Question

我正在编写一个Android应用程序而且我遇到了问题。该应用程序使用双重连接列表。活动创建一个记录，并在单击按钮时保存调用一个方法，该方法在列表的add方法中传递创建的记录。它只是第一次工作，然后抛出一个NullPointerException，调用List Node的构造函数。错误只发生在android中，在PC上运行良好。这是代码和抛出的异常。

public boolean add(Object data) {
    boolean control = false;
    try {
        if (isEmpty()) {
            ListNode newNode = new ListNode(data);
            setFirstNode(newNode);
            setCurrentNode(newNode);
            incrementNumberOfNodes();
            control = true;
        }
        else {
            ListNode newNode = new ListNode(data, currentNode.getNextNode(), currentNode);
            if (currentNode.getNextNode() != null) {
                currentNode.getNextNode().setPreviousNode(newNode);
            }
            currentNode.setNextNode(newNode);
            currentNode = newNode;
            incrementNumberOfNodes();
            control = true;
        }
    } catch (NullPointerException e) {
        System.err.println(e);
    }
    return control;
}


public void save(View v){
    String action = getIntent().getAction();
    if(action.compareTo(GlobalVariables.ACTION_NEW) == 0) {
        newRecord();
        System.out.println("Save finish with new Record");
    }
}

private void newRecord(){
    EditText title = (EditText) findViewById(R.id.title);
    EditText password = (EditText) findViewById(R.id.password);

    int key = GlobalVariables.firstFreePosition();

    Record newRecord = new Record(key,title.getText().toString());
    newRecord.setPassword(password.getText().toString());
    System.out.printf("RECORD CREATO: %s\n", newRecord);

    // Aggiungo il record alla lista
    boolean control = GlobalVariables.recordsList.add(newRecord);
    System.out.println("New Record = " + control);
}

这是构造函数：

protected ListNode(Object data, ListNode nextNode, ListNode previousNode){
    setData(data);
    setNextNode(nextNode);
    setPreviousNode(previousNode);
}

这是例外（list.java＆＃39;第120行是列表节点构造的调用）：

09-09 21:27:39.711  19605-19605/cf.portaChiavi E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.IllegalStateException: Could not execute method of the activity
Caused by: java.lang.NullPointerException
        at cf.list.List.add(List.java:120)
        at cf.portaChiavi.NewRecord.newRecord(NewRecord.java:161)
        at cf.portaChiavi.NewRecord.save(NewRecord.java:90)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)

请帮帮我。感谢。

构造函数调用中的NullPointerException

0 个答案: