Question

So im trying to make an adroid application that draws a stream of circles as touchevent takes place. If i draw on the left side of the screen it should draw a green circle, and if its on the right , it should draw a blue circle. The app is doing this, but it changes the color of all the circles already drawn. SO i made a Draw circle Class and a array list of objects to treat each cricle as an individual objec, still not working Even after a Touchup event. the code for it is given below

 private class Drawcirlce  {

        public Drawcirlce(Canvas c) {
        // TODO Auto-generated constructor stub


        for (Point point : points) {

             if(flag==true)
                    c.drawCircle(point.x, point.y, 5, paint);
                    else
                    c.drawCircle(point.x, point.y, 5, p2);
        }
    invalidate();
    }
    /*for (Point point : points) {
     if(flag==true)
        mcan.drawCircle(point.x, point.y, 5, paint);
        else
        mcan.drawCircle(point.x, point.y, 5, p2);
}*/

}


public void onDraw(Canvas canvas) {


    i++;
     //Drawcirlce d=new Drawcirlce();
dc.add(new Drawcirlce(canvas));

Log.d(TAG, "i: " + i);invalidate();
}
public boolean onTouch(View view, MotionEvent event) {
    // if(event.getAction() != MotionEvent.ACTION_DOWN)
    // return super.onTouchEvent(event);
    Point point = new Point();
    point.x = event.getX();
    point.y = event.getY();
    if(point.x>200){
        paint.setColor(Color.BLUE);
    flag=true;
    }
    else{
        p2.setColor(Color.GREEN);
    flag=false;
    }

    points.add(point);
    //dc.add(new Drawcirlce(mcan));

    invalidate();
    Log.d(TAG, "point: " + point);
    return true;
}

public boolean onTouch(View view, MotionEvent event) {
    // if(event.getAction() != MotionEvent.ACTION_DOWN)
    // return super.onTouchEvent(event);
    Point point = new Point();
    point.x = event.getX();
    point.y = event.getY();
    if(point.x>200){
        paint.setColor(Color.BLUE);
    flag=true;
    }
    else{
        p2.setColor(Color.GREEN);
    flag=false;
    }

    points.add(point);
    //dc.add(new Drawcirlce(mcan));

    invalidate();
    Log.d(TAG, "point: " + point);
    return true;
}

Any one know aht im doing wrong, or if theres a way around this?

Answer 1

Your Drawcirlce class needs to have a Paint object in it. (You can make this public to the class, or give it getPaint() and setPaint(), whichever.) Then, when you call c.drawCircle(point.x, point.y, 5, paint);, call it with the Paint object in the class instead.

Something like this:

private class Drawcirlce {
    public Paint myPaint;

    public void draw(Canvas c) { // Don't use a constructor here...
        if (myPaint == null)
            return;

        for (Point point : points) {
            c.drawCircle(point.x, point.y, 5, myPaint);
            invalidate();
        }
    }
}

Then, in your onTouch event, you do something like this:

Drawcirlce myCircle = new Drawcirlce();
if (flag == true)
    myCircle.myPaint = new Paint(paint); // Copies the current paint object.
else
    myCircle.myPaint = new Paint(p2); // Copies the current p2 object.
dc.add(); // Adds our circle with its own Paint object.

Lastly, you would have to change your onDraw event.

for (Drawcirlce d : dc) { // Loop through everything in the dc array.
    d.draw(canvas); // Draw it to this canvas!
}

This code, in effect, assigns a circle the ability to have its own Paint object. Then, when touching, you create a Paint to give it. Lastly, when drawing, you use that Paint instead of the current one.