Android APIs
public class

LayerDrawable

extends Drawable
implements Drawable.Callback
java.lang.Object
   ↳ android.graphics.drawable.Drawable
     ↳ android.graphics.drawable.LayerDrawable
Known Direct Subclasses

Class Overview

A Drawable that manages an array of other Drawables. These are drawn in array order, so the element with the largest index will be drawn on top.

It can be defined in an XML file with the <layer-list> element. Each Drawable in the layer is defined in a nested <item>. For more information, see the guide to Drawable Resources.

Summary

XML Attributes
Attribute Name Related Method Description
android:bottom Bottom coordinate of the layer. 
android:drawable Drawable used to render the layer. 
android:id Identifier of the layer. 
android:left Left coordinate of the layer. 
android:right Right coordinate of the layer. 
android:top Top coordinate of the layer. 
Public Constructors
LayerDrawable(Drawable[] layers)
Create a new layer drawable with the list of specified layers.
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).
Drawable findDrawableByLayerId(int id)
Look for a layer with the given id, and returns its Drawable.
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(int index)
Returns the drawable at the specified layer index.
int getId(int index)
Returns the id of the specified layer.
int getIntrinsicHeight()
Return the intrinsic height of the underlying drawable object.
int getIntrinsicWidth()
Return the intrinsic width of the underlying drawable object.
int getNumberOfLayers()
Returns the number of layers contained within this.
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 isAutoMirrored()
Tells if this Drawable will be automatically mirrored when its layout direction is RTL right-to-left.
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 setAutoMirrored(boolean mirrored)
Set whether this Drawable is automatically mirrored when its layout direction is RTL (right-to left).
void setColorFilter(ColorFilter cf)
Specify an optional colorFilter for the drawable.
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.
boolean setDrawableByLayerId(int id, Drawable drawable)
Sets (or replaces) the Drawable for the layer with the given id.
void setId(int index, int id)
Sets the ID of a layer.
void setLayerInset(int index, int l, int t, int r, int b)
Specify modifiers to the bounds for the drawable[index].
void setOpacity(int opacity)
Sets the opacity of this drawable directly, instead of collecting the states from the layers
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:bottom

Bottom coordinate of the layer.

Must be a dimension value, which is a floating point number appended with a unit such as "14.5sp". Available units are: px (pixels), dp (density-independent pixels), sp (scaled pixels based on preferred font size), in (inches), mm (millimeters).

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 bottom.

Related Methods

android:drawable

Drawable used to render the layer.

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:id

Identifier of the layer. This can be used to retrieve the layer from a drawbable container.

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 id.

Related Methods

android:left

Left coordinate of the layer.

Must be a dimension value, which is a floating point number appended with a unit such as "14.5sp". Available units are: px (pixels), dp (density-independent pixels), sp (scaled pixels based on preferred font size), in (inches), mm (millimeters).

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 left.

Related Methods

android:right

Right coordinate of the layer.

Must be a dimension value, which is a floating point number appended with a unit such as "14.5sp". Available units are: px (pixels), dp (density-independent pixels), sp (scaled pixels based on preferred font size), in (inches), mm (millimeters).

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 right.

Related Methods

android:top

Top coordinate of the layer.

Must be a dimension value, which is a floating point number appended with a unit such as "14.5sp". Available units are: px (pixels), dp (density-independent pixels), sp (scaled pixels based on preferred font size), in (inches), mm (millimeters).

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 top.

Related Methods

Public Constructors

public LayerDrawable (Drawable[] layers)

Added in API level 1

Create a new layer drawable with the list of specified layers.

Parameters
layers A list of drawables to use as layers in this new drawable.

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 Drawable findDrawableByLayerId (int id)

Added in API level 1

Look for a layer with the given id, and returns its Drawable.

Parameters
id The layer ID to search for.
Returns
  • The Drawable of the layer that has the given id in the hierarchy or null.

public int getAlpha ()

Added in API level 19

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 (int index)

Added in API level 1

Returns the drawable at the specified layer index.

Parameters
index The layer index of the drawable to retrieve.
Returns
  • The Drawable at the specified layer index.

public int getId (int index)

Added in API level 1

Returns the id of the specified layer.

Parameters
index The index of the layer.
Returns
  • The id of the layer or NO_ID if the layer has no id.

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 getNumberOfLayers ()

Added in API level 1

Returns the number of layers contained within this.

Returns
  • The number of layers.

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.

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 isAutoMirrored ()

Added in API level 19

Tells if this Drawable will be automatically mirrored when its layout direction is RTL right-to-left. See LayoutDirection.

Returns
  • boolean Returns true if this Drawable will be automatically mirrored.

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 setAutoMirrored (boolean mirrored)

Added in API level 19

Set whether this Drawable is automatically mirrored when its layout direction is RTL (right-to left). See LayoutDirection.

Parameters
mirrored Set to true if the Drawable should be mirrored, false if not.

public void setColorFilter (ColorFilter cf)

Added in API level 1

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

public void setDither (boolean dither)

Added in API level 1

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 boolean setDrawableByLayerId (int id, Drawable drawable)

Added in API level 1

Sets (or replaces) the Drawable for the layer with the given id.

Parameters
id The layer ID to search for.
drawable The replacement Drawable.
Returns
  • Whether the Drawable was replaced (could return false if the id was not found).

public void setId (int index, int id)

Added in API level 1

Sets the ID of a layer.

Parameters
index The index of the layer which will received the ID.
id The ID to assign to the layer.

public void setLayerInset (int index, int l, int t, int r, int b)

Added in API level 1

Specify modifiers to the bounds for the drawable[index]. left += l top += t; right -= r; bottom -= b;

public void setOpacity (int opacity)

Added in API level 11

Sets the opacity of this drawable directly, instead of collecting the states from the layers

Parameters
opacity The opacity to use, or PixelFormat.UNKNOWN for the default behavior

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.