android.graphics.drawable
public abstract class
public abstract class
android.graphics.drawable.Drawable
| java.lang.Object | ||
| 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 setBackground(Drawable) and ImageView.
- 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
| Drawable.Callback | Implement this interface if you want to create an animated drawable that extends Drawable. |
| Drawable.ConstantState |
Known Direct Subclasses
Known Indirect Subclasses
Summary
Public Constructors
| Drawable() |
Public Methods
| void | clearColorFilter() | ||||
| final | Rect | copyBounds() | |||
| Return a copy of the drawable's bounds in a new Rect. | |||||
| final | void | copyBounds(Rect bounds) | |||
| Return a copy of the drawable's bounds in the specified Rect (allocated by the caller). | |||||
| static | Drawable | createFromPath(String pathName) | |||
| Create a drawable from file path name. | |||||
| static | Drawable | createFromStream(InputStream is, String srcName) | |||
| Create a drawable from an inputstream | |||||
| static | Drawable | createFromXml(Resources r, XmlPullParser parser) | |||
| Create a drawable from an XML document. | |||||
| static | Drawable | createFromXmlInner(Resources r, XmlPullParser parser, AttributeSet attrs) | |||
| Create from inside an XML document. | |||||
| 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). | |||||
| final | Rect | getBounds() | |||
| Return the drawable's bounds Rect. | |||||
| ConstantState | getConstantState() | ||||
| int | getIntrinsicHeight() | ||||
| Return the intrinsic height of the underlying drawable object. | |||||
| int | getIntrinsicWidth() | ||||
| Return the intrinsic width of the underlying drawable object. | |||||
| final | int | getLevel() | |||
| Retrieve the current level. | |||||
| int | getMinimumHeight() | ||||
| Returns the minimum height suggested by this Drawable. | |||||
| int | getMinimumWidth() | ||||
| Returns the minimum width suggested by this Drawable. | |||||
| abstract | 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. | |||||
| int[] | getState() | ||||
| Describes the current state, as a union of primitve states, such as state_focused, state_selected, etc. | |||||
| Region | getTransparentRegion() | ||||
| Returns a Region representing the part of the Drawable that is completely transparent. | |||||
| void | inflate(Resources r, XmlPullParser parser, AttributeSet attrs) | ||||
| void | invalidateSelf() | ||||
| Use the current Drawable.Callback implementation to have this Drawable redrawn. | |||||
| boolean | isStateful() | ||||
| Indicates whether this view will change its appearance based on state. | |||||
| final | boolean | isVisible() | |||
| final | static | int | resolveOpacity(int op1, int op2) | ||
| Return the appropriate opacity value for two source opacities. | |||||
| void | scheduleSelf(Runnable what, long when) | ||||
| Use the current Drawable.Callback implementation to have this Drawable scheduled. | |||||
| abstract | void | setAlpha(int alpha) | |||
| Specify an alpha value for the drawable. | |||||
| void | setBounds(Rect bounds) | ||||
| Specify a bounding rectangle for the Drawable. | |||||
| void | setBounds(int left, int top, int right, int bottom) | ||||
| Specify a bounding rectangle for the Drawable. | |||||
| final | void | setCallback(Callback cb) | |||
| Bind a Drawable.Callback object to this Drawable. | |||||
| abstract | void | setColorFilter(ColorFilter cf) | |||
| Specify an optional colorFilter for the drawable. | |||||
| void | setColorFilter(int color, Mode mode) | ||||
| Specify a color and porterduff mode to be the colorfilter for this drawable. | |||||
| void | setDither(boolean dither) | ||||
| final | boolean | setLevel(int level) | |||
| Specify the level for the drawable. | |||||
| boolean | setState(int[] stateSet) | ||||
| Specify a set of states for the drawable. | |||||
| boolean | setVisible(boolean visible, boolean restart) | ||||
| Set whether this Drawable is visible. | |||||
| void | unscheduleSelf(Runnable what) | ||||
| Use the current Drawable.Callback implementation to have this Drawable unscheduled. | |||||
Protected Methods
| void | onBoundsChange(Rect bounds) | ||||
| Override this in your subclass to change appearance if you recognize the specified state. | |||||
| 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. | |||||
Methods inherited
from class
java.lang.Object
Details
Public Constructors
public Drawable()
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). |
|---|
public static Drawable createFromStream(InputStream is, String srcName)
Create a drawable from an inputstream
public static Drawable createFromXml(Resources r, XmlPullParser parser)
Create a drawable from an XML document. For more information on how to
create resources in XML, see
Resources and
Internationalization.
Throws
| XmlPullParserException | |
|---|---|
| IOException |
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.
Throws
| XmlPullParserException | |
|---|---|
| IOException |
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 |
|---|
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 ConstantState getConstantState()
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.
See Also
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 inflate(Resources r, XmlPullParser parser, AttributeSet attrs)
Throws
| XmlPullParserException | |
|---|---|
| IOException |
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.
See Also
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.
See Also
public final boolean isVisible()
public static final 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.
See Also
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.
public final void setCallback(Callback cb)
Bind a Drawable.Callback object to this Drawable. Required for clients
that want to support animated drawables.
Parameters
| cb | The client's Callback implementation. |
|---|
public abstract void setColorFilter(ColorFilter cf)
Specify an optional colorFilter for the drawable. Pass null to remove
any filters.
public void setColorFilter(int color, Mode mode)
Specify a color and porterduff mode to be the colorfilter for this
drawable.
public void setDither(boolean dither)
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.