自定义View(2)canas绘制基本图形的示例

效果

代码：

 　　void drawSample(Canvas canvas) {
         /*
          * 方法 说明 drawRect 绘制矩形 drawCircle 绘制圆形 drawOval 绘制椭圆 drawPath 绘制路径
          * drawLine 绘制直线 drawPoin 绘制点
          */
         // 创建画笔
         Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
         int txtSize = ;
         paint.setTextSize(txtSize);
         /*画点*/
         paint.setStyle(Paint.Style.FILL);
         canvas.drawText("画点：", , txtSize, paint);
         paint.setColor(Color.RED);
         float stroke = paint.getStrokeWidth();
         paint.setStrokeWidth();
         canvas.drawPoint(, , paint);// 画一个点
         canvas.drawPoints(new float[] { , , , , ,  }, paint);// 画多个点
         paint.setStrokeWidth(stroke);

         /*画线*/
         paint.setColor(Color.BLACK);
         canvas.drawText("画线：", , , paint);
         canvas.drawLine(, , , , paint);// 画线
         canvas.drawLine(, , , , paint);// 斜线

         /*画虚线*/
         canvas.drawText("画虚线：", ,, paint);
         paint.setStyle(Paint.Style.STROKE);
         Path path3 = new Path();
         path3.moveTo(, );
         path3.lineTo(,);
         /*DashPathEffect第一个参数必须为偶数个整数，其中偶数位上的整数表示绘制的间隔，奇数位上的整数表示不绘制的间隔。*/
         PathEffect effects = new DashPathEffect(new float[]{,,,,,},);
         PathEffect oldEffect = paint.getPathEffect();
         paint.setPathEffect(effects);
         canvas.drawPath(path3, paint);

         /*画弧线*/
         paint.setPathEffect(oldEffect);
         canvas.drawText("画弧线：", , , paint);

         RectF oval1 = new RectF(, , , );    // 弧线是画在矩形中的
         canvas.drawArc(oval1, , , false, paint);    // 左眼弧线 ^_^

         oval1.set(, , , );
         canvas.drawArc(oval1, , , false, paint);    // 右眼弧线 ^_^

         oval1.set(, , , );
         canvas.drawArc(oval1, , , false, paint);    // 嘴弧线 ^_^

         /*画贝塞尔曲线*/
         /* Path类封装复合(多轮廓几何图形的路径
          * 由直线段*、二次曲线,和三次方曲线，也可画以油画。drawPath(路径、油漆),要么已填充的或抚摸
          * (基于油漆的风格),或者可以用于剪断或画画的文本在路径。
          */
         canvas.drawText("画贝塞尔曲线:", , , paint);
         Path path2 = new Path();
         path2.moveTo(, );                // 设置Path的起点
         path2.quadTo(, , , );     // 设置贝塞尔曲线的控制点坐标和终点坐标
         canvas.drawPath(path2, paint);        // 画出贝塞尔曲线

         /*画圆*/
         canvas.drawText("画圆：", , , paint);    // 画文本
         canvas.drawCircle(, , , paint);        // 小圆
         paint.setAntiAlias(true);                    // 设置画笔的锯齿效果。true是去除
         canvas.drawCircle(, , , paint);        // 大圆

         /*画扇形和椭圆*/
         canvas.drawText("画扇形和椭圆:", , , paint);
         /*设置渐变色 这个正方形的颜色是改变的 */
         Shader mShader = new LinearGradient(, , , ,
                 new int[] { Color.RED, Color.GREEN, Color.BLUE, Color.YELLOW,
                         Color.LTGRAY }, null, Shader.TileMode.REPEAT); // 一个材质,打造出一个线性梯度沿著一条线。
         paint.setShader(mShader);
         // p.setColor(Color.BLUE);

         // 画扇形，drawArc第一个参数是RectF：该类是第二个参数是角度的开始，第三个参数是多少度，第四个参数是真的时候画扇形，是假的时候画弧线
         RectF oval2 = new RectF(, , , );// 设置个新的长方形，扫描测量
         canvas.drawArc(oval2, , , true, paint);

         // 画椭圆，把oval改一下
         oval2.set(, ,,);
         canvas.drawOval(oval2, paint);

         /*画矩形*/
         canvas.drawText("画矩形：", , , paint);
         paint.setStyle(Paint.Style.FILL);// 设置填满
         canvas.drawRect(, , , , paint);// 正方形
         canvas.drawRect(, , , , paint);// 长方形

         /*画圆角矩形*/
         canvas.drawText("画圆角矩形:", , , paint);
         paint.setStyle(Paint.Style.FILL);// 充满
         paint.setColor(Color.LTGRAY);
         paint.setAntiAlias(true);// 设置画笔的锯齿效果
         RectF oval3 = new RectF(, , , );// 设置个新的长方形
         canvas.drawRoundRect(oval3, , , paint);// 第二个参数是x半径，第三个参数是y半径

         /*画三角形*/
         canvas.drawText("画三角形：", , , paint);
         // 绘制这个三角形,你可以绘制任意多边形
         Path path = new Path();
         path.moveTo(, );// 此点为多边形的起点
         path.lineTo(, );
         path.lineTo(, );
 //        path.lineTo(160, 380);
         path.close(); // 使这些点构成封闭的多边形，就不用画回到起点 path.lineTo(160, 380);
         canvas.drawPath(path, paint);

         /*画任意多边形，*/
         paint.setShader(null);
         canvas.drawText("画任意多边形：", , , paint);
         paint.setColor(Color.LTGRAY);
         paint.setStyle(Paint.Style.STROKE);// 设置空心
         Path path1 = new Path();
         path1.moveTo(, );
         path1.lineTo(, );
         path1.lineTo(, );
         path1.lineTo(, );
         path1.close();        // 封闭形状
         canvas.drawPath(path1, paint);

         /*画图片，就是贴图*/
         canvas.drawText("画图片：", , , paint);
         Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher);
         canvas.drawBitmap(bitmap, , , paint);

         /*画文本*/
         paint.setColor(Color.BLACK);
         canvas.drawText("画文本：", , , paint);
         paint.setTextSize(txtSize * );
         paint.setStyle(Paint.Style.FILL);

         FontMetrics fontMetrics = paint.getFontMetrics();
         float originX = ;
         float originY = ;
         float topY = originY + fontMetrics.top;
         float ascentY = originY + fontMetrics.ascent;
         float descentY = originY + fontMetrics.descent;
         float bottomY = originY + fontMetrics.bottom;
         float leading = fontMetrics.leading;

         //文本
         paint.setColor(Color.RED);
         paint.setTextAlign(Align.CENTER);
         canvas.drawText("text1", originX , originY, paint);

         //origin point
         canvas.drawCircle(originX, originY, , paint);
         paint.setTextAlign(Align.LEFT);

         //baseline
         paint.setColor(Color.LTGRAY);
         paint.setTextSize(txtSize);
         canvas.drawText("baseline", originX -  , originY, paint);
         canvas.drawLine(originX, originY, originX + , originY, paint);

         //top line
         paint.setColor(Color.GREEN);
         canvas.drawText("topline", originX - , topY, paint);
         canvas.drawLine(originX, topY, originX + , topY, paint);

         //ascent line
         paint.setColor(Color.CYAN);
         canvas.drawText("ascent line", originX + , ascentY, paint);
         canvas.drawLine(originX+, ascentY, originX + , ascentY, paint);

         //descent line
         paint.setColor(Color.YELLOW);
         canvas.drawText("descent line", originX + , descentY, paint);
         canvas.drawLine(originX+, descentY, originX + , descentY, paint);

         //bottom line
         paint.setColor(Color.BLUE);
         canvas.drawText("bottom line", originX - , descentY, paint);
         canvas.drawLine(originX-, bottomY, originX + , bottomY, paint);
     }

注意其中画弧形时要指定一个矩形区域，画文字时各种线的位置