Question

ONCREATE I PUT

   ListView listView = (ListView) findViewById(R.id.listView3);

以下是我的listview获取空指针崩溃应用程序的代码由于某种原因我的listview从下面的代码找不到请告诉我在做什么

 @Override
        protected void onPostExecute(Void result) {

            parsedHtmlNode.setText(htmlContentInStringFormat);
            String  input = amarrdatta;
            String  dayyz = dayys;
            dayyz = dayyz.replace(" ", System.getProperty("line.separator"));
            input = input.replace(" ", System.getProperty("line.separator"));
          //  textViewwww.setText(dayyz +" " +input);
            ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
            count++;
            temp=temp+count;
            HashMap<String,String> temp=new HashMap<String, String>();
            temp.put(FIRST_COLUMN, dayyz);
            temp.put(SECOND_COLUMN, input);
            temp.put(THIRD_COLUMN, "22");
            temp.put(FOURTH_COLUMN, "Unmarried");
            list.add(temp);
            ListViewAdapter adapter=new ListViewAdapter(MainActivity.this, list);

            listView.setAdapter(adapter);  // getting nullpointer here listview

        }
    }

java null指针仍然是

 @Override
        protected void onPostExecute(Void result) {

            parsedHtmlNode.setText(htmlContentInStringFormat);
            String  input = amarrdatta;
            String  dayyz = dayys;
            dayyz = dayyz.replace(" ", System.getProperty("line.separator"));
            input = input.replace(" ", System.getProperty("line.separator"));
          //  textViewwww.setText(dayyz +" " +input);
            ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
            count++;
            temp=temp+count;
            HashMap<String,String> temp=new HashMap<String, String>();
            temp.put(FIRST_COLUMN, dayyz);
            temp.put(SECOND_COLUMN, input);
            temp.put(THIRD_COLUMN, "22");
            temp.put(FOURTH_COLUMN, "Unmarried");
            list.add(temp);
            ListViewAdapter adapter=new ListViewAdapter(MainActivity.this, list);
            ListView listView = (ListView) findViewById(R.id.listView3);
            listView.setAdapter(adapter);

        }

Answer 1

您未初始化listView变量。

您在ListView listView = (ListView) findViewById(R.id.listView3);中onCreate()。但是，使用此代码重新声明listView变量，它隐藏全局listView，全局listView保持为空。

删除onCreate()中的类型：

listView = (ListView) findViewById(R.id.listView3);

或将完整行移至onPostExecute()。

Answer 2

尝试将ListView listView;移到onCreate：

之外

 ListView listView;

 protected void onCreate(Bundle savedInstanceState) {

     listView = (ListView) findViewById(R.id.listView3);
 }

@Override
protected void onPostExecute(Void result) {

    parsedHtmlNode.setText(htmlContentInStringFormat);
    String  input = amarrdatta;
    String  dayyz = dayys;
    dayyz = dayyz.replace(" ", System.getProperty("line.separator"));
    input = input.replace(" ", System.getProperty("line.separator"));
    //  textViewwww.setText(dayyz +" " +input);
    ArrayList<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
    count++;
    temp=temp+count;
    HashMap<String,String> temp=new HashMap<String, String>();
    temp.put(FIRST_COLUMN, dayyz);
    temp.put(SECOND_COLUMN, input);
    temp.put(THIRD_COLUMN, "22");
    temp.put(FOURTH_COLUMN, "Unmarried");
    list.add(temp);
    ListViewAdapter adapter=new ListViewAdapter(MainActivity.this, list);

    listView.setAdapter(adapter);  // getting nullpointer here listview
}

Answer 3

正确检查您的XML ListView ID，然后您需要使用如下

片段或其他布局膨胀

View view = inflater.inflate(R.layout.layoutname, container, false);

ListView listView = (ListView) view.findViewById(R.id.listView3);

<强>活动

ListView listView = (ListView) findViewById(R.id.listView3);

Answer 4

我猜你没有把你的AsyncTask放在你的Activity类中。确保你的AsyncTask是你Activity的内部类

Android列表视图由id nullpointer查找

4 个答案: