onItem滚动后单击列表视图中的项目会抛出空指针异常

Question

我开发了一个显示Android手机所有联系人的活动，我正在使用ListView来显示检索到的联系人。问题是直到我不滚动我的 ListView，每当我单击任何列表项时 - 它都会显示该特定的联系人记录详细信息。但是，当我滚动并单击列表中的任何项目时，应用程序崩溃并抛出 NullPointerException。谁能指导我哪里出错了以及如何实现我的结果。这可能是一个重复的问题，但我尝试在网上搜索但没有成功。下面是显示联系人的活动的代码片段：

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.contact_manager);
    filterText = (EditText) findViewById(R.id.search_box);     
    filterText.addTextChangedListener(filterTextWatcher); 
    mContactList = (ListView) findViewById(R.id.contactList);
    populateContactList();      
}
private void populateContactList()
{
    // Another class used to retrieve contacts
              ContactAPI contactAPI = ContactAPI.getAPI();
    ContentResolver cr = getContentResolver();
    contactAPI.setCr(cr);
    ArrayList<Contact> a = new ArrayList<Contact>();
    a = contactAPI.newContactList(this).getContacts();
    contactsAL = new ArrayList<Contact>(a);     
    adapter = new CustomAdapter(this, R.layout.contact_entry, a);       
    mContactList.setAdapter(adapter);   
    mContactList.setOnItemClickListener(new OnItemClickListener(){
    public void onItemClick(AdapterView<?> parent, View view, int position, long id)
    {               
               ***// The below is the line where I am getting NullPointerException***
        LinearLayout l = (LinearLayout) parent.getChildAt(position);
        TextView tv = (TextView) l.getChildAt(1);
        Intent myIntent = new Intent(view.getContext(), ContactDetailsActivity.class);
        Bundle b = new Bundle();
        b.putString("ContactID", tv.getText().toString());
        myIntent.putExtras(b);
        startActivityForResult(myIntent, 0);
    }
    });

private TextWatcher filterTextWatcher = new TextWatcher() 
{      
    public void afterTextChanged(Editable s) 
    {     
    }      
    public void beforeTextChanged(CharSequence s, int start, int count, int after) 
    {     
    }      
    public void onTextChanged(CharSequence s, int start, int before, int count) 
    {         
        adapter.getFilter().filter(s);
    }  
};
protected void onDestroy() 
{     
    super.onDestroy();     
    filterText.removeTextChangedListener(filterTextWatcher); 
}   

---

下面是我的自定义适配器类代码片段：

private ArrayList<Contact> original; 
private ArrayList<Contact> fitems;
private Filter filter;
private LayoutInflater mInflater;
public CustomAdapter(Context context, int layoutResourceId, ArrayList<Contact> data) 
{
    super(context, layoutResourceId, data);
    this.layoutResourceId = layoutResourceId;
    this.context = context;
    this.original = new ArrayList<Contact>(data);         
    this.fitems = new ArrayList<Contact>(data);
}   
public long getItemId(int position) {
    return position;
}
public View getView(int position, View convertView, ViewGroup parent) 
{       
    ViewHolder holder;
    if (convertView == null) 
    {
        mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);         
        convertView = mInflater.inflate(R.layout.contact_entry, null);
        holder = new ViewHolder();          
        holder.txtName = (TextView) convertView.findViewById(R.id.contactEntryText);
        holder.txtID = (TextView) convertView.findViewById(R.id.contactID);
        convertView.setTag(holder);         
    } 
    else 
    {           
        holder = (ViewHolder) convertView.getTag();         
    }
    if(fitems != null)
    {
        Contact ct = fitems.get(position);
        if(ct != null)
        {
            holder.txtName.setText((String)ct.getDisplayName());
            holder.txtID.setText((String)ct.getId());
        }
    }
    //this.notifyDataSetChanged();
    return convertView;
}
@Override
public Filter getFilter() {
    // TODO Auto-generated method stub
    // return super.getFilter();
    if (filter == null)         
        filter = new ContactFilter();      
    return filter;
}

private class ContactFilter extends Filter 
{ 
    @Override 
    protected FilterResults performFiltering(CharSequence constraint) 
    { 
        FilterResults results = new FilterResults(); 
        String prefix = constraint.toString().toLowerCase(); 
        if (prefix == null || prefix.length() == 0) 
        { 
            ArrayList<Contact> list = new ArrayList<Contact>(original); 
            results.values = list; 
            results.count = list.size(); 
        } 
        else 
        { 
            final ArrayList<Contact> list = new ArrayList<Contact>(original); 
            final ArrayList<Contact> nlist = new ArrayList<Contact>(); 
            int count = list.size(); 
            for (int i=0; i<count; i++) 
            { 
                final Contact cont = list.get(i); 
                final String value = cont.getDisplayName().toLowerCase(); 
                if (value.contains(prefix)) 
                { 
                    nlist.add(cont); 
                } 
            } 
            results.values = nlist; 
            results.count = nlist.size(); 
        } 
        return results; 
    } 
    @SuppressWarnings("unchecked") 
    @Override 
    protected void publishResults(CharSequence constraint, FilterResults results) 
    { 
        fitems = (ArrayList<Contact>)results.values; 
        clear(); 
        int count = fitems.size(); 
        for (int i=0; i<count; i++) 
        { 
            Contact cont = (Contact)fitems.get(i); 
            add(cont); 
        } 
    } 
}
static class ViewHolder {
    TextView txtName;
    TextView txtID;
}

---

谁能建议我哪里做错了？

Answer 1

int onItemClick调用 CustomAdapter.getItem（int） 以检索位置处的Contact对象，使用联系人检索启动新活动所需的信息。

Answer 2

删除主活动中的

设置。

在 CustomAdapter 中，在 getView 方法中，您只需将 clicklistener 添加到文本视图

holder.txtName.setOnclickListener(new OnClickListener() {
   @Override
  public void onClick() {
  Intent myIntent = new Intent(view.getContext(), ContactDetailsActivity.class);
    Bundle b = new Bundle();
    b.putString("ContactID", holder.txtName.getText().toString());
    myIntent.putExtras(b);
    startActivityForResult(myIntent, 0);
   }
})