Android CustomListAdapter notifydatachange() 不工作 [英] Android CustomListAdapter notifydatachange() is not working

问题描述

我想使用自定义 ArrayAdapter 显示项目列表.

I want to disply list of items using Custom ArrayAdapter.

我将通过单击按钮插入数据.

I will insert data by clicking a button.

MainFragment.java

@Override
        public void onClick(View v) {
            DatabaseClass feed = new DatabaseClass(getActivity());
            new DatabaseClass(getActivity()).getList();
            new MyFragment().updateList();
        }

我的布局文件如下.

ma​​in.xml

 <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="vertical" >

                <fragment
                    android:id="@+id/update"
                    android:name="com.android.MyFragment"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent" />
            </LinearLayout>

MyFragment.java

import java.util.List;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class MyFragment extends ListFragment {

    // creating database reference
    private static DatabaseClass feed;
    private List<CustomModel> customList;
    private static CustomListAdapter adapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        feed = new DatabaseClass(getActivity());
    }

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

        // To get List of CustomModel objects
        feed.getList();

        // CUSTOM_LIST is list constant
        adapter = new CustomListAdapter(getActivity(),
                R.layout.update, Utils.CUSTOM_LIST);

        // setting adapter      
        setListAdapter(adapter);
        View view = inflater.inflate(R.layout.update, container, false);

        return view;
    }

    @Override
    public void onStart() {
        super.onStart();
    }

    // this method is called after inserting data into database
    public void updateList() {
        if (adapter != null) {
            adapter.notifyDataSetChanged();
        } else {
            adapter = new CustomListAdapter(getActivity(),
                    R.layout.update, Utils.CUSTOM_LIST);
            adapter.notifyDataSetChanged();
        }
    }

    private class CustomListAdapter extends ArrayAdapter<CustomModel> {

        private final Context context;
        private final List<CustomModel> list;
        private TextView name, message;

        public CustomListAdapter(Context context, int resource,
                List<CustomModel> list) {
            super(context, resource, list);
            this.context = context;
            this.list = list;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View view = inflater.inflate(R.layout.single_row, parent,
                    false);

            name = (TextView) view.findViewById(R.id.name);
            message = (TextView) view.findViewById(R.id.message);
            CustomModel obj = list.get(position);

            name.setText(obj.getName());
            message.setText(obj.getMessage());

            return view;
        }
    }
}

MyFragment.java 的布局文件是

And layout file for MyFragment.java is

update.xml

<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@android:id/list"
 />

我的数据库类是

DatabaseClass.java

    public void getList(){
        ourDatabase = this.getReadableDatabase();
        String sql = "SELECT * FROM " + DATABASE_TABLE;
        Cursor c = ourDatabase.rawQuery(sql, null);

        int iName = c.getColumnIndex(KEY_NAME);
        int iMessage = c.getColumnIndex(KEY_MESSAGE);

        for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
            CustomModel model = new CustomModel();


            model.setName(c.getString(iFromName));
            model.setMessage(c.getString(iMessage));

            Utils.LIST.add(model);
        }
}

点击按钮，数据被插入到数据库中.但它没有反映在 UI 中.为什么我的列表视图没有更新?

onclick of button, data is inserted into db. but it is not reflecting in UI. Why my list view is not updated?

谢谢

推荐答案

按如下方式更改您的适配器

Change your adapter as follows

    private class CustomListAdapter extends ArrayAdapter<CustomModel> {

    private final Context context;
    private final List<CustomModel> list;
    private TextView name, message;

    public CustomListAdapter(Context context, int resource,
            List<CustomModel> list) {
        super(context, resource, list);
        this.context = context;
        this.list = list;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.single_row, parent, false);

        name = (TextView) view.findViewById(R.id.name);
        message = (TextView) view.findViewById(R.id.message);
        CustomModel obj = list.get(position);

        name.setText(obj.getName());
        message.setText(obj.getMessage());

        return view;
    }

    public void updateList(List<CustomModel> list) {

        this.list = list;
        notifyDataSetChanged();

    }
}

因此在您的适配器本身中添加方法 updateList 并调用方法 notifyDataSetChanged();

so add the method updateList in your adapter itself and call the method notifyDataSetChanged();

所以从你的活动而不是调用 notifyDataSetChanged(); call updateList(List newList)

so from your activity instead of calling notifyDataSetChanged(); call updateList(List<CustomModel> newList)

我相信这会奏效.

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