Android之Canvas
一、概述
TheCanvasclassholdsthe"draw"calls.Todrawsomething,youneed4basiccomponents:ABitmaptoholdthepixels,aCanvastohostthedrawcalls(writingintothebitmap),adrawingprimitive(e.g.Rect,Path,text,Bitmap),andapaint(todescribethecolorsandstylesforthedrawing).
Canvas类支持“draw”的调用，可以去绘制别的事物。你需要四种基本的组成成分：
(1)Bitmap(图像)
(2)Canvas(画布，主办描绘调用等，即等待绘制到bitmap中)
(3)primitive(绘制的原始事物（例如矩形、路径、文本、图像）)
(4)paint（颜料,描述描绘的颜色和风格）
二、嵌套类
NestedClasses
enum
Canvas.EdgeType
enum
Canvas.VertexMode
三、常量
Constans
int
ALL_SAVE_FLAG
当restore()方法被调用时，恢复全部东西
int
CLIP_SAVE_FLAG
当restore()方法被调用时，恢复当前剪辑
int
CLIP_TO_LAYER_SAVE_FLAG
clipagainstthelayer'sbounds
剪辑对立层的边界
int
FULL_COLOR_LAYER_SAVE_FLAG
thelayerneedsto8-bitspercolorcomponent
int
HAS_ALPHA_LAYER_SAVE_FLAG
thelayerneedstoper-pixelalpha
int
MATRIX_SAVE_FLAG
restorethecurrentmatrixwhenrestore()iscalled
当调用restore()方法时，恢复现有矩阵
四、公共构造函数
PublicConstructors
Canvas()
Constructanemptyrastercanvas
Canvas(Bitmapbitmap)
Constructacanvaswiththespecifiedbitmaptodrawinto
Canvas(GLgl)
Constructacanvaswiththespecifiedglcontext