如何在Android画布中绘制一个填充三角形？

Question

所以我在我的绘图方法中使用下面的代码在android地图中绘制这个三角形:

paint.setARGB(255, 153, 29, 29);
paint.setStyle(Paint.Style.FILL_AND_STROKE);
paint.setAntiAlias(true);

Path path = new Path();
path.moveTo(point1_returned.x, point1_returned.y);
path.lineTo(point2_returned.x, point2_returned.y);
path.moveTo(point2_returned.x, point2_returned.y);
path.lineTo(point3_returned.x, point3_returned.y);
path.moveTo(point3_returned.x, point3_returned.y);
path.lineTo(point1_returned.x, point1_returned.y);
path.close();

canvas.drawPath(path, paint);

pointX_returned是我从字段中获得的坐标.它们基本上是纬度和经度.结果是一个漂亮的三角形,但内部人员是空的,因此我可以看到地图.有办法以某种方式填补它吗？

Answer 1

好的,我已经做到了.我正在分享这段代码以防其他人需要它:

super.draw(canvas, mapView, true);

Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

paint.setStrokeWidth(2);
paint.setColor(android.graphics.Color.RED);     
paint.setStyle(Paint.Style.FILL_AND_STROKE);
paint.setAntiAlias(true);

Point point1_draw = new Point();        
Point point2_draw = new Point();    
Point point3_draw = new Point();

mapView.getProjection().toPixels(point1, point1_draw);
mapView.getProjection().toPixels(point2, point2_draw);
mapView.getProjection().toPixels(point3, point3_draw);

Path path = new Path();
path.setFillType(Path.FillType.EVEN_ODD);
path.moveTo(point1_draw.x,point1_draw.y);
path.lineTo(point2_draw.x,point2_draw.y);
path.lineTo(point3_draw.x,point3_draw.y);
path.lineTo(point1_draw.x,point1_draw.y);
path.close();

canvas.drawPath(path, paint);

//canvas.drawLine(point1_draw.x,point1_draw.y,point2_draw.x,point2_draw.y, paint);

return true;

感谢尼古拉斯的暗示!

Answer 2

您可能需要执行以下操作:

Paint red = new Paint();

red.setColor(android.graphics.Color.RED);
red.setStyle(Paint.Style.FILL);

并使用此颜色作为您的路径,而不是您的ARGB.确保路径的最后一点在第一点结束,这也是有道理的.

告诉我它是否有效!

Answer 3

你也可以使用vertice:

private static final int verticesColors[] = {
    Color.LTGRAY, Color.LTGRAY, Color.LTGRAY, 0xFF000000, 0xFF000000, 0xFF000000
};
float verts[] = {
    point1.x, point1.y, point2.x, point2.y, point3.x, point3.y
};
canvas.drawVertices(Canvas.VertexMode.TRIANGLES, verts.length, verts, 0, null, 0, verticesColors,   0, null, 0, 0, new Paint());

Answer 4

此函数显示如何从位图创建三角形.也就是说,创建三角形裁剪图像.请尝试下面的代码或下载演示示例

 public static Bitmap getTriangleBitmap(Bitmap bitmap, int radius) {
        Bitmap finalBitmap;
        if (bitmap.getWidth() != radius || bitmap.getHeight() != radius)
            finalBitmap = Bitmap.createScaledBitmap(bitmap, radius, radius,
                    false);
        else
            finalBitmap = bitmap;
        Bitmap output = Bitmap.createBitmap(finalBitmap.getWidth(),
                finalBitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, finalBitmap.getWidth(),
                finalBitmap.getHeight());

        Point point1_draw = new Point(75, 0);
        Point point2_draw = new Point(0, 180);
        Point point3_draw = new Point(180, 180);

        Path path = new Path();
        path.moveTo(point1_draw.x, point1_draw.y);
        path.lineTo(point2_draw.x, point2_draw.y);
        path.lineTo(point3_draw.x, point3_draw.y);
        path.lineTo(point1_draw.x, point1_draw.y);
        path.close();
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(Color.parseColor("#BAB399"));
        canvas.drawPath(path, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(finalBitmap, rect, rect, paint);

        return output;
    }

上面的函数返回在画布上绘制的三角形图像.阅读更多

Answer 5

使用@Pavel的答案作为指导，如果您没有这些点，但以x，y和高度和宽度开头，则可以使用以下帮助方法。还可以绘制倒置/倒置的图形，这对我很有用，因为它被用作垂直条形图的末端。

 private void drawTriangle(int x, int y, int width, int height, boolean inverted, Paint paint, Canvas canvas){

        Point p1 = new Point(x,y);
        int pointX = x + width/2;
        int pointY = inverted?  y + height : y - height;

        Point p2 = new Point(pointX,pointY);
        Point p3 = new Point(x+width,y);


        Path path = new Path();
        path.setFillType(Path.FillType.EVEN_ODD);
        path.moveTo(p1.x,p1.y);
        path.lineTo(p2.x,p2.y);
        path.lineTo(p3.x,p3.y);
        path.close();

        canvas.drawPath(path, paint);
    }

Answer 6

不要moveTo()在每个之后lineTo()

换句话说，删除除moveTo()第一个之外的所有内容。

说真的，如果我只是复制粘贴OP的代码并删除不必要的moveTo()调用，它就可以工作。

无需执行任何其他操作。

编辑：我知道OP已经发布了他的“最终工作解决方案”，但他没有说明为什么它有效。真正的原因让我很惊讶，所以我觉得有必要补充一下答案。