自定义 listView 数组，搜索，在 NotifyDataSetChanged 上崩溃，加上 listView 没有得到更新
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【中文标题】自定义 listView 数组，搜索，在 NotifyDataSetChanged 上崩溃，加上 listView 没有得到更新【英文标题】：Custom listView Array, Search, crash on NotifyDataSetChanged, plus the listView is not getting updated 【发布时间】：2021-06-08 18:32:30 【问题描述】：我正在调试问题，我可以得到它已被过滤，但刷新应用程序会崩溃，
我正在从数据库中获取列表，显示没有问题，
过滤列表时，应用在 notifyDataSetChanged() 时崩溃
请帮忙
public class ViewListContents extends AppCompatActivity implements Filterable
DatabaseHelper myDB;
ArrayList<User> userList;
ArrayList<User> userListFiltered;
ListView listView;
User user;
TextView firstName;
TextView lastName;
TextView favFood;
MediaPlayer player;
private int featureCustomTitle;
ThreeColumn_ListAdapter adapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.viewcontents_layout);
myDB = new DatabaseHelper(this);
userList = new ArrayList<>();
Cursor data = myDB.getListContents();
ListView listView = (ListView) findViewById(R.id.listView);
TextView firstName = (TextView) findViewById(R.id.textFirstName);
TextView lastName = (TextView) findViewById(R.id.textLastName);
TextView favFood = (TextView) findViewById(R.id.textFavFood);
ThreeColumn_ListAdapter adapter = new ThreeColumn_ListAdapter(this, R.layout.list_adapter_view, userList);
listView.setAdapter(adapter);
MenuItem menuItem = findViewById(R.id.search_view);
this.userList = userList;
this.userListFiltered = userList;
player = MediaPlayer.create(this, Settings.System.DEFAULT_ALARM_ALERT_URI);
int numRows = data.getCount();
if (numRows == 0)
Toast.makeText(ViewListContents.this, "The Database is empty :(.", Toast.LENGTH_SHORT).show();
else
int i = 0;
while (data.moveToNext())
user = new User(data.getString(1), data.getString(2), data.getString(3));
userList.add(i, user);
System.out.println(data.getString(1) + " " + data.getString(2) + " " + data.getString(3));
System.out.println(userList.get(i).getFirstName());
i++;
menuItem.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener()
@Override
public boolean onMenuItemClick(MenuItem item)
if (item.getGroupId() == R.id.search_view)
Log.e("main activity","item clicked");
//startActivity(new Intent(getContext(),ThreeColumn_ListAdapter.class).putExtra("itemss",userListFiltered.get(position)));
Intent intent = new Intent(getApplicationContext(), ThreeColumn_ListAdapter.class);
intent.putExtra("nvp", userListFiltered);
startActivity(intent);
return true;
else
// edit shape menu
return false;
);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener()
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
TextView v;
player.setLooping(true);
player.start();
v = view.findViewById(R.id.textFirstName);
Toast.makeText(getApplicationContext(), "selected Item Name is " + v.getText().toString(), Toast.LENGTH_SHORT).show();
);
@Override
public boolean onCreateOptionsMenu(Menu menu)
getMenuInflater().inflate(R.menu.menu, menu);
MenuItem menuItem = menu.findItem(R.id.search_view);
SearchView searchView = (SearchView) menuItem.getActionView();
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener()
@Override
public boolean onQueryTextSubmit(String query)
return false;
@Override
public boolean onQueryTextChange(String newText)
//ThreeColumn_ListAdapter adapter = new ThreeColumn_ListAdapter(getApplicationContext(), R.layout.list_adapter_view, userList);
// Toast.makeText(getApplicationContext(),newText,Toast.LENGTH_SHORT).show();
getFilter().filter(newText);
return true;
);
return true;
@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item)
int id = item.getItemId();
if(id == R.id.search_view)
return true;
return super.onOptionsItemSelected(item);
@Override
public Filter getFilter()
Filter filter = new Filter()
@Override
protected FilterResults performFiltering(CharSequence constraint)
FilterResults filterResults = new FilterResults();
if (constraint == null || constraint.length() == 0 )
filterResults.count = userList.size();
filterResults.values = userList;
else
ArrayList<User> resultData = new ArrayList<>();
String searchStr = constraint.toString().toLowerCase();
Toast.makeText(getApplicationContext(),constraint,Toast.LENGTH_SHORT).show();
for (User user: userList)
if(user.getFirstName().contains(searchStr))
resultData.add(user);
filterResults.count = resultData.size();
filterResults.values = resultData;
return filterResults;
@Override
protected void publishResults(CharSequence constraint, FilterResults results)
userListFiltered = (ArrayList<User>) results.values;
adapter.notifyDataSetChanged();
;
return filter;
Viewbtn 在 Fragment 中，所以我正在对如何创建列表搜索进行一些测试。
public class ThreeColumn_ListAdapter extends ArrayAdapter<User>
ArrayList<User> userList;
ArrayList<User> userListFiltered;
LayoutInflater mInflater;
ArrayList<User> users;
int mViewResourceId;
private Context context;
public ThreeColumn_ListAdapter(Context context, int textViewResourceId, ArrayList<User> users)
super(context, textViewResourceId, users);
this.users = users;
this.userList = users;
this.userListFiltered = users;
this.context = context;
mInflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
mViewResourceId = textViewResourceId;
@Override
public int getCount()
return userListFiltered.size();
@Override
public User getItem(int position)
return userListFiltered.get(position);
@Override
public long getItemId(int position)
return position;
public void updateData(ArrayList<User> userList)
this.userList = userList;
notifyDataSetChanged();
@Override
public View getView(int position, View convertView, ViewGroup parent)
convertView = mInflater.inflate(mViewResourceId, null);
User user = users.get(position);
if (user !=null)
TextView firstName = (TextView) convertView.findViewById(R.id.textFirstName);
TextView lastName = (TextView) convertView.findViewById(R.id.textLastName);
TextView favFood = (TextView) convertView.findViewById(R.id.textFavFood);
if (firstName != null)
firstName.setText((user.getFirstName()));
if (lastName != null)
lastName.setText((user.getLastName()));
if (favFood != null)
favFood.setText((user.getFavFood()));
// Toast.makeText(getContext(), "we are ok!!!", Toast.LENGTH_SHORT ).show();
return convertView;
【问题讨论】：
您需要发布堆栈跟踪。有这么多代码，很难通读一遍并想出一个解决方案。 【参考方案1】：-
您的应用程序将因 NPE 崩溃，因为您的适配器未初始化。在 OnCreate 中，您正在初始化适配器，但这是一个本地适配器。您已经在 Global one 中清除了，但尚未初始化。
替换这个
ThreeColumn_ListAdapter adapter = new ThreeColumn_ListAdapter(this, R.layout.list_adapter_view, userList);
与
adapter = new ThreeColumn_ListAdapter(this, R.layout.list_adapter_view, userList);
-
现在在过滤器之后，您只更新
userListFiltered，但在适配器类中您已通过userList。所以 listview 不会在过滤器上更新。
更新过滤列表的列表
在适配器中创建 1 个方法
public void updateData(ArrayList<User> userList)
this.userList = userList;
notifyDataSetChanged();
和
@Override
protected void publishResults(CharSequence constraint, FilterResults results)
userListFiltered = (ArrayList<User>) results.values;
adapter.updateData(userListFiltered);
【讨论】：
谢谢，现在它正在工作:)，@Kishan 我如何将列表更新为新的 userListFilter？ 仍然无法正常工作:(，我将在上面更新适配器当前代码 我调试过，我选的字母不存在，比如“Z”，我可以在更新中看到 iselist 值为零，但视图中的列表仍然没有更新。跨度> 我正在尝试添加这个 menuItem.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() @Override public boolean onMenuItemClick(MenuItem item) if (item.getGroupId() == R.id.search_view) Log.e("主要活动","项目点击"); Intent intent = new Intent(getApplicationContext(), ThreeColumn_ListAdapter.class); intent.putExtra("nvp", userListFiltered); startActivity(intent); return true;以上是关于自定义 listView 数组，搜索，在 NotifyDataSetChanged 上崩溃，加上 listView 没有得到更新的主要内容，如果未能解决你的问题，请参考以下文章
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