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Android APIs
public class

ScaleDrawable

extends Drawable
implements Drawable.Callback
java.lang.Object
   ↳ android.graphics.drawable.Drawable
     ↳ 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)
Public Methods
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 getAlpha ()
Gets the current alpha value for the drawable.
int getChangingConfigurations ()
Return a mask of the configuration parameters for which this drawable may change, requiring that it be re-created.
Drawable.ConstantState getConstantState ()
Return a Drawable.ConstantState instance that holds the shared state of this Drawable.
Drawable getDrawable ()
Returns the drawable scaled by this ScaleDrawable.
int getIntrinsicHeight ()
Return the intrinsic height of the underlying drawable object.
int getIntrinsicWidth ()
Return the intrinsic width of the underlying drawable object.
int getOpacity ()
Return the opacity/transparency of this Drawable.
boolean getPadding ( Rect padding)
Return in padding the insets suggested by this Drawable for placing content inside the drawable's bounds.
void inflate ( Resources r, XmlPullParser parser, AttributeSet attrs)
Inflate this Drawable from an XML resource.
void invalidateDrawable ( Drawable who)
Called when the drawable needs to be redrawn.
boolean isStateful ()
Indicates whether this view will change its appearance based on state.
Drawable mutate ()
Make this drawable mutable.
void scheduleDrawable ( Drawable who, Runnable what, long when)
A Drawable can call this to schedule the next frame of its animation.
void setAlpha (int alpha)
Specify an alpha value for the drawable.
void setColorFilter ( ColorFilter cf)
Specify an optional colorFilter for the drawable.
boolean setVisible (boolean visible, boolean restart)
Set whether this Drawable is visible.
void unscheduleDrawable ( Drawable who, Runnable what)
A Drawable can call this to unschedule an action previously scheduled with scheduleDrawable(Drawable, Runnable, long) .
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.
boolean onStateChange (int[] state)
Override this in your subclass to change appearance if you recognize the specified state.
[Expand]
Inherited Methods
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.

Constant Value Description
top 0x30 Push object to the top of its container, not changing its size.
bottom 0x50 Push object to the bottom of its container, not changing its size.
left 0x03 Push object to the left of its container, not changing its size.
right 0x05 Push object to the right of its container, not changing its size.
center_vertical 0x10 Place object in the vertical center of its container, not changing its size.
fill_vertical 0x70 Grow the vertical size of the object if needed so it completely fills its container.
center_horizontal 0x01 Place object in the horizontal center of its container, not changing its size.
fill_horizontal 0x07 Grow the horizontal size of the object if needed so it completely fills its container.
center 0x11 Place the object in the center of its container in both the vertical and horizontal axis, not changing its size.
fill 0x77 Grow the horizontal and vertical size of the object if needed so it completely fills its container.
clip_vertical 0x80 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_horizontal 0x08 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.
start 0x00800003 Push object to the beginning of its container, not changing its size.
end 0x00800005 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

Public Methods

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 The canvas to draw into

public int getAlpha ()

Gets the current alpha value for the drawable. 0 means fully transparent, 255 means fully opaque. This method is implemented by Drawable subclasses and the value returned is specific to how that class treats alpha. The default return value is 255 if the class does not override this method to return a value specific to its use of alpha.

public int getChangingConfigurations ()

Added in API level 1

Return a mask of the configuration parameters for which this drawable may change, requiring that it be re-created. The default implementation returns whatever was provided through setChangingConfigurations(int) or 0 by default. Subclasses may extend this to or in the changing configurations of any other drawables they hold.

Returns
  • Returns a mask of the changing configuration parameters, as defined by Configuration .

public Drawable.ConstantState getConstantState ()

Added in API level 1

Return a Drawable.ConstantState instance that holds the shared state of this Drawable. q

Returns
  • The ConstantState associated to that Drawable.

public Drawable getDrawable ()

Added in API level 3

Returns the drawable scaled by this ScaleDrawable.

public int getIntrinsicHeight ()

Added in API level 1

Return the intrinsic height of the underlying drawable object. Returns -1 if it has no intrinsic height, such as with a solid color.

public int getIntrinsicWidth ()

Added in API level 1

Return the intrinsic width of the underlying drawable object. Returns -1 if it has no intrinsic width, such as with a solid color.

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 .

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 take into account a custom alpha or color filter that has been applied by the client through the setAlpha(int) or setColorFilter(ColorFilter) methods.

Returns
  • int The opacity class of the Drawable.

public boolean getPadding ( Rect padding)

Added in API level 1

Return in padding the insets suggested by this Drawable for placing content inside the drawable's bounds. Positive values move toward the center of the Drawable (set Rect.inset). Returns true if this drawable actually has a padding, else false. When false is returned, the padding is always set to 0.

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

Added in API level 1

Inflate this Drawable from an XML resource.

Throws
XmlPullParserException
IOException

public void invalidateDrawable ( Drawable who)

Added in API level 1

Called when the drawable needs to be redrawn. A view at this point should invalidate itself (or at least the part of itself where the drawable appears).

Parameters
who The drawable that is requesting the update.

public boolean isStateful ()

Added in API level 1

Indicates whether this view will change its appearance based on state. Clients can use this to determine whether it is necessary to calculate their state and call setState.

Returns
  • True if this view changes its appearance based on state, false otherwise.

public Drawable mutate ()

Added in API level 3

Make this drawable mutable. This operation cannot be reversed. A mutable drawable is guaranteed to not share its state with any other drawable. This is especially useful when you need to modify properties of drawables loaded from resources. By default, all drawables instances loaded from the same resource share a common state; if you modify the state of one instance, all the other instances will receive the same modification. Calling this method on a mutable Drawable will have no effect.

Returns
  • This drawable.

public void scheduleDrawable ( Drawable who, Runnable what, long when)

Added in API level 1

A Drawable can call this to schedule the next frame of its animation. An implementation can generally simply call postAtTime(Runnable, Object, long) with the parameters (what, who, when) to perform the scheduling.

Parameters
who The drawable being scheduled.
what The action to execute.
when The time (in milliseconds) to run. The timebase is uptimeMillis()

public void setAlpha (int alpha)

Added in API level 1

Specify an alpha value for the drawable. 0 means fully transparent, and 255 means fully opaque.

public void setColorFilter ( ColorFilter cf)

Added in API level 1

Specify an optional colorFilter for the drawable. Pass null to remove any filters.

public boolean setVisible (boolean visible, boolean restart)

Added in API level 1

Set whether this Drawable is visible. This generally does not impact the Drawable's behavior, but is a hint that can be used by some Drawables, for example, to decide whether run animations.

Parameters
visible Set to true if visible, false if not.
restart You can supply true here to force the drawable to behave as if it has just become visible, even if it had last been set visible. Used for example to force animations to restart.
Returns
  • boolean Returns true if the new visibility is different than its previous state.

public void unscheduleDrawable ( Drawable who, Runnable what)

Added in API level 1

A Drawable can call this to unschedule an action previously scheduled with scheduleDrawable(Drawable, Runnable, long) . An implementation can generally simply call removeCallbacks(Runnable, Object) with the parameters (what, who) to unschedule the drawable.

Parameters
who The drawable being unscheduled.
what The action being unscheduled.

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.

protected boolean onLevelChange (int level)

Added in API level 1

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

Returns
  • 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.

protected boolean onStateChange (int[] state)

Added in API level 1

Override this in your subclass to change appearance if you recognize the specified state.

Returns
  • Returns true if the state 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 state.