检查与自己的android.graphics.path交集 [英] Check android.graphics.path intersection with itself

问题描述

我想检查是否（如果是的话，碰撞是在哪里（x，y） - 只是为了突出显示）路径本身是相交的。
这也将是非常有趣的，我如何检查一条路径是否与另一条路径相交。
下面是截图，以更好地解释我的意思：

http://i.stack.imgur.com/JrEmN.png

解决方案

最简单的方法是检查任何线段是否与其他线段相交。线段由路径中的一对相邻点组成。具有10个点的路径具有9个线段。

下面是一个例子，说明如何去做。

 导入android.graphics.Point; 
 import java.util.List; 
 
静态布尔值isPathComplex（List< Point>路径）{
 
 if（path == null || path.size（）<= 2）{
返回false; 
} 
 
 int len = path.size（）; 
 
 for（int i = 1; i< len; i ++）{
 Point lineAStart = path.get（i  -  1）; 
 Point lineAEnd = path.get（i）; 
 
 for（int j = i + 1; j  Point lineBStart = path.get（j  -  1）; 
 Point lineBEnd = path.get（j）; 
 if（lineSegmentsIntersect（lineAStart，lineAEnd，lineBStart，lineBEnd））{
 return true; 
} 
 
} //内循环
 
} //外循环
 
} 
 
 static Boolean lineSegmentsIntersect（Point aInitial，Point aFinal，Point bInitial，Point bFinal）{
 //作为练习留给读者
} 
  

请参阅如何是否检测到两条线段相交的位置？，以获取如何实现lineSegmentsIntersect函数的示例。

I'd like to check if (and if yes, where the collission is(x,y) - just for highlighting) a path does intersect itself. It would also be very interesting how i do check if a path does intersect with another path. Here is a screenshot to better explain what i mean:

http://i.stack.imgur.com/JrEmN.png

解决方案

The simplest way is to check if any line segment intersects with any other line segment. A line segment is made up of pairs of adjacent points in the path. A path with 10 points has 9 line segments.

Here's an example of how one might go about that.

import android.graphics.Point;
import java.util.List;

static Boolean isPathComplex(List<Point> path) {

    if (path == null || path.size() <= 2) {
        return false;
    }

    int len = path.size();  

   for (int i = 1; i < len; i++) {
        Point lineAStart = path.get(i - 1);
        Point lineAEnd = path.get(i);

        for (int j = i + 1; j < len; j++) {
            Point lineBStart = path.get(j - 1);
            Point lineBEnd = path.get(j);
            if (lineSegmentsIntersect(lineAStart, lineAEnd, lineBStart, lineBEnd)) {
                return true;
            }

        } // inner loop

   } // outer loop

}

static Boolean lineSegmentsIntersect(Point aInitial, Point aFinal, Point bInitial, Point bFinal) {
    // left as an exercise to the reader
}

See How do you detect where two line segments intersect? for an example of how to implement the lineSegmentsIntersect function.

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