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申し訳ありませんが、それが私がやっている愚かなことである場合に備えて投稿しますが、私が気付いていない奇妙な Java の原因があり、他の人を助けることができることを願っています. ここで何かを見落としていますか？なぜNPE？

これが私のコードです：

SwingUtilities.invokeLater(new Runnable() {
    @Override
    public void run() {
        int itemSoldCount = Integer.parseInt(afterAt[1]);
        System.out.println("itemSoldCount: " + itemSoldCount);
        ShopJInternalFrame.shopHolderWAIType = new JLabel[itemSoldCount];

        int i = 2;
        for (int k = 0; k < itemSoldCount; k++){
            String waiType = afterAt[i];
            System.out.println("ShopJInternalFrame.shopHolderWAIType.length: " + ShopJInternalFrame.shopHolderWAIType.length);
            System.out.println("waiType: " + waiType);
            System.out.println("k: " + k);
            ShopJInternalFrame.shopHolderWAIType[k].setText(waiType);  //line 530

ここに私の出力があります：

itemSoldCount: 2
ShopJInternalFrame.shopHolderWAIType.length: 2
waiType: A
k: 0
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.jayavon.game.client.MyCommandReceiver$8.run(MyCommandReceiver.java:530)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$200(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)
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2 に答える 2

5 
ShopJInternalFrame.shopHolderWAIType = new JLabel[itemSoldCount];

これにより、 arrayにストレージが割り当てられますが、JLabelオブジェクトには割り当てられません。この時点で、配列にはすべてヌルが含まれています。たどり着いたら

ShopJInternalFrame.shopHolderWAIType[k].setText(waiType);

shopHolderWAIType[k]無効です。

于 2013-07-18T03:14:35.010 に答える