Moving image in circular motion based on touch events in android
I am trying to move an ImageView (not rotate). The movement should be at the edge of the circle. This circle also represents the image.
based on onTouch event, ACTION_MOVE, I am trying to move it.
Dilem's Noah is that using cannot move the finger in a completely circular fashion, but I would like to make sure that the image still moves around the edge of that circle.
I am currently using the following inside ACTION_MOVE:
mCurrTempIndicator.setTranslationX(event.getX());
mCurrTempIndicator.setTranslationY(event.getY());
But it won't move in a perfect circle.
someone can help.
UPDATE: code
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mInitialX = event.getX();
mInitialY = event.getY();
break;
case MotionEvent.ACTION_MOVE:
mEndX = event.getX();
mEndY = event.getY();
float deltaX = mEndX - mInitialX;
float deltaY = mEndY - mInitialY;
double angleInDegrees = Math.atan(deltaY / deltaX) * 180 / Math.PI;
mInitialX = mEndX;
mInitialY = mEndY;
mCurrTempIndicator.setRotation((float)angleInDegrees);
mCurrTempIndicator.setTranslationX((float)(310*(Math.cos(angleInDegrees))));
mCurrTempIndicator.setTranslationY((float)(310*(Math.sin(angleInDegrees))));
break;
case MotionEvent.ACTION_UP:
allowRotating = true;
break;
}
return true;
}
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1 answer
- calculate the center point of the circle
- get the current touch point
- calculate the angle between the center and the new touch point
- Calculate a point on a circle using the angle and radius of the circle (x = r * cos (angle), y = r * sin (angle)).
- Reset the image position to a new point.
To get the angle use the below equation
deltaY = P2_y - P1_y
deltaX = P2_x - P1_x
angleInDegrees = arctan(deltaY / deltaX) * 180 / PI
//Code inside ACTION_MOVE case
mInitialX = event.getX();
mInitialY = event.getY();
float deltaX = circleCenter.x - mInitialX;
float deltaY = circleCenter.y - mInitialY;
double angleInRadian = Math.atan2(yDiff, xDiff);
PointF pointOnCircle = new PointF();
pointOnCircle.x = circleCenter.x + ((float)(circleRadius*(Math.cos(angleInRadian))));
pointOnCircle.y = circleCenter.y + ((float)(circleRadius*(Math.cos(angleInRadian))));
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