I'm trying to recognize if the (x,y) of my finger is touching any part of the triangle object.
This is how I draw the triangle
public void drawTriangle(Canvas canvas, Paint paint, int x, int y, int width) {
int halfWidth = width / 2;
Path path = new Path();
path.moveTo(x, y - halfWidth); // Top
path.lineTo(x - halfWidth, y + halfWidth); // Bottom left
path.lineTo(x + halfWidth, y + halfWidth); // Bottom right
path.lineTo(x, y - halfWidth); // Back to Top
path.close();
canvas.drawPath(path, paint);
}
This is how I draw to the screen + examples of how I recognize other shapes like square and circle:
public boolean onTouchEvent(MotionEvent event) {
int X = (int) event.getX();
int Y = (int) event.getY();
int eventaction = event.getAction();
switch (eventaction) {
/*
case MotionEvent.ACTION_DOWN:
Toast.makeText(this, "ACTION_DOWN AT COORDS "+"X: "+X+" Y: "+Y, Toast.LENGTH_SHORT).show();
isTouch = true;
break;
*/
case MotionEvent.ACTION_MOVE:
{
int s = triangle.getY() * triangle.getWidth()/ triangle.getY()-triangle.getWidth()/2;
if(X>=circle.getX()-circle.getRadius()&&X<=circle.getX()+circle.getRadius()
&&Y>=circle.getY()-circle.getRadius()&&Y<=circle.getY()+circle.getRadius()) {
circle.setX(X);
circle.setY(Y);
//square.setX(X);
//square.setY(Y);
}
if(X < square.getX() + square.getWidth() && X + square.getWidth() > square.getX() &&
Y < square.getY() + square.getHeight() && Y + square.getHeight() > square.getY())
{
square.setX(X);
square.setY(Y);
}
if(//triangle help)
{
triangle.setX(X);
triangle.setY(Y);
}
break;
}
}
return true;
}
Source link of pseudocode solution.
There are multiple ways to check if the point is in or out of a triangle.
Let's say that each of the vertices of a triangle has inner and outer sides. Inner is the one that is inside of a triangle, outer is therefore outside of a triangle.
To check if a point is inside of a triangle we can check if the point is on the inner side of each triangle vertex. Note: this solution might require some minor changes from you as I do not know the exact structure of your triangle class.
public boolean onTouchEvent(MotionEvent event) {
int X = (int) event.getX();
int Y = (int) event.getY();
int eventaction = event.getAction();
switch (eventaction) {
case MotionEvent.ACTION_MOVE:
{
...
int halfWidth = triangle.getWidth()/2;
Pair<Integer, Integer> v1 = new Pair(triangle.getX(), triangle.getY() - halfWidth);
Pair<Integer, Integer> v2 = new Pair(triangle.getX() - halfWidth, triangle.getY() + haldWidth);
Pair<Integer, Integer> v3 = new Pair(triangle.getX() + halfWidth, triangle.getY() + halfWidth);
if (isPointInTriangle(x, y, v1, v2, v3)) {
// point is inside of a triangle
}
break;
}
}
return true;
}
private int sign(int x, int y, Pair<Integer, Integer> vertex1, Pair<Integer, Integer> vertex2) {
return (x - vertex2.first) * (vertex1.second - vertex2.second) - (vertex1.first - vertex2.first) * (y - vertex2.second);
}
private boolean isPointInTriangle(int x, int y, Pair<Integer, Integer> vertex1, Pair<Integer, Integer> vertex2, Pair<Integer, Integer> vertex3)
{
int r1 = sign(x, y, vertex1, vertex2);
int r2 = sign(x, y, vertex2, vertex3);
int r3 = sign(x, y, vertex3, vertex1);
boolean hasNegative = (r1 < 0) || (r2 < 0) || (r3 < 0);
boolean hasPositive = (r1 > 0) || (r2 > 0) || (r3 > 0);
return !(hasNegative && hasPositive);
}