使用onTouchEvent更改字段后未调用onDraw（）

Question

I am creating an Android connect 4 game, I am at the stage where I am trying to place the counter depending on the circle that is selected by the user, but right now the code is not working, the counter basically not moving no matter where I click

// onDraw() defined above
@Override 
public boolean onTouchEvent(MotionEvent event) {
    rows = (int)event.getX();
    cols = (int)event.getY();
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_MOVE:
        case MotionEvent.ACTION_UP:
    }
    return false;
}

Answer 1

After you change your rows/cols field values, call invalidate() . This will ask Android to call your onDraw() method at some point in the future.

Your code should look like this:

@Override 
public boolean onTouchEvent(MotionEvent event) {

    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN: // Fall through
        case MotionEvent.ACTION_MOVE: // Fall through
        case MotionEvent.ACTION_UP: // Fall through
            rows = (int)event.getX();
            cols = (int)event.getY();
            invalidate();
            return true;
    }
    return false;
}