I gt problem in createImage method, Please Help Me!

Question

This part of code is from Ticker.Class:
public void createParams()
     {//tickerTape.x = 900;
          //tickerTape.y = 40;
          int width = getSize().width;
          //System.out.println("getSize().width "+getSize().width);
          int height = getSize().height;
          lastS.width = width;
          lastS.height = height;
          System.out.println("width"+width);
          //System.out.println("width: " + width + " height: " + height);
          tickerTape.createParamsgr();
          Font font = tickerTape.getDefaultFont();
          this.setFont(font);
          FontMetrics metrics = getFontMetrics(font);
          metrics = getFontMetrics(font);
          int k = getFontMetrics(font).getHeight();
          //tickerTape.cParams();
          //tickerTape.createParams1(lastS);
          //setSize(tickerTape.cParamsHeight(),tickerTape.cParamsWidth());
     //     messageY = tickerTape.cParamsY();
          messageX = width;
          messageY = (height - k >> 1) + metrics.getAscent();
               image = createImage(getSize().width,getSize().height);
               tickerTape.initImage(image);
               //gr=image.getGraphics();
     public  void paint(Graphics g)
      update(g);
     public synchronized void update(Graphics g)
          //gr.clearRect(0, 0, d.getSize().width, d.getSize().height);
          //gr.setColor(bgCo);
          //gr.drawRect(0, 0, d.getSize().width - 1, d.getSize().height - 1);
          //gr.fillRect(0, 0, d.getSize().width, d.getSize().height);
          //g.drawImage(image, 0, 0, this);
          if (Ticker.LOADING_DATA) {
               System.out.println("Refreshing data. Please wait....");
               return;
          try {
               if(image==null)
               image = createImage(getSize().width, getSize().height);
               tickerTape.initImage(image);
               //if (tickerTape.cParamsHeight() != lastS.height|| tickerTape.cParamsWidth() != lastS.width)
               if (getSize().height != lastS.height|| getSize().width != lastS.width)
               createParams();
               if (tickerTape.getDisplayItems().size() > 0) {
                    //System.out.print("lastS.width: " + lastS.width + " lastS.height: " + lastS.height + "\n");
                    tickerTape.setBackground(lastS,bgCo,messageX,messageY);
                    if (display_URL) {
                         int k = mouseX;
                          //System.out.println("k=" + k + " messageX=" + messageX);
                         if (k > messageX) {
                              //System.out.println("(k > messageX) is true!!");
                              //System.out.println("messageCount----> " + messageCount);
                              messageCount = tickerTape.displayItemsCnt;
                              k -= messageX;
                              switch (this.mouseEvent) {
                              case TickerTape.SCROLL_LEFT:
                                   break;
                              case TickerTape.SCROLL_RIGHT:
                                   // for (int i1 = 0; i1 <= messageCount - 1; i1++)
                                   // i += ((Integer) msgsW.elementAt(i1)).intValue();
                                   // if (k >= i)
                                   // continue;
                                   // messageIndex = i1;
                                   // break;
                                   // break;
                              if (this.mouseEvent == MOUSE_CLICK) {
                                   // showStatus((String)
                                   // msgsURL.elementAt(messageIndex));
                    //Font itemFont = null;
                    //FontMetrics fontMetrics = null;
                    //Color textColor = null;
                    //Vector msgs = tickerTape.getDisplayItems();
                              switch (tickerTape.getScrollDirection()) {
                              case TickerTape.SCROLL_LEFT:
                                   tickerTape.moveLeft(messageX,messageY);
                                   g.drawImage(image, 0, 0, this);
                                   break;
                              case TickerTape.SCROLL_RIGHT:
                                   tickerTape.moveRight(messageX,messageY,ItemToDisplay);
                                   g.drawImage(image, 0, 0, this);
                                   break;
                              case TickerTape.SCROLL_UP:
                              case TickerTape.SCROLL_DOWN:
                                   tickerTape.moveDown(messageX,messageY);
                                   g.drawImage(image, 0, 0, this);
                                   //g.drawImage(image, 0, 0, this);
                                   break;
               }     else {
                         image = createImage(getSize().width, getSize().height);
                         tickerTape.initImage(image);
                         //gr=image.getGraphics();
                         tickerTape.setBackground(lastS,bgCo,messageX,messageY);
                         g.drawImage(image, 0, 0, this);
          } catch (Exception e) {
               e.printStackTrace();
     }This part of code from TickerTape.Class:
public void createParamsgr(){
          if (gr != null)
               gr.finalize();
          if (image != null)
               image = null;
     public void initImage(Image image){
          gr = image.getGraphics();
     }This code already runable. But my question is Why when I decide to move the createImage method into the method of initImage in TickerTape.class, then it come out the error with nullpointer, why like that? is it im make any wrong thing? Or any solution for me to make it correct. Thanks and appreciate!

Answer 1

hi, thanks for your reply.
let me briefly explain to you,
now, you try to look at the createParams() method and update(Graphics g) method int Ticker.class, inside there also got
image = createImage(getSize().width, getSize().height);
tickerTape.initImage(image);
So, now I want to move the code:
image = createImage(getSize().width, getSize().height);
into the TickerTape.class but dont Why come out the error with:
java.lang.NullPointerException
     at TickerTape.initImage(TickerTape.java:90)
     at Ticker.update(Ticker.java:503)
     at sun.awt.RepaintArea.updateComponent(RepaintArea.java:239)
     at sun.awt.RepaintArea.paint(RepaintArea.java:216)
     at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:254)
     at java.awt.Component.dispatchEventImpl(Component.java:4031)
     at java.awt.Container.dispatchEventImpl(Container.java:2024)
     at java.awt.Component.dispatchEvent(Component.java:3803)
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
     at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
     at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
but it doesnt work!
Is it I put wrong thing or I forgot to put any important code?