Canvas中用drawPoint方法绘制点，代码如下所示：

private void drawPoint(Canvas canvas){ int canvasWidth = canvas.getWidth(); int canvasHeight = canvas.getHeight(); int x = canvasWidth / 2; int deltaY = canvasHeight / 3; int y = deltaY / 2; paint.setColor(0xff8bc5ba);//设置颜色 paint.setStrokeWidth(50 * density);//设置线宽，如果不设置线宽，无法绘制点 //绘制Cap为BUTT的点 paint.setStrokeCap(Paint.Cap.BUTT); canvas.drawPoint(x, y, paint); //绘制Cap为ROUND的点 canvas.translate(0, deltaY); paint.setStrokeCap(Paint.Cap.ROUND); canvas.drawPoint(x, y, paint); //绘制Cap为SQUARE的点 canvas.translate(0, deltaY); paint.setStrokeCap(Paint.Cap.SQUARE); canvas.drawPoint(x, y, paint); }

界面如下所示：

下面对以上代码进行说明：

drawLine

Canvas通过drawLine方法绘制一条线段，通过drawLines方法绘制多段线，使用代码如下所示：

下面对以上代码进行说明：

上面在讲drawPoint时提到了strokeCap对所绘制点的形状的影响，通过drawLine绘制的线段也受其影响，体现在绘制的线段的两个端点的形状上。

Paint.Cap.BUTT
当用BUTT作为帽端时，所绘制的线段恰好在起点终点位置处戛然而止，两端是方形，上图中第一条加粗的线段就是用BUTT作为帽端绘制的。

Paint.Cap.ROUND
当用ROUND作为帽端时，所绘制的线段的两端端点会超出起点和终点一点距离，并且两端是圆形状，上图中第二条加粗的线段就是用ROUND作为帽端绘制的。

Paint.Cap.SQUARE
当用SQUARE作为帽端时，所绘制的线段的两端端点也会超出起点和终点一点距离，两端点的形状是方形，上图中最后一条加粗的线段就是用SQUARE作为帽端绘制的。

drawRect

Canvas通过drawRect方法绘制矩形，使用代码如下所示：

private void drawRect(Canvas canvas){ int canvasWidth = canvas.getWidth(); int canvasHeight = canvas.getHeight(); //默认画笔的填充色是黑色 int left1 = 10; int top1 = 10; int right1 = canvasWidth / 3; int bottom1 = canvasHeight /3; canvas.drawRect(left1, top1, right1, bottom1, paint); //修改画笔颜色 paint.setColor(0xff8bc5ba);//A:ff,R:8b,G:c5,B:ba int left2 = canvasWidth / 3 * 2; int top2 = 10; int right2 = canvasWidth - 10; int bottom2 = canvasHeight / 3; canvas.drawRect(left2, top2, right2, bottom2, paint); }

界面如下所示：

其方法签名是drawRect(float left, float top, float right, float bottom, Paint paint)，left和right表示矩形的左边和右边分别到绘图坐标系y轴正半轴的距离，top和bottom表示矩形的上边和下边分别到绘图坐标系x轴正半轴的距离。

drawCircle

Canvas中用drawCircle方法绘制圆形，使用代码如下所示：

private void drawCircle(Canvas canvas){ paint.setColor(0xff8bc5ba);//设置颜色 paint.setStyle(Paint.Style.FILL);//默认绘图为填充模式 int canvasWidth = canvas.getWidth(); int canvasHeight = canvas.getHeight(); int halfCanvasWidth = canvasWidth / 2; int count = 3; int D = canvasHeight / (count + 1); int R = D / 2; //绘制圆 canvas.translate(0, D / (count + 1)); canvas.drawCircle(halfCanvasWidth, R, R, paint); //通过绘制两个圆形成圆环 //1. 首先绘制大圆 canvas.translate(0, D + D / (count + 1)); canvas.drawCircle(halfCanvasWidth, R, R, paint); //2. 然后绘制小圆，让小圆覆盖大圆，形成圆环效果 int r = (int)(R * 0.75); paint.setColor(0xffffffff);//将画笔设置为白色，画小圆 canvas.drawCircle(halfCanvasWidth, R, r, paint); //通过线条绘图模式绘制圆环 canvas.translate(0, D + D / (count + 1)); paint.setColor(0xff8bc5ba);//设置颜色 paint.setStyle(Paint.Style.STROKE);//绘图为线条模式 float strokeWidth = (float)(R * 0.25); paint.setStrokeWidth(strokeWidth); canvas.drawCircle(halfCanvasWidth, R, R, paint); }

界面如下所示：