Android原生绘图工具Canvas详细 Android原生绘图工具Canvas详细

1.Canvas提供的绘制函数
2.绘制背景
3.绘制矩形drawRect
4.绘制圆角矩形drawRoundRect
5.绘制圆形drawCircle
6.绘制路径drawPath
7.绘制直线drawLine
8.绘制圆弧drawArc
9.绘制椭圆drawOval
10.绘制点drawPoint
11.绘制文本drawText 沿路径绘制文本drawTextOnPath
12.绘制bitmap drawBitmap

如果对上一篇感兴趣的话可以看看Android原生绘图Paint
下面步入正题：先看看效果图

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1.Canvas提供的绘制函数

canvas.drawColor(); canvas.drawRGB(); canvas.drawRect(); canvas.drawRoundRect(); canvas.drawCircle(); canvas.drawPath(); canvas.drawLine(); canvas.drawArc(); canvas.drawOval(); canvas.drawPoint(); canvas.drawPoints(); canvas.drawText(); canvas.drawTextOnPath(); canvas.drawBitmap();

2.绘制背景用于初始化和清空画布

//绘制颜色，默认模式public void drawColor(@ColorInt int color) {super.drawColor(color); }//颜色绘制，设置modepublic void drawColor(@ColorInt int color, @NonNull PorterDuff.Mode mode) {super.drawColor(color, mode); }//参数0-255public void drawARGB(int a, int r, int g, int b) {super.drawARGB(a, r, g, b); }//参数0-255public void drawRGB(int r, int g, int b) {super.drawRGB(r, g, b); }

第二个函数中用到PorterDuff.Mode，PorterDuff.Mode主要用于图像混合模式，后面细说

3.绘制矩形drawRect

//传入RectF public void drawRect(@NonNull RectF rect, @NonNull Paint paint) {super.drawRect(rect, paint); }//传入Rectpublic void drawRect(@NonNull Rect r, @NonNull Paint paint) {super.drawRect(r, paint); }//把Rect的四个点坐标传入public void drawRect(float left, float top, float right, float bottom, @NonNull Paint paint) {super.drawRect(left, top, right, bottom, paint); }

Rect 和RectF都是提供一个矩形局域。

(1)精度不一样，Rect是使用int类型作为数值，RectF是使用float类型作为数值。
(2)两个类型提供的方法也不是完全一致。

Rect rect = new Rect(100,100,300,300); RectF rectf = new RectF(100,400,300,600); canvas.drawRect(rect, mPaint); canvas.drawRect(rectf, mPaint); canvas.drawRect(100, 700, 300, 900, mPaint);

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4.绘制圆角矩形drawRoundRect

public void drawRoundRect(@NonNull RectF rect, float rx, float ry, @NonNull Paint paint) {super.drawRoundRect(rect, rx, ry, paint); }//不利用RectF,直接设置四个点public void drawRoundRect(float left, float top, float right, float bottom, float rx, float ry,@NonNull Paint paint) {super.drawRoundRect(left, top, right, bottom, rx, ry, paint); }

rect：RectF对象，一个矩形区域。
rx：x方向上的圆角半径。
ry：y方向上的圆角半径。
paint：绘制时所使用的画笔。

Rect rect = new Rect(100,100,300,300); RectF rectf = new RectF(100,400,300,600); canvas.drawRect(rect, mPaint); canvas.drawRoundRect(rectf, 5, 20, mPaint); canvas.drawRoundRect(100, 700, 300, 900, 20, 5, mPaint);

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5.绘制圆形drawCircle

public void drawCircle(float cx, float cy, float radius, @NonNull Paint paint) {super.drawCircle(cx, cy, radius, paint); }

参数解释：

cx：圆心x
cy：圆心y
radius：半径

canvas.drawCircle(500, 300, 100, mPaint);

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6.绘制路径drawPath

public void drawPath(@NonNull Path path, @NonNull Paint paint) {super.drawPath(path, paint); }

需要一个Path

Path path = new Path(); path.moveTo(100, 100); path.lineTo(100, 200); path.lineTo(200, 300); mPaint2.setStrokeJoin(Paint.Join.MITER); canvas.drawPath(path, mPaint2);

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7.绘制直线drawLine

//提供起点，终点和画笔public void drawLine(float startX, float startY, float stopX, float stopY,@NonNull Paint paint) {super.drawLine(startX, startY, stopX, stopY, paint); }public void drawLines(@Size(multiple = 4) @NonNull float[] pts, int offset, int count,@NonNull Paint paint) {super.drawLines(pts, offset, count, paint); }public void drawLines(@Size(multiple = 4) @NonNull float[] pts, @NonNull Paint paint) {super.drawLines(pts, paint); }

绘制线的集合，参数中pts是点的集合，两个值代表一个点，四个值代表一条线，互相之间不连接。
offset跳过的点，count跳过之后要绘制的点的总数，可以用于集合中部分点的绘制。

canvas.drawLine(500, 500, 500, 300, mPaint); float[] pos = {20, 30, 40 , 100, 120, 160, 200, 290}; canvas.drawLines(pos, mPaint);

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8.绘制圆弧drawArc

public void drawArc(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter,@NonNull Paint paint) {super.drawArc(oval, startAngle, sweepAngle, useCenter, paint); }public void drawArc(float left, float top, float right, float bottom, float startAngle,float sweepAngle, boolean useCenter, @NonNull Paint paint) {super.drawArc(left, top, right, bottom, startAngle, sweepAngle, useCenter, paint); }

RectF oval:生成弧的矩形，中心为弧的圆心
float startAngle：弧开始的角度，以X轴正方向为0度，顺时针
float sweepAngle：弧持续的角度
boolean useCenter:是否有弧的两边，True，还两边，False，只有一条弧

RectF rectF = new RectF(100, 100, 400, 400); canvas.drawArc(rectF, 0, 270, false, mPaint2); rectF = new RectF(500, 500, 800, 800); canvas.drawArc(rectF, 0, 270, true, mPaint2);

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9.绘制椭圆drawOval

public void drawOval(@NonNull RectF oval, @NonNull Paint paint) {super.drawOval(oval, paint); }public void drawOval(float left, float top, float right, float bottom, @NonNull Paint paint) {super.drawOval(left, top, right, bottom, paint); }

在矩形框内画一个椭圆，如果是个正方形会画出一个圆。

RectF rectF = new RectF(100, 100, 400, 400); canvas.drawOval(rectF, mPaint2); rectF = new RectF(500, 500, 900, 800); canvas.drawOval(rectF, mPaint2);

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10.绘制点drawPoint

public void drawPoint(float x, float y, @NonNull Paint paint) {super.drawPoint(x, y, paint); }public void drawPoints(@Size(multiple = 2) float[] pts, int offset, int count,@NonNull Paint paint) {super.drawPoints(pts, offset, count, paint); }public void drawPoints(@Size(multiple = 2) @NonNull float[] pts, @NonNull Paint paint) {super.drawPoints(pts, paint); }

只需要提供两个点一个坐标就可以绘制点。

canvas.drawPoint(100, 100, mPaint2); float[] points = {30, 40, 50, 60, 70, 80}; canvas.drawPoints(points, mPaint2);

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11.绘制文本drawText 沿路径绘制文本drawTextOnPath

public void drawText(@NonNull char[] text, int index, int count, float x, float y,@NonNull Paint paint) {super.drawText(text, index, count, x, y, paint); }public void drawText(@NonNull String text, float x, float y, @NonNull Paint paint) {super.drawText(text, x, y, paint); }public void drawText(@NonNull String text, int start, int end, float x, float y,@NonNull Paint paint) {super.drawText(text, start, end, x, y, paint); }public void drawText(@NonNull CharSequence text, int start, int end, float x, float y,@NonNull Paint paint) {super.drawText(text, start, end, x, y, paint); }

canvas.drawText("MatumbaMan的博客",100,100,mTextPaint);

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Path path = new Path(); path.addArc(new RectF(100, 100, 600, 600), 0, 260); canvas.drawTextOnPath("MatumbaMan的博客", path, 10, 20, mTextPaint); canvas.drawText("MatumbaMan的博客",100,100, mTextPaint);

drawTextOnPath
沿着一条 Path 来绘制文字
text 为所需要绘制的文字
path 为文字的路径
hOffset 文字相对于路径的水平偏移量，用于调整文字的位置
vOffset 文字相对于路径竖直偏移量，用于调整文字的位置

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12.绘制bitmap drawBitmap

public void drawBitmap(@NonNull Bitmap bitmap, @Nullable Rect src, @NonNull RectF dst,@Nullable Paint paint) {super.drawBitmap(bitmap, src, dst, paint); }public void drawBitmap(@NonNull Bitmap bitmap, @Nullable Rect src, @NonNull Rect dst,@Nullable Paint paint) {super.drawBitmap(bitmap, src, dst, paint); }

Rect src：指定绘制图片的区域
Rect dst或RectF dst：指定图片在屏幕上的绘制（显示）区域
首先指定图片区域，然后指定绘制图片的区域。

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.rocket2); canvas.drawBitmap(bitmap, 100, 100, mPaint); Rect src = https://www.it610.com/article/new Rect(0, 0, 100,100); Rect dst = new Rect(200, 500, 300, 600); canvas.drawBitmap(bitmap, src, dst, mPaint);