Android - An Open Handset Alliance Project

android.graphics
public class

android.graphics.Canvas

java.lang.Object
	android.graphics.Canvas

The Canvas class holds the "draw" calls. To draw something, you need 4 basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls (writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap), and a paint (to describe the colors and styles for the drawing).

Nested Classes

Canvas.EdgeType

Summary

Constants

			Value
int	CLIP_SAVE_FLAG	restore the current clip when restore() is called	2	0x00000002
int	CLIP_TO_LAYER_SAVE_FLAG	clip against the layer's bounds	16	0x00000010
int	FULL_COLOR_LAYER_SAVE_FLAG	the layer needs to 8-bits per color component	8	0x00000008
int	HAS_ALPHA_LAYER_SAVE_FLAG	the layer needs to per-pixel alpha	4	0x00000004
int	MATRIX_SAVE_FLAG	restore the current matrix when restore() is called	1	0x00000001

Public Constructors

					Canvas()
					Construct an empty canvas.
					Canvas(Bitmap bitmap)
					Construct a canvas with the specified bitmap to draw into.

Public Methods

	boolean	clipPath(Path path)
		Intersect the current clip with the specified path.
	boolean	clipPath(Path path, Op op)
		Modify the current clip with the specified path.
	boolean	clipRect(float left, float top, float right, float bottom)
		Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRect(Rect rect)
		Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRect(float left, float top, float right, float bottom, Op op)
		Modify the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRect(Rect rect, Op op)
		Modify the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRect(RectF rect)
		Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRect(RectF rect, Op op)
		Modify the current clip with the specified rectangle.
	boolean	clipRect(int left, int top, int right, int bottom)
		Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
	boolean	clipRegion(Region region, Op op)
		Modify the current clip with the specified region.
	boolean	clipRegion(Region region)
		Intersect the current clip with the specified region.
	void	concat(Matrix matrix)
		Preconcat the current matrix with the specified matrix.
	void	drawARGB(int a, int r, int g, int b)
		Fill the entire canvas' bitmap (restricted to the current clip) with the specified ARGB color, using srcover porterduff mode.
	void	drawArc(RectF oval, float startAngle, float sweepAngle, Paint paint)
		Draw the specified arc, which will be scaled to fit inside the specified oval.
	void	drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint)
		Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle.
	void	drawBitmap(Bitmap bitmap, float left, float top, Paint paint)
		Draw the specified bitmap, with its top/left corner at (x,y), using the specified paint, transformed by the current matrix.
	void	drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint)
		Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle.
	void	drawCircle(float cx, float cy, float radius, Paint paint)
		Draw the specified circle using the specified paint.
	void	drawColor(int color)
		Fill the entire canvas' bitmap (restricted to the current clip) with the specified color, using srcover porterduff mode.
	void	drawColor(int color, Mode mode)
		Fill the entire canvas' bitmap (restricted to the current clip) with the specified color and porter-duff xfermode.
	void	drawLine(float startX, float startY, float stopX, float stopY, Paint paint)
		Draw a line segment with the specified start and stop x,y coordinates, using the specified paint.
	void	drawOval(RectF oval, Paint paint)
		Draw the specified oval using the specified paint.
	void	drawPaint(Paint paint)
		Fill the entire canvas' bitmap (restricted to the current clip) with the specified paint.
	void	drawPath(Path path, Paint paint)
		Draw the specified path using the specified paint.
	void	drawPicture(Picture picture)
		Save the canvas state, draw the picture, and restore the canvas state.
	void	drawPoint(float x, float y, Paint paint)
		Helper for drawPoints() for drawing a single point.
	void	drawPoints(float[] pts, int offset, int length, Paint paint)
		Draw a series of points.
	void	drawPoints(float[] pts, Paint paint)
		Helper for drawPoints() that assumes you want to draw the entire array
	void	drawPosText(char[] text, int index, int count, float[] pos, Paint paint)
		Draw the text in the array, with each character's origin specified by the pos array.
	void	drawPosText(String text, float[] pos, Paint paint)
		Draw the text in the array, with each character's origin specified by the pos array.
	void	drawRGB(int r, int g, int b)
		Fill the entire canvas' bitmap (restricted to the current clip) with the specified RGB color, using srcover porterduff mode.
	void	drawRect(RectF rect, Paint paint)
		Draw the specified Rect using the specified paint.
	void	drawRect(float left, float top, float right, float bottom, Paint paint)
		Draw the specified Rect using the specified paint.
	void	drawRect(Rect r, Paint paint)
		Draw the specified Rect using the specified Paint.
	void	drawRoundRect(RectF rect, float rx, float ry, Paint paint)
		Draw the specified round-rect using the specified paint.
	void	drawText(String text, int start, int end, float x, float y, Paint paint)
		Draw the text, with origin at (x,y), using the specified paint.
	void	drawText(char[] text, int index, int count, float x, float y, Paint paint)
		Draw the text, with origin at (x,y), using the specified paint.
	void	drawText(String text, float x, float y, Paint paint)
		Draw the text, with origin at (x,y), using the specified paint.
	void	drawText(CharSequence text, int start, int end, float x, float y, Paint paint)
		Draw the specified range of text, specified by start/end, with its origin at (x,y), in the specified Paint.
	void	drawTextOnPath(String text, Path path, float hOffset, float vOffset, Paint paint)
		Draw the text, with origin at (x,y), using the specified paint, along the specified path.
	void	drawTextOnPath(char[] text, int index, int count, Path path, float hOffset, float vOffset, Paint paint)
		Draw the text, with origin at (x,y), using the specified paint, along the specified path.
	int	getBitmapHeight()
		Returns the height of the current drawing layer
	int	getBitmapWidth()
		Returns the width of the current drawing layer
final	Matrix	getCTM()
		Return a new matrix with a copy of the canvas' current transformation matrix.
	void	getCTM(Matrix ctm)
		Return, in ctm, the current transformation matrix.
	boolean	getClipBounds(Rect bounds)
		Retrieve the clip bounds, returning true if they are non-empty.
final	Rect	getClipBounds()
		Retrieve the clip bounds.
	DrawFilter	getDrawFilter()
	int	getSaveCount()
		Returns the number of matrix/clip states on the Canvas' private stack.
	boolean	isBitmapOpaque()
		Return true if the bitmap that the current layer draws into is opaque (i.e.
	boolean	quickReject(Path path, EdgeType type)
		Return true if the specified path, after being transformed by the current matrix, would lie completely outside of the current clip.
	boolean	quickReject(float left, float top, float right, float bottom, EdgeType type)
		Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip.
	boolean	quickReject(RectF rect, EdgeType type)
		Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip.
	void	restore()
		This call balances a previous call to save(), and is used to remove all modifications to the matrix/clip state since the last save call.
	void	restoreToCount(int saveCount)
		Efficient way to pop any calls to save() that happened after the save count reached saveCount.
final	void	rotate(float degrees, float px, float py)
		Preconcat the current matrix with the specified rotation.
	void	rotate(float degrees)
		Preconcat the current matrix with the specified rotation.
	int	save()
		Saves the current matrix and clip onto a private stack.
	int	save(int saveFlags)
		Based on saveFlags, can save the current matrix and clip onto a private stack.
	int	saveLayer(float left, float top, float right, float bottom, Paint paint, int saveFlags)
		Helper version of saveLayer() that takes 4 values rather than a RectF.
	int	saveLayer(RectF bounds, Paint paint, int saveFlags)
		This behaves the same as save(), but in addition it allocates an offscreen bitmap.
	int	saveLayerAlpha(float left, float top, float right, float bottom, int alpha, int saveFlags)
		Helper for saveLayerAlpha() that takes 4 values instead of a RectF.
	int	saveLayerAlpha(RectF bounds, int alpha, int saveFlags)
		This behaves the same as save(), but in addition it allocates an offscreen bitmap.
final	void	scale(float sx, float sy, float px, float py)
		Preconcat the current matrix with the specified scale.
	void	scale(float sx, float sy)
		Preconcat the current matrix with the specified scale.
	void	setDevice(Bitmap bitmap)
		Specify a bitmap for the canvas to draw into.
	void	setDrawFilter(DrawFilter filter)
	void	skew(float sx, float sy)
		Preconcat the current matrix with the specified skew.
	void	translate(float dx, float dy)
		Preconcat the current matrix with the specified translation

Protected Methods

				void	finalize()
					Called by the virtual machine when there are no longer any (non-weak) references to the receiver.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

	Object	clone()
		Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
	boolean	equals(Object o)
		Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
	void	finalize()
		Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
final	Class	getClass()
		Answers the unique instance of java.lang.Class which represents the class of the receiver.
	int	hashCode()
		Answers an integer hash code for the receiver.
final	void	notify()
		Causes one thread which is `wait` ing on the receiver to be made ready to run.
final	void	notifyAll()
		Causes all threads which are `wait` ing on the receiver to be made ready to run.
	String	toString()
		Answers a string containing a concise, human-readable description of the receiver.
final	void	wait(long time, int frac)
		Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by `notify` or `notifyAll`) or the expiration of the timeout.
final	void	wait(long time)
		Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by `notify` or `notifyAll`) or the expiration of the timeout.
final	void	wait()
		Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by `notify` or `notifyAll`).

Details

Constants

public static final int CLIP_SAVE_FLAG

restore the current clip when restore() is called

Constant Value: 2 (0x00000002)

public static final int CLIP_TO_LAYER_SAVE_FLAG

clip against the layer's bounds

Constant Value: 16 (0x00000010)

public static final int FULL_COLOR_LAYER_SAVE_FLAG

the layer needs to 8-bits per color component

Constant Value: 8 (0x00000008)

public static final int HAS_ALPHA_LAYER_SAVE_FLAG

the layer needs to per-pixel alpha

Constant Value: 4 (0x00000004)

public static final int MATRIX_SAVE_FLAG

restore the current matrix when restore() is called

Constant Value: 1 (0x00000001)

Public Constructors

public Canvas()

Construct an empty canvas. Use setDevice() to specify a bitmap to draw into.

public Canvas(Bitmap bitmap)

Construct a canvas with the specified bitmap to draw into. The bitmap must be mutable, or an exception will be thrown.

Parameters

bitmap	Specifies a mutable bitmap for the canvas to draw into.

Public Methods

public boolean clipPath(Path path)

Intersect the current clip with the specified path.

Parameters

path	The path to intersect with the current clip

Returns

true if the resulting is non-empty

public boolean clipPath(Path path, Op op)

Modify the current clip with the specified path.

Parameters

path	The path to operate on the current clip
op	How the clip is modified

Returns

true if the resulting is non-empty

public boolean clipRect(float left, float top, float right, float bottom)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

left	The left side of the rectangle to intersect with the current clip
top	The top of the rectangle to intersect with the current clip
right	The right side of the rectangle to intersect with the current clip
bottom	The bottom of the rectangle to intersect with the current clip

Returns

true if the resulting clip is non-empty

public boolean clipRect(Rect rect)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

rect	The rectangle to intersect with the current clip.

Returns

true if the resulting clip is non-empty

public boolean clipRect(float left, float top, float right, float bottom, Op op)

Modify the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

left	The left side of the rectangle to intersect with the current clip
top	The top of the rectangle to intersect with the current clip
right	The right side of the rectangle to intersect with the current clip
bottom	The bottom of the rectangle to intersect with the current clip
op	How the clip is modified

Returns

true if the resulting clip is non-empty

public boolean clipRect(Rect rect, Op op)

Modify the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

rect	The rectangle to intersect with the current clip.
op	How the clip is modified

Returns

true if the resulting clip is non-empty

public boolean clipRect(RectF rect)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

rect	The rectangle to intersect with the current clip.

Returns

true if the resulting clip is non-empty

public boolean clipRect(RectF rect, Op op)

Modify the current clip with the specified rectangle.

Parameters

rect	The rect to intersect with the current clip
op	How the clip is modified

Returns

true if the resulting clip is non-empty

public boolean clipRect(int left, int top, int right, int bottom)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters

left	The left side of the rectangle to intersect with the current clip
top	The top of the rectangle to intersect with the current clip
right	The right side of the rectangle to intersect with the current clip
bottom	The bottom of the rectangle to intersect with the current clip

Returns

true if the resulting clip is non-empty

public boolean clipRegion(Region region, Op op)

Modify the current clip with the specified region. Note that unlike clipRect() and clipPath() which transform their arguments by the current matrix, clipRegion() assumes its argument is already in the coordinate system of the current layer's bitmap, and so not transformation is performed.

Parameters

region	The region to operate on the current clip, based on op
op	How the clip is modified

Returns

true if the resulting is non-empty

public boolean clipRegion(Region region)

Intersect the current clip with the specified region. Note that unlike clipRect() and clipPath() which transform their arguments by the current matrix, clipRegion() assumes its argument is already in the coordinate system of the current layer's bitmap, and so not transformation is performed.

Parameters

region	The region to operate on the current clip, based on op

Returns

true if the resulting is non-empty

public void concat(Matrix matrix)

Preconcat the current matrix with the specified matrix.

Parameters

matrix	The matrix to preconcatenate with the current matrix

public void drawARGB(int a, int r, int g, int b)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified ARGB color, using srcover porterduff mode.

Parameters

a	alpha component (0..255) of the color to draw onto the canvas
r	red component (0..255) of the color to draw onto the canvas
g	green component (0..255) of the color to draw onto the canvas
b	blue component (0..255) of the color to draw onto the canvas

public void drawArc(RectF oval, float startAngle, float sweepAngle, Paint paint)

Draw the specified arc, which will be scaled to fit inside the specified oval.

Parameters

oval	The bounds of oval used to define the shape and size of the arc
startAngle	Starting angle (in degrees) where the arc begins
sweepAngle	Sweep angle (in degrees) measured clockwise
paint	The paint used to draw the arc

public void drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint)

Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle. If the source rectangle is not null, it specifies the subset of the bitmap to draw. Note: if the paint contains a maskfilter that generates a mask which extends beyond the bitmap's original width/height (e.g. BlurMaskFilter), then the bitmap will be drawn as if it were in a Shader with CLAMP mode. Thus the color outside of the original width/height will be the edge color replicated.

Parameters

bitmap	The bitmap to be drawn
src	May be null. The subset of the bitmap to be drawn
dst	The rectangle that the bitmap will be scaled/translated to fit into
paint	May be null. The paint used to draw the bitmap

public void drawBitmap(Bitmap bitmap, float left, float top, Paint paint)

Draw the specified bitmap, with its top/left corner at (x,y), using the specified paint, transformed by the current matrix. Note: if the paint contains a maskfilter that generates a mask which extends beyond the bitmap's original width/height (e.g. BlurMaskFilter), then the bitmap will be drawn as if it were in a Shader with CLAMP mode. Thus the color outside of the original width/height will be the edge color replicated.

Parameters

bitmap	The bitmap to be drawn
left	The position of the left side of the bitmap being drawn
top	The position of the top side of the bitmap being drawn
paint	The paint used to draw the bitmap (may be null)

public void drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint)

Parameters

bitmap	The bitmap to be drawn
src	May be null. The subset of the bitmap to be drawn
dst	The rectangle that the bitmap will be scaled/translated to fit into
paint	May be null. The paint used to draw the bitmap

public void drawCircle(float cx, float cy, float radius, Paint paint)

Draw the specified circle using the specified paint. If radius is <= 0, then nothing will be drawn. The circle will be filled or framed based on the Style in the paint.

Parameters

cx	The x-coordinate of the center of the cirle to be drawn
cy	The y-coordinate of the center of the cirle to be drawn
radius	The radius of the cirle to be drawn
paint	The paint used to draw the circle

public void drawColor(int color)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified color, using srcover porterduff mode.

Parameters

color	the color to draw onto the canvas

public void drawColor(int color, Mode mode)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified color and porter-duff xfermode.

Parameters

color	the color to draw with
mode	the porter-duff mode to apply to the color

public void drawLine(float startX, float startY, float stopX, float stopY, Paint paint)

Draw a line segment with the specified start and stop x,y coordinates, using the specified paint. NOTE: since a line is always "framed", the Style is ignored in the paint.

Parameters

startX	The x-coordinate of the start point of the line
startY	The y-coordinate of the start point of the line
paint	The paint used to draw the line

public void drawOval(RectF oval, Paint paint)

Draw the specified oval using the specified paint. The oval will be filled or framed based on the Style in the paint.

Parameters

oval	The rectangle bounds of the oval to be drawn

public void drawPaint(Paint paint)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified paint. This is equivalent (but faster) to drawing an infinitely large rectangle with the specified paint.

Parameters

paint	The paint used to draw onto the canvas

public void drawPath(Path path, Paint paint)

Draw the specified path using the specified paint. The path will be filled or framed based on the Style in the paint.

Parameters

path	The path to be drawn
paint	The paint used to draw the path

public void drawPicture(Picture picture)

Save the canvas state, draw the picture, and restore the canvas state.

Parameters

picture	The picture to be drawn

public void drawPoint(float x, float y, Paint paint)

Helper for drawPoints() for drawing a single point.

public void drawPoints(float[] pts, int offset, int length, Paint paint)

Draw a series of points. Each point is centered at the coordinate specified by pts[], and its diameter is specified by the paint's stroke width (as transformed by the canvas' CTM), with special treatment for a stroke width of 0, which always draws exactly 1 pixel (or at most 4 if antialiasing is enabled). The shape of the point is controlled by the paint's Cap type. The shape is a square, unless the cap type is Round, in which case the shape is a circle.

Parameters

pts	Array of points to draw [x0 y0 x1 y1 x2 y2 ...]
offset	Logical index of the first point to draw (internally this becomes offset*2 to find the first [x ...] value)
length	The logical number of points to draw (internally this becomes length*2 to know how many floats to process)
paint	The paint used to draw the points

public void drawPoints(float[] pts, Paint paint)

Helper for drawPoints() that assumes you want to draw the entire array

public void drawPosText(char[] text, int index, int count, float[] pos, Paint paint)

Draw the text in the array, with each character's origin specified by the pos array.

Parameters

text	The text to be drawn
index	The index of the first character to draw
count	The number of characters to draw, starting from index.
pos	Array of [x,y] positions, used to position each character
paint	The paint used for the text (e.g. color, size, style)

public void drawPosText(String text, float[] pos, Paint paint)

Draw the text in the array, with each character's origin specified by the pos array.

Parameters

text	The text to be drawn
pos	Array of [x,y] positions, used to position each character
paint	The paint used for the text (e.g. color, size, style)

public void drawRGB(int r, int g, int b)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified RGB color, using srcover porterduff mode.

Parameters

r	red component (0..255) of the color to draw onto the canvas
g	green component (0..255) of the color to draw onto the canvas
b	blue component (0..255) of the color to draw onto the canvas

public void drawRect(RectF rect, Paint paint)

Draw the specified Rect using the specified paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters

rect	The rect to be drawn
paint	The paint used to draw the rect

public void drawRect(float left, float top, float right, float bottom, Paint paint)

Draw the specified Rect using the specified paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters

left	The left side of the rectangle to be drawn
top	The top side of the rectangle to be drawn
right	The right side of the rectangle to be drawn
bottom	The bottom side of the rectangle to be drawn
paint	The paint used to draw the rect

public void drawRect(Rect r, Paint paint)

Draw the specified Rect using the specified Paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters

r	The rectangle to be drawn.
paint	The paint used to draw the rectangle

public void drawRoundRect(RectF rect, float rx, float ry, Paint paint)

Draw the specified round-rect using the specified paint. The roundrect will be filled or framed based on the Style in the paint.

Parameters

rect	The rectangular bounds of the roundRect to be drawn
rx	The x-radius of the oval used to round the corners
ry	The y-radius of the oval used to round the corners
paint	The paint used to draw the roundRect

public void drawText(String text, int start, int end, float x, float y, Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters

text	The text to be drawn
start	The index of the first character in text to draw
end	(end - 1) is the index of the last character in text to draw
x	The x-coordinate of the origin of the text being drawn
y	The y-coordinate of the origin of the text being drawn
paint	The paint used for the text (e.g. color, size, style)

public void drawText(char[] text, int index, int count, float x, float y, Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters

text	The text to be drawn
x	The x-coordinate of the origin of the text being drawn
y	The y-coordinate of the origin of the text being drawn
paint	The paint used for the text (e.g. color, size, style)

public void drawText(String text, float x, float y, Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters

text	The text to be drawn
x	The x-coordinate of the origin of the text being drawn
y	The y-coordinate of the origin of the text being drawn
paint	The paint used for the text (e.g. color, size, style)

public void drawText(CharSequence text, int start, int end, float x, float y, Paint paint)

Draw the specified range of text, specified by start/end, with its origin at (x,y), in the specified Paint. The origin is interpreted based on the Align setting in the Paint.

Parameters

text	The text to be drawn
start	The index of the first character in text to draw
end	(end - 1) is the index of the last character in text to draw
x	The x-coordinate of origin for where to draw the text
y	The y-coordinate of origin for where to draw the text
paint	The paint used for the text (e.g. color, size, style)

public void drawTextOnPath(String text, Path path, float hOffset, float vOffset, Paint paint)

Draw the text, with origin at (x,y), using the specified paint, along the specified path. The paint's Align setting determins where along the path to start the text.

Parameters

text	The text to be drawn
path	The path the text should follow for its baseline
hOffset	The distance along the path to add to the text's starting position
vOffset	The distance above(-) or below(+) the path to position the text
paint	The paint used for the text (e.g. color, size, style)

public void drawTextOnPath(char[] text, int index, int count, Path path, float hOffset, float vOffset, Paint paint)

Draw the text, with origin at (x,y), using the specified paint, along the specified path. The paint's Align setting determins where along the path to start the text.

Parameters

text	The text to be drawn
path	The path the text should follow for its baseline
hOffset	The distance along the path to add to the text's starting position
vOffset	The distance above(-) or below(+) the path to position the text
paint	The paint used for the text (e.g. color, size, style)

public int getBitmapHeight()

Returns the height of the current drawing layer

Returns

the height of the current drawing layer

public int getBitmapWidth()

Returns the width of the current drawing layer

Returns

the width of the current drawing layer

public final Matrix getCTM()

Return a new matrix with a copy of the canvas' current transformation matrix.

public void getCTM(Matrix ctm)

Return, in ctm, the current transformation matrix. This does not alter the matrix in the canvas, but just returns a copy of it.

public boolean getClipBounds(Rect bounds)

Retrieve the clip bounds, returning true if they are non-empty.

Parameters

bounds	Return the clip bounds here. If it is null, ignore it but still return true if the current clip is non-empty.

Returns

true if the current clip is non-empty.

public final Rect getClipBounds()

Retrieve the clip bounds.

Returns

the clip bounds, or [0, 0, 0, 0] if the clip is empty.

public DrawFilter getDrawFilter()

public int getSaveCount()

Returns the number of matrix/clip states on the Canvas' private stack. This will equal # save() calls - # restore() calls.

public boolean isBitmapOpaque()

Return true if the bitmap that the current layer draws into is opaque (i.e. does not support per-pixel alpha).

Returns

true if the bitmap that the current layer draws into is opaque

public boolean quickReject(Path path, EdgeType type)

Return true if the specified path, after being transformed by the current matrix, would lie completely outside of the current clip. Call this to check if an area you intend to draw into is clipped out (and therefore you can skip making the draw calls). Note: for speed it may return false even if the path itself might not intersect the clip (i.e. the bounds of the path intersects, but the path does not).

Parameters

path	The path to compare with the current clip
type	true if the path should be considered antialiased, since that means it may affect a larger area (more pixels) than non-antialiased.

Returns

true if the path (transformed by the canvas' matrix) does not intersect with the canvas' clip

public boolean quickReject(float left, float top, float right, float bottom, EdgeType type)

Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip. Call this to check if an area you intend to draw into is clipped out (and therefore you can skip making the draw calls).

Parameters

left	The left side of the rectangle to compare with the current clip
top	The top of the rectangle to compare with the current clip
right	The right side of the rectangle to compare with the current clip
bottom	The bottom of the rectangle to compare with the current clip
type	true if the rect should be considered antialiased, since that means it may affect a larger area (more pixels) than non-antialiased.

Returns

true if the rect (transformed by the canvas' matrix) does not intersect with the canvas' clip

public boolean quickReject(RectF rect, EdgeType type)

Parameters

rect	the rect to compare with the current clip
type	specifies how to treat the edges (BW or antialiased)

Returns

true if the rect (transformed by the canvas' matrix) does not intersect with the canvas' clip

public void restore()

This call balances a previous call to save(), and is used to remove all modifications to the matrix/clip state since the last save call. It is an error to call restore() more times than save() was called.

public void restoreToCount(int saveCount)

Efficient way to pop any calls to save() that happened after the save count reached saveCount. It is an error for saveCount to be less than getSaveCount()


e.g. "intent" or "activity"

Android - An Open Handset Alliance Project

Documentation

Goodies

android.graphics.Canvas

Nested Classes

Summary

Constants

Public Constructors

Public Methods

Protected Methods

Methods inherited from class java.lang.Object

Details

Constants

public static final int CLIP_SAVE_FLAG

public static final int CLIP_TO_LAYER_SAVE_FLAG

public static final int FULL_COLOR_LAYER_SAVE_FLAG

public static final int HAS_ALPHA_LAYER_SAVE_FLAG

public static final int MATRIX_SAVE_FLAG

Public Constructors

public Canvas()

public Canvas(Bitmap bitmap)

Parameters

Public Methods

public boolean clipPath(Path path)

Parameters

Returns

public boolean clipPath(Path path, Op op)

Parameters

Returns

public boolean clipRect(float left, float top, float right, float bottom)

Parameters

Returns

public boolean clipRect(Rect rect)

Parameters

Returns

public boolean clipRect(float left, float top, float right, float bottom, Op op)

Parameters

Returns

public boolean clipRect(Rect rect, Op op)

Parameters

Returns

public boolean clipRect(RectF rect)

Parameters

Returns

public boolean clipRect(RectF rect, Op op)

Parameters

Returns

public boolean clipRect(int left, int top, int right, int bottom)

Parameters

Returns

public boolean clipRegion(Region region, Op op)

Parameters

Returns

public boolean clipRegion(Region region)

Parameters

Returns

public void concat(Matrix matrix)

Parameters

public void drawARGB(int a, int r, int g, int b)

Parameters

public void drawArc(RectF oval, float startAngle, float sweepAngle, Paint paint)

Parameters

public void drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint)

Parameters

public void drawBitmap(Bitmap bitmap, float left, float top, Paint paint)

Parameters

public void drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint)

Parameters

public void drawCircle(float cx, float cy, float radius, Paint paint)

Parameters

public void drawColor(int color)

Parameters

public void drawColor(int color, Mode mode)

Parameters

public void drawLine(float startX, float startY, float stopX, float stopY, Paint paint)

Parameters

public void drawOval(RectF oval, Paint paint)

Parameters

public void drawPaint(Paint paint)

Parameters