaps should have a src value referring to solid image (not xml).

What you can do is to insert the layer_one, layer_two and other layer’s xml into your layer_list xml. For example:

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item>
        <shape
            android:shape="rectangle" >
            <solid android:color="#FFFFFF" />

            <corners
                android:bottomLeftRadius="15dp"
                android:bottomRightRadius="15dp"
                android:topLeftRadius="15dp"
                android:topRightRadius="15dp" />
        </shape>
    </item>

    <!-- and so on with your other shapes -->

</layer-list>

Hope it should work 🙂