android - draw resizable circle on google map

Question

I\'m trying to draw a resizable circle on top of my google map, which the user will be able to expand or shrink using touch gestures (for example to shrink the circle the us

Answer 1

it has been a while since the question was asked but I used this in the past before switching to something different than a circle.

its not perfect but maybe it will help someone.

public class CircleView extends View {

private static final String TAG = "CircleView";
private static final double MOVE_SENSITIVITY = 1.25;
private Paint circlePaint;
private boolean isPinchMode;
private int lastCircleX;
private int lastCircleY;
public Circle circle;
private boolean isDoneResizing = true;

public CircleView(Context context) {
    super(context);
    setCirclePaint(0x220000ff);
}

public CircleView(Context context, AttributeSet attrs) {
    super(context, attrs);
    setCirclePaint(0x220000ff);
}

public CircleView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    setCirclePaint(0x220000ff);
}

private void setCirclePaint(int color) {
    circle = new Circle();
    circlePaint = new Paint();
    circlePaint.setColor(color);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawCircle(circle.centerX, circle.centerY, circle.radius, circlePaint);      
}

@Override
public boolean onTouchEvent(final MotionEvent event) {

    int historySize;
    double lastDistance;
    double oneBeforeLastDistance;

    switch (event.getActionMasked()) {
        case MotionEvent.ACTION_DOWN:
            lastCircleX = circle.centerX;
            lastCircleY = circle.centerY;
            break;

        case MotionEvent.ACTION_POINTER_DOWN:
            isPinchMode = true;
            isDoneResizing = false;
            break;

        case MotionEvent.ACTION_MOVE:
            circle.centerX = lastCircleX;
            circle.centerY = lastCircleY;; 

            if (getTouchedCircle((int) event.getX(), (int) event.getY()) && !isPinchMode && isDoneResizing) {

                historySize = event.getHistorySize();
                if (historySize > 0) {

                    oneBeforeLastDistance = Math.sqrt((event.getX() - event.getHistoricalX(0, historySize - 1)) * 
                                                      (event.getX() - event.getHistoricalX(0, historySize - 1)) + 
                                                      (event.getY() - event.getHistoricalY(0, historySize - 1)) * 
                                                      (event.getY() - event.getHistoricalY(0, historySize - 1)));


                    if (oneBeforeLastDistance > MOVE_SENSITIVITY) {
                        circle.centerX = (int) event.getX();
                        circle.centerY = (int) event.getY();
                        lastCircleX = circle.centerX;
                        lastCircleY = circle.centerY;

                    }
                }
            }
            if (isPinchMode) {
                circle.centerX = lastCircleX;
                circle.centerY = lastCircleY;

                historySize = event.getHistorySize();
                if (historySize > 0) {

                    lastDistance = Math.sqrt((event.getX(0) - event.getX(1)) * (event.getX(0) - event.getX(1)) + 
                                             (event.getY(0) - event.getY(1)) * (event.getY(0) - event.getY(1)));

                    oneBeforeLastDistance = Math.sqrt((event.getHistoricalX(0, historySize - 1) - event.getHistoricalX(1, historySize - 1)) * 
                                                      (event.getHistoricalX(0, historySize - 1) - event.getHistoricalX(1, historySize - 1)) + 
                                                      (event.getHistoricalY(0, historySize - 1) - event.getHistoricalY(1, historySize - 1)) * 
                                                      (event.getHistoricalY(0, historySize - 1) - event.getHistoricalY(1, historySize - 1)));


                    if (lastDistance < oneBeforeLastDistance) {
                        circle.radius -= Math.abs(lastDistance - oneBeforeLastDistance);
                    } else {
                        circle.radius += Math.abs(lastDistance - oneBeforeLastDistance);
                    }
                }
            }
            lastCircleX = circle.centerX;
            lastCircleY = circle.centerY;
            invalidate();
            break;

        case MotionEvent.ACTION_POINTER_UP:
            circle.centerX = lastCircleX;
            circle.centerY = lastCircleY;
            isPinchMode = false;
            break;

        case MotionEvent.ACTION_UP:
            circle.centerX = lastCircleX;
            circle.centerY = lastCircleY;
            isPinchMode = false;
            isDoneResizing = true;
            break;

        case MotionEvent.ACTION_CANCEL:
            break;

        case MotionEvent.ACTION_HOVER_MOVE:
            break;



        default:
            super.onTouchEvent(event);
            break;

    }
    return true;
}

private Boolean getTouchedCircle(final int xTouch, final int yTouch) {
    if ((circle.centerX - xTouch) * (circle.centerX - xTouch) + 
        (circle.centerY - yTouch) * (circle.centerY - yTouch)   <= circle.radius * circle.radius) {
        return true;
    } else {
        return false;
    }

}

static class Circle {
    int radius;
    int centerX;
    int centerY;

    Circle() {
        this.radius = 150;
        this.centerX = 378;
        this.centerY = 478;
    }        
}



}