有没有一条线包含点 [英] Does a line contain a point
问题描述
我希望用户能够拖动画布周围的正方形的边缘。由于我目前的解决方案,它的工作原理,但有毛刺,有时边缘无法选择。有没有干净的方式告诉我们,如果一个线已被点击(例如,通过坐标通过)?这是如何我目前正在测试:
I want the user to be able to drag the edges of a square around the canvas. With my current solution it works but has glitches, sometimes an edge cannot be selected. Is there a clean way to tell if a line has been clicked (e.g. passes through a coordinate)? This is how I'm currently testing:
// check edge pressed, edge is the line between to
// coords e.g. (i) & (i = 1)
for (int i = 0; i < coords.size(); i++) {
p1 = coords.get(i);
if ((i + 1) > (coords.size() - 1)) p2 = coords.get(0);
else p2 = coords.get(i + 1);
// is this the line pressed
if (p1.x <= event.getX() + 5 && event.getX() - 5 <= p2.x && p1.y <= event.getY() + 5 && event.getY() - 5 <= p2.y) {
// points found, set to non temp
// variable for use in ACTION_MOVE
point1 = p1;
point2 = p2;
break;
} else if (p1.x >= event.getX() + 5 && event.getX() - 5 >= p2.x && p1.y >= event.getY() + 5 && event.getY() - 5 >= p2.y) {
// points found, set to non temp
// variable for use in ACTION_MOVE
point1 = p1;
point2 = p2;
break;
}
}
在code波纹管//这行pressed是最重要的,也是最有可能的问题。在5和-5是用来给使用较大面积点击。
The code bellow //is this the line pressed is the most important and also most likely the issue. The +5 and -5 are used to give the use a larger area to click on.
下面是整个的单击事件:
Here is the whole on click event:
public void EditEdge() {
//TODO this works like shit
// Detect the two coordinates along the edge pressed and drag
// them
scene.setOnTouchListener(new View.OnTouchListener() {
private int startX;
private int startY;
private Point point1 = new Point(0, 0);
private Point point2 = new Point(0, 0);
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startX = (int) event.getX();
startY = (int) event.getY();
Point p1;
Point p2;
// check edge pressed, edge is the line between to
// coords e.g. (i) & (i = 1)
for (int i = 0; i < coords.size(); i++) {
p1 = coords.get(i);
if ((i + 1) > (coords.size() - 1)) p2 = coords.get(0);
else p2 = coords.get(i + 1);
// is this the line pressed
if (p1.x <= event.getX() + 5 && event.getX() - 5 <= p2.x && p1.y <= event.getY() + 5 && event.getY() - 5 <= p2.y) {
// points found, set to non temp
// variable for use in ACTION_MOVE
point1 = p1;
point2 = p2;
break;
} else if (p1.x >= event.getX() + 5 && event.getX() - 5 >= p2.x && p1.y >= event.getY() + 5 && event.getY() - 5 >= p2.y) {
// points found, set to non temp
// variable for use in ACTION_MOVE
point1 = p1;
point2 = p2;
break;
}
}
break;
case MotionEvent.ACTION_UP:
point1 = new Point(0, 0);
point2 = new Point(0, 0);
// scene.setOnTouchListener(scene.editModeOnTouchListener);
break;
case MotionEvent.ACTION_MOVE:
for (Point p: new Point[] {
point1, point2
}) {
int modX = (int)(p.x + (event.getX() - startX));
int modY = (int)(p.y + (event.getY() - startY));
p.set(modX, modY);
}
SetCoords(coords);
startX = (int) event.getX();
startY = (int) event.getY();
break;
default:
return false;
}
return true;
}
});
}
那么,有没有更简单的方式来告诉是一条线被点击/通过一个点或者是不是问题?
So is there a easier way to tell is a line is clicked/ passes through a point or is that not the issue?
感谢
推荐答案
使用直线方程 Y = MX + B
来看看该点是行
use the line equation y = mx + b
to find out if the point is on a line
float EPSILON = 0.001f;
public boolean isPointOnLine(Point linePointA, Point linePointB, Point point)
{
float m = (linePointB.y - linePointA.y) / (linePointB.x - linePointA.x);
float b = linePointA.y - m * linePointA.x;
if ( Math.abs(point.y - (m*point.x+b)) < EPSILON){
return true;
}
return false;
}
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