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如何在android画布中绘制一个填充三角形？
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？
8个解决方案
70 votes
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！
Pavel answered 2019-04-16T01:17:38Z
39 votes
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！
Nicolas C. answered 2019-04-16T01:17:04Z
10 votes
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());
GBouerat answered 2019-04-16T01:18:03Z
6 votes
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。
Daniel Nyamasyo answered 2019-04-16T01:18:33Z
4 votes
private void drawArrows(Point[] point, Canvas canvas, Paint paint) {
float [] points = new float[8];
points[0] = point[0].x;
points[1] = point[0].y;
points[2] = point[1].x;
points[3] = point[1].y;
points[4] = point[2].x;
points[5] = point[2].y;
points[6] = point[0].x;
points[7] = point[0].y;
canvas.drawVertices(VertexMode.TRIANGLES, 8, points, 0, null, 0, null, 0, null, 0, 0, paint);
Path path = new Path();
path.moveTo(point[0].x , point[0].y);
path.lineTo(point[1].x,point[1].y);
path.lineTo(point[2].x,point[2].y);
canvas.drawPath(path,paint);
}
Faakhir answered 2019-04-16T01:18:50Z
4 votes
使用@ Pavel的答案作为指导，如果你没有点但是有x，y和高度和宽度的起点，这里有一个辅助方法。 也可以倒置/倒置 - 这对我来说很有用，因为它被用作垂直条形图的结尾。
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);
}
scottyab answered 2019-04-16T01:19:13Z
3 votes
首次初始化后，您需要删除path.moveTo。
Path path = new Path();
path.moveTo(point1_returned.x, point1_returned.y);
path.lineTo(point2_returned.x, point2_returned.y);
path.lineTo(point3_returned.x, point3_returned.y);
path.lineTo(point1_returned.x, point1_returned.y);
path.close();
kaftanati answered 2019-04-16T01:19:37Z
1 votes
每个lineTo()后不要moveTo()
换句话说，删除除第一个之外的每个moveTo()。
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，它就可以了。
没有别的事情需要做。
编辑：我知道OP已经发布了他的“最终工作解决方案”，但他没有说明它的工作原理。 实际的原因让我非常惊讶，所以我觉得有必要添加一个答案。
oli.G answered 2019-04-16T01:20:27Z