Codigo

package com.dotjogoqualquer;

import java.util.ArrayList;
import java.util.Random;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

public class JogoView extends View implements Runnable{

    private static final int INTERVALO = 50;
    private boolean running = true;
    private Paint paint;
    private Thread Jogo_Thread;
    private int adicionados = 0;
    private ArrayList<objetos> obj = new ArrayList<objetos>();

    public JogoView(Context context) {
        super(context);

        paint = new Paint();
        Jogo_Thread = new Thread(this);
        Jogo_Thread.setPriority(Thread.MIN_PRIORITY);
        Jogo_Thread.start();
    }

    @Override
    public void run() {
        while (running){
            try {
                Thread.sleep(INTERVALO);
            } catch (InterruptedException e) {
                Log.e("THREAD", e.getMessage());
            }
            update();
        }
    }
    public void update() {
        if (obj.size() >= 1){
            for(int x = 0; x < obj.size(); x++) {
                obj.get(x).y -= 15;
                if (obj.get(x).y < -50) {
                    obj.remove(x);                   // <<<=================== AQUI
                }
            }
        }
        postInvalidate();
    }
    public void draw(Canvas canvas) {
        super.draw(canvas);
        canvas.drawColor(Color.BLACK);

        for(objetos e: obj) {
            paint.setColor(e.cor);
            canvas.drawCircle(e.x, e.y, e.raio, paint);
        }
    }

    public void release() {
        running = false;
    }

    public boolean onTouchEvent(MotionEvent event) {
        // ......
        switch(event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                 int touchX = (int) event.getX();
                 int touchY = (int) event.getY();
                 obj.add(new objetos());
                 obj.get(adicionados).x = touchX;
                 obj.get(adicionados).y = touchY;
                 obj.get(adicionados).raio = 10;
                 obj.get(adicionados).CorAleatoria();
                 adicionados++;
                 break;
        }
        return super.onTouchEvent(event);
    }
}
class objetos{
    int x;
    int y;
    int raio;
    int cor = Color.BLUE;
    public void CorAleatoria() {
        int[] cores = {Color.BLUE, Color.RED, Color.YELLOW, Color.GREEN};
        int ale  = new Random().nextInt(cores.length);
        this.cor = cores[ale];
    }
}