Question

我想在listview中添加catnames。但是它显示我的运行时错误。这是我的代码和logcat.i能够添加静态数组但是当我动态使用它时显示mw错误。

 public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
   //setContentView(R.layout.main);


    TextView attribute[];
    ArrayAdapter adapter;
    try 
    {
        SAXParserFactory spf = SAXParserFactory.newInstance();
        SAXParser sp = spf.newSAXParser();
        XMLReader xr = sp.getXMLReader();

        URL sourceUrl = new URL("http://mobileecommerce.site247365.com/admin/catdata.xml");

        MyXMLHandler myXMLHandler = new MyXMLHandler();
        xr.setContentHandler(myXMLHandler);
        xr.parse(new InputSource(sourceUrl.openStream()));

    }catch(Exception e)
    {
        System.out.println("XML Pasing Excpetion = " + e);
    }

    sitesList = MyXMLHandler.sitesList;

    Cat_id = new TextView[sitesList.getCat_id().size()];
    Cat_Parentid = new TextView[sitesList.getCat_id().size()];
    Cat_Name = new TextView[sitesList.getCat_id().size()];
    Cat_Desc=new TextView[sitesList.getCat_id().size()];
    String mystr,newstr;

    for (int i = 0; i <sitesList.getCat_Name().size(); i++) 
    {
        catNames=new String[sitesList.getCat_Name().size()];

        Cat_Name[i] = new TextView(this);
        Cat_Name[i].setText("Cat_Name = "+sitesList.getCat_Name().get(i));
        catNames[i]=sitesList.getCat_Name().get(i);
        Log.v("catnames",catNames[i]);
        str[i]=sitesList.getCat_Desc().get(i);
            temp[i]=str[i];


        }

    setListAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1,catNames));
    getListView().setTextFilterEnabled(true);


}
static final String[] PENS = new String[]{
    "MONT Blanc",
    "Gucci",
    "Parker",
    "Sailor",
    "Porsche Design",
    "Rotring",
    "Sheaffer",
    "Waterman"
   };
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);
    Object o = this.getListAdapter().getItem(position);
    String pen = o.toString();
    Toast.makeText(this, "You have chosen ::" + " " + pen, Toast.LENGTH_LONG).show();
   }

我的LOGCAT -

10-17 19:29:17.230: ERROR/AndroidRuntime(2517): FATAL EXCEPTION: main
10-17 19:29:17.230: ERROR/AndroidRuntime(2517): java.lang.NullPointerException
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:355)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.AbsListView.obtainView(AbsListView.java:1315)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ListView.makeAndAddView(ListView.java:1727)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ListView.fillDown(ListView.java:652)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ListView.fillFromTop(ListView.java:709)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.ListView.layoutChildren(ListView.java:1580)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.AbsListView.onLayout(AbsListView.java:1147)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.View.layout(View.java:7035)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.View.layout(View.java:7035)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1249)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1125)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1042)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.View.layout(View.java:7035)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.View.layout(View.java:7035)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1045)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.os.Looper.loop(Looper.java:123)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at android.app.ActivityThread.main(ActivityThread.java:4627)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at java.lang.reflect.Method.invokeNative(Native Method)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at java.lang.reflect.Method.invoke(Method.java:521)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-17 19:29:17.230: ERROR/AndroidRuntime(2517):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

您有一个NullPointerException，因为未初始化适配器，它是一个ArrayAdapter。调用它的构造函数，正确初始化它，这个问题将成为历史。当您尝试调用此（不存在）对象的方法时，会发生运行时错误。如果为适配器赋值，则不应再使用此对象发生NullPointerException。您可能还有其他错误，但是我们的问题是当您调用未初始化对象的方法时抛出NullPointerException（这是一个没有初始化的空指针）。

ListView项动态添加

1 个答案: