Question

I have written an app that basically shows a bouncing ball on the screen. I want to add a SeekBar that increases the velocity of the ball when I change its value. I made functions in my Ball class to get and set the x and y velocities.

package perseus.gfx.test;
import everything;
public class GfxActivity extends Activity implements OnSeekBarChangeListener {

ViewGroup.LayoutParams vg = new ViewGroup.LayoutParams(-1, -1);
double velx, vely;
double x, y;
double finx, finy;
SeekBar velo;
TextView tv;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);                     
    Ball ball = new Ball(this);
    setContentView(R.layout.main);
    addContentView(ball, vg);        
    tv = (TextView)findViewById(R.id.test);
    velo = (SeekBar)findViewById(R.id.vel);
    velo.setOnSeekBarChangeListener(this);   


    x = ball.getSpeedX();
    y = ball.getSpeedY();
    ball.setSpeedX(finx);
    ball.setSpeedY(finy);
}
@Override
public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {       


    finx = x + arg1;
    finy = y +arg1;
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
    //nothing
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
    //nothing
}
}

The problem is, (I think), only the local values of fin1 and fin2 are affected, and so the ball doesn’t move at all.
How do I pass the values of fin1 and fin2 back to onCreate()?

Answer 1

You don’t need to pass them back to onCreate (not really possible, anyhow), you should just need to set the ball’s speed again at the end of onProgresschanged()

@Override
public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {       

  finx = x + arg1;
  finy = y +arg1;

  ball.setSpeedX(finx);
  ball.setSpeedY(finy);
}