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ScaleDrawable

public class ScaleDrawable
extends DrawableWrapper

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


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.

The default level may be specified from XML using the android:level property. When this property is not specified, the default level is 0, which corresponds to zero height and/or width depending on the values specified for android.R.styleable#ScaleDrawable_scaleWidth scaleWidth and android.R.styleable#ScaleDrawable_scaleHeight scaleHeight. At run time, the level may be set via setLevel(int).

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

Summary

XML attributes

android:drawable Reference to a drawable resource to draw with the specified scale. 
android:level Specifies the initial drawable level in the range 0 to 10000. 
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.

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.

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

android:level

Specifies the initial drawable level in the range 0 to 10000.

May be an integer value, such as "100".

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
bottom50Push object to the bottom of its container, not changing its size.
center11Place the object in the center of its container in both the vertical and horizontal axis, not changing its size.
center_horizontal1Place object in the horizontal center of its container, not changing its size.
center_vertical10Place object in the vertical center of its container, not changing its size.
clip_horizontal8Additional 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.
clip_vertical80Additional 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.
end800005Push object to the end of its container, not changing its size.
fill77Grow the horizontal and vertical size of the object if needed so it completely fills its container.
fill_horizontal7Grow the horizontal size of the object if needed so it completely fills its container.
fill_vertical70Grow the vertical size of the object if needed so it completely fills its container.
left3Push object to the left of its container, not changing its size.
right5Push object to the right of its container, not changing its size.
start800003Push object to the beginning of its container, not changing its size.
top30Push object to the top of its container, not changing its size.

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.

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

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.

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

Public constructors

ScaleDrawable

added in API level 1
ScaleDrawable (Drawable drawable, 
                int gravity, 
                float scaleWidth, 
                float scaleHeight)

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

applyTheme

added in API level 21
void applyTheme (Resources.Theme t)

Applies the specified theme to this Drawable and its children.

Parameters
t Resources.Theme: the theme to apply

This value must never be null.

draw

added in API level 1
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).

Parameters
canvas Canvas: The canvas to draw into

getOpacity

added in API level 1
int getOpacity ()

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.

inflate

added in API level 21
void inflate (Resources r, 
                XmlPullParser parser, 
                AttributeSet attrs, 
                Resources.Theme theme)

Inflate this Drawable from an XML resource optionally styled by a theme. This can't be called more than once for each Drawable. Note that framework may have called this once to create the Drawable instance from XML resource.

Parameters
r Resources: Resources used to resolve attribute values

This value must never be null.

parser XmlPullParser: XML parser from which to inflate this Drawable

This value must never be null.

attrs AttributeSet: Base set of attribute values

This value must never be null.

theme Resources.Theme: Theme to apply, may be null

Throws
XmlPullParserException
IOException

Protected methods

onBoundsChange

added in API level 1
void onBoundsChange (Rect bounds)

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

Parameters
bounds Rect

onLevelChange

added in API level 1
boolean onLevelChange (int level)

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.

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