android Canvas参考

很多时候android本身提供的控件并不能满足我们实现一些复杂或是酷炫的效果，这时候就得自定义View了，当然这里不会写写关于自定义View的，只是介绍下canvas常见的方法。

画圆弧：drawArc

drawArc(@NonNull RectF oval, float startAngle, float                                                    sweepAngle, boolean useCenter, @NonNull Paint paint)drawArc(float left, float top, float right, float bottom, float startAngle, float sweepAngle, boolean useCenter, @NonNull Paint paint)

具体从参数方面来说可以绘制圆、椭圆、圆环、圆弧、扇形。
RectF oval：表示一个矩形，即绘制范围，正方形范围绘制圆，长方形范围绘制椭圆
float left, float top, float right, float bottom：可组成矩形
float startAngle：起始绘制角度，中心为原点，水平向右为0度，按顺时针方向绘制
float sweepAngle：圆弧扫过的角度，值360则绘制圆、椭圆、圆环，否则绘制圆弧、扇形，亦相当于设置进度条进度(0-360)，是圆形进度条的实现方法之一
boolean useCenter：true绘制扇形，false绘制圆弧
Paint paint：设置画笔参数，以下将列出常用方法：

paint.setAntiAlias(true);// 抗锯齿paint.setStyle(Paint.Style.STROKE);// 线条画笔，可绘制圆环paint.setColor(Color.RED);// 设置画笔颜色paint.setStrokeWidth(10);// 设置画笔粗细paint.setShader(shader);// 设置颜色渐变，比如在这里可绘制彩色圆环进度条paint.setStrokeCap(Paint.Cap.ROUND);// 设置圆弧两端为圆弧闭合渐变Shader：LinearGradient：线性渐变：LinearGradient(float x0, float y0, float x1, float y1, int color0, int color1, TileMode tile)

画位图：drawBitmap

drawBitmap(@NonNull Bitmap bitmap, @Nullable Rect src, @NonNull Rect(F) dst, @Nullable Paint paint)Bitmap bitmap：要绘制的bitmapRect src：要绘制的bitmap的某部分或全部RectF dst：绘制bitmap的位置Paint paint：画笔，目测不知道有啥用

drawBitmap(@NonNull Bitmap bitmap, float left, float top, @Nullable Paint paint)Bitmap bitmap：要绘制的bitmapfloat left：左边偏移量float top：顶部偏移量Paint paint：画笔

填充颜色：drawColor

drawColor(@ColorInt int color, @NonNull PorterDuff.Mode mode)int color：绘制的画布颜色Mode mode：绘制模式

画线：drawLine

drawLine(float startX, float startY, float stopX, float stopY,         @NonNull Paint paint)float startX：线条起始x坐标，左上角坐标(0, 0)float startY：线条起始y坐标float stopX：线条终止x坐标float stopY：线条终止y坐标Paint paint：画笔

画笔绘制：drawPaint

drawPaint(@NonNull Paint paint)Paint.Style.STROKE：给画布画边框Paint.Style.FILL：给画布填充颜色

画矩形：drawRect(F)

drawRect(F)(@NonNull RectF rect, @NonNull Paint paint)Paint.Style.STROKE：画边框，大小为rectPaint.Style.FILL：画背景，大小为rect

画圆：drawCircle

drawCircle(float cx, float cy, float radius, @NonNull Paint paint)float cx, float cy：圆心坐标(cx, cy)Paint paint：画笔，STROKE空心；FILL实心

画椭圆：drawOval

drawOval(@NonNull RectF oval, @NonNull Paint paint)drawOval(float left, float top, float right, float bottom, @NonNull Paint paint)RectF oval = new RectF(left, top, right, bottom);RectF oval：绘制区域Paint paint：画笔，STROKE空心；FILL实心

画点：drawPoint

drawPoint(float x, float y, @NonNull Paint paint)float x, float y：画点位置(x, y)Paint paint：画笔

画圆角矩形：drawRoundRect

drawRoundRect(@NonNull RectF rect, float rx, float ry, @NonNull Paint paint)drawRoundRect(float left, float top, float right, float bottom, float rx, float ry, @NonNull Paint paint)RectF rect = new RectF(left, top, right, bottom);RectF rect：绘制区域float rx, float ry：圆角半径Paint paint：画笔

drawText

drawText(@NonNull char[] text, int index, int count, float x, float y, @NonNull Paint paint)drawText(@NonNull String text, float x, float y, @NonNull Paint paint)drawText(@NonNull String text, int start, int end, float x, float y, @NonNull Paint paint)drawText(@NonNull CharSequence text, int start, int end, float x, float y, @NonNull Paint paint)int start, int end：截取部分文本绘制float x, float y：再坐标(x, y)处开始绘制文本Paint paint：可设置字体大小等参数

绘制路径：drawPath

这个方法可以绘制比较复杂的一些函数曲线，这个不太熟悉，各位看官还是谷歌百度吧，这里简单介绍下常见方法：

drawPath(@NonNull Path path, @NonNull Paint paint)Path path：绘制路径Paint paint：画笔画个三角形：path.moveTo(0, getHeight()/4);path.lineTo(0, (getHeight() * 3) / 4);path.lineTo(getWidth(), getHeight()*3/4);path.close();画圆弧：相当于drawArc，参数useCenter为falseaddArc(RectF oval, float startAngle, float sweepAngle)addArc(float left, float top, float right, float bottom, float startAngle, float sweepAngle)画圆弧：默认闭合，forceMoveTo为true即圆弧，不闭合arcTo(RectF oval, float startAngle, float sweepAngle)arcTo(RectF oval, float startAngle, float sweepAngle, boolean forceMoveTo)画圆：圆心(x, y)，半径radius，dir绘制方向addCircle(float x, float y, float radius, Direction dir)画椭圆：addOval(RectF oval, Direction dir)addOval(float left, float top, float right, float bottom, Direction dir)画矩形：addRect(RectF rect, Direction dir)addRect(float left, float top, float right, float bottom, Direction dir)画圆角矩形：addRoundRect(RectF rect, float rx, float ry, Direction dir)addRoundRect(float left, float top, float right, float bottom, float rx, float ry, Direction dir)画曲线：cubicTo(float x1, float y1, float x2, float y2, float x3, float y3)在(x1, y1)和(x3, y3)之间画曲线，以(x2, y2)为转折点画(曲)线：quadTo(float x1, float y1, float x2, float y2)(x1, y1)是控制点，(x2, y2)是终点，起点是当前点，默认(0, 0)，可用moveTo设置当前点。