java - Stanford cs106a - Breakout exersize -

i'm trying learn java following cs106a course online. i've arrived @ breakout exersize , i'm having trouble bugs

i haven't finished want solves these issues first before go further.

problem 1:

when ball collides bricks don't seem removed canvas. brick removed on second time collides. there 1 row (of yellow bricks) doesn't respond @ ball collisions.

problem 2:

my paddle can moved dragging mouse. problem is. bricks can moved paddle.

i know has piece of code

gobj = getelementat(lastx, lasty); 

if remove altogether bricks aren't moveable anymore. good. i'm still able move paddle no matter click , drag.

can give me hint can correct mistakes?

here's code below. thanks

   /*    * file: breakout.java   * -------------------   * file implement game of breakout.   */ import acm.graphics.*; import acm.program.*; import acm.util.*; import java.applet.*; import java.awt.*; import java.awt.event.*;  import org.omg.corba.public_member;  public class breakout extends graphicsprogram {     /** width , height of application window in pixels */     public static final int application_width = 400;     public static final int application_height = 600;     /** dimensions of game board (usually same) */     private static final int width = application_width;     private static final int height = application_height;     /** dimensions of paddle */     private static final int paddle_width = 60;     private static final int paddle_height = 10;     /** offset of paddle bottom */     private static final int paddle_y_offset = 30;     /** number of bricks per row */     private static final int nbricks_per_row = 10;     /** number of rows of bricks */     private static final int nbrick_rows = 8;     /** separation between bricks */     private static final int brick_sep = 4;     /** width of brick */     private static final int brick_width = (width - (nbricks_per_row - 1)* brick_sep)/ nbricks_per_row;     /** height of brick */     private static final int brick_height = 8;     /** radius of ball in pixels */     private static final int ball_radius = 10;     /** offset of top brick row top */     private static final int brick_y_offset = 70;     /** number of turns */     private static final int nturns = 3;       private static final int delay = 50;     private static final double x_start = width / 2;     private static final double y_start = 450;      public void run() {         world();         play();     }      private void ball() {          ball = new goval(x_start, y_start, ball_radius, ball_radius);         ball.setfillcolor(color.black);         ball.setfilled(true);         add(ball);      }      private void paddle() {          paddle = new grect(100, 500, paddle_width, paddle_height);         paddle.setcolor(color.black);         paddle.setfilled(true);         add(paddle);     }       private void brick(int x, int y, color c) {          grect brick = new grect(x, y, brick_width, brick_height);         brick.setcolor(getbackground());         brick.setfillcolor(c);         brick.setfilled(true);         add(brick);      }      private void brickrow(int x, int y, color c) {         x = brick_sep / 2;         y += brick_y_offset;         (int = 0; < nbricks_per_row; i++) {             brick(x, y, c);             x += brick_width + brick_sep;         }      }   private void world() {          //initialize x , y position rows of bricks         int x = 0;         int y = 0;         // set starting color first row         color c = color.red;          paddle();          //create 2 rows of bricks , switch colors         (int = 0; < nbrick_rows; i++) {             if (i <= 1) {                 c = color.orange;              } else if (i > 1 && <= 3) {                 c = color.yellow;              } else if (i > 3 && <= 5) {                 c = color.green;              } else if (i > 5 && <= 7) {                 c = color.cyan;             }              brickrow(x, y, c);             y += brick_height + brick_sep;         }      }        private void moveball() {         ball.move(xvel, yvel);      }       public void mousepressed(mouseevent e) {          lastx = e.getx();         lasty = e.gety();         gobj = getelementat(lastx, lasty);      }      public void mousedragged(mouseevent e) {         if (paddle != null) {             paddle.move(e.getx() - lastx, gety());             lastx = e.getx();             lasty = e.gety();         }          //constrain paddle movement         if (paddle.getx() < 0){             paddle.setlocation(0, 500);         }else if (paddle.getx()+brick_width > width ){             paddle.setlocation(width-brick_width, 500);         }       }      private void checkforcollision() {          // ball collission walls         if (ball.gety() > getheight() - ball_radius                 || ball.gety() < 0 + ball_radius) {             yvel = -yvel;         } else if (ball.getx() > getwidth() - ball_radius                 || ball.getx() < 1 + ball_radius) {             xvel = -xvel;              // ball collission paddle         } else if (getelementat(ball.getx() + ball_radius, ball.gety()                 + ball_radius) == paddle) {             yvel = -yvel;              // check collision bricks remove them ignore collision paddle         } else if (getelementat(ball.getx(), ball.gety()) != null                 && getelementat(ball.getx(), ball.gety()) != paddle) {             remove(getcollidingobject(ball.getx(), ball.gety()));             yvel = -yvel;          } else if (getelementat(ball.getx() + ball_radius, ball.gety()                 + ball_radius) != null                 && getelementat(ball.getx() + ball_radius, ball.gety()                         + ball_radius) != paddle) {             remove(getcollidingobject(ball.getx() + ball_radius, ball.gety()                     + ball_radius));             yvel = -yvel;          } else if (getelementat(ball.getx() + ball_radius, ball.gety()                 + ball_radius) != null                 && getelementat(ball.getx() + ball_radius, ball.gety()                         + ball_radius) != paddle) {             remove(getcollidingobject(ball.getx() + ball_radius, ball.gety()                     + ball_radius));             yvel = -yvel;          } else if (getelementat(ball.getx(), ball.gety() + ball_radius) != null                 && getelementat(ball.getx(), ball.gety() + ball_radius) != paddle) {             remove(getcollidingobject(ball.getx(), ball.gety() + ball_radius));             yvel = -yvel;         }     }      private void play() {         addmouselisteners();         ball();         while (true) {             checkforcollision();             moveball();             pause(delay);         }      }       private gobject getcollidingobject(double x, double y) {         return getelementat(x, y);      }      private double lastx;     private double lasty;      private double xvel = 5;     private double yvel = 15;      private goval ball;     private grect paddle;     private gobject gobj;  } 

why don't use suggested method in handout 19:

private gobject getcollidingobject() 

use collider:

gobject collider = getcollidingobject(); 

first of separate conditions walls collisions , (paddle bricks) game elements collisions 2 separate methods cause simplify else if cascading (decomposition think know means). have 2 objects should worry paddle , bricks, need compare on (collider == paddle) , collider != null. use radius in comparisons should use diameter (2 * radius). have fun :)