Android APIs
public class

ScaleDrawable

extends DrawableWrapper
java.lang.Object
   ↳ android.graphics.drawable.Drawable
     ↳ android.graphics.drawable.DrawableWrapper
       ↳ android.graphics.drawable.ScaleDrawable

Class Overview

A Drawable that changes the size of another Drawable based on its current level value. You can control how much the child Drawable changes in width and height based on the level, as well as a gravity to control where it is placed in its overall container. Most often used to implement things like progress bars.

It can be defined in an XML file with the <scale> element. For more information, see the guide to Drawable Resources.

Summary

XML Attributes
Attribute Name Related Method Description
android:drawable Reference to a drawable resource to draw with the specified scale. 
android:scaleGravity Specifies where the drawable is positioned after scaling. 
android:scaleHeight Scale height, expressed as a percentage of the drawable's bound. 
android:scaleWidth Scale width, expressed as a percentage of the drawable's bound. 
Public Constructors
ScaleDrawable(Drawable drawable, int gravity, float scaleWidth, float scaleHeight)
Creates a new scale drawable with the specified gravity and scale properties.
Public Methods
void applyTheme(Resources.Theme t)
Applies the specified theme to this Drawable and its children.
void draw(Canvas canvas)
Draw in its bounds (set via setBounds) respecting optional effects such as alpha (set via setAlpha) and color filter (set via setColorFilter).
int getOpacity()
Return the opacity/transparency of this Drawable.
void inflate(Resources r, XmlPullParser parser, AttributeSet attrs, Resources.Theme theme)
Inflate this Drawable from an XML resource optionally styled by a theme.
Protected Methods
void onBoundsChange(Rect bounds)
Override this in your subclass to change appearance if you vary based on the bounds.
boolean onLevelChange(int level)
Override this in your subclass to change appearance if you vary based on level.
[Expand]
Inherited Methods
From class android.graphics.drawable.DrawableWrapper
From class android.graphics.drawable.Drawable
From class java.lang.Object
From interface android.graphics.drawable.Drawable.Callback

XML Attributes

android:drawable

Reference to a drawable resource to draw with the specified scale.

Must be a reference to another resource, in the form "@[+][package:]type:name" or to a theme attribute in the form "?[package:][type:]name".

This corresponds to the global attribute resource symbol drawable.

Related Methods

android:scaleGravity

Specifies where the drawable is positioned after scaling. The default value is left.

Must be one or more (separated by '|') of the following constant values.

ConstantValueDescription
top0x30 Push object to the top of its container, not changing its size.
bottom0x50 Push object to the bottom of its container, not changing its size.
left0x03 Push object to the left of its container, not changing its size.
right0x05 Push object to the right of its container, not changing its size.
center_vertical0x10 Place object in the vertical center of its container, not changing its size.
fill_vertical0x70 Grow the vertical size of the object if needed so it completely fills its container.
center_horizontal0x01 Place object in the horizontal center of its container, not changing its size.
fill_horizontal0x07 Grow the horizontal size of the object if needed so it completely fills its container.
center0x11 Place the object in the center of its container in both the vertical and horizontal axis, not changing its size.
fill0x77 Grow the horizontal and vertical size of the object if needed so it completely fills its container.
clip_vertical0x80 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 will be based on the vertical gravity: a top gravity will clip the bottom edge, a bottom gravity will clip the top edge, and neither will clip both edges.
clip_horizontal0x08 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 will be based on the horizontal gravity: a left gravity will clip the right edge, a right gravity will clip the left edge, and neither will clip both edges.
start0x00800003 Push object to the beginning of its container, not changing its size.
end0x00800005 Push object to the end of its container, not changing its size.

This corresponds to the global attribute resource symbol scaleGravity.

Related Methods

android:scaleHeight

Scale height, expressed as a percentage of the drawable's bound. The value's format is XX%. For instance: 100%, 12.5%, etc.

Must be a string value, using '\\;' to escape characters such as '\\n' or '\\uxxxx' for a unicode character.

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol scaleHeight.

Related Methods

android:scaleWidth

Scale width, expressed as a percentage of the drawable's bound. The value's format is XX%. For instance: 100%, 12.5%, etc.

Must be a string value, using '\\;' to escape characters such as '\\n' or '\\uxxxx' for a unicode character.

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol scaleWidth.

Related Methods

Public Constructors

public ScaleDrawable (Drawable drawable, int gravity, float scaleWidth, float scaleHeight)

Added in API level 1

Creates a new scale drawable with the specified gravity and scale properties.

Parameters
drawable Drawable: the drawable to scale
gravity int: gravity constant (see Gravity used to position the scaled drawable within the parent container
scaleWidth float: width scaling factor [0...1] to use then the level is at the maximum value, or -1 to not scale width
scaleHeight float: height scaling factor [0...1] to use then the level is at the maximum value, or -1 to not scale height

Public Methods

public void applyTheme (Resources.Theme t)

Added in API level 21

Applies the specified theme to this Drawable and its children.

Parameters
t Resources.Theme

public void draw (Canvas canvas)

Added in API level 1

Draw in its bounds (set via setBounds) respecting optional effects such as alpha (set via setAlpha) and color filter (set via setColorFilter).

Parameters
canvas Canvas: The canvas to draw into

public int getOpacity ()

Added in API level 1

Return the opacity/transparency of this Drawable. The returned value is one of the abstract format constants in PixelFormat: UNKNOWN, TRANSLUCENT, TRANSPARENT, or OPAQUE.

An OPAQUE drawable is one that draws all all content within its bounds, completely covering anything behind the drawable. A TRANSPARENT drawable is one that draws nothing within its bounds, allowing everything behind it to show through. A TRANSLUCENT drawable is a drawable in any other state, where the drawable will draw some, but not all, of the content within its bounds and at least some content behind the drawable will be visible. If the visibility of the drawable's contents cannot be determined, the safest/best return value is TRANSLUCENT.

Generally a Drawable should be as conservative as possible with the value it returns. For example, if it contains multiple child drawables and only shows one of them at a time, if only one of the children is TRANSLUCENT and the others are OPAQUE then TRANSLUCENT should be returned. You can use the method resolveOpacity(int, int) to perform a standard reduction of two opacities to the appropriate single output.

Note that the returned value does not necessarily take into account a custom alpha or color filter that has been applied by the client through the setAlpha(int) or setColorFilter(ColorFilter) methods. Some subclasses, such as BitmapDrawable, ColorDrawable, and GradientDrawable, do account for the value of setAlpha(int), but the general behavior is dependent upon the implementation of the subclass.

Returns
int int The opacity class of the Drawable.

public void inflate (Resources r, XmlPullParser parser, AttributeSet attrs, Resources.Theme theme)

Added in API level 21

Inflate this Drawable from an XML resource optionally styled by a theme.

Parameters
r Resources: Resources used to resolve attribute values
parser XmlPullParser: XML parser from which to inflate this Drawable
attrs AttributeSet: Base set of attribute values
theme Resources.Theme: Theme to apply, may be null
Throws
XmlPullParserException
IOException

Protected Methods

protected void onBoundsChange (Rect bounds)

Added in API level 1

Override this in your subclass to change appearance if you vary based on the bounds.

Parameters
bounds Rect

protected boolean onLevelChange (int level)

Added in API level 1

Override this in your subclass to change appearance if you vary based on level.

Parameters
level int
Returns
boolean Returns true if the level change has caused the appearance of the Drawable to change (that is, it needs to be drawn), else false if it looks the same and there is no need to redraw it since its last level.