Android รบกวนสอบถามผู้รู้ทั้งหลายด้วยครับ เขียนยังไงครับ ให้ลูกบอลสามารถเด้งกลับไปที่เดิม

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.CountDownTimer;
import android.util.Log;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.widget.TextView;

public class DrawView extends View {

    public int[] ball = new int[] 
    		{ R.drawable.icebag, R.drawable.icebagh,};
    
    public int[][] ball_position = new int[][] 
    		{ { 400, 50 }, { 500, 50 } };
    
    public Bitmap bm[] = new Bitmap[ball.length];
    
    public boolean[] goal = new boolean[ball.length];
    
    public int screen_width, screen_height ;

    int goal_line = 200;
    int ball_id = -1;
    int score = 0;
    
    
    
    int order_ball = 1; //ประกาศไว้ในเรื่องของการทำแบบเงื่อนไข
    
    
    
    public DrawView(Context context, Display display) {
    	super(context);
    	this.setBackgroundResource(R.drawable.fa9);
    	screen_width = display.getWidth();
    	screen_height = display.getHeight();
    	for(int i = 0 ; i < ball.length ; i++) {
    	bm[i] = BitmapFactory.decodeResource(getResources(), ball[i]);
    	goal[i] = false;
    	}
    }
    	
    
    protected void onDraw(Canvas canvas) {

    	Paint p = new Paint();
        p.setColor(Color.rgb(0x3e, 0x9c, 0xbc));
        p.setAntiAlias(true);
    	
    //	canvas.drawRect(0, screen_height - goal_line
    //			, screen_width, screen_height, p);

      //  p.setTextSize(50);
    //  p.setColor(Color.WHITE);
   //     canvas.drawText("Drag to Here", (screen_width / 2) - 140
    //    		, screen_height - (( goal_line / 2) - 10), p);
    //    canvas.drawColor(0xFFFFFF);
        
  
        p.setTextSize(70);
        p.setColor(Color.rgb(0x3e, 0x9c, 0xbc));
        canvas.drawText(String.valueOf(score), 50, 100, p);

        for(int i = 0 ; i < ball.length ; i++) {
        	if(!goal[i]) {
        		canvas.drawBitmap(bm[i], ball_position[i][0] - (bm[i].getWidth() / 2)
        				, ball_position[i][1] - (bm[i].getHeight() / 2), null);
        	}
        	
        }
        
    }
    
    
    public boolean onTouchEvent(MotionEvent event) {
        int eventaction = event.getAction(); 
        int X = (int)event.getX(); 
        int Y = (int)event.getY(); 

        switch (eventaction ) { 

        case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball
        	ball_id = -1;
        	for(int i = 0 ; i < ball.length ; i++) {
        		double radCircle  = Math.sqrt( Math.pow(Math.abs(X - ball_position[i][0]), 2) 
        				+ Math.pow(Math.abs(Y - ball_position[i][1]), 2) );
        		if(radCircle < bm[i].getWidth() / 2 && !goal[i]) {
        			ball_id = i;
        		}
        	}
        
        case MotionEvent.ACTION_MOVE:
        	
        	if(ball_id != -1 && !goal[ball_id]  ) {
	        	ball_position[ball_id][0] = X;
	        	ball_position[ball_id][1] = Y;
        	}
            break; 

        case MotionEvent.ACTION_UP: 
        	if(ball_id != -1 && !goal[ball_id]  ) {
	        	if(Y > screen_height - goal_line) {
	        		goal[ball_id] = true;
	        		score++;
	        	}
        	}
        	break; 
        	
        
        } 

        invalidate(); 
        
        return true;
    
}
}