Drawable Resources
See also
A drawable resource is a general concept for a graphic that can be drawn to the screen and which you can retrieve with APIs such as getDrawable(int) or apply to another XML resource with attributes such as android:drawable and android:icon . There are several different types of drawables:
Bitmap File A bitmap graphic file ( .png , .jpg , or .gif ). Creates a BitmapDrawable . Nine-Patch File A PNG file with stretchable regions to allow image resizing based on content ( .9.png ). Creates a NinePatchDrawable . Layer List A Drawable that manages an array of other Drawables. These are drawn in array order, so the element with the largest index is be drawn on top. Creates a LayerDrawable . State List An XML file that references different bitmap graphics for different states (for example, to use a different image when a button is pressed). Creates a StateListDrawable . Level List An XML file that defines a drawable that manages a number of alternate Drawables, each assigned a maximum numerical value. Creates a LevelListDrawable . Transition Drawable An XML file that defines a drawable that can cross-fade between two drawable resources. Creates a TransitionDrawable . Inset Drawable An XML file that defines a drawable that insets another drawable by a specified distance. This is useful when a View needs a background drawble that is smaller than the View’s actual bounds. Clip Drawable An XML file that defines a drawable that clips another Drawable based on this Drawable’s current level value. Creates a ClipDrawable . Scale Drawable An XML file that defines a drawable that changes the size of another Drawable based on its current level value. Creates a ScaleDrawable Shape Drawable An XML file that defines a geometric shape, including colors and gradients. Creates a ShapeDrawable .
Also see the Animation Resource document for how to create an AnimationDrawable .
Note: A color resource can also be used as a drawable in XML. For example, when creating a state list drawable, you can reference a color resource for the android:drawable attribute ( android:drawable=»@color/green» ).
Bitmap
A bitmap image. Android supports bitmap files in three formats: .png (preferred), .jpg (acceptable), .gif (discouraged).
You can reference a bitmap file directly, using the filename as the resource ID, or create an alias resource ID in XML.
Note: Bitmap files may be automatically optimized with lossless image compression by the aapt tool during the build process. For example, a true-color PNG that does not require more than 256 colors may be converted to an 8-bit PNG with a color palette. This will result in an image of equal quality but which requires less memory. So be aware that the image binaries placed in this directory can change during the build. If you plan on reading an image as a bit stream in order to convert it to a bitmap, put your images in the res/raw/ folder instead, where they will not be optimized.
Bitmap File
A bitmap file is a .png , .jpg , or .gif file. Android creates a Drawable resource for any of these files when you save them in the res/drawable/ directory.
file location: res/drawable/filename.png ( .png , .jpg , or .gif )
The filename is used as the resource ID. compiled resource datatype: Resource pointer to a BitmapDrawable . resource reference: In Java: R.drawable.filename
In XML: @[package:]drawable/filename example: With an image saved at res/drawable/myimage.png , this layout XML applies the image to a View:
The following application code retrieves the image as a Drawable :
XML Bitmap
An XML bitmap is a resource defined in XML that points to a bitmap file. The effect is an alias for a raw bitmap file. The XML can specify additional properties for the bitmap such as dithering and tiling.
Note: You can use a element as a child of an element. For example, when creating a state list or layer list, you can exclude the android:drawable attribute from an element and nest a inside it that defines the drawable item.
file location: res/drawable/filename.xml
The filename is used as the resource ID. compiled resource datatype: Resource pointer to a BitmapDrawable . resource reference: In Java: R.drawable.filename
In XML: @[package:]drawable/filename syntax: elements: Defines the bitmap source and its properties.
xmlns:android String. Defines the XML namespace, which must be «http://schemas.android.com/apk/res/android» . This is required only if the is the root element—it is not needed when the is nested inside an . android:src Drawable resource. Required. Reference to a drawable resource. android:antialias Boolean. Enables or disables antialiasing. android:dither Boolean. Enables or disables dithering of the bitmap if the bitmap does not have the same pixel configuration as the screen (for instance: a ARGB 8888 bitmap with an RGB 565 screen). android:filter Boolean. Enables or disables bitmap filtering. Filtering is used when the bitmap is shrunk or stretched to smooth its apperance. android:gravity Keyword. Defines the gravity for the bitmap. The gravity indicates where to position the drawable in its container if the bitmap is smaller than the container.
Must be one or more (separated by ‘|’) of the following constant values:
| Value | Description |
|---|---|
| top | Put the object at the top of its container, not changing its size. |
| bottom | Put the object at the bottom of its container, not changing its size. |
| left | Put the object at the left edge of its container, not changing its size. |
| right | Put the object at the right edge of its container, not changing its size. |
| center_vertical | Place object in the vertical center of its container, not changing its size. |
| fill_vertical | Grow the vertical size of the object if needed so it completely fills its container. |
| center_horizontal | Place object in the horizontal center of its container, not changing its size. |
| fill_horizontal | Grow the horizontal size of the object if needed so it completely fills its container. |
| center | Place the object in the center of its container in both the vertical and horizontal axis, not changing its size. |
| fill | Grow the horizontal and vertical size of the object if needed so it completely fills its container. This is the default. |
| clip_vertical | Additional option that can be set to have the top and/or bottom edges of the child clipped to its container’s bounds. The clip is based on the vertical gravity: a top gravity clips the bottom edge, a bottom gravity clips the top edge, and neither clips both edges. |
| clip_horizontal | Additional option that can be set to have the left and/or right edges of the child clipped to its container’s bounds. The clip is based on the horizontal gravity: a left gravity clips the right edge, a right gravity clips the left edge, and neither clips both edges. |
android:mipMap Boolean. Enables or disables the mipmap hint. See setHasMipMap() for more information. Default value is false. android:tileMode Keyword. Defines the tile mode. When the tile mode is enabled, the bitmap is repeated. Gravity is ignored when the tile mode is enabled.
Must be one of the following constant values:
| Value | Description |
|---|---|
| disabled | Do not tile the bitmap. This is the default value. |
| clamp | Replicates the edge color if the shader draws outside of its original bounds |
| repeat | Repeats the shader’s image horizontally and vertically. |
| mirror | Repeats the shader’s image horizontally and vertically, alternating mirror images so that adjacent images always seam. |
example: see also:
- BitmapDrawable
- Creating alias resources
Nine-Patch
A NinePatch is a PNG image in which you can define stretchable regions that Android scales when content within the View exceeds the normal image bounds. You typically assign this type of image as the background of a View that has at least one dimension set to «wrap_content» , and when the View grows to accomodate the content, the Nine-Patch image is also scaled to match the size of the View. An example use of a Nine-Patch image is the background used by Android’s standard Button widget, which must stretch to accommodate the text (or image) inside the button.
Same as with a normal bitmap, you can reference a Nine-Patch file directly or from a resource defined by XML.
For a complete discussion about how to create a Nine-Patch file with stretchable regions, see the 2D Graphics document.
Nine-Patch File
XML Nine-Patch
An XML Nine-Patch is a resource defined in XML that points to a Nine-Patch file. The XML can specify dithering for the image.
file location: res/drawable/filename.xml
The filename is used as the resource ID. compiled resource datatype: Resource pointer to a NinePatchDrawable . resource reference: In Java: R.drawable.filename
In XML: @[package:]drawable/filename syntax: elements: Defines the Nine-Patch source and its properties.
xmlns:android String. Required. Defines the XML namespace, which must be «http://schemas.android.com/apk/res/android» . android:src Drawable resource. Required. Reference to a Nine-Patch file. android:dither Boolean. Enables or disables dithering of the bitmap if the bitmap does not have the same pixel configuration as the screen (for instance: a ARGB 8888 bitmap with an RGB 565 screen). example:
Layer List
A LayerDrawable is a drawable object that manages an array of other drawables. Each drawable in the list is drawn in the order of the list—the last drawable in the list is drawn on top.
Each drawable is represented by an element inside a single element.
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How to Create Drawable Resource XML File in Android Studio?
A drawable resource is a common concept for a graphic that can be drawn to the screen and which one can retrieve with APIs such as getDrawable(int) or apply to another XML resource with attributes such as android:drawable and android:icon. There are several different types of drawable resources files and let’s discuss all the types in a tabular manner.
Drawable Resources Files
As it is known to all that Android Studio is the official integrated development environment for Google’s Android operating system, built on JetBrains’ IntelliJ IDEA software and designed specifically for Android development. So as a beginner in android app development , the developer should know about the tools vividly before building some awesome projects in Android. So in this article let’s learn to create a drawable resource XML file in Android Studio. Drawable Resource XML is mostly created in the drawable folder and is used in Android to add more customization for views. Here is the step by step process to create a new Drawable Resource XML in Android Studio.
Step by Step Process to Create a New Drawable Resource XML in Android Studio
Step 1: Go to the app > res > drawable and right-click on it. Please refer to the screenshot below to get a clear cut view of the steps.
Step 2: After right-clicking on the drawable file go to New > Drawable resource file as shown in the figure below.
Step 3: When you click on the Drawable resource file a dialog box will open on your compute screen. Enter the file name in the text box and then click on OK.
Note: File names must start with a lowercase letter.
Step 4: After that the drawable resource XML file will be created and one can find the file in app > res > drawable as shown in the figure below. In this case, we have named the file as round_button as shown in the above image.
Step 5: Now click on the file name and one can customize the views by writing the necessary codes inside this file.
After doing all the steps the important questions arise are why to create a drawable resource XML file in Andoird? What’s its application? To get the answer to these questions please refer to this article to get a clear-cut idea about its real usage.
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