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JAVA试图在Android中将数据添加到类的对象时发生lang.NullPointerException

1 周，5 日 Questions & Answers

我正面临一个愚蠢的问题。我只是试图向类的对象添加数据，但没有成功

我通过片段中的异步任务获取数据，并希望使用生成的JSON填充我的ListView。我正在使用ArrayAdapter，并为此创建了一个类

我已经解析了JSON字符串，现在我试图将从API检索到的数据添加到我的类的对象中，但它给了我“java”。lang.NullPointerException'

我猜我无法向类的对象添加数据。但我不明白原因，我更习惯C#中的cding，但JAVA是面向对象的，应该是一样的，对吧？正在使用的代码如下所示

    JSONArray jsonArrayPendingBills = new JSONArray();
    jsonArrayPendingBills = jsonObjectPendingBills.getJSONArray(TAG_RESPONSE_MESSAGE);
    ArrayList<HashMap<String, String>> arrayPendingBills = new ArrayList<HashMap<String,String>>();
    ArrayList<PendingBills> arrayClassPendingBills = new ArrayList<PendingBills>();

    for(int i = 0;i < jsonArrayPendingBills.length(); i++){
        JSONObject jsonObjectPendingBill = jsonArrayPendingBills.getJSONObject(i);

        String strDate = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_DATE);
        String strTxCode = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_TX_CODE);
        String strFromAccount = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_FROM_ACCOUNT);
        String strAmount = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_AMOUNT);
        String strDetails = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_DETAILS);
        String strBillCode = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_BILL_CODE);

        PendingBills objPendingBills = new PendingBills();
        objPendingBills.setBillAmount(strAmount);
        objPendingBills.setBillDate(strDate);
        objPendingBills.setBillName(strFromAccount);
        //arrayClassPendingBills.add(new PendingBills(strAmount, strDate, strFromAccount));
        arrayClassPendingBills.add(objPendingBills);
    }

    PendingBillsAdapter pendingBillsAdapter = new PendingBillsAdapter(getActivity(), R.layout.pending_bills_list_view_row, arrayClassPendingBills);
    listViewPendingBills.setAdapter(pendingBillsAdapter);

    progressDialogPendingBills.dismiss();
}
catch (Exception e){
    e.printStackTrace();
    Log.i("Error", "Error", e);
}

这是我的课程代码：

public class PendingBills {

    // Declaring the strings for the class
    public String BillAmount;
    public String BillDate;
    public String BillName;

    // Writing down the constructor for this class  
    public PendingBills(String BillAmount, String BillDate, String BillName){
        this.BillAmount = BillAmount;
        this.BillDate = BillDate;
        this.BillName = BillName;
    }

    public PendingBills(){

    }

    // Getter for BillAmount
    public String getBillAmount(){
        return BillAmount;
    }

    // Setter for BillAmount
    public void setBillAmount(String BillAmount){
        this.BillAmount = BillAmount;
    }

    public String getBillDate(){
        return BillDate;
    }

    public void setBillDate(String BillDate){
        this.BillDate = BillDate;
    }

    public String getBillName(){
        return BillName;
    }

    public void setBillName(String BillName){
        this.BillName = BillName;
    }

}

我想我错过了什么。我不确定是什么？我查阅了一些与此相关的问题。我发现了很多，但解决方案对我来说并不奏效

Adding data to an array list

How to properly add data to ArrayList - Android

任何帮助都将不胜感激。谢谢

这是LogCat

12-02 07:02:04.235: E/AndroidRuntime(4648): FATAL EXCEPTION: main
12-02 07:02:04.235: E/AndroidRuntime(4648): java.lang.NullPointerException
12-02 07:02:04.235: E/AndroidRuntime(4648):     at com.zipcash.zipcashbetaversion.PendingBillsAdapter.getView(PendingBillsAdapter.java:43)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.AbsListView.obtainView(AbsListView.java:2159)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.ListView.measureHeightOfChildren(ListView.java:1246)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.ListView.onMeasure(ListView.java:1158)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.LinearLayout.measureVertical(LinearLayout.java:695)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.LinearLayout.onMeasure(LinearLayout.java:588)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:681)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:681)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.FrameLayout.onMeasure(FrameLayout.java:310)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.support.v4.view.ViewPager.onMeasure(ViewPager.java:1029)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:681)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.FrameLayout.onMeasure(FrameLayout.java:310)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.LinearLayout.measureVertical(LinearLayout.java:847)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.LinearLayout.onMeasure(LinearLayout.java:588)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.widget.FrameLayout.onMeasure(FrameLayout.java:310)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at com.安卓.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2176)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.View.measure(View.java:15518)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.Choreographer.doCallbacks(Choreographer.java:562)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.Choreographer.doFrame(Choreographer.java:532)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.os.Handler.handleCallback(Handler.java:725)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.os.Handler.dispatchMessage(Handler.java:92)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.os.Looper.loop(Looper.java:137)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at 安卓.app.ActivityThread.main(ActivityThread.java:5041)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at java.lang.reflect.Method.invokeNative(Native Method)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at java.lang.reflect.Method.invoke(Method.java:511)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-02 07:02:04.235: E/AndroidRuntime(4648):     at dalvik.system.NativeStart.main(Native Method)

共 (3) 个答案

  1. # 1 楼答案

    k dude只需将arrayPendingBills保持为静态，或使用类似singleton类的datacontroller类，简称u只需将arrayPendingBills保持为静态，然后运行即可：）祝您好运

  2. # 2 楼答案 

    - add try & Catch to handle nullPointerException & any Exceptions 
- Make trace the code to find where made excption.
- add system.out.Println to print the values then they find the exception

    try{
    JSONArray jsonArrayPendingBills = new JSONArray(); jsonArrayPendingBills = jsonObjectPendingBills.getJSONArray(TAG_RESPONSE_MESSAGE); ArrayList> arrayPendingBills = new ArrayList>(); ArrayList arrayClassPendingBills = new ArrayList();

        for(int i = 0;i < jsonArrayPendingBills.length(); i++){
        JSONObject jsonObjectPendingBill = jsonArrayPendingBills.getJSONObject(i);

        String strDate = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_DATE);
        String strTxCode = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_TX_CODE);
        String strFromAccount = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_FROM_ACCOUNT);
        String strAmount = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_AMOUNT);
        String strDetails = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_DETAILS);
        String strBillCode = jsonObjectPendingBill.getString(TAG_PENDING_BILLS_BILL_CODE);

        PendingBills objPendingBills = new PendingBills();
        objPendingBills.setBillAmount(strAmount);
        objPendingBills.setBillDate(strDate);
        objPendingBills.setBillName(strFromAccount);
        //arrayClassPendingBills.add(new PendingBills(strAmount, strDate, strFromAccount));
        arrayClassPendingBills.add(objPendingBills);
    }
  PendingBillsAdapter pendingBillsAdapter = new PendingBillsAdapter(getActivity(),        
R.layout.pending_bills_list_view_row, arrayClassPendingBills);
    listViewPendingBills.setAdapter(pendingBillsAdapter);

    progressDialogPendingBills.dismiss();
}catch ( NullPointerException e)
{
e.printStackTrace();
 Log.i("Error", "Error", e);
}
catch (Exception e){
    e.printStackTrace();
    Log.i("Error", "Error", e);
}
  3. # 3 楼答案

    试试这个

    按照下面的代码膨胀布局context.getSystemService或this

    LayoutInflater inflater = (LayoutInflater) context.getSystemService( Context.LAYOUT_INFLATER_SERVICE );

    或者

    LayoutInflater inflater = LayoutInflater.from(context);