ListView不会随着notifydatasetchanged刷新

Question

我在Android ListView中显示了两列的MySQL数据库。我使用Retrofit 1.9从MySQL获取数据。 ListView的适配器是BaseAdapter，而我没有DatabaseHelper类。当我从手机向ListView添加数据时，它不会刷新ListView。我必须关闭并重新启动应用程序。我尝试用listViewAdapter.notifyDataSetChanged();刷新。

这是列表视图所在的片段：

public class rightFragment extends Fragment {

String BASE_URL = "http://awebsite.com";

View view;
ListView listView;
ListViewAdapter listViewAdapter;

Button buttondisplay;
Button buttonadd;
EditText new_id;
EditText newWordFra;
EditText newWordDeu;

ArrayList<String> id = new ArrayList<>();
ArrayList<String> fra = new ArrayList<>();
ArrayList<String> deu = new ArrayList<>();

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    view = inflater.inflate(com.example.geeko.Deu.R.layout.fragment_right, container, false);

    listView = (ListView) view.findViewById(com.example.geeko.Deu.R.id.listView); //<<<< ADDED NOTE use your id
    listViewAdapter = new ListViewAdapter(getActivity(), id, fra, deu);

    displayData();

    buttondisplay = (Button) view.findViewById(com.example.geeko.Deu.R.id.buttondisplay);
    buttonadd = (Button) view.findViewById(com.example.geeko.Deu.R.id.buttonadd);
    buttondelete = (Button) view.findViewById(com.example.geeko.Deu.R.id.newID);
    newWordFra = (EditText) view.findViewById(com.example.geeko.Deu.R.id.newWordFra);
    newWordDeu = (EditText) view.findViewById(com.example.geeko.Deu.R.id.newWordDeu);

    buttonadd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Toast.makeText(MainActivity.this , "button add", Toast.LENGTH_LONG).show();
            insert_data();
           listViewAdapter.notifyDataSetChanged();

        }
    });

    buttondisplay.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if (buttondisplay.getText().toString().contains("Show")) {
                listView.setAdapter(listViewAdapter);
                buttondisplay.setText("Hide");
            } else {
                listView.setAdapter(null);
                buttondisplay.setText("Show");
            }
        }
    });


    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long ids) {

            new_id.setText(id.get(position));
            newWordFra.setText(fra.get(position));
            newWordDeu.setText(deu.get(position));

        }
    });

    return view;

}

public void insert_data() {

    RestAdapter adapter = new RestAdapter.Builder()
            .setEndpoint(BASE_URL) //Setting the Root URL
            .build();

    AppConfig.insert api = adapter.create(AppConfig.insert.class);

    api.insertData(
            newWordFra.getText().toString(),
            newWordDeu.getText().toString(),
            new Callback<Response>() {
                @Override
                public void success(Response result, Response response) {

                    try {

                        BufferedReader reader = new BufferedReader(new InputStreamReader(result.getBody().in()));
                        String resp;
                        resp = reader.readLine();
                        Log.d("success", "" + resp);

                        JSONObject jObj = new JSONObject(resp);
                        int success = jObj.getInt("success");

                        if(success == 1){
                            Toast.makeText(getActivity(), "Successfully inserted", Toast.LENGTH_SHORT).show();
                        } else{
                            Toast.makeText(getActivity(), "Insertion Failed", Toast.LENGTH_SHORT).show();
                        }

                    } catch (IOException e) {
                        Log.d("Exception", e.toString());
                    } catch (JSONException e) {
                        Log.d("JsonException", e.toString());
                    }
                }

                @Override
                public void failure(RetrofitError error) {
                    Toast.makeText(getActivity(), error.toString(), Toast.LENGTH_LONG).show();
                }
            }
    );
}

public void displayData() {

    RestAdapter adapter = new RestAdapter.Builder()
            .setEndpoint(BASE_URL) //Setting the Root URL
            .build();

    AppConfig.read api = adapter.create(AppConfig.read.class);

    api.readData(new Callback<JsonElement>() {
                     @Override
                     public void success(JsonElement result, Response response) {

                         String myResponse = result.toString();
                         Log.d("response", "" + myResponse);

                         try {
                             JSONObject jObj = new JSONObject(myResponse);

                             int success = jObj.getInt("success");

                             if (success == 1) {

                                 JSONArray jsonArray = jObj.getJSONArray("details");
                                 for (int i = 0; i < jsonArray.length(); i++) {

                                     JSONObject jo = jsonArray.getJSONObject(i);

                                     id.add(jo.getString("id"));
                                     fra.add(jo.getString("fra"));
                                     deu.add(jo.getString("deu"));


                                 }

                                 listView.setAdapter(listViewAdapter);


                             } else {
                                 Toast.makeText(getActivity(), "No Details Found", Toast.LENGTH_SHORT).show();
                             }
                         } catch (JSONException e) {
                             Log.d("exception", e.toString());
                         }
                     }

                     @Override
                     public void failure(RetrofitError error) {
                         Log.d("Failure", error.toString());
                         Toast.makeText(getActivity(), error.toString(), Toast.LENGTH_LONG).show();
                     }
                 }
    );
  }

}

这是listViewAdpater类：

public class ListViewAdapter extends BaseAdapter {

private final Context context;
private ArrayList<String> id = new ArrayList<String>();
private ArrayList<String> fra = new ArrayList<String>();
private ArrayList<String> deu = new ArrayList<String>();
LayoutInflater layoutInflater;

public ListViewAdapter(Context ctx, ArrayList<String> id, ArrayList<String> fra, ArrayList<String> deu) {

    this.context = ctx;
    this.id = id;
    this.fra = fra;
    this.deu = deu;

}

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

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

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

@SuppressLint("ViewHolder")
@Override
public View getView(final int position, View view, ViewGroup parent) {

    final Holder holder;
    if (view == null) {
        layoutInflater = (LayoutInflater) context.getSystemService
                (Context.LAYOUT_INFLATER_SERVICE);

        view = layoutInflater.inflate(R.layout.list_item, null);
        holder = new Holder();
        holder.txt_fra = (TextView) view.findViewById(R.id.fra);
        holder.txt_deu = (TextView) view.findViewById(R.id.deu);
        view.setTag(holder);
    } else {

        holder = (Holder) view.getTag();
    }

        holder.txt_fra.setText(fra.get(position));
        holder.txt_deu.setText(deu.get(position));


        return view;
    }

    static class Holder {
        TextView txt_fra, txt_deu;
    }

}

我应该创建一种刷新ListView的方法吗？

Answer 1

首先，我建议删除适配器内部不必要的变量初始化：

private ArrayList<String> id = new ArrayList<String>();
private ArrayList<String> fra = new ArrayList<String>();
private ArrayList<String> deu = new ArrayList<String>();

通过从片段中分配指针，您将已经分配了一个初始化的ArrayList。您希望两个指针都指向同一个ArrayList对象，以便对它们都应用更改。

显然，适配器中存储的数据未正确更新。我建议调试您的应用程序-设置断点，以便您可以在更新后查看适配器存储的数据。

使用notifyDataSetChanged()已经实现了编写更新方法的想法。只需在调用super.notifyDataSetChanged()之前覆盖适配器中的方法并进行最终更改即可。

如果您在这些更改方面取得了成功，请告诉我们。

Answer 2

buttonadd.setOnClickListener(new View.OnClickListener() {
        ...
        insert_data();
       listViewAdapter.notifyDataSetChanged();

    }
});

在您的onClickListener中，您正在呼叫insert_data()，然后是listViewAdapter.notifyDataSetChanged()

insert_data()方法正在发送网络请求以检索数据以填充列表。但是，您在完成网络请求之前正在呼叫notifyDataSetChanged。这就是listView为空并且将保持为空的原因。您需要在网络请求之后等待，然后在ArrayList中填充数据以调用notifyDataSetChanged。 我们如何知道网络请求已完成？只需在回调的末尾（已实现）：

new Callback<Response>() {
            @Override
            public void success(Response result, Response response) {...

在success方法的末尾，您调用listViewAdapter.notifyDataSetChanged()方法。

希望如此！试试吧，让我们知道会发生什么

Answer 3

我已经找到了解决方案。我在方法 insert_data 中添加了getActivity.recreate();。

public void success(Response result, Response response) {

                    try {

                        BufferedReader reader = new BufferedReader
                                (new InputStreamReader(result.getBody().in()));
                        String resp;
                        resp = reader.readLine();
                        Log.d("success", "" + resp);

                        JSONObject jObj = new JSONObject(resp);
                        int success = jObj.getInt("success");

                        if(success == 1){
                            Toast.makeText(getActivity(), "Successfully inserted",
                                    Toast.LENGTH_SHORT).show();
                            getActivity().recreate();

                        } else{
                            Toast.makeText(getActivity(), "Insertion Failed",
                                    Toast.LENGTH_SHORT).show();
                        }

                    } catch (IOException e) {
                        Log.d("Exception", e.toString());
                    } catch (JSONException e) {
                        Log.d("JsonException", e.toString());
                    }


                }

我不确定这是否是最好的解决方案，但它是否有效。