自定义可搜索微调器在单击微调器时引发空指针异常

Posted 2023-04-18

【中文标题】自定义可搜索微调器在单击微调器时引发空指针异常

【英文标题】：Custom searchable spinner throws null pointer exception while clicking on the spinner

【发布时间】：2021-12-12 10:45:26

【问题描述】：

主要活动

public class CustomSpinnerActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener 


    ArrayList<String> data = new ArrayList<String>();
    ArrayList<String> data1 = new ArrayList<String>();
    ArrayList<String> data2 = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.chit_spinner);
        //Getting the instance of Spinner and applying OnItemSelectedListener on it

        SearchableSpinner spin = (SearchableSpinner) findViewById(R.id.simpleSpinner) ;
        spin.setOnItemSelectedListener(this);

        //spinner variyable
        CloudDBConnection connect = new CloudDBConnection();
        Connection con = connect.CONN();
        if (con != null) 
            try 
                Statement statement = con.createStatement();
                String query = "select * from chitCardDet;";
                ResultSet rs = statement.executeQuery(query);
                //Toast.makeText(getApplicationContext(), "You are out.", Toast.LENGTH_SHORT).show();

                if (rs.next()) 

                    String custName = rs.getString(3);
                    if(custName.equals(null))
                        custName = "NA";
                    
                    String cell = rs.getString(8);
                    if(cell.equals(null))
                        cell = "NA";
                    
                    String city = rs.getString(9);
                    if(city.equals(null))
                        city = "NA";
                    
                    data.add(custName);
                    data1.add(cell);
                    data2.add(city);
                   // Toast.makeText(getApplicationContext(), custName+cell+city, Toast.LENGTH_SHORT).show();
                else
                    Toast.makeText(getApplicationContext(), "You are out.....", Toast.LENGTH_SHORT).show();
                

                CustomSpinnerAdapter customAdapter=new CustomSpinnerAdapter(getApplicationContext(),data,data1,data2);
                spin.setAdapter(customAdapter);

                rs.close();
                statement.close();
                con.close();
             catch (SQLException throwables) 
                throwables.printStackTrace();
            
         else 
            Toast.makeText(getApplicationContext(), "Server Unable......", Toast.LENGTH_SHORT).show();
        

    


    //Performing action onItemSelected and onNothing selected
    @Override
    public void onItemSelected(AdapterView<?> arg0, View arg1, int position,long id) 
        Toast.makeText(getApplicationContext(), data.get(position), Toast.LENGTH_LONG).show();
    

    @Override
    public void onNothingSelected(AdapterView<?> arg0) 
        // TODO Auto-generated method stub
    

CustomSpinner 适配器：

public class CustomSpinnerAdapter extends ArrayAdapter 
    Context context;
    ArrayList<String> data;
    ArrayList<String> data1;
    ArrayList<String> data2;
    LayoutInflater inflter;

    public CustomSpinnerAdapter(Context applicationContext, ArrayList<String> data, ArrayList<String> data1, ArrayList<String> data2) 
        super(applicationContext,custom_spinner_items);
        this.context = applicationContext;
        this.data = data;
        this.data1 = data1;
        this.data2 = data2;
        inflter = (LayoutInflater.from(applicationContext));
    


    @Override
    public int getCount() 
        return data.size();
    

    @Override
    public Object getItem(int i) 
        return null;
    

    @Override
    public long getItemId(int i) 
        return 0;
    

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) 
        view = inflter.inflate(custom_spinner_items, null);
        TextView cust = (TextView) view.findViewById(R.id.custName);
        TextView mobile = (TextView) view.findViewById(R.id.mobileNumber);
        TextView cityname = (TextView) view.findViewById(R.id.city);
        cust.setText(data.get(i));
        mobile.setText(data1.get(i));
        cityname.setText(data2.get(i));
        return view;
    

点击the spinner时会抛出以下error message

NullpointerException:Attempt to invoke virtual method java.lang.String java.lang.Object.toString() on a null object reference

仅供参考：它在加载时有效，但在单击微调器时无效

请有人帮助我...我正在尝试解决它，但我无法解决问题。

enter image description here

【参考方案1】：

我认为是因为排序

Spinner sItems = (Spinner) findViewById(R.id.select_size_spinner);


  ArrayList<String> options = new ArrayList<>();
    options.add("custName");
    options.add("cell");
    options.add("city");

ArrayAdapter<String> langAdapter = new ArrayAdapter<String>(getActivity(), R.layout.spinner_text, options);
    langAdapter.setDropDownViewResource(R.layout.simple_spinner_dropdown);
    sItems.setAdapter(langAdapter);

sItems.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener( )

    @Override
    public void onItemSelected( AdapterView< ? > parent, View view, int pos, long id )
    
        String selected = String.valueOf(adapterView.getItemAtPosition(position));

        int  Select = Integer.parseInt(selected);

        Toast.makeText(getApplicationContext(), Select, Toast.LENGTH_SHORT).show();

     
    

    @Override
    public void onNothingSelected(AdapterView<?> adapterView) 
    

    
);

spinner_text.xml：

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@android:id/text1"
    style="?attr/spinnerDropDownItemStyle"
    android:layout_
    android:layout_
    android:ellipsize="marquee"
    android:singleLine="true"
    tools:text="hello" />

simple_spinner_dropdown.xml 文件

<?xml version="1.0" encoding="utf-8"?>
<CheckedTextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    style="@style/spinnerDropDownItemStyle"
    android:layout_
    android:layout_
    android:ellipsize="marquee"
    android:paddingBottom="5dp"
    android:paddingLeft="10dp"
    android:paddingRight="10dp"
    android:paddingTop="5dp"
    android:singleLine="true" />

【讨论】：

我是否必须单独在我的活动中添加此代码并且不需要自定义适配器。我说得对吗兄弟？

你试过这个 onItemSelected 并检查它是否工作

spin.setOnItemSelectedListener(this);删除它并调用 spin.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener( )

是的，兄弟，我试过你的代码，它只适用于微调器中的一列，但我需要显示所有三列，并且可以按所有三列过滤它。

我按照你的说法更改了代码（ spin.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener( ) ）并尝试了，但结果与我在原帖中提到的相同