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Android Reference

Drawable


android.graphics.drawable

Class Drawable

  • Direct Known Subclasses:
    AnimatedRotateDrawable, BitmapDrawable, ClipDrawable, ColorDrawable, DrawableContainer, GradientDrawable, InsetDrawable, LayerDrawable, NinePatchDrawable, PictureDrawable, RotateDrawable, ScaleDrawable, ScrollBarDrawable, ShapeDrawable


    public abstract class Drawable
    extends Object
    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(int, int, int, int) 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(android.graphics.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(android.graphics.drawable.Drawable.Callback)) so that animations will work. A simple way to do this is through the system facilities such as View.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.

    Developer Guides

    For more information about how to use drawables, read the Canvas and Drawables developer guide. For information and examples of creating drawable resources (XML or bitmap files that can be loaded in code), read the Drawable Resources document.

    • Constructor Detail

      • Drawable

        public Drawable()
    • Method Detail

      • draw

        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
      • setBounds

        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.
      • setBounds

        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.
      • copyBounds

        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).
      • copyBounds

        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
      • getBounds

        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. You should also not change the object returned by this method as it may be the same object stored in the drawable.
        Returns:
        The bounds of the drawable (which may change later, so caller beware). DO NOT ALTER the returned object as it may change the stored bounds of this drawable.
        See Also:
        copyBounds(), copyBounds(android.graphics.Rect)
      • setChangingConfigurations

        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.
        See Also:
        Configuration
      • getChangingConfigurations

        public int getChangingConfigurations()
        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.
        See Also:
        Configuration
      • setDither

        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.
      • setFilterBitmap

        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.
      • setCallback

        public final void setCallback(Drawable.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.
        See Also:
        getCallback()
      • setLayoutDirection

        public void setLayoutDirection(int layoutDirection)
        Set the layout direction for this drawable. Should be a resolved direction as the Drawable as no capacity to do the resolution on his own.
        Parameters:
        layoutDirection - One of View.LAYOUT_DIRECTION_LTR, View.LAYOUT_DIRECTION_RTL
      • setAlpha

        public abstract void setAlpha(int alpha)
        Specify an alpha value for the drawable. 0 means fully transparent, and 255 means fully opaque.
      • setColorFilter

        public abstract void setColorFilter(ColorFilter cf)
        Specify an optional colorFilter for the drawable. Pass null to remove any filters.
      • setColorFilter

        public void setColorFilter(int color,
                          PorterDuff.Mode mode)
        Specify a color and porterduff mode to be the colorfilter for this drawable.
      • clearColorFilter

        public void clearColorFilter()
      • isStateful

        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:
        setState(int[])
      • setState

        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: [android.R.attr#state_focused, android.R.attr#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.
      • getState

        public int[] getState()
        Describes the current state, as a union of primitve states, such as android.R.attr#state_focused, android.R.attr#state_selected, etc. Some drawables may modify their imagery based on the selected state.
        Returns:
        An array of resource Ids describing the current state.
      • jumpToCurrentState

        public void jumpToCurrentState()
        If this Drawable does transition animations between states, ask that it immediately jump to the current state and skip any active animations.
      • getCurrent

        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.
      • setLevel

        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.
      • getLevel

        public final int getLevel()
        Retrieve the current level.
        Returns:
        int Current level, from 0 (minimum) to 10000 (maximum).
      • setVisible

        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.
      • isVisible

        public final boolean isVisible()
      • getOpacity

        public abstract int getOpacity()
        Return the opacity/transparency of this Drawable. The returned value is one of the abstract format constants in PixelFormat: PixelFormat.UNKNOWN, PixelFormat.TRANSLUCENT, PixelFormat.TRANSPARENT, or PixelFormat.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(android.graphics.ColorFilter) methods.

        Returns:
        int The opacity class of the Drawable.
        See Also:
        PixelFormat
      • resolveOpacity

        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.
        See Also:
        getOpacity()
      • getTransparentRegion

        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.
      • onStateChange

        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.
      • onLevelChange

        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.
      • onBoundsChange

        protected void onBoundsChange(Rect bounds)
        Override this in your subclass to change appearance if you recognize the specified state.
      • getIntrinsicWidth

        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.
      • getIntrinsicHeight

        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.
      • getMinimumWidth

        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.
      • getMinimumHeight

        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.
      • getPadding

        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.
      • getLayoutInsets

        public Insets getLayoutInsets()
        Return in insets the layout insets suggested by this Drawable for use with alignment operations during layout.
      • mutate

        public Drawable mutate()
        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.
        See Also:
        Drawable.ConstantState, getConstantState()
      • createFromStream

        public static Drawable createFromStream(InputStream is,
                                String srcName)
        Create a drawable from an inputstream
      • createFromResourceStream

        public static Drawable createFromResourceStream(Resources res,
                                        TypedValue value,
                                        InputStream is,
                                        String srcName)
        Create a drawable from an inputstream, using the given resources and value to determine density information.
      • createFromPath

        public static Drawable createFromPath(String pathName)
        Create a drawable from file path name.


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