java - when using the arrow keys my image disappears -


the problem when press down button, image (blueboy) disappears, , doesn't move can move side side, cant understand why? please help. (i'm using realj). if there website can me on 2d side scrolling games me well.

import java.applet.applet; import java.awt.event.*;      import java.awt.*;   public class projectblue extends applet implements     actionlistener,keylistener,mouselistener {  image blueboy,trees;    //image variable int size = 4,jump = 50, cx = 1, cy = 1;      public void init() {     blueboy = getimage(getdocumentbase(),"png.png");     trees=     getimage(getdocumentbase(),"background.jpg"); addkeylistener( );  addmouselistener( ); }  public void paint(graphics g) {      int width = trees.getwidth(this);        int height = trees.getheight(this);      //system.out.println("" + cx +","+ cy);       //the later images drawn on top of earlier ones.   g.drawimage(trees, 1 ,1, width*size,height*7,this);   g.drawimage(blueboy, cx, cy, this); }   public void actionperformed(actionevent e) {  repaint();  }  public void left(){       cx = cx -100;       // blueboy moves left }  public void keytyped(keyevent e) { } public void keypressed(keyevent e) {  system.out.println("key pressed");     int key = e.getkeycode();     if (key == keyevent.vk_left) {         left();     }      if (key == keyevent.vk_right) {         cx = cx + 100;         //blueboy moves right     }      if (key == keyevent.vk_up) {         while (cy >= 0 && cy <=1000)         cy = cy - 100;             if (cy < 0){                 cy = 1;                //blueboy moves up, if goes out of bounds goes top                }     }      if (key == keyevent.vk_down) {        while (cy >= 0 && cy <=1000)         cy = cy + 100;             if (cy > 1001){                 cy = 999;                }         //blueboy moves down, if goes out of bounds goes bottim     }     repaint(); }  public void keyreleased(keyevent e) { }  public void mouseentered( mouseevent e ) { }  public void mouseexited( mouseevent e ) { }  public void mousepressed( mouseevent e ) { }   public void mousereleased( mouseevent e ) { }    public void mouseclicked( mouseevent e ) {    int x = getx();    int y = gety(); system.out.println("clicked @ (" + x + ", " + y + ")"); } }

those while loops tie gui thread, rendering animation useless. shouldn't if blocks instead? also, should enclose all blocks in curly braces. indentation lying you, , braces show why.

also need call super.paint(g) method in paint override.

also, assignment, , if required code awt/applets , not swing?


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