使用 AutocompleteTextView 和 BaseAdapter 时出现空指针异常

Question

我有一个 AutocompleteTextView，我为此编写了以下适配器。我想从 Web API 获取数据，这工作正常，我可以从服务器获取数据。当我在 autocompleteTextView 上写文本时，下面的代码显示了以下错误。我调试我的代码，这个错误在调用 notifyDataSetChanged 和调用 getViewMethod 后显示。我不知道我的问题是什么。

另一件事，我从服务器得到一个对象列表（我的意思是名字、家庭、id）我只想显示其中的一部分（我的意思是我想显示名字）为此，我创建了一个自定义适配器。

我的适配器：

public class DropDownAdapter extends BaseAdapter implements Filterable {
private static final int MAX_RESULTS = 10;
private Context mContext;
private List<TestModel> resultList = new ArrayList<TestModel>();
private boolean placeResults = false;
private Object lockTwo = new Object();
private Object lock = new Object();


public DropDownAdapter(Context context) {
    mContext = context;
}

@Override
public int getCount() {
    return resultList.size();
}

@Override
public Object getItem(int position) {
    return resultList.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View view, ViewGroup viewGroup) {
    View v = view;
    if (v == null) {
        LayoutInflater inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(R.layout.one_row_dropdown, viewGroup, false);
    }
    TextView textView = v.findViewById(R.id.textview);
    textView.setText(resultList.get(position).code);
    return view;
}


@Override
public Filter getFilter() {

    Filter filter = new Filter() {

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            final FilterResults filterResults = new FilterResults();

            if (constraint == null || constraint.length() == 0) {
                synchronized (lock) {
                    filterResults.values = new ArrayList<String>();
                    filterResults.count = 0;
                }
            } else {
                JSONObject jsonObject = new JSONObject();
                try {
                    jsonObject.put("token", OfflineData.getGUID(mContext));
                    jsonObject.put("code", constraint.toString());
                    jsonObject.put("state", false);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

                Type type = new TypeToken<ServiceResult<List<TestModel>>>() {
                }.getType();
                WebService getBranchCodeListWebService = new WebService(AppConstant.URL_LISTINGDATA, "TestMethod", type);
                getBranchCodeListWebService.addOnCompletedCallBack(new WebService.OnCompletedCallBack() {

                    @Override
                    public void onCompletedCallBack(boolean isSucceed, Object returnedObject) {
                        if (isSucceed) {
                            if (returnedObject != null) {
                                ServiceResult<List<TestModel>> response = (ServiceResult<List<TestModel>>) returnedObject;
                                if (response.IsSuccess) {
                                    if (response.Result.size() > 0) {
                                        resultList.clear();
                                        resultList = response.Result;
                                        filterResults.values = resultList;
                                        filterResults.count = resultList.size();
                                    }
                                }
                            }
                        }
                        placeResults = true;
                        synchronized (lockTwo) {
                            lockTwo.notifyAll();
                        }
                    }
                });
                getBranchCodeListWebService.execute(jsonObject);

                while (!placeResults) {
                    synchronized (lockTwo) {
                        try {
                            lockTwo.wait();
                        } catch (InterruptedException ex) {
                        }
                    }
                }
            }
            return filterResults;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            if (results != null && results.count > 0) {

                notifyDataSetChanged();
            } else {
                notifyDataSetInvalidated();
            }
        }
    };
    return filter;
}

错误结果：

Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
    at android.widget.AbsListView.obtainView(AbsListView.java:2382)
    at android.widget.DropDownListView.obtainView(DropDownListView.java:305)
    at android.widget.ListView.measureHeightOfChildren(ListView.java:1408)
    at android.widget.ListPopupWindow.buildDropDown(ListPopupWindow.java:1257)
    at android.widget.ListPopupWindow.show(ListPopupWindow.java:613)
    at android.widget.AutoCompleteTextView.showDropDown(AutoCompleteTextView.java:1217)
    at android.widget.AutoCompleteTextView.updateDropDownForFilter(AutoCompleteTextView.java:1086)
    at android.widget.AutoCompleteTextView.onFilterComplete(AutoCompleteTextView.java:1068)
    at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:285)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

在 MainActivity 中创建适配器：

 autoCompleteTextView = findViewById(R.id.branchCodeEdittextAutocomplete);
    autoCompleteTextView.setThreshold(2);

    DropDownAdapter dropDownAdapter=new DropDownAdapter(this);
    autoCompleteTextView.setAdapter(dropDownAdapter);

    autoCompleteTextView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            //go to next page... or anything like this
        }
    });

Answer 1

您没有返回正确的视图，请将您的 return view 更改为 return v

@Override
public View getView(int position, View view, ViewGroup viewGroup) {
    View v = view;
    if (v == null) {
        LayoutInflater inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(R.layout.one_row_dropdown, viewGroup, false);
    }
    TextView textView = v.findViewById(R.id.textview);
    textView.setText(resultList.get(position).code);
    return v;
}

并且您不必每次都可以使用 view 分配视图，它将在适配器中保存您的视图的引用，因此您可以删除行 View v = view; 并替换您的代码为

@Override
public View getView(int position, View view, ViewGroup viewGroup) {
    if (view == null) {
        LayoutInflater inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(R.layout.one_row_dropdown, viewGroup, false);
    }
    TextView textView = v.findViewById(R.id.textview);
    textView.setText(resultList.get(position).code);
    return view;
}

希望这对您有所帮助...

使用 AutocompleteTextView 和 BaseAdapter 时出现空指针异常

Null Pointer Exception in working with AutocompleteTextView and BaseAdapter

android

autocomplete

nullpointerexception

baseadapter