Paint - PathEffect 详解

PathEffect

PathEffect is the base class for objects in the Paint that affect the geometry of a drawing primitive before it is transformed by the canvas' matrix and drawn.

该系列类没有实例方法，只有构造方法，只须要构造后，传入 Paint.setPathEffect(PathEffect effect) 便可。


概览

原图：

CornerPathEffect

CornerPathEffect(float radius)

Parameters
radius	float: Amount to round sharp angles between line segments.

Transforms geometries that are drawn (either STROKE or FILL styles) by replacing any sharp angles between line segments into rounded angles of the specified radius.

DiscretePathEffect

DiscretePathEffect(float segmentLength, float deviation)

Parameters
segmentLength	float
deviation	float

Chop the path into lines of segmentLengthdeviation**.

segmentLength=1dp, deviation=10dp

segmentLength=10dp, deviation=10dp

DashPathEffect

DashPathEffect(float[] intervals, float phase)

Parameters
intervals	float: array of ON and OFF distances
phase	float: offset into the intervals array 总体偏移, 动态设置 phase, 能够产生蚂蚁线效果

The intervals array must contain an even number of entries (>=2), with the even indices specifying the "on" intervals, and the odd indices specifying the "off" intervals.
phase is an offset into the intervals array (mod the sum of all of the intervals).
The intervals array controls the length of the dashes. The paint's strokeWidth controls the thickness of the dashes.
Note: this patheffect only affects drawing with the paint's style is set to STROKE or FILL_AND_STROKE. It is ignored if the drawing is done with style == FILL.

PathDashPathEffect

PathDashPathEffect(Path shape, float advance, float phase, PathDashPathEffect.Style style)

Parameters
shape	Path: The path to stamp along shape 须要是闭合路径
advance	float: spacing between each stamp of shape shape 之间的间距, 忽略 shape 自己的大小
phase	float: amount to offset before the first shape is stamped 总体偏移, 动态设置 phase, 能够产生蚂蚁线效果
style	PathDashPathEffect.Style: how to transform the shape at each position as it is stamped 枚举取值: MORPH, ROTATE, TRANSLATE MORPH: 方向跟路径一致, 在拐角处变形 ROTATE: 方向跟路径一致, 拐角处保持不变, 有断开效果 TRANSLATE: 保持shape方向不变, 不随路径变化 MORPH 效果最好

Dash the drawn path by stamping it with the specified shape.
This only applies to drawings when the paint's style is STROKE or STROKE_AND_FILL. If the paint's style is FILL, then this effect is ignored.
The paint's strokeWidth does not affect the results.

MORPH

ROTATE

TRANSLATE

SumPathEffect

SumPathEffect(PathEffect first, PathEffect second)

Construct a PathEffect whose effect is to apply two effects, in sequence. (e.g. first(path) + second(path))
将两个 PathEffect 效果叠加，至关与绘制了2次。first 和 second 的顺序无影响。

DashPathEffect + CornerPathEffect

ComposePathEffect

ComposePathEffect(PathEffect outerpe, PathEffect innerpe)

Construct a PathEffect whose effect is to apply first the inner effect and the the outer pathEffect. (e.g. outer(inner(path)))
将两个 PathEffect 效果进行组合，先进行 innerpe，在此次的结果上在进行 outerpe。两次的顺序不一样，结果也有差别。

CornerPathEffect(DashPathEffect())

DashPathEffect(CornerPathEffect())

源码

github.com/wenmin92/An…