android.graphics.drawable.Drawable
A Drawable is a general abstraction for "something that can be drawn." Most
often you will deal with Drawable as the type of resource retrieved for
drawing things to the screen; the Drawable class provides a generic API for
dealing with an underlying visual resource that may take a variety of forms.
Unlike a View, a Drawable does not have any facility to
receive events or otherwise interact with the user.
In addition to simple drawing, Drawable provides a number of generic
mechanisms for its client to interact with what is being drawn:
- The setBounds(Rect) method must be called to tell the
Drawable where it is drawn and how large it should be. All Drawables
should respect the requested size, often simply by scaling their
imagery. A client can find the preferred size for some Drawables with
the getIntrinsicHeight() and getIntrinsicWidth() methods.
- The getPadding(Rect) method can return from some Drawables
information about how to frame content that is placed inside of them.
For example, a Drawable that is intended to be the frame for a button
widget would need to return padding that correctly places the label
inside of itself.
- The setState(int[]) method allows the client to tell the Drawable
in which state it is to be drawn, such as "focused", "selected", etc.
Some drawables may modify their imagery based on the selected state.
- The setLevel(int) method allows the client to supply a single
continuous controller that can modify the Drawable is displayed, such as
a battery level or progress level. Some drawables may modify their
imagery based on the current level.
- A Drawable can perform animations by calling back to its client
through the Drawable.Callback interface. All clients should support this
interface (via setCallback(Drawable.Callback)) so that animations will work. A
simple way to do this is through the system facilities such as
setBackgroundDrawable(Drawable) and
ImageView.
Though usually not visible to the application, Drawables may take a variety
of forms:
- Bitmap: the simplest Drawable, a PNG or JPEG image.
- Nine Patch: an extension to the PNG format allows it to
specify information about how to stretch it and place things inside of
it.
- Shape: contains simple drawing commands instead of a raw
bitmap, allowing it to resize better in some cases.
- Layers: a compound drawable, which draws multiple underlying
drawables on top of each other.
- States: a compound drawable that selects one of a set of
drawables based on its state.
- Levels: a compound drawable that selects one of a set of
drawables based on its level.
- Scale: a compound drawable with a single child drawable,
whose overall size is modified based on the current level.
For information and examples of creating drawable resources (XML or bitmap files that
can be loaded in code), see Resources
and Internationalization.
Nested Classes
Known Direct Subclasses
BitmapDrawable,
ClipDrawable,
ColorDrawable,
DrawableContainer,
GradientDrawable,
InsetDrawable,
LayerDrawable,
NinePatchDrawable,
PictureDrawable,
RotateDrawable,
ScaleDrawable,
ScrollBarDrawable,
ShapeDrawable
BitmapDrawable |
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ClipDrawable |
A drawable that clips another drawable based on this drawable's current
level value. |
ColorDrawable |
A ColorDrawable is a specialized drawable that fills the Canvas with a specified color,
and with respect to the clip region. |
DrawableContainer |
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GradientDrawable |
A simple color gradient for buttons, backgrounds, etc. |
InsetDrawable |
A Drawable that insets another Drawable by a specified distance. |
LayerDrawable |
Drawable that manages an array of other drawables. |
NinePatchDrawable |
A resizeable bitmap, with stretchable areas that you define. |
PictureDrawable |
Drawable subclass that wraps a Picture, allowing the picture to be used
whereever a Drawable is supported. |
RotateDrawable |
A drawable that can rotate another drawable based on the current level
value. |
ScaleDrawable |
A drawable that changes the size of another drawable based on its current
level value. |
ScrollBarDrawable |
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ShapeDrawable |
An object that draws primitive shapes. |
Known Indirect Subclasses
AnimationDrawable |
An object used to define frame-by-frame animations that can be used as a View object's
background. |
LevelListDrawable |
A resource that contains a number of alternate images, each assigned a maximum numerical value. |
PaintDrawable |
Drawable that draws its bounds in the given paint, with optional
rounded corners. |
StateListDrawable |
Lets you assign a number of graphic images to a single Drawable and swap out the visible item by a string
ID value. |
TransitionDrawable |
Transition drawables are an extension of LayerDrawables and are intended to cross fade between
the first and second layers. |
Summary
Public Constructors
Public Methods
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void |
clearColorFilter() |
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final |
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Rect |
copyBounds() |
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final |
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void |
copyBounds(Rect bounds) |
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static |
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Drawable |
createFromPath(String pathName) |
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static |
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Drawable |
createFromStream(InputStream is, String srcName) |
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static |
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Drawable |
createFromXml(Resources r, XmlPullParser parser) |
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static |
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Drawable |
createFromXmlInner(Resources r, XmlPullParser parser, AttributeSet attrs) |
abstract |
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void |
draw(Canvas canvas) |
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final |
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Rect |
getBounds() |
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int |
getChangingConfigurations() |
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Drawable.ConstantState |
getConstantState() |
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Drawable |
getCurrent() |
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int |
getIntrinsicHeight() |
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int |
getIntrinsicWidth() |
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final |
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int |
getLevel() |
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int |
getMinimumHeight() |
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int |
getMinimumWidth() |
abstract |
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int |
getOpacity() |
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boolean |
getPadding(Rect padding) |
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int[] |
getState() |
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Region |
getTransparentRegion() |
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void |
inflate(Resources r, XmlPullParser parser, AttributeSet attrs) |
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void |
invalidateSelf() |
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boolean |
isStateful() |
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final |
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boolean |
isVisible() |
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static |
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int |
resolveOpacity(int op1, int op2) |
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void |
scheduleSelf(Runnable what, long when) |
abstract |
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void |
setAlpha(int alpha) |
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void |
setBounds(Rect bounds) |
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void |
setBounds(int left, int top, int right, int bottom) |
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final |
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void |
setCallback(Drawable.Callback cb) |
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void |
setChangingConfigurations(int configs) |
abstract |
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void |
setColorFilter(ColorFilter cf) |
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void |
setColorFilter(int color, PorterDuff.Mode mode) |
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void |
setDither(boolean dither) |
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void |
setFilterBitmap(boolean filter) |
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final |
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boolean |
setLevel(int level) |
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boolean |
setState(int[] stateSet) |
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boolean |
setVisible(boolean visible, boolean restart) |
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void |
unscheduleSelf(Runnable what) |
Protected Methods
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait
Details
Public Constructors
Public Methods
public
void
clearColorFilter()
public
final
Rect
copyBounds()
Return a copy of the drawable's bounds in a new Rect. This returns the
same values as getBounds(), but the returned object is guaranteed to not
be changed later by the drawable (i.e. it retains no reference to this
rect). If the caller already has a Rect allocated, call copyBounds(rect)
Returns
- A copy of the drawable's bounds
public
final
void
copyBounds(Rect bounds)
Return a copy of the drawable's bounds in the specified Rect (allocated
by the caller). The bounds specify where this will draw when its draw()
method is called.
Parameters
bounds
| Rect to receive the drawable's bounds (allocated by the
caller).
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public
static
Drawable
createFromPath(String pathName)
Create a drawable from file path name.
Create a drawable from an inputstream
public
static
Drawable
createFromXmlInner(Resources r, XmlPullParser parser, AttributeSet attrs)
Create from inside an XML document. Called on a parser positioned at
a tag in an XML document, tries to create a Drawable from that tag.
Returns null if the tag is not a valid drawable.
public
abstract
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
| The canvas to draw into
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public
final
Rect
getBounds()
Return the drawable's bounds Rect. Note: for efficiency, the returned
object may be the same object stored in the drawable (though this is not
guaranteed), so if a persistent copy of the bounds is needed, call
copyBounds(rect) instead.
Returns
- The bounds of the drawable (which may change later, so caller
beware).
public
int
getChangingConfigurations()
Return a mask of the configuration parameters for which this drawable
mau 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
getCurrent()
Returns
- The current drawable that will be used by this drawable. For simple drawables, this
is just the drawable itself. For drawables that change state like
StateListDrawable and LevelListDrawable this will be the child drawable
currently in use.
public
int
getIntrinsicHeight()
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()
Return the intrinsic width of the underlying drawable object. Returns
-1 if it has no intrinsic width, such as with a solid color.
public
final
int
getLevel()
Retrieve the current level.
Returns
- int Current level, from 0 (minimum) to 10000 (maximum).
public
int
getMinimumHeight()
Returns the minimum height suggested by this Drawable. If a View uses this
Drawable as a background, it is suggested that the View use at least this
value for its height. (There will be some scenarios where this will not be
possible.) This value should INCLUDE any padding.
Returns
- The minimum height suggested by this Drawable. If this Drawable
doesn't have a suggested minimum height, 0 is returned.
public
int
getMinimumWidth()
Returns the minimum width suggested by this Drawable. If a View uses this
Drawable as a background, it is suggested that the View use at least this
value for its width. (There will be some scenarios where this will not be
possible.) This value should INCLUDE any padding.
Returns
- The minimum width suggested by this Drawable. If this Drawable
doesn't have a suggested minimum width, 0 is returned.
public
abstract
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.
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)
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
int[]
getState()
Describes the current state, as a union of primitve states, such as
state_focused,
state_selected, etc.
Some drawables may modify their imagery based on the selected state.
Returns
- An array of resource Ids describing the current state.
public
Region
getTransparentRegion()
Returns a Region representing the part of the Drawable that is completely
transparent. This can be used to perform drawing operations, identifying
which parts of the target will not change when rendering the Drawable.
The default implementation returns null, indicating no transparent
region; subclasses can optionally override this to return an actual
Region if they want to supply this optimization information, but it is
not required that they do so.
Returns
- Returns null if the Drawables has no transparent region to
report, else a Region holding the parts of the Drawable's bounds that
are transparent.
public
void
invalidateSelf()
Use the current
Drawable.Callback implementation to have this Drawable
redrawn. Does nothing if there is no Callback attached to the
Drawable.
public
boolean
isStateful()
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
final
boolean
isVisible()
public
static
int
resolveOpacity(int op1, int op2)
Return the appropriate opacity value for two source opacities. If
either is UNKNOWN, that is returned; else, if either is TRANSLUCENT,
that is returned; else, if either is TRANSPARENT, that is returned;
else, OPAQUE is returned.
This is to help in implementing getOpacity().
Parameters
op1
| One opacity value. |
op2
| Another opacity value. |
Returns
- int The combined opacity value.
public
void
scheduleSelf(Runnable what, long when)
Use the current
Drawable.Callback implementation to have this Drawable
scheduled. Does nothing if there is no Callback attached to the
Drawable.
Parameters
what
| The action being scheduled. |
when
| The time (in milliseconds) to run. |
public
abstract
void
setAlpha(int alpha)
Specify an alpha value for the drawable. 0 means fully transparent, and
255 means fully opaque.
public
void
setBounds(Rect bounds)
Specify a bounding rectangle for the Drawable. This is where the drawable
will draw when its draw() method is called.
public
void
setBounds(int left, int top, int right, int bottom)
Specify a bounding rectangle for the Drawable. This is where the drawable
will draw when its draw() method is called.
Bind a
Drawable.Callback object to this Drawable. Required for clients
that want to support animated drawables.
Parameters
cb
| The client's Callback implementation.
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public
void
setChangingConfigurations(int configs)
Set a mask of the configuration parameters for which this drawable
may change, requiring that it be re-created.
Parameters
configs
| A mask of the changing configuration parameters, as
defined by Configuration. |
public
abstract
void
setColorFilter(ColorFilter cf)
Specify an optional colorFilter for the drawable. Pass null to remove
any filters.
public
void
setColorFilter(int color, PorterDuff.Mode mode)
Specify a color and porterduff mode to be the colorfilter for this
drawable.
public
void
setDither(boolean dither)
Set to true to have the drawable dither its colors when drawn to a device
with fewer than 8-bits per color component. This can improve the look on
those devices, but can also slow down the drawing a little.
public
void
setFilterBitmap(boolean filter)
Set to true to have the drawable filter its bitmap when scaled or rotated
(for drawables that use bitmaps). If the drawable does not use bitmaps,
this call is ignored. This can improve the look when scaled or rotated,
but also slows down the drawing.
public
final
boolean
setLevel(int level)
Specify the level for the drawable. This allows a drawable to vary its
imagery based on a continuous controller, for example to show progress
or volume level.
If the new level you are supplying causes the appearance of the
Drawable to change, then it is responsible for calling
invalidateSelf() in order to have itself redrawn, and
true will be returned from this function.
Parameters
level
| The new level, from 0 (minimum) to 10000 (maximum). |
Returns
- Returns true if this change in level has caused the appearance
of the Drawable to change (hence requiring an invalidate), otherwise
returns false.
public
boolean
setState(int[] stateSet)
Specify a set of states for the drawable. These are use-case specific,
so see the relevant documentation. As an example, the background for
widgets like Button understand the following states:
[
state_focused,
state_pressed].
If the new state you are supplying causes the appearance of the
Drawable to change, then it is responsible for calling
invalidateSelf() in order to have itself redrawn, and
true will be returned from this function.
Note: The Drawable holds a reference on to stateSet
until a new state array is given to it, so you must not modify this
array during that time.
Parameters
stateSet
| The new set of states to be displayed. |
Returns
- Returns true if this change in state has caused the appearance
of the Drawable to change (hence requiring an invalidate), otherwise
returns false.
public
boolean
setVisible(boolean visible, boolean restart)
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
unscheduleSelf(Runnable what)
Use the current
Drawable.Callback implementation to have this Drawable
unscheduled. Does nothing if there is no Callback attached to the
Drawable.
Parameters
what
| The runnable that you no longer want called. |
Protected Methods
protected
void
onBoundsChange(Rect bounds)
Override this in your subclass to change appearance if you recognize the
specified state.
protected
boolean
onLevelChange(int level)
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)
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.